An open letter about ESEO telemetry specifications

Dear Piero Galeone and Antonio de Luca,

As an Amateur Radio operator experienced in the field of Amateur satellites and in the space industry, I am publishing this open letter to motivate and request the release of the complete technical specifications for the telemetry that the ESEO satellite will transmit in the frequency 437.00MHz, in the 70cm Amateur satellite band.

According to the ITU Radio Regulations for the Amateur and Amateur-satellite Services, “Transmissions between amateur stations of different countries shall not be encoded for the purpose of obscuring their meaning, except for control signals exchanged between earth command stations and space stations in the amateur-satellite service.” A strict interpretation of this rule means that the specifications of all digital protocols used by Amateur stations should be publicly available, so that anyone is able decode the data. The use of protocols with undisclosed specifications can be seen as a try to obscure the meaning of the data.

Continuing with the ITU Radio Regulations, the definition of the Amateur service describes it as “a radiocommunication service for the purpose of self-training, intercommunication and technical investigations carried out by amateurs, that is, by duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.” In my opinion, the use of protocols with undisclosed specifications goes against the spirit of this definition, in particular, it can hinder technical investigations and self-training.

For these reasons, I am a strong proponent of requiring that all the protocols used by Amateur stations have publicly available specifications, allowing anyone to decode the data, study the protocols, learn, experiment and improve upon the state of the art. In view of the paragraphs cited above, publishing the full specifications so that anyone can build a complete decoder independently is both an obligation and the best practice.

This is especially important for Amateur satellites, which often use at least some form of ad-hoc protocols in their telemetry downlink. The public specifications for this telemetry downlink are often incomplete or inexistent. As an attempt to remedy this situation, I develop gr-satellites, which aims to decode every satellite that transmits in Amateur bands. Developing this tool usually requires some reverse engineering, due to the lack of documentation. Some similar tools by other Amateurs are the Soundmodem decoders by Andrey Kopanchuk UZ7HO and the Telemetry decoders by Mike Rupprecht DK3WN, who face similar challenges.

A large number of Amateur operators and enthusiasts throughout the world routinely use these tools to decode telemetry from Amateur satellites, contributing valuable data to the satellite operators through the SatNOGS network and other databases. Also, these tools can be an invaluable reference to educational or research institutions or companies that start building satellites.

Regarding the ESEO satellite, I believe that the educational and collaborative aims of the project is in line with the self-training and investigation aspects of the Amateur service. Thus, publishing complete specifications for the telemetry downlink seems the best practice to respect the goals of the project.

Additionally I think ESA should be held to the highest standards and be exemplary in publishing the specifications. This is specially important, since currently it is often hard to get documentation from the developers of many Amateur satellites.

While some documentation for ESEO has already been published, this is not enough to build a complete telemetry decoder. For instance, the equations needed to interpret the raw telemetry readings such as voltage, current and temperature are missing.

I hope that this letter serves to raise awareness about the need of publishing specifications for the protocols used in the Amateur service and that a complete set of documentation is published for ESEO, allowing Amateurs to build their own telemetry decoders.

Best regards,

Dr. Daniel Estévez, EA4GPZ.



Batch processing of DSLWP-B Moonbounce: part I

In previous posts I’ve talked about how the DSLWP-B 70cm signal can sometimes be received in the Dwingeloo 25m radiotelescope via a reflection off the Moon’s surface. I’ve studied the geometry of this reflection, the cross-correlation against the direct signal, and even decoded some reflected JT4G.

However, so far the reflection has been detected by hand by looking at the recording waterfalls. We don’t have any statistics about how often it happens or which conditions favour it. I want to make some scripts to process all the Dwingeloo recordings in batch and try to extract some useful conclusions from the data.

Here I show my first script, which computes the power of the direct and reflected signals (if any). The analysis of the results will be done in a future post.

Continue reading “Batch processing of DSLWP-B Moonbounce: part I”

Es’hail 2 launch in GMAT

After a long wait by many Amateur radio operators, Es’hail 2, the first geostationary satellite carrying an Amateur radio transponder launched yesterday on a SpaceX Falcon 9 Full Thrust from the historical LC-39A pad in Kennedy Space Centre, which was used by many Apollo and Space Shuttle launches in the past.

Es’hail 2 is the second communications satellite operated by the Qatari company Es’hailSat. It was built by Mitsubishi Electric Corporation (MELCO). It carries several Ku and Ka band transponders intended for digital television, Internet access and other data services. It also carries an Amateur radio payload designed by AMSAT-DL, in collaboration with the Qatar Amateur Radio Society. The payload has two transponders, with S-band uplink and X-band downlink. One of the transponders is 250kHz wide and intended for narrowband modes, and the other one is 8MHz wide and intended for DVB-S and other wideband data modes.

SpaceX live-streamed the launch, and the recording can be seen in YouTube. Today, Space-Track has published the first TLEs for Es’hail 2 and the second stage of the Falcon 9 rocket. Here I look at these TLEs using GMAT.

Continue reading “Es’hail 2 launch in GMAT”

November DSLWP-B images of the Moon and Earth

In previous posts, I have already spoken about the chance of DSLWP-B taking images of the Moon and Earth during the beginning of November. The window to take these images was between November 6 and 9. This window included the possibility of taking an Earthrise image, with the Earth appearing from behind the Moon.

The planning for the activations of the Amateur payload made by Wei Mingchuan BG2BHC was as follows.

7 Nov 2018 08:13 to 7 Nov 2018 10:13
8 Nov 2018 09:40 to 8 Nov 2018 11:40
9 Nov 2018 12:00 to 9 Nov 2018 14:00
10 Nov 2018 14:00 to 10 Nov 2018 16:00
11 Nov 2018 13:30 to 11 Nov 2018 15:30

On November 7, from 8:13 to 9:33 UTC, a total of 9 images with 10 minutes of spacing between each would be taken. These images would be downloaded during the activations on the next days. As usual, an image would also be taken when the Amateur payload powered up on November 8 to 11, but the main focus was on downloading the sequence of images taken on November 7. This is a complete report of the images taken and downloaded.

Continue reading “November DSLWP-B images of the Moon and Earth”

Updated DSLWP-B camera planning

In my last post, I detailed the DSLWP-B camera planning for the beginning of November. There, I used orbital state taken from the 20181027 tracking file to compute good times to take images of the Moon and the Earth, especially looking for an Earthrise-like image.

Now that the planned dates are closer, it is good to rerun the calculations with a newer orbital state. It turns out that there has been an important change in the mean anomaly, which shifts all the predictions by a few hours.

Continue reading “Updated DSLWP-B camera planning”