Riddles in the Sky

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Introduction

As space becomes increasingly congested, contested, and commercialized, the need for reliable, secure, and professional-grade space situational awareness (SSA) has never been greater. While the democratization of satellite observation through open-source ground station networks appears promising, it presents significant under-discussed risks. This paper uses SatNOGS as a central example to explore the operational, economic, and ethical implications of these networks. Other emerging initiatives attempting similar models—such as TinyGS and NyanSat—further reinforce the need for clear boundaries, standards, and governance in the amateur space operations landscape.

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1. Quality Control Deficiencies

SatNOGS, a globally distributed open-source ground station network, enables amateurs to track and receive data from satellites and anyone else to review and use this data as it appears comprehensive. While the model fosters participation, its lack of standardized data validation introduces measurable risk:

• Observational data is accepted without formal quality checks.
• Misidentifications, false positives, or incomplete telemetry are not uncommon.
• Operator experience and equipment quality vary widely.

Other projects experimenting with open-access satellite tracking systems—such as TinyGS, which focuses on LoRa communications, or NyanSat, which emphasizes low-cost VHF/UHF reception—face similar issues. This underscores a systemic challenge in maintaining data reliability across decentralized, volunteer-run SSA initiatives.ning data reliability across decentralized, volunteer-run SSA initiatives.

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2. Governance and Motivations of the Libre Space Foundation

The Libre Space Foundation (LSF), which oversees SatNOGS, promotes open-access development in space technology. However, its transparency in financial and governance practices remains limited:

• No publicly available audited financial statements or annual reports.
• Project revenue flows and decision-making structures are unclear.
• SatNOGS appears to serve as a key vehicle for foundation visibility and funding.

This raises concerns about whether public claims of openness are matched by transparent and accountable practices. By contrast, newer initiatives like TinyGS appear to operate on more ad hoc, community-driven bases without the formal structure of a foundation—though this too limits their accountability and long-term sustainability.

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3. Impact on the Commercial SSA Ecosystem

SatNOGS illustrates how amateur networks can impact the commercial SSA market:

• Some satellite operators, particularly academic and small commercial ventures, appear to rely on amateur networks for telemetry, avoiding commercial service investment.
• This may discourage the development of scalable, high-integrity SSA capabilities.
• The availability of unregulated, free data shifts norms around operational responsibility.

TinyGS and similar efforts may exacerbate this issue further, as their extremely low-cost model can lead operators to undervalue professional ground station services altogether.

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4. Mission Oversight and Responsibility

The SatNOGS experience reveals how community networks can become an unspoken crutch for under-resourced missions:

• Operators have launched payloads without telemetry plans, relying on amateur support for recovery.
• Delayed uplinks and missed detections have occurred due to over-reliance on volunteer efforts.
• These behaviours introduce real risks to mission success and broader orbital management.

The challenge is not limited to SatNOGS. Other groups testing decentralized SSA tools—regardless of intent—must confront the same question: how do we ensure responsible behaviour when the barrier to participation is low but the consequences of failure are high?

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5. Toward a Responsible Amateur Framework

A sustainable path for amateur involvement in SSA must recognize the difference between learning and logistics. SatNOGS serves as a case study for how good intentions can overstep into operational territory without adequate safeguards.

A better model would integrate:

• Clear boundaries between educational and operational use.
• Recognition that high-value SSA work deserves compensation, accountability, and professional rigour.
• Pathways for skilled amateurs to transition into commercial or institutional roles.

My own path reflects this shift. After years in the amateur domain, I now support missions commercially. This change has led to:

• Paid engagements with mission teams who value data quality and accountability.
• Collaborations with professionals focused on reliable SSA service delivery.
• Marked improvements in technical standards and service consistency.

This hybrid model—where amateur experience evolves into commercial capacity—represents a constructive alternative to current open-use models.

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Recommendations

1. Introduce Quality Standards: Amateur networks should include validation mechanisms and confidence scoring.
2. Clarify Use Boundaries: Separate exploratory efforts from mission-critical applications.
3. Ensure Mission Accountability: Regulatory oversight should require documented telemetry and ground support plans for all satellites launched.
4. Improve Transparency: Public-facing projects should publish financial audits and governance disclosures.
5. Foster Professional Pathways: Enable skilled amateurs to enter the commercial SSA workforce.

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Conclusion

SatNOGS and similar initiatives represent the promise and complexity of open innovation in space. But without accountability, quality control, and professional boundaries, these systems risk undermining the very infrastructure they aim to democratize. As the SSA field evolves, a responsible framework is needed—one that honours amateur contribution while protecting the operational integrity of space.

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This is the author’s personal opinion only and is not intended to represent any other contributor to Riddles in the Sky.

On a dark late December winter night the United States military launched its secretive X-37B spaceplane atop a Falcon 9 heavy rocket from Kennedy Space Center. After watching the rocket slip from sight and the side boosters return nothing was seen from the spaceplane until the night of February 7, 2024 when amateur satellite observer Tomi Simola found something unusual, read his story below…

Read more: The Hunt for OTV-7 Into the Dark

At 01:07 UTC December 29, 2023, the US Space Force (USSF) launched their latest X-37B spaceplane mission referred to at Orbital Test Vehicle (OTV) 7 into a highly classified secret orbit.

Unlike earlier missions this launch was not targeting a low Earth orbit (LEO). The limited details shared to the public in Notice To Airmen (NOTAMs) revealed the spaceplane was likely targeting a high Earth orbit (HEO). Dr. Marco Langbroek conducted an analysis of the NOTAM information and shared a plausible trajectory for OTV-7.

Unfortunately, the time of the launch placed most of the trajectory in Earth’s shadow hiding the spaceplane from view during most of its initial coast orbit and while climbing to apogee it would be lost in the glare of the Sun during daylight.

To make the search more challenging X-37B’s are not known to emit on traditional Tracking Telemetry and Control (TT&C) radio frequency bands and likely use the National Reconnaissance Office’s (NRO) classified Satellite Data Service (SDS) and inter-satellite communications links making it exceeding difficult to track emissions from the spaceplane. 

One thing we did have going for us to search for on radio in the dark and later in the glare of the Sun was the final stage of the Falcon 9 Heavy. Given the NOTAMs revealed the rocket stage would be de-orbited over the northern Pacific Ocean thus its mission would likely carry on to at least apogee where it would conduct a de-orbit burn to lower its perigee to below the Earth’s surface to safely de-orbit the stage in the remote ocean area noted on the NOTAM.

Using Federal Communications Commission (FCC) filings we found the particular paperwork for the USSF-52 launch as submitted by SpaceX and knew that the final stage rocket should be emitting on 2232.5, 2247.5, 2255.5 and/or 2272.5MHz.

A group of amateur satellite trackers in Europe and western Australia where organized in an attempt to gather radio data from the Falcon 9’s final stage in an attempt to confirm the actual trajectory of the OTV-7 through this indirect means and hopefully allow for its optical recovery later.

The observer in western Australia maintained vigilance for the entire expected pass of OTV-7 and its respective rocket booster. Guidance was provided to the station to conduct scans of the clear sky from 2200-2300MHz from the site using their 1m dish antenna in an effort to find the rocket booster’s emissions on S-band. We heard many signals from many other missions but nothing form OTV-7’s rocket booster. Therefore, either the rocket booster wasn’t emitting, which would be highly unlikely considering past observing experience or the trajectory guess for OTV-7 was not accurate enough to place the rocket booster in the sky above the observer in western Australia. 

To Planar Scan or Stare into Space…?

It seemed like our only chance to find OTV-7 using Marco Langbroek’s reasonable analysis of NOTAM data had resulted in failure and most likely a long search would need to be performed to find OTV-7. Two possible strategies to find OTV-7 could have been reasonably considered. One, a planar search which assumes OTV-7 was on the orbital plane Marco’s trajectory stated but it was not in the location in the plane we thought. Two, multiple observers could just stare into space and with patience OTV-7 would pass sooner or most likely later through the field of view of someone.

What is a planar search? A satellite once launched into space is in a fixed plane with respect to the stars and it will stay in that orbital plane for all practical purposes unless something adds or removes energy from the object. The effects of atmospheric drag ,solar radiation pressure, venting etc. can cause the spacecraft’s position within an orbital plane to change over time creating uncertainty of where within the orbital plane the satellite is. To recover an object in a known orbital plane one can search the plane by scanning along it for a prolonged period of time and eventually you will find your wayward satellite. However, this assumes you know the orbital plane correctly.

In our radio search for the final rocket stage which should have been very close to OTV-7, we actually compensated for this by conducting a broader search of the track and sky for some hours and would have likely found the rocket’s emissions had the orbital plane guess been close. Another factor is the timing of arriving in the orbit was fairly constrained limiting the search area along the orbit plane. This left us to conclude that OTV-7 was most likely not in the orbital plane Marco’s analysis suggested. Thus an planar search of the plane Marco suggested was likely going to be very laborious and not result in recovering OTV-7.

Based on what we knew, it was agreed that staring into space may be the best strategy. You may be wondering and rightfully point out that space is pretty vast and staring at a fixed small spot may never produce results. It’s counter-intuitive but the fact is a satellite is in a fixed orbit. In this case we roughly knew the orbital geometry of our target and had a pretty good idea that if we aimed a camera at an intelligently chosen fixed spot and waited long enough the satellite would pass through and we would know it was our target because almost all other objects on orbit are known and catalogued or would be in different orbits and could be excluded. 

This is what Tomi Simola did to find OTV-7, he setup a light sensitive camera and connected it to a computer to record the results and excluded every object that passed through his field of view for literally weeks until an unidentified object passed through the field of view that matched OTV-7’s characteristics. 

On the night of February 7, 2024, Tomi Simola recovered OTV-7 and made these observations with his staring camera. Once you have even a limited set of short arc observations you can start to generate orbital elements from the data and start to narrow down the identity of the object. After consulting Mike McCants an expert on classified objects on orbit the identity was quickly firmed up as the orbital data came in on successive nights.

It turned out that our assumption that OTV-7 was in a different orbital plane than Marco’s reasoned guess was correct. Below you can see the dramatic difference in the sky track from the observer in western Australia for OTV-7. Much of the track was obscured by trees and other obstacles at the ground station. OTV-7 quickly passed through the ground station’s clear area of sky spent most of the pass low on the south eastern horizon obscured by trees and then as it descended from apogee passed quickly through the observable sky and disappeared…

For the record here are the initial guess TLE vs. the TLE developed from Tomi Simola’s observations of OTV-7 after it was recovered.

USSF-52 OTV 7 for launch on 29 Dec 2023 01:07:00 UTC
1 70000U 23999A 23363.06545139 .00000000 00000-0 00000-0 0 02
2 70000 074.0000 341.4480 7418186 136.2072 360.0000 02.14201823 02

OTV 7
1 58666U 23210A 24039.74420665 0.00000000 00000-0 00000-0 0 04
2 58666 59.1161 4.8483 7418435 167.3793 193.0310 2.07574710 01

An Interview with Tomi Simola on Finding OTV-7

Scott Tilley – Can you describe your observing strategy you used to recover OTV7?

Tomi Simola – Stare long enough and it will pass your Field-of-view!

Earlier I have been pointing my camera at different parts of the sky, depending on the object or area of interest. Because OTV-7 has gained great interest in the satellite watching and space technology community I elected to keep the camera stationary. Early orbital predictions showed that OTV-7 will eventually pass the FOV! As you pointed out (and it makes perfect sense), there is no point to chase a satellite when you don’t know where it is!

Scott Tilley – Can you tell us more about how you and Mike McCants came to the conclusion that the object you observed was OTV7?

Tomi Simola – After I posted my first observations to Seesat-L on February 8, Mike McCants emailed me three hours later with orbital elements for “Unknown 020724”. He could not match it with anything in his catalogues. He reckoned “it was a small piece of space debris catching sunlight just right.”

I respectfully disagreed, explaining that visually the UNID was steady over the whole pass and “eyeball” magnitude similar to large USA 144 Deb (25746 / 99028C), which has passed a couple of times on a similar distance.

Next night I observed it again and very close to Mike’s earlier prediction. He told me that I’ve found the OTV-7!

Scott Tilley – Can you describe your observing equipment. What kind of camera, lens and software are you using?

Tomi Simola – I use the Watec 902H Ultimate analog video camera with a Chinese TTArtisan 50mm f1.2 lens. There is a 3D printed adapter in between. The lens was a lucky find for only 100 euros!

The software is Cees Bassa’s STVID and SATTOOLS. I have the camera in an IP68 camera housing with a servo driven sunshield in front of the lens. Separate mini PC has STVID doing the capture to a NAS storage in my network. A virtual machine has a STVID and SATTOOLS installed and I use it for processing the observations.

Scott Tilley – How did you feel when you first noticed the unidentified satellite in your data?

Tomi Simola – I was browsing the images that STVID had tagged as UNID. There was one set of images (20 or so) with an object with a rather short trail, meaning it was in a higher orbit. And while scrolling the images back and front I noticed the object was “accelerating”! The trail got longer (almost doubled) at the end of the set of images! Then I knew that this was something different!

My amateurish initial analysis for a circular orbit showed it in 56.5518 inclination, 6.6 revs/day. That inclination didn’t sound like Dr Marco Langbroek’s pre-launch prediction of 74 degrees. 6.6 revolutions per day was too much for a Molniya kind of orbit. I stated my doubts in an email to Seesat-L.

Scott Tilley – When did you know that you had found OTV7? How did that feel?

Tomi Simola – After Mike McCants email where he told me the UNID was OTV-7! I might have done a wild, but private “goal celebration”!

Scott Tilley – Can you tell us about your observing site and how it makes satellite observing unique? I.e. your northern latitude and how that affects satellite illumination.

Tomi Simola – My observing site is in my south facing backyard. But there is an area where I can set up my camera and point it over the neighbours roof, pointing low at the Northern sky. Area of the sky is busy with NOSS satellites which are very predictable and they are good targets to practice observations!

My latitude is 60 North, so some satellites are more visible earlier in the spring / later in the autumn, than for those in lower latitudes.

The site is very close to an international airport, but that has no great effect in my observations.

Scott Tilley – In this process of building an observing station and operating it what have you learned and what are your next steps?

Tomi Simola – I was not that much interested in visual satellite observing until two years ago, when I found the Watec camera for a very good price! Cees Bassa’s STVID was at that time getting rapid updates. Then I started to read tutorials from www.satobs.org.

I have done some RF observations with Bassa’s STRF (interest in this was sparked by Scott Tilley’s recovery of IMAGE in 2018), but the visual side was something different. SATTOOLS and STVID are very powerful software, but learning curve is…”steepish” – especially when one has no prior experience in visual satellite tracking!

Tutorials, articles and members of the Seesat-L have helped me to understand a bit better orbital dynamics and therefore I can pre-analyze my observations a bit better now. But there is so much more in orbital dynamics, visual tracking, that only way is forward! Interesting hobby that I never thought I’d get into!

More technical side, I have to improve the Wife-Acceptance-Factor of the camera setup. Also, a motorized mount would be nice in winter time!

Scott Tilley – Why do you look up and observe the sky to monitor satellites?

Tomi Simola – My interest in space flights and satellites was sparked when I was a small boy. I was living in a small village, far from the nearest city, with a stunning night sky! Moving stars in the sky were quickly explained as satellites.

The school library had lots of old books and my favourites were translated versions of “Die Mondlandung / Moon landing, 1969”, by Herbert J. Pichler and “Man and space, (Life science library), 1972” by Arthur C. Clarke. I have read these tens of times! I later acquired these books for my ever growing space library!

In my teens I received weather satellite pictures from NOAA and old Meteor satellites and kosmonauts talking with Moscow from MIR.

Satellites are fascinating! They are so close, just 200-300 km away, but getting there requires the smartest minds on the planet!

Spaceflights were for a long time only for superpowers and government backed institutions! They were rather rare occasions. Now, when technological advancements have brought satellites to the masses (you can almost literally buy your own satellite!), the “saturation” of the lower Earth orbit is getting more serious. I think satellite collisions are still rare, but astronomers using the whole electromagnetic spectrum (from DC to daylight and beyond) are getting frustrated with RF and visual noise in their data! Future space companies should have more responsibility to keep near space clean.

Amateur observers, not only for classified payloads, have an important task to bring these problems to the public and more importantly, to lawmakers! Good example is BLUEWALKER 3, which has a very large and visible antenna and dubious RF characteristics!

Conclusion

Once again amateur satellite observers with modest means and lots of patience find a classified object in space. We hope that sharing this story inspires others to look up and ensure the transparency in the use of space by all nations. 

We often post data online showing the results of a Doppler analysis. The concepts can be a bit intimidating to understand but with a little explanation it’s accessible to anyone.

Read more: Understand Doppler Analysis What is the Doppler Effect?

When something emits electromagnetic radiation and is moving relative to an observer the observed wavelength of the emitting radiation will be different. Essentially when things are moving their movement effects how the waves of radiation arrive at the observer. If they are moving toward each other the wave crests successively arrive earlier thereby decreasing the wavelength observed. If the objects where moving apart then the opposite happens and the wavelength increases.

So how does this apply to observing satellites? Imagine you are at a very large train station that has an infinite number of tracks coming and going from the station in all directions. East, West, North, South and even up into the sky and down into the Earth. Further imagine you are listening to the whistles of all these trains passing through the station. Some are moving fast some slow all going in different directions. As almost everyone has experienced the pitch of the whistles note will change based on the change in velocity of the train as it passes you by. If you really pay attention you will notice the pitch of all the trains coming and going is different depending on their orientation to you, their speed and even if you decide to walk around the station and move yourself.

Using this knowledge one could use the Doppler effect to map out the train’s trajectories as they pass and determine which are which especially if they follow schedules and are on predefined routes. This is what we are doing to track satellites with the Doppler effect. Instead of whistles the satellites have radio transmitters. Instead of tracks they have orbits in which they are locked into by the force of gravity. These orbits are periodic and predictable. Therefore, if you know about how your moving and have observed data from the satellite’s radio transmitter you can compare this to a large number of guesses about the orbit it’s in and find matches that best fit the orbit. If you have a list of known satellites in known orbits you can compare that list to the data you collect to find the best match too.

All that is going on is systematically observing the change in frequency of the satellite’s radio emissions and then comparing that to a large number or educated guesses to find the best fitting guess to the data.

Understanding Doppler Analysis Plots

The following provides a brief walk through to orientate a reader on what Cees Bassa’s Satellite Tools Radio Frequency (STRF) displays as a result of a Doppler analysis of a signal. This should provide the reader with enough context to understand the display given our comments earlier.

The Doppler plot noted above provides the raw Doppler frequency data (left y-axis) and the resulting range rate (line of sight velocity) on the right y-axis. The x-axis is time in Modified Julian Date (MJD).

Frequency is self evident as it’s the data we collect with our radio and antenna from the satellite. The range rate is a bit more obtuse. Range rate can also be better described as the line of sight velocity between two things. I.e. the resultant velocity at that time of perhaps two things moving with respect to each other. Doppler frequency tells us directly about this line of sight velocity and is what is actually used to compare the orbital models against.

Modified Julian Date (MJD) is a computationally friendly time system that allows for easy consecutive calculation of time based on a defined epoch (start date) of the system. MJD is used a lot in astronomy and astronautics.

Inside the plot the white lines (dots) are selected Doppler data. The grey line is the predicted Doppler curve when the object is below the observer’s horizon. The red line segments are when the object should be above the observer’s horizon.

The Two Line Element block displays the current ‘template’ orbital elements being modelled. If you want to learn more see my article on Basic Orbital Dynamics. The user can use template orbits, old orbits to update and also change the settings based on knowledge and intuition.

The fitted elements block allows the user to select which elements should be fitted for the best fit to the data. Careful selection of these given understanding of the orbital dynamics allows the user to find the best correct fit to a data set.

The sky track block allows the user to visualize the satellite’s path through the observer’s sky during times data is present. This is helpful when comparing to other data sources like antenna position etc.

The analysis results block provides the basic summary of the current Doppler analysis. Measurements is the total number of Doppler samples in the analysis. Frequency is the measured spacecraft emitted frequency once Doppler is accounted for. The rms is Root Mean Square error of the data compared to the model. TCA is Time of Closest Approach to the observing station performing the analysis. The name and COSPAR # for the observing station is next. The RED 8049 means that observing station 8049 data is present. If another station also contributed data their number and a different colour would be used to represent that.

To understand how good or bad an analysis is look at the rms number. The lower the better.

How Accurate is Doppler Analysis?

Accurate Doppler analysis relies on the observer recording very accurate frequency samples of the observed satellite signal. Therefore, using a very accurate clock for timing is required. In my case I use a GPS referenced oscillator to perform this function. This leads to the other source of error the spacecraft itself. Most spacecraft in Earth orbit and in Lunar orbit don’t usually have super stable radio oscillators. The reason is they don’t usually need this as the control stations will use other methods of determining the range and range rate to the spacecraft like two-way Doppler that uses a transponder on the spacecraft and therefore eliminates the spacecraft’s oscillator as a source of error. However, in our case we are limited to the one-way Doppler and must deal with the errors. If you want to learn more read NASA JPL’s Range and Doppler Tracking Observables.

STEREO-A is coming home in the summer of 2023 for the first time since it was launched 17 years ago and is providing amateur astronomers with a unique opportunity to do some citizen science. The spacecraft has inferior conjunction with Earth on August 17, 2023 and will be approximately 8.2 million kilometres distant then. While still far from Earth, STEREO-A will be unusually close to Earth and produce a unique opportunity to decode its deep space beacon and view stunning images of the Sun as it approaches solar maximum. In solving this riddle in the sky we present how we figured out how to decode STEREO-A’s images and present a suggestion of how to celebrate STEREO-A’s return to the vicinity of home.

Read more: STEREO-A Comes Home Inferior Conjunction is not a Complex…

Inferior conjunction has nothing to do with a spacecraft having an unrealistic feeling of general inadequacy, rather it refers to its arriving at a position in it’s orbit where it lies between the Earth and the Sun. As you can see from the graphic below this is also the closest position STEREO-A can be to Earth in its given orbit.

Using this GMAT script here one can model the arrival of STEREO-A at inferior conjunction and and get a sense of the distances still involved. At closest approach STEREO-A will be a little more than 0.055 astronomical units (AU) from Earth. As we will see this has a profound impact of the radio signal from STEREO-A for listeners here on Earth.

Animation of STEREO-A approaching inferior conjunction with Earth. This is a rotating frame from the Earth’s perspective.

As one can note from the solar orbit of STEREO-A that it is quite similar to Earth’s orbit. But just a little faster so over a period of about 17 years STEREO-A will lap us and pass by for an inferior conjunction.

As noted above, this has a profound impact of the radio signal amplitude on Earth when STEREO-A is around inferior conjunction. The free space path loss (FSPL) of STEREO-A’s decreases with the square of the distance between Earth and the spacecraft. As can be seen on the plot below since STEREO-A was launched it has been on average very distant from Earth with a very large FSPL. But as inferior conjunction approaches the signal dramatically improves by about 30dB. The plots below show normalized signal strength levels relative to the peak signal level in the time period of the plot.

Zooming in on the inferior conjunction event one can see the dramatic effect on the signal levels at Earth from the rapidly approaching STEREO-A spacecraft.

Since about mid June 2023 the amateur radio station here with it’s small 66cm aperture dish antenna has been noticing a dramatic increase in signal levels and the emergence of data side-bands on the signal.

Once we’d figured out what was going on we found an obscure page on the STEREO Science Centre website that provides info on the conjunction and a tool to calculate STEREO-A’s position relative to the Earth, Moon and Earth-Sun L1 science missions.

Reception of STEREO-A Deep Space Beacon

You might be surprised to know that STEREO-A has a ‘deep space beacon’ that sends low rate data of the space environment and images of the Sun and surrounding area near constantly. It transmits +/- Doppler at 8443.58MHz.

The purpose of the beacon is to provide near real-time space weather forecasting ability. The real-time data from STEREO-A and other space weather monitoring missions at the Earth-Sun L1 point and in Earth orbit provide the world with a near constant flow of data on the space weather going on so we here on Earth can manage infrastructure that is sensitive to it such as power grids, satellite navigation and high frequency radio communication to name a few. This low rate data includes compressed images of some of the high resolution science data known as COR2, EUVI, HI1 and HI2 at an interval of few 10s of minutes depending on the payload. Other data it sends is numeric space weather data from the IMPACT, PLASTIC and S/WAVES payloads.

Presently there is a limited network of participating ground stations around the world that provide partial coverage to collect the real time forecast data from STEREO-A. The following stations are presently actively participating in STEREO-A space weather beacon reception and reporting the data to NASA for distribution.

• APL: Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
• KSWC: Korean Space Weather Center, Jeju, South Korea
• BOCH: AMSAT-DL/Bochum Observatory, Germany
• KIEL: Amateur station DL0SHF, Kiel-Ronne, Germany
• KOGA: National Institute of Information and Communications Technology: Koganei, Japan

One of the most interesting is the amateur station DL0SHF, a 7.5m dish antenna located in Germany that is run by amateurs and provides a Earth Moon Earth (EME) beacon service and also gathers data from STEREO-A. It is the smallest of the beacon monitoring stations that formally participates in data gathering for NASA.

The X-band station at VE7TIL used at present is right on the edge of working for STEREO-A deep space beacon reception a little over a month from its arrival at inferior conjunction. The dish antenna is a 66cm prime focus type and is mounted on a modified telescope mount to automatically track STEREO-A and other objects in space.

VE7TIL X-Band Dish Antenna Specifications:

66 cm at 50% illumination at 8.44 GHz is 32.3 dBi 

136K is 21.3 dBK. Hence G/T = +11 dB/K 

The overall system block diagram is provided below. This system has proved successful in hearing signals at Mars and in the vicinity of Mercury from BepiColombo as well as providing some great Earth images from LEO weather and science missions such as AQUA, TERRA, NOAA 21 etc.

Obtaining and Making Sense of STEREO-A’s Data

Back in 2022, Daniel Estévez, EA4GPZ published a blog post on Decoding the STEREO-A Space Weather Beacon where he used data obtained from the 13m dish at the Harbin Institute of Technology in China by amateur Wei Mingchuan BG2BHC to develop a demodulator and decoded the data into constituent components. Daniel’s work provided significant insight into STEREO-A’s low rate beacon signal structure and provided a means of plotting the S/WAVES experimental data. However, a vast majority of the data copied remained unknown and not decoded into the specific products being sent just the constituent data blocks containing the various sensors output’s. So much work was still to be done.

Alan Antoine, F4LAU, @Aang23, also added a demodulator to the SatDump tool kit which greatly simplified the demodulation of the signal as GNU Radio was not needed.

VE7TIL now had a signal from STEREO-A and a means to demodulate it but after some initial attempts no frames were decoded. Digging into SatDump a bit further the pipeline for the demodulator was found and the various parameters were tuned until near 100% demodulation and decoding of the STEREO-A signal resulted. Due to the low SNR tuning the PLLs very tightly resulted in the most significant improvement in the performance of the system. The updated parameters used can be found here. As SNR improves these tight values don’t really improve performance much, but at low SNR they helped dramatically.

 "pm_demod": {
                    "symbolrate": 3800,
                    "resample_after_pll": true,
                    "agc_rate": 0.0005,
                    "pll_bw": 0.0025,
                    "pll_max_offset": 3.14,
                    "rrc_alpha": 0.2,
                    "rrc_taps": 31,
                    "costas_bw": 0.0001,
                    "clock_omega_relative_limit": 0.005
                }
            },
            "frames": {
                "ccsds_turbo_r6_k8920_decoder": {
                    "turbo_iters": 20

So how can an amateur station with such a small antenna have a hope of demodulation of spacecraft over 15 million kilometres away? The secret is the Turbo coding used by the spacecraft to encode it’s signal. As Daniel noted in his analysis STEREO-A uses the most robust method available from the standard.

The symbol rate is 3.8 kbaud. The FEC is CCSDS Turbo coding with r=1/6 and 8920 informations bits. From the different FECs described in the TM Synchronization and Channel Coding Blue Book, this is the one that gives the best Eb/N0 performance.

Daniel Estévez

In the image below one can see just how marginal the demodulation and decoding of the STEREO-A signal is and also appreciate the incredible performance of the Turbo code used to make this possible as it approached the Shannon limit.

As noted above the data is sent at a very low rate, so to gather a MB of data takes hours. But after patient waiting one is rewarded with a data file full of STEREO-A data and many compressed images.

Daniel had largely made sense of the major structures in the data and gave clues as to where to look to build on finding and extracting image and further numeric science and telemetry data from the data.

This is where Alan did some detective work on the STEREO Science Centre website and found some tidbits of information and code that made the process of finding the images and then decompressing them to allow us to view the raw images being sent from STEREO-A via its low rate deep space beacon.

Alan found the document that describes the STEREO/SECCHI Level-0 to Level-0.5 FITS Pipeline CMAD on the STEREO website and two C files, rdSc.c and hdr.c in a directory on the STEREO site /instruments/software/secchi/utils/rdSh. These documents provide considerable insight into how the data from the spacecraft is processed on the ground to be used for generating images. The proceeding document provided details on some formats that were used to figure out the packet format and know how to extract the header, data, and trailer block and allowed Alan with a bit of reverse engineering to gather together the first image files by extracting the header, data, and trailer blocks from the raw data files.

The next step unique to this mission was to decompress the highly compressed deep space beacon images. Alan found a Linux binary on the STEREO site that did the job. Called ‘idecomp.linux’ it decompressed the data so an image could be extracted and viewed. Unfortunately, the source code hasn’t been found yet as NASA doesn’t have a copy, we asked! We’re exploring other avenues to obtain the source code for integration into SatDump to make the extraction of images from STEREO-A not platform dependant.

You need to download the idecomp.linux file and change the Stereo.json file in the SatDump pipelines folder to direct your version of SatDump to the local path of the executable. Ensure you have the latest build of SatDump before setting this up.

"products": {
                "stereo_instruments": {
                    "icer_path": "./icer_decomp_linux"

Alan’s SatDump code found in the GITHUB SatDump repository tells all the gory details of how the images are extracted and decompressed for those seeking those details.

A summary of the process of extracting STEREO-A data and images is as follows:

1. Demodulate: Convert the modulated signal back to its original form.
2. Correlator: Use correlation techniques to detect and synchronize the received signal.
3. De-randomize: The bit stream is de-randomized. It is randomized to ensure synchronization is possible and a clean modulation
4. Turbo Decoder: Employ turbo decoding techniques to recover the original data.
5. VCID Selection: Choose the appropriate Virtual Channel ID (VCID) to process.
6. Extract CCSDS Packets: Extract CCSDS Packets from the data stream and filter by APID.
7. Recompose File Blocks: Reassemble the packets into their respective file blocks.
8. Dump Payload Part: Isolate the payload part of each file block.
9. Decompress: If the payload is compressed, decompress it to obtain the original data.
10. Image: Process the decompressed data as an image.

Further a review of the actual FITS images found in the beacon data files provided a further clue as to how to identify the APID, telescope and unique image information. The raw binary data from the spacecraft also includes ASCII filenames found to correlate with the source filenames located in the FITS headers of the images found on NASA’s STEREO website. Alan’s work revealed that the SECCHI images raw off the spacecraft were not the images seen on the SECCHI beacon summary site and this caused us some initial confusion about what the actual APIDs were for each type of image until we unlocked the riddle of the ASCII filenames.

Further research on the STEREO website lead to finding the filename convention for images sent by STEREO-A and B in a document called SECCHI FITS Header Keyword Definition, page 12. So the filename is a very powerful tool to identify all this info in a compact way. Based on our experience thus far this is the only ASCII data sent by STEREO-A.

EXAMPLE:

Filename format is YMMDDaaaa.APT

Where,
Y = Year
MM = Month
DD = Day
aaaa = image counter and sequence number
AP  = APID
T = Telescope used

Decoding filename N63004MD.743

Given,
N =  'N' in base 36 is equal to 23 in decimal, thus the year from 2000
6 = is the month of June, note this is also in base 36
30 = is the day of the month
04FM = is the image counter & sequence number in base 36
. = extension point
74 = APID 1140, given that the APID in hex minus 0x400, i.e. 0x474 - 0x400 = 0x74

Where, APID 1137 (0x471), 1138 (0x472), 1139 (0x473) and 1140 (0x474)

3 = The telescope is EUVI

Where, 1=COR2, 2=COR1, 3=EUVI, 4=HI2 and 5=HI1, for STEREO-B add 5.

Further research turned up some processing code on the NASA STEREO site that revealed other image filename extensions and their relationships to the naming conventions used in the data repository on the NASA site called getscifileinfo.pro.

With the knowledge extracted from the spacecraft data, and the NASA STEREO website a complete understanding of the presently observed APIDs was obtained and this was cross referenced with data received from STEREO-A and that recorded on the NASA website as a double check. The table below provides a convenient summary.

Behaviour of the STEREO-A Beacon

STEREO-A has largely two modes of normal operation. High rate data while in lock with a ground station and low rate data when not in lock and sending deep space beacon data including the compressed images used for space weather forecasting.

Understanding the beacon’s behaviour and knowing how to plan observing sessions to gather the deep space beacon data is important. The following spectra show the unlocking/locking behaviour when STEREO-A ends and starts DSN communications. You can plan your observing sessions around the DSN sessions by referring to the STEREO DSN Schedule Summary posted on the STEREO-A website.

DSN Now doesn’t show all the activity as other ground stations from ESA and NASA ones not on the live website are used and we’ve noted a few times where the STEREO-A schedule shows activity which we can see happening on the air but the DSN NOW site shows no activity for the respective deep space station antenna. So the STEREO-A website schedule appears the golden source of scheduling info.

The data download speed is very low and to gather images long data gathering runs are needed. To gather enough for animations entire passes should be recorded.

Doppler rates will be dramatically changing as STEREO-A approaches and passes inferior conjunction. The plots below will provide an overview since launch and a zoomed in analysis of the Doppler resulting around the inferior conjunction.

The best strategy for demodulation/decoding the data is to setup and make a long recording of STEREO-A’s low rate data when the spacecraft is not in a high rate data session with a ground station. Record lots of data (more than an hour) and then run the SatDump decoder and allow the signal to lock and write the .cadu file and then process the images. The lower the SNR you have the longer the decoder needs to lock onto the signal and start producing data. Since STEREO-A sends it’s data at such a low rate you need to record for long periods of time to get many images.

The Glorious Images!

A complete repository of all the images used to make these animations and the raw data recovered by STEREO-A during this process can be found here.

Inferior Conjunction Citizen Science Opportunity

STEREO-A will be quite close to Earth for some months to come and some amateurs with larger dish antennas have been able to decode STEREO-A for about a year now. This proximity provides a unique opportunity for amateur observation of the STEREO-A signal and the recovery of data from the low rate beacon that may fill some data gaps in the present system. Being that it’s near solar maximum gathering of the this data in near real-time with limited gaps may be of value to space weather forecasters as amateurs can fill in gaps in the existing low rate beacon receiving network.

There are plans to allow for the real time data from a running SatDump STEREO-A receiving system to be posted to the Internet and allow NASA or any other interested party access to the raw data so it can be processed and used as they see fit. This would allow the growing community of deep space network radio observers to contribute to science and the forecasting of space weather events during a time of higher than usual solar activity and allow all involved to learn more about the Sun and the resulting space weather it creates.

This is a unique way the world can celebrate the first inferior conjunction of the 17 year old STEREO-A mission!

Welcome home STEREO-A may you have another inferior conjunction in you.

Acknowledgements

Alan Antoine, F4LAU – The driving force behind the open source SatDump software package for the decoding of satellite imagery. He provided the decoder and the expertise to extract the images from the STEREO-A data stream while teaching this old dog some new tricks!

Daniel Estévez, EA4GPZ – Rigorously documents each deep space mission to learn about it signal’s characteristics and reports many educational details on his highly useful blog to the amateur radio community. Daniel’s work laid the groundwork for us to carry on the study of STEREO-A’s signal.

USA SATCOM – Joe provided data from his impressive 2.3m X-band system and filled in gaps at times to help improve the rigour of our data analysis. USA SATCOM offers a range of highly reliable software in Windows for tracking, decoding and presenting space based imagery.

Paul Marsh (UHF SATCOM) and Jean-Luc Milette for reporting the ever increasing STEREO-A signal and prompting me to wonder what was going on.

Dr. Cees Bassa – It goes without saying that Cees’ work on STRF (SatTools RF) makes for easy and accurate work on any form of Doppler analysis project. See his GITHUB site for code and details. Thank-you Cees!

NASA STEREO Science Centre – A shinning example of open space science to be modelled by other missions and agencies. Many thanks to the team for timely responses to questions and their proactive open behaviour in sharing mission data and operational details.

Recent media reports indicate the US has developed a way to track the recent Chinese airships passing over North America. Here, a hypothesis is offered on how this may work and how observers can contribute.

In July of 2022, the Chinese commercial JILIN Earth imaging constellation of satellites was found to be emitting strange short burst data signals on spectrum reserved for the mobile-satellite (Earth-to-Space and visa-versa) radio service. This observation while curious at first caused the author to reconsider the meaning of that observation after the recent arrival of a large Chinese airship over North America and how it may communicate with its handlers as a bit more research revealed a clear connection to the Chinese BeiDou satellite navigation system and the emissions from JILIN.

Radio-determination vs Radio-navigation

Most everyone is familiar with a Radio Navigation Satellite Service (GNSS) like GPS, GLONASS, GALILEO etc. A GNSS service is a one-way service where a user listens for multiple satellite signals and from them is able to determine their location and the time accurately. There is no communication between the user and the satellite service.

A Radio Determination Satellite Service (RDSS) that not only allows the user to navigate but also communicate as the very service itself is two-way between the user and the satellite(s) it is navigating via. This uplink provision can be used to allow a user to send messages to orbiting satellites as well for purely communications purposes. Interestingly, the Chinese BeiDou system is capable of RDSS which means it’s a full blown two way communications system with a global reach.

The BeiDou constellation is constructed with assets in three different orbit types. Three satellites in Geostationary (GEO), three in Inclined Geostationary (IGSO) and 24 in Medium Earth Orbit (MEO) as can be seen in the graphic below.

Let’s examine the public domain literature on the BeiDou message system. There are two messaging services that are used in the BeiDou system one is a regional system primarily using the GEO satellite arm of the system and is known as the regional short message communication service (RSMC). A summary of its properties are noted below.

The RSMC service is limited to communication largely in regions in view of China and not a global system as that is were the BeiDou GEO assets are located. The BeiDou system does however, offer a true global communications system via it global short message communications (GSMC) service. The global system is more limited in the amount of data that can be sent in a single message to 70 bytes which is believed to be a civilian limitation and not one imposed on the People’s Liberation Army’s (PLA) use of the system. Specifications of the GSMC system as follows.

Public source documents also discuss the frequency allocations for this service. The following text and table from the source documents is presented for context below. Pay particular notice to the uplink for the GSMC service being on L-band.

Researching ITU records for China’s COMPASS-MEO reveals that they have two current fillings under this name that appear to related to the versions two and three of the BeiDou series as can be noted by the filling below that relates to information obtained on the BeiDou-3 series of MEO spacecraft.

Pay particular attention to the reception of signals from 1610.5-1627MHz, this correlates to the emissions from JILIN. I.e. the JILIN’s or perhaps other ‘users’ of the BeiDou GSMC system emit at these frequencies and the BeiDou spacecraft hear them here.

The following graphic provides further information on the evolution of the BeiDou emissions over the three generations of spacecraft used. As the reader can see the system has evolved and has now begun using a global GNSS system capable of true global short message communication.

Based on the open source information, China has a full blown global short message communication service with satellite inter-links that can allow telemetry, tracking and control of assets. The location of which the assets can be communicated with is provided in the excerpt below.

Here’s a summary of the specifications for the global short message system:

• Service to any object on the surface of Earth or up to 1000km above it.
• Uplinks on L-band and downlinks on S-band.
• Civilian messages are 70 bytes long.
• The system has a >95% success rate on message handling.
• 300000 messages per hour up and 200000 per hour down.
• Response times normally better than 1 minute.
• Uplink terminal uses a power of <10 watts.
• The system uses inter-satellite links.

Inter-satellite Telemetry, Tracking and Control (TT&C)

Over the past few years more a more western satellite operators have been using Globalstar to augment or provide TT&C. You can integrate a Globalstar transmitter (STX3) into small asset to track its moments around the Earth or even Low Earth Orbit (LEO) and have it send basic telemetry, position and other data at a periodic basis but regulations require the operator to be able to cease the transmission of the transmitter if on a satellite. Thus missions will integrate two-way communications by using the STX4 system which allows for transmission and reception of data of an asset on Earth or in LEO. The Globalstar system has been in use for a variety of missions over the past decade and has been increasing use as it reduces the ground infrastructure a small satellite would normally need to provide communications with an asset.

Today I'm conducing some research on L-band and tracked this interesting satellite AMS [52745, 2022-057P]. It has an emission on L-band. Here's the satellite just starting to clear the trees and emitting a burst. pic.twitter.com/0ZVhHlaPzC

— Scott Tilley (@coastal8049) July 24, 2022

Chinese nationals can buy and subscribe to the BeiDou short message service and purchase hardware to integrate their application with the system. The hardware closely resembles systems sold for the Globalstar system.

Unlike Globalstar, BeiDou allows for satellites out of view of ground stations in China to communicate via inter-satellite links. This means that the satellite can be communicated with via other satellites and relay it’s data via other satellites to Earth stations outside of it’s footprint. A helpful feature if you plan on a global short message communication system.

Case for JILIN and other ‘floating’ assets using BeiDou

The JILIN signals that were unexpectedly received last year on L-band are BPSK with about 4Msps, the signals appear encrypted as there was no cross-correlation peaks noted during the analysis. This correlates to published information on the signal type as noted below.

Given our understanding of the BeiDou GSMC system it appears entirely reasonable that JILIN is using the BeiDou GSMC system to communicate with their satellites on a global basis. This also provides the first confirmation that the BeiDou GSMC system is operational and being used for assets well outside the regional view of China and for objects in orbit around the Earth.

Further research also shows that the BeiDou system is being used for a similar purpose globally for ships at sea. Therefore, it’s not a stretch to consider that TT&C of an airship could be accomplished using the BeiDou GSMC and RSMC systems.

Readers should be aware China doesn’t operate any GEO satellites over North America and until recently has only just begun to operate two satellites (Shiyan-10 and Shiyan-10 02) in a Molniya class orbit that have loitering apogees over North America. The purpose of these two missions is not presently known in the public domain and no emissions from them have been detected as far as the author is aware. This implies they may be on signals intelligence missions as opposed to communications assets like the Russian Meridian system or the US SDS platforms in HEO. This underlines how important a system like the BeiDou GSMC would be for any airship mission with a global reach as China has limited reliable global communications options.

Therefore, I theorize that it is reasonable to assess that Chinese airships with a global mission would incorporate the BeiDou GSMC system for TT&C purposes as there is no other systemic domestic system known to be available to the Chinese. However, given the limited bandwidth of the GSMC and amount of data that could be sent, mission data may need another path. Based on a lack of known relay satellites over North America I would assess that high volume data is stored on such a payload for later downlink either to Chinese GEO assets over areas of the world covered by them or mobile ground/sea stations that can intercept the payload and perform a local download and forwarding of the airships data once it has travelled to an area accessible to such assets. It’s possible those assets could be within the target area too.

Observers looking for possible balloon objects using the BeiDou system should monitor the 1610.5-1627MHz band for emissions and characterize them by looking for the absence of Doppler and the duration the signal remains. Bear in mind that Globalstar uses this band when making assessments of what you are monitoring.

Why is an imaging satellite constellation acting like a mobile-satellite communications system?

China’s first self-developed commercial remote sensing satellite system known as JILIN is sending strange wideband data pips in a quiet piece of spectrum on L-band. The JILIN system is operated by Chang Guang Satellite Technology Company in Beijing. No public references have been found by the author about what these emissions from the satellites purpose is.

Mysterious ‘Pips’ from the Ether…

While investigating the portion of L-band between 1613.8-1626.5MHz, I stumbled across some brief ‘pip’ emissions that clearly had LEO Doppler effecting the signal.

A bit of analysis later the ID came back to one of the many JILIN satellites in a constellation in sun synchronous orbit at about 535KM altitude with a plane spanning approximately 260-295 degrees of RAAN.

A prolonged scan of over a day was then completed to get a sense of the extent of the spacecraft involved displaying this behaviour. As of July 26th, 2022, a total of 29 spacecraft from the JILIN constellation have been observed emitting these signals. A list of observed ‘pipping’ JILIN spacecraft below:

INDEXIDCOSPARST NAMEFREQ1464542000-065AJILIN-01 GAOFEN 3B1615.6591042464572000-065DJILIN-01 GAOFEN 3E1615.6616453464582000-065EJILIN-01 GAOFEN 3F1615.6640824464592000-065FJILIN-01 GAOFEN 3G1615.6655215464602000-065GJILIN-01 GAOFEN 3H1615.6655316464622000-065JJILIN-01 GAOFEN 3J1615.6558377490042021-061BOBJECT B1615.6602868490062021-061DOBJECT D1615.6658049490072021-061EOBJECT E1615.66066710518312022-019HOBJECT H1615.65671811518342022-019LOBJECT L1615.65855212518352022-019MOBJECT M1615.65909113518382022-019QOBJECT Q1615.66391814518392022-019ROBJECT R1615.6636515518402022-019SOBJECT S1615.66549616518412022-019TOBJECT T1615.66691717518462022-019YOBJECT Y1615.66101518523882022-046AJILIN-01 GAOFEN 4A1615.67683119523892022-046BJILIN-01 GAOFEN 3D 41615.66659320523902022-046CJILIN-01 GAOFEN 3D 51615.65475521523912022-046DJILIN-01 GAOFEN 3D 61615.65732922523922022-046EJILIN-01 GAOFEN 3D 71615.66033523524442022-048BJILIN-01 GAOFEN 3D 271615.66237724524452022-048CJILIN-01 GAOFEN 3D 281615.66383925524462022-048DJILIN-01 GAOFEN 3D 291615.66782826524472022-048EJILIN-01 GAOFEN 3D 301615.65358627524482022-048FJILIN-01 GAOFEN 3D 311615.66922928524492022-048GJILIN-01 GAOFEN 3D 321615.66949229524502022-048HJILIN-01 GAOFEN 3D 331615.671647

Diurnal Behaviour of the ‘Pipping’…

The piping appears to be most pronounced during the daytime at my observing site. They are active at night but much less so than during daylight.

So what’s in a ‘Pip’?

The ‘pips’ appear to be about +3MHz in bandwidth and ~0.5 seconds in duration. The transmission interval is around 4-10 seconds when they are active but many spacecraft are not active on each pass and when they are they may not ‘pip’ for the entire pass and may even change their ‘pipping’ rate.

As noted the ‘pips’ are ~0.5 seconds in length. An analysis of the temporal characteristics reveals two distinct components of the signal. A brief dissection of the signal characteristics follows.

So why ‘Pip’?

Why would a constellation of Earth imaging satellites be sending brief wideband data bursts on L-band? To perhaps gain some insight, I reviewed how the People’s Republic of China allocates this part of the spectrum.

1 613.8-1 626.5 (MHz)
MOBILE-SATELLITE(Earth-to-space)  S5.SSS
AERONAUTICAL RADIONAVIGATION
RADIODETERMINATION-SATELLITE (Earth-to-space)  S5.369
Mobile-satellite(space-to-Earth)
S5.341  S5.364  S5.365
S5.366  S5.367  S5.368
S5.372   CHN18

Out of all the services allowed to operate in this band on, “Mobile-Satellite(space-to-Earth) matches what we are observing. After much research we can find no reference on ITU filings or in news reports about why there would be data ‘pips’ coming from the JILIN satellites. The only other service that remotely matches the Mobile-satellite service from China that is presently active is the GEO based TIANTONG system which uses different frequencies etc.

A reference was found to HONGYAN which has only one prototype in orbit. The orbit of which closely resembles that the of US GLOBALSTAR system which also uses the band in question. In fact, the Globalstar system uses 1616.26MHz to allow for satellites in LEO to uplink to the Globalstar satellites to allow for 1-way and 2-way telemetry and control. They also use this band to allow Earth based assets to report data via the Globalstar constellation as well. With only one old spacecraft HONGYAN-1 in orbit it’s unlikely the Chinese owners of the JILIN’s are doing something similar to Globalstar so what ever the purpose it could be something related to JILIN’s operations.

The diurnal behaviour of the system could mean that it is either driven by human activity (most people like to sleep at night) or it could be part of the primary known purpose of the JILIN constellation which is Earth imagery at optical wavelengths, perhaps allowing a client to place a transponder on an asset and have the spacecraft interrogate it and image its location as it moves around…? It is possible it is used for other purposes but that would be outside the official allocation for the People’s Republic of China. If you review Chang Guang Satellite Technology Company‘s website you can see from their sample images individual cars can be seen so it is possible this could be some sort of asset tracking system.

Samples of the signal have been shared with a few different colleagues and we’ll report back if anything interesting is determined from those analysis efforts to answer this Chinese Riddle in the Sky!

History Repeats Itself

Russia operates a constellation of satellites in high Earth orbit called Meridian (меридиан). These satellites perform a critical communications purpose for Russia as much of its land mass is not well served by geostationary satellites. Therefore, you would think this constellation would be held to the highest operational level. Well it’s not as radio amateurs have observed. This fact could raise questions about Russia’s ability and preparedness to act on their recent veiled threats of nuclear war.

For a country bent on claiming they are trying to liberate Ukraine from the scourge of Nazism, some in their leadership seem to be making the same type of hubris claims that one dead Nazi did.

“No enemy bomber can reach the Ruhr. If one reaches the Ruhr, my name is not Hermann Goering. You may call me Hermann Meyer.”

Hermann Göring, September, 1939

In this post we are going to explore how the history, operation and observations of the Russian Meridian satellite constellation may reveal that Russian claims about their nuclear deterrence forces being on high alert may be technically questionable. And that another senior Russian leader apparently dreams of being “a ballerina of the Bolshoi Theater.” Yes, it’s that bizarre…

Lightning Orbits…

As most people know, Russia is located geographically on average far north. Therefore, if you where to provide a system of geostationary satellites to provide communications for your military, there would be challenges with obtaining satisfactory views of those satellites in many geographic locations due to the low elevation of those satellites in the sky. Objects such as trees, buildings and other features would challenge ground stations to get a clear view of the satellites as elevation angles would be very low for GEO satellites. This would be particularly challenging for a military application where mobility would be a key requirement for survivability and tactical surprise.

On the other side, Russia is also limited to fairly high latitude satellite launch sites and early in their space program they lacked the large rockets needed to reach geostationary orbit as the energy requirements to make the large inclination change was prohibitive. Therefore, a different solution emerged. The Molniya (молния) orbit, meaning lightning in Russian.

The Molniya orbit was first successfully used in 1965 by the Soviet Union. The orbit is highly eccentric and cleverly designed to balance off the perturbations of the Earth and Sun to fix the satellite’s Argument of Perigee (AoP) at 270 degrees, thus locking the perigee of the orbit in the southern hemisphere and the apogee high over the north hemisphere. With a period of half the sidereal rate of a day the satellite will return to the same point in the sky each day approximately four minutes earlier and loiter in the same relatively fixed spot in the sky for approximately six hours making tracking easy. If you place four satellites in a constellation then you have 24/7 coverage even at your secret high latitude military site without needing to worry about obstacles in your way to establish communications.

Contemporary Russian military hardware operations manuals remind Russian soldiers to avoid placing high value mobile ground station assets in open view of a prying enemy’s eyes. So what better way to allow you communications equipment to hide then deep in valleys, urban canyons or in the trees with your high gain antennas pointed nearly straight up rather than needing an open clear view to the south that could expose you to easier detection then using a satellite orbit that places the satellite high overhead at high northern latitudes..

By the mid-1970s amateur observations of the Molniya-1 satellites began by Stephen J Birkill. His work was later provided as evidence to the US Congress in hearings on the Soviet space program. Stephen is as can be seen below, still has good notes from those days.

(1) My first Molniya-1 sighting was May 7th 1976 at 07:00 UT, 140kHz FSK nominally 998 MHz (no SDR back then, rudimentary gear meant only approx estimate of freq.) at Russian apogee. Later, hand-over observed 20:45, signals duplicated with ~500kHz freq sep'n, 10 deg apart.

— Stephen J Birkill (@midvodian) March 9, 2022

The Meridian satellite constellation has been used by Russia since 2006. Molniya-1T and -3 satellite operations where noted to fade away by 2011 by radio amateurs as the first two truly operational Meridian satellites came online in 2011/2012.

Guessing that Molniya 3-51 and 3-53 are dead due to absolutely nothing detected on their known C-Band downlink frequencies ;-(

— UHF Satcom (@uhf_satcom) May 8, 2011

Russia had some growing pains with the program as Meridian 1 prematurely failed and Meridian 2 was launched into an incorrect orbit, but did have a prolonged useful life. Meanwhile Meridian 3, 4 and 6 well exceeded their expected operational lives and appeared to be fully operational for the their entire lives. Meridian 7 seems to be a partial success as we will see. Meridian 5 was lost in a launch failure. Later Meridian-M missions 8 and 9 are on orbit and fully operational.

But something was missed after the transition from the Molniya to Meridian flight hardware… In references obtained and reported on in the west the 990MHz band seemed to be dropped and amateur observation of the band ended. Here’s a quote from a Russian military satellite operations manual on available communication resources on the new Meridian system.

"Each repeater trunk operates in its own frequency band of a certain range. Currently, the system uses the 4/6; 7/8 and 0.2/0.4 GHz bands (the first digit refers to the "ZS-RS" section, the second - to the "RS-ZS" section). The frequency band allocated to one trunk ranges from hundreds of kilohertz to hundreds of megahertz, depending on the purpose of the trunk."

Amateurs have logged activity from the Meridian constellation on all of the bands noted above. But 990MHz was not one of them…

Breakthrough Listen Candidate 1

In December 2020, news leaked out that the Parkes Observatory made a possible SETI detection on about 982MHz. Intrigued by this a satellite receiving station was lashed up to see if something in Earth orbit could have been the source of this detection.

Time to take a good long look around 982MHz for any emissions from human space activity… pic.twitter.com/NlU7PFY13Q

— Scott Tilley (@coastal8049) December 22, 2020

Days of data was recorded and something unexpected was found on ~992.4MHz, evidence of a constellation of emitting satellites. The Doppler data didn’t fit well to known satellites so timing and directional aiming was used to narrow down the source.

The suspected zombie Molniya activity is growing more interesting as the data rolls in:
– Three suspected spacecraft,
– Doppler rate is not following natural expectation,
– The s/c seem to be switching on/off their beacons before and after apogee much like modern Meridian. 1/2 pic.twitter.com/cT1rZjwre9

— Scott Tilley (@coastal8049) December 28, 2020

By early January 2021, we were able to confirm the emissions where coming from Meridian 4, 6 and 8. Interestingly Meridian 7 as the plot above shows was not at the party. Also interesting was the fact the signal we where monitoring wasn’t a beacon, it was a retransmitted signal via a non-regenerative transponder; hence, the lack of Doppler fit success.

This has got to be the most redneck thing I've ever arranged. Using the word 'built' would be a misuse of the word. Yes that's my burn barrel… This arrangement has improve Meridian transponder reception by 10dB+ on 990MHz. pic.twitter.com/bWplKWYdbr

— Scott Tilley (@coastal8049) January 5, 2021

Over North America the transponder seemed largely empty except for what appears to be attenuated cellular signals at the lower end of the transponder and interestingly a SECAM TV channel. Later investigation revealed that this TV channel was coming from Turkmenistan. The SIGINT aspect of this story is a topic for another post…

Well well well, the mystery of what the signal on ~992.4MHz/~1000.44MHz and FM audio on ~998.94MHz from the Meridian satellites is resolved. It's SECAM TV channels from Turkmenistan. SECAM channel spacing is 8MHz and video carrier to audio carrier is 6.5MHz which matches. pic.twitter.com/H8eyFId9VG

— Scott Tilley (@coastal8049) January 16, 2021

On the Eurasian apogee reports came in that there was data traffic on the transponder. Indicating that what ever it’s purpose it was actively used. Observers in Europe remarked on the similarity to old Molniya-1T traffic.

@coastal8049 Meridian 8 UHF downlinks near 1GHz – this certainly reminds me of the old Molniya traffic I last looked at in 2006! Congrats to Scott for finding this stuff, great!!! pic.twitter.com/VPej236Xts

— UHF Satcom (@uhf_satcom) January 23, 2021

Apparently by 1983 the Soviet Union had evolved the Molniya satellite system into two distinct models, Molniya-1T and -3. The latter was a TV broadcast satellite. The Molniya-1T purpose was to provide communications for the Strategic Rocket Forces using a codename “Korund-M”. This system included fixed and mobile ground stations as exampled by Central Satellite Communications Centre of the Strategic Missile Forces (product “Geyser” and the P-443 mobile complex)x.

UPDATE:
Russian website that contains information on the possible purpose of the MERIDIAN 990MHz xponder.

"Korund-M" to equip the Central Satellite Communication Center of the Strategic Missile Forces"

The Russians could have a big hole in their nuclear command and control. pic.twitter.com/fxlpqps19t

— Scott Tilley (@coastal8049) March 5, 2022

As in the west, former soldiers often discuss military nostalgia online and in a thread “Korund-M” is discussed and referenced to the current Meridian satellite system that also used, yes you guessed it, a Molniya class orbit.

Here's the first direct reference I've seen of the communications payload on 990MHz and MERIDIAN.
Highlighted bit translated:
"SSS "Korund" (R-443) used the onboard resource of the satellites "Molniya", "Raduga", "Meridian" in highly elliptical orbits." pic.twitter.com/sPZg1gVec2

— Scott Tilley (@coastal8049) March 6, 2022

So it seems the “Korund” system still exists and that Meridian is providing services to the Russian strategic rocket forces.

As you will note after doing a bit of research these rocket forces heavily rely on mobile launchers.

These missile systems need mobile communications links and the Meridian satellites are outfitted to provide those links.

I also found some dated images of early versions of the 990MHz communications vehicles used for MOLNIYA-1T et. al… Nice white walls! Maybe a way of preventing sun rot for tires…

This is the Korund P-443 complex. Note the version mounted on the roof too. pic.twitter.com/Qiq8JLgDBm

— Scott Tilley (@coastal8049) March 6, 2022

Realizations…

On February 24, 2022 Russia launched a “special military operation”against the country of Ukraine. As a result, I installed the appropriate feeds on my antennas and tuned into the Meridian satellite operations to observe their status. Normal activity was noted on all of the satellites except Meridian 4 and 7.

As noted earlier Meridian 7 seems to have an anomaly that unlike all the other Meridian satellites observed since the discovery of the 990MHz transponder it does not appear to operate there. Perhaps indication of a malfunction of that payload element.

Meridian 4 on the other hand was completely missing from all bands that it had been active on.

MERIDIAN 4 is again a no-show on X-band and 990MHz, three days running since initially checking in on it. Based on my experience monitoring this constellation over the years this is indicative of the asset having ended service. pic.twitter.com/hXm3EMOSuO

— Scott Tilley (@coastal8049) February 27, 2022

TLE data revealed that on January 27, 2022, Meridian 4 had experienced some sort of orbital change.

Meridian No. 14 (the manufacturer name for this satellite) did raise its orbit around Jan 27 in what looks like a retirement manuever. pic.twitter.com/V2xbWZEuUp

— Jonathan McDowell (@planet4589) February 27, 2022

A call for optical observations was made and within a few days evidence Meridian 4 was tumbling in space was found. I.e. the satellite has either failed or its mission was intentionally ended. Oddly timed if your plan is to invade another country and place your nuclear deterrence forces on high alert, no?

Here’s the first optical report of MERIDIAN 4 since the call for data went out. The spacecraft is demonstrating a dramatic periodic light curve with a period of ~17 seconds. I believe this is indicative of the spacecraft no longer having attitude control. I.e. it’s tumbling. https://t.co/uNmjPO3Ah4

— Scott Tilley (@coastal8049) March 1, 2022

Given these observations two Meridian satellites that provide half of the satellite constellation’s coverage on the 990MHz transponder, now known to be affiliated with the Russian militaries strategic rocket forces is unavailable to provide communications for a total of 12 hours a day. Given the context that Russian president Putin had ordered Russian nuclear deterrence forces to high alert on February 27, 2022 could make one wonder how a significant pillar of the Russian nuclear deterrence system can be on high alert given they lack 50% of the satellite coverage dedicated to their command and control.

Have a look at the Russian Military MERIDIAN communications satellites over a day. Without M4 and M7 operating on 990MHz this creates a possible coverage gap of 12 hours for Russian Strategic Missile Forces.https://t.co/ItKZuzQGfphttps://t.co/NfE5IU3sgh pic.twitter.com/FE8F3XqWMJ

— Scott Tilley (@coastal8049) March 5, 2022

Yes, of course Russia will have other means of communication. High frequency radio, landline links, GEO satellites in the south of Russia etc. But the idea that the mobile Russian rocket force doesn’t have 24/7 coverage to reliable satellite communications all over Russia especially if located at high latitudes is a reasonable assumption and could raise doubts about Russia’s true capabilities.

Meyer…

On the evening of March 7, 2022, I commented on a post on Twitter by the Director General of Roscosmos, Dmitry Olegovich Rogozin, @Rogozin, about repurposing Russian rockets to launch home-grown satellites in response to western sanctions. His response to my suggestion was this:

Hence, I look forward to Dmitry Meyer’s ballerina performance at the Bolshoi Theatre… Perhaps Meyer’s Trumpets will be sounding in Moscow for the performance?

Off Station

In mid August 2021, the Chang’e 5 service module without any notice was noted to not be on station near the Sun-Earth L1 point where it had been since mid-March 2021. Observers were quick to reacquire the spacecraft’s X-band beacon and it was not long before it was clear from the data that Chang’e 5 was headed back to the Earth-Moon system where it would ultimately enter a Distant Retrograde Orbit (DRO) of the Moon.

Close Encounters with the Moon

As Chang’e 5 made it’s way closer to the Earth-Moon system radio positional data was used to develop a state vector and that state vector revealed that the spacecraft would have a close approach to the Moon on September 12, 2021.

Chang'e 5 is rapidly returning to the Earth-Moon system. Amateur observations of the radio signal have allowed it's position in space to be precisely determined. Here's an animation of the trajectory of CE5 until lunar periapsis. pic.twitter.com/8cF7Qt02cZ

— Scott Tilley (@coastal8049) September 5, 2021

Observers monitored Chang’e 5 as it passed the Moon and entered a very high orbit of the Earth.

Amateurs have been quietly watching #Change5 in Earth orbit not only by radio but also optically. Here's @mickeywzx's observations from October 31st. Today I'm reducing over a months worth of observations to produce a new amateur state vector. THREAD pic.twitter.com/obl5kO4Vhj

— Scott Tilley (@coastal8049) November 14, 2021

Based on refined radio positional data and optical data shared by amateurs it became clear that Chang’e 5 would have another close encounter with the Moon on November 18, 2021.

#Change5 is now well within the Moon's hill sphere and 'perilunes' tomorrow. It's anticipated that the Chinese will use this close approach to redirect CE5 to a new unknown destination. Radio observations with RA/DEC and timings would be helpful to keep the world informed. pic.twitter.com/nFJy4UdFHS

— Scott Tilley (@coastal8049) November 16, 2021

Doppler data of the close encounter was collected and surprisingly there was no strong evidence of a burn at perilune. Observers continued to monitor Chang’e 5 for the next couple of weeks when the signal was lost on December 2nd some 19 degrees west of the Moon.

https://twitter.com/df2mz/status/1461264027737329667

Angles and Signal to Noise Ratios

On January 6th, 2022, observers reacquired the signal from Chang’e 5 and noted it was angularly close to the Moon over the coming days then the probe swung out further east of the Moon to ~16 degrees elongation.

https://twitter.com/df2mz/status/1479158371680931841

At this point a comparison of the spacecraft’s signal level was made to the signal level when it was at approximately a lunar distance from Earth and it closely matched. Using the angular distance from the Moon and the lunar distance it was calculated that Chang’e 5 was approximately 100000km from the Moon. Looking back at when observation was lost on December 2, 2021 revealed that Chang’e 5’s position was consistent with a DRO.

The last observation before #Change5 'disappeared' after Dec 2nd, was 19 degrees from the Moon on the western side. Perhaps just before a burn!? This as you will see is significant to understand CE5's present trajectory and why I'm pretty much convinced it is in a DRO now. (1/n) pic.twitter.com/DJcogeEwPs

— Scott Tilley (@coastal8049) January 13, 2022

At this point the observers considered that Chang’e 5 trajectory could be consistent with a Distant Retrograde Orbit (DRO) of the Moon.

What in tarnation is a Distant Retrograde Orbit (DRO)?

For those wondering what I'm waving my hands about these days about here's a THREAD about what a DRO is and why it may be something you hear a lot more of soon… (1/n) pic.twitter.com/j1S2A8mYVP

— Scott Tilley (@coastal8049) January 12, 2022

DROs are a family of orbits that can exist in a three body system around the smaller of the bodies. We reviewed published literature on NASA’s planned use of a DRO for the upcoming EM-1 test mission in Trajectory Design Considerations for Exploration Mission 1. The parameters looked very similar and an estimated state vector was generated that followed the general trajectory trends observed but refinement from a long arc of data was needed for a more precise estimate.

#Change5 DRO state vector estimate with rationale.

Amateurs lost signal ~2021-12-03. About 3 integer periods of ~13 days, which is around the optimal DRO period. We appear to be seeing spacecraft at eastern elongation now. So… (1/n) pic.twitter.com/ycsMR26okS

— Scott Tilley (@coastal8049) January 9, 2022

From Hypothesis to Truth…

Over the coming weeks the radio position of Chang’e 5 was monitored by a ground station with known stable aiming capability and at least daily reports of the position was obtained, thus a long arc of observations was obtained.

CE5 report at 03h03 UTC, 22th of january
RA=11:03:01.39 DEC=11:16:02.8@coastal8049 pic.twitter.com/sdbc1tQWRi

— Jean-Luc Milette (@LucMilette) January 22, 2022

Another station collected Doppler data on a near daily basis. The goal was to develop a state vector from the radio positional observations and compare that to the Doppler data by using NASA’s General Mission Analysis Tool (GMAT) to create an orbital model.

After analysing the radio positional data the following state-vector was obtained:

Epoch = 22 Jan 2022 23:03:29

Coordinate System = Earth Equatorial

X = -303953.6243849

Y = -4703.2085043

Z = 20451.4288987

VX = 0.0334510387589

VY = -1.2032499575841

VZ = -0.6523284377768

The above state vector was then modelled in GMAT and the range rate estimates where then compared to the Doppler data obtained.

An archive of radio positional data, Doppler data and some of the analysis scripts are provided here.

Chang’e 5 in a Distant Retrograde Orbit of the Moon

Reviewing the GMAT models generated from real data in a lunar rotating reference frame clearly shows Chang’e 5 is in a DRO of the Moon.

The general parameters of the orbit are ~70000km in the x-axis (just beyond the Earth-Moon L1 and L2 points) and ~100000km from the Moon’s centre at it’s elongation points along the y-axis. The orbit is retrograde as it orbits in the direction opposite of the Moon’s orbital motion around Earth and the plane of the orbit is pretty much aligned with the ecliptic plane. As a DRO is somewhat chaotic in nature these parameters due vary over time, but this class of orbit is very stable in a general sense over time, so Chang’e 5 could stay here for a long time.

The parameters of the orbit are similar to that planned for the upcoming NASA SLS EM-1 mission presently scheduled to launch later in 2022. China has yet to make a public statement about the status of Chang’e 5’s service module since March of 2021 which seems unusual as this is the first time a spacecraft has used a DRO.

It’s be a quarter of a year since LES-5 was recovered and we began decoding telemetry.  The spacecraft sends 128 words (8 bit bytes) every 10.24 seconds which is called a format.  That format is comprised of four frames of 32 words.  Of the 128 words eight are used for syncing and 24 used for parity checking.  This leaves 96 that contain telemetry data.  Until now we only fully understand eight of the words used for the Radio Frequency Interference (RFI) experiment, leaving 88 words with unknown meaning.  What follows is how we determined the meaning of four more words that reveal the health of LES-5’s solar power system and the present rotational period of the spacecraft.

Pass After Pass…

Since recovery in late March 2020, we have documented nine passes.  Of these eight passes have been recorded with timestamps on each telemetry word recorded, thus allowing us to study the data in detail.  You can review this data on my Github page.

In the animated GIF above one can see all of the telemetry received by my station since LES-5 was recovered and we began timestamping the data.  Distinct patterns in the words being sent can be seen in this animation.  Colour is used to identify what we know of the telemetry’s meaning as follows:

RED – Sync words

GREEN – Parity words

BLUE – Data words with unknown meaning

ORANGE – RFI Experiment words

After studying the eight passes of data one can start to see patterns in how the data words behave over a relatively long period of time and we can therefore start to classify this behaviour by what we are seeing.  The figure below shows the breakdown based on a review of the eight passes studied.

As you can see there are a great number of telemetry words that remain fixed either at 0, a fixed none 0 value or at 255, a total of 48.  Interestingly there are also 31 words that exhibit dynamic periodic behaviour.  Three words are fixed during each pass yet vary from pass to pass and six are dynamic during the eclipse season yet fixed during the rest of the observations.

Much like Taylor Bates discovery of the RFI experiment’s data where we used the historical papers found on the web about the research done with LES-5 we have some basic information about the power system on LES-5 that gives us hints of what to look for and expect when reviewing enough data over time to make some sense out of it.

In the paper, LINCOLN EXPERIMENTAL SATELLITE-5 (LES-5) TRANSPONDER PERFORMANCE IN ORBIT the author provides details of how the solar power system operates on page 43.  LES-5 has four DC-to-DC power converters connected to the solar cells arranged around the spacecraft.

As you can see from the table about the system is arranged is such a way that two of the converters feed the telemetry system and all other equipment on the spacecraft except the power amplifiers (PAs) for the transponder experiment.  Two converters are dedicated for powering the transponder power amplifiers.

The paper also provides details of a failure on LES-5 where one of the solar arrays malfunctioned and displayed a dead spot in the output voltage of converter #4.  Details of this failure and the resulting analysis are found on page 56.

The most interesting aspect about the failure description is the author’s comment about using the technique of de-aliasing the data and the relationship between the telemetry sample rate and the rotation of LES-5.

Given this knowledge we can understand the aliased period of the data in the four power converter telemetry words if we can find the words.  Thus we have what we need to know to go looking through the data to find four channels exhibiting an aliased period related to the sample rate of the telemetry and the rotation rate of the LES-5.  We are searching for four words that have periodic behaviour that are related to the rotation rate of LES-5 and even evidence of the failure mode observed in 1968.

And then there were Four Words…

In studying the months worth of data, four words where noted to be behaving in a consistent manner with respect to each other.

 

The figures above show four telemetry words behaving in a similar manner over months of data collection.  No other words in the data correlate to what we are expecting to find given the description in the transponder performance paper referenced above.

I zoomed into the data in the above noted words and found an interesting correlation in the period of the data of the four words.

As you can see in the above these four words have data with a period of ~164 seconds.  Two of the words have data that goes to zero periodically and the other two are fairly stable around a fixed value.  Here’s a Jupyter-Notebook that will allow you to explore the four DC-to-DC converter words. 

So how does 164 seconds related to the known rotational period of the LES-5 of ~5.3 seconds?  As noted above this period we are seeing in the telemetered data is aliased based on the sample rate and rotation rate of the spacecraft.  With the help of Daniel Estévez, I was able to make sense out of the data and see that the period of 164 seconds is related to the rotational rate of LES-5.

The Math…

LES-5’s historical Rotation Rate (RR) is ~5.3 seconds.

The telemetry Sample Rate (SR) is 10.24 seconds.  We know this precisely as our decoder relies on this to decode the telemetry.

Therefore,

Rotations per sample = SR / RR

Using historical data we can write,

Rotations per sample (RS0) = 10.24s / 5.3s = 1.9321

One can also say that the following is true,

RS1 = RS0 – 1 = 1.9321 – 1 = 0.9321

We can also say that if the satellite is rotating the other way the rotations per sample are as follows,

RS2 = 1 – RS1 = 1 – 0.9321 = 0.06793

Therefore,

Samples to Complete One Apparent Rotation (SCOAR) = 1 / RS2 = 1 / 0.06793 = 14.72

Then,

Apparent Rotation Time (ART) = SCOAR x SR = 14.72 x 10.24 = 150.7 seconds

As you can see the aliased period we see in the telemetered data is close to this historical value 150.7 seconds vs 164 seconds.  If we reverse the process using the contemporary data of the aliased period we can reverse the process and determine the present Rotation Rate (RR) of LES-5.

Given,

ART = SCOAR x SR

We can rewrite,

SCOAR = ART / SR = 164s / 10.24s = 16.02

RS2 = 1 / SCOAR = 1 / 16.02 = 0.06244

RS1 = -RS2 + 1 = -0.06244 + 1 = 0.9376

RS0 = RS1 + 1 = 1.9376

Therefore, we can solve for the present Rotation Rate (RR) of LES-5 by writing,

RR = SR / RS0 = 10.24s / 1.9376 = 5.285 seconds.

A Compelling Case?

I feel that given the following observations we have a compelling case to say that these four telemetry words are indeed the solar voltage converter telemetry channels and that the power system on LES-5 maybe in decent health:

1. Only four channels in all of the telemetry collected to date show a similar expected pattern.  Thus narrowing down what they could possibly mean.
2. The de-aliased period of the telemetry is in close agreement with the historical rotational period of LES-5.
3. Two of the channels reveal deep drops to zero.  Perhaps showing the fault known to have occurred to converter 4 in 1968 when a group of solar cells in the array feeding that converter failed.  The data seems to support further failures have occurred. But that two converters are still receiving power during a full rotation and the other two are receiving power for most of their rotation.
4. Two of the four channels appear to be stable around a fixed value with a minimum of change.  Perhaps indicating that two of the converters are receiving nominal solar power.  While the other two have faults in their elements.  Given the historical references it indicates that the power system on LES-5 while degraded may actually be operational as the fault in 1968 was not considered catastrophic.
5. Two of the channels have higher nominal levels.  This could indicate they are not connected to a load as the other two channel’s nominal value is lower perhaps indicating they are connected to loads.  Given our knowledge converters 1 and 2 are connected to the telemetry and other spacecraft systems it it possible that these are the loaded channels noted in the telemetry and the two high nominal value words are the converters feeding the turned off transponder power amplified (PA) loads.  The failure in 1968 showed converter 4 had a large dip in output due to the solar array degradation.  So this supports this hypothesis.

I’m fairly confident we now understand four more telemetry channels on LES-5.  These four words are very significant in the understanding of LES-5’s health.  It seems to me that given what we are seeing from the RFI experiment that uses the command receiver and these words about the spacecraft’s power system health there is possibility that LES-5 may be able to be commanded to return to transponder operation.

Soberingly we still have 84 words to understand!

 

Iran’s new military satellite, NOUR 01, most interesting fact may not be that it resembles a college engineering experiment but rather that it may have a connection to a Mexican military payload launched quietly from New Zealand last year.

It’s also with great pleasure that I can share Scott Chapman, K4KDR’s story of how he found Iran’s NOUR 01 [45529, 2020-024A] radio emissions and confirmed it was alive and well in orbit and noted a twist to the story in a brief interview we had.

Iran’s Boogeymen Launch Terror into Orbit?

On April 21, 2020, Iran’s Islamic Revolutionary Guard Corps (IRGC) launched a rocket from a new launch site near Shahroud.  This sounded initially ominous as the IRGC is a declared terrorist organization in many western countries [ED: IRGC is in fact only a designated terrorist organization in the USA, Saudi Arabia and Bahrain] and this mission successfully entered orbit.  However, within a few days amateur observing efforts and a statement from the top US Space Force general made it clear NOUR 01 was far from something to worry about.  Rather it raises questions that given the present state of import restrictions to Iran how did a western educational satellite bus possibly end up in Iran?

Jonathan McDowell a respected space activity observer reported shortly after launch of his analysis of a decal on the side of the QASED rocket booster that clearly showed a 6U cubesat with antennas for VHF and perhaps UHF.

On April 24th, 2020, Scott Chapman, K4KDR reported on Twitter that he had detected an object emitting 9600 baud FSK packet radio signals from an object that appeared to match the orbit of NOUR 01.  Interestingly, Scott noted that the satellite was easily decoded using amateur protocols (more on that shortly).

Shortly afterwards Edgar Kaiser in Northern Germany reported a corroborating observation.

From there a number of reports came in from around the world indicating the signal was apparently consistent during the entire orbit of the satellite.  An Italian observer was able to note the satellite entering a rapid data transmission mode while it was over Iran.  All completely normal activities for a satellite…  Nothing to see here, move along…

Then the commander of the US Space Force, general Jay Raymond tweeted that NOUR 01 was a 3U cubesat not the 6U as noted on the decal on the side of the booster.

Up until this point amateurs had developed a very strong case that the emission of 401.5MHz was in fact NOUR 01.  Some single pass Doppler analysis and timing where used.  I then performed a day long data collection run and combined Scott Chapman’s data with mine and concluded beyond a doubt that NOUR 01 is the source of the signals using Dr. Cees Bassa’s ‘Sat Tools RF’.

Finally the first known attempt to visually see NOUR 01 came up negative.  NOUR 01 was too dim to detect for experienced observer Marco Langbroek in the Netherlands.  This implies that the satellite is very small and provides some limited support that the satellite is not the 6U cubesat imaged on the rocket’s decal.

Based on all the emerging evidence Iran’s first stated military mission doesn’t appear to be too terrifying and perhaps there was even a little false advertising.  But the most interesting observation was revealed in a subtle twist in how the satellite referred to itself.

“From Space to Earth…”

During Scott Chapman’s initial observation and subsequent observations of decoded data from the NOUR 01 downlink he noted what he thought could be a generic configuration in the data that was being sent.

The packets all began with the specific format to identify the call-signs respectively ‘SPACE’ and ‘EARTH’ as can be noted in the image below.  In amateur radio, a station calls another station in the same order.  So NOUR 01 is call-sign SPACE and is calling call-sign EARTH.  These are part of the stations AX 25 UI Frame.  In the AX 25 protocol a to and from call-sign is required and is often set to some default value in a new radio modem.

Well it turns out this same call sign sequence has been seen before on a relatively recent military launch by Mexico’s Secretaría de la Defensa Nacional (SEDENA) on a Rocket Labs Electron from New Zealand called PAINANI 1 [44365, 2019-037A] on June 29, 2019.

Painani 1 used an identical source and destination addresses (call-signs) in the configuration of its communication system.  Perhaps implying this was a default or original setting that wasn’t changed by the satellite operators.

The byte sequence below is from Painani 1 with the shared sequence highlighted:

2020-03-14 18:00:31.770 UTC: from SPACE to EARTH (UI, payload: 56 byte)
000 > C0 00 8A 82 A4 A8 90 40 E0 A6 A0 82 86 8A 40 61 03 F0 3C C3
020 > 35 00 00 00 00 00 00 00 00 00 00 00 2D 7F 00 00 00 D5 FF E1
040 > FF F2 01 00 73 00 02 07 02 01 15 10 3A 00 00 00 33 00 00 00
060 > 0C BD 0F AB 00 9B 13 4F 04 A6 0F 44 04 58 C0

À.Š‚¤¨@ঠ‚†Š@a.ð<Ã5………..-…Õÿáÿò..s…….:…3….½.«.›.O.¦.D.XÀ

Digging into the Painani 1’s limited references on the Internet gives some clues as to were the hardware came from, a company called CubeSat Kit

A quick browse of CubeSat Kit’s website reveals they sell a 3U cubesat kit.

So we could be left to draw some interesting yet plausibly deniable inferences from this.

Why is their cubesat configured very similar to a recently launched Mexican military cubesat of similar configuration and size?

If Iran has acquired a 3U cubesat from a Californian cubesat kit vendor how did they get it given ITR regulations?

Could this mean that perhaps a flight spare somehow got lost and found it’s way to Iran?

Oh dear, my imagination is running wild…

A Textbook Recovery Effort – Interview with Scott Chapman, K4KDR

I asked Scott Chapman a few questions about how he recovered NOUR 01 and thought the amateur tracking community could benefit from the discussion.

Scott Tilley – “What made you consider searching the 400MHz band for NOUR 01? What was your inspiration?”

Scott Chapman – “After TLEs were published for two objects from this launch, of course the immediate thought was “can we receive a downlink?” But where to look? For some reason, the thought came to mind, “What if they follow the rules & use an approved frequency”? So I did a Google Search for the phrase “Iran Satellite Frequencies” which led to the following colorful chart“

Scott Chapman – ” … the legend had a designation for “Downlink” “

Scott Chapman – “… so I scanned the frequency chart for frequency blocks with that designation. Ruling out parts of the spectrum that I am not equipped to receive, the most likely spot was small patch at the bottom of the 400 MHz band. When the first orbit came over the Eastern U.S. in the late-night hours of 23-April, imagine my surprise to see strong signals on a 10-second interval! However, when the familiar-looking packets decoded as standard 9600 baud FSK packets, doubt crept in and I had second thoughts about this being a military satellite. I kept silent and set an alarm for the early morning hours of 24-April when there would be a MUCH higher elevation pass. Everything went as planned and I had the good fortune of capturing many more packets – again on a 10-second interval and decoding as standard 9600 FSK. Strangely, the source/destination addresses on each packet were “from SPACE to EARTH”, which has been seen on other educational cubesats. After plotting the doppler track in the STRF application and finding a significant match to Object # 45529 (ID’d in the TLE listing as “NOOR”, i.e., “NOUR 01”), I posted a tweet with my findings with the hope that others would monitor the frequency and either confirm my finding or report on a more likely source.”

Scott Tilley – “What is your antenna and related RF path?”

Scott Chapman – “These signals were received with an AZ/EL controlled Wimo X-Quad, 70-cm version, with an SP-70 LNA, LMR-400, to an Airspy R2 & recorded using GQRX”

Scott Tilley – “When you decoded the telemetry why did you feel it was just a standard radio engine on the satellite? Can you provide some context about your experiences with decoding telemetry from satellites?”

Scott Chapman – “Because of the willingness of the Amateur Satellite community to share knowledge & how-to information, I have greatly enjoyed learning how to receive & decode satellite telemetry for a few years now. There is an incredible pool of knowledge in this community, so there is no limit to how far you can develop whatever aspect of the hobby interests you the most. Consequently, I have been able to learn how to track & decode a wide variety of objects in orbit that use many of the various modulation techniques. So, having seen the general appearance of 9600 baud FSK packets from so many other cubesats, it wasn’t a far reach to try to decode these signals with software tools that I already had installed.”

Scott Tilley – “Based on your experience as a VERY active radio satellite tracker what is your opinion of the NOUR 01 satellite’s capabilities based on your own observations and that of others that have shared observations?”

Scott Chapman – “We can only speculate at this point. Small satellites typically downlink telemetry that includes spacecraft health parameters such as battery voltage, solar panel current, the temperature of various components, etc. Many now include a camera, so it’s not uncommon to see the periodic telemetry packets replaced by a steady stream of data that can be decoded as a picture. It’s significant that Amateurs in Europe & elsewhere have in fact seen the 10-second packets from NOUR 01 replaced with a more intense stream of data when in-range of the Middle East, but the one sample of those decodes that I have seen did not include the standard JPG image file format that is common on today’s cubesats. So, for the moment the actual meaning of all the various downlink packets from NOUR 01 remains a mystery.”

Scott Tilley – “Tell me more about your interest into amateur satellite communications and tracking. How did you get into this and why do you find it so fun?”

Scott Chapman – “I knew zero about any of this but the low cost of the basic RTL-SDRs was too tempting to resist. Like so many others, I learned from what I came to find out was an amazing community of incredibly knowledgeable people who enjoy the various aspects of satellites and spacecraft in general. I learned how to decode NOAA Weather satellite APT downlinks, later discovered that there was a packet digipeater on the ISS, and it took off from there. I sincerely hope that people like Jan (PE0SAT), Mike (DK3WN), Dani (EA4GPZ) and many others don’t still have any of the early questions I emailed them out of the blue because they would be as embarrassing as 8th grade class pictures! But I am so grateful to those gentlemen and so many others for sharing what they knew about this hobby to the benefit of all of us.”

Looking Up!

NOUR 01’s recovery was a absolute pleasure to watch unfold.  The amateur satellite tracking community rallied and using creativity, limited gear and some elbow grease peeled back the layers of yet another potential mystery in orbit and gave the world perspective on this news.  For those that sit on the sidelines watching a few of us have all the fun, I invite you to get involved and join us in looking up and reporting what you see for the benefit of us all.

Congratulations Scott on trusting your instincts and grabbing your prize!