Last Sunday 2020-07-19, the first mission of United Arab Emirates to Mars, known as Emirates Mars Mission “Hope probe” launched from Tanegashima, Japan. This probe is expect to reach Mars in approximately 200 days and study its atmosphere over the course of two years. The scientific instruments onboard the probe are a digital camera, an infrared spectrometer, and an ultraviolet spectrometer.
Shortly after launch, several Amateur radio operators and Amateur spacecraft trackers received signals from the X-band beacon of the Hope probe at 8402.655 MHz and posted reports on Twitter, such as Paul Marsh M0EYT, Ferrucio IW1DTU, Edgar Kaiser DF2MZ, and others. Since the spacecraft was still near Earth, its signal was so strong that a data modulation with a main lobe of approximately 20kHz wide and several sidelobes could easily be seen in the spectrum, which is shown below.
Paul has been quite kind to send me a recording that he made with his station on 2019-07-19 at 23:29 UTC and I have been decoding the data in GNU Radio and looking at the frames. The recording can be downloaded here (193MB). It is an int16 IQ recording at 99998 samples per second. This post is an account of my results.
The launch last Saturday of Crew Dragon Demo-2 undoubtedly was an important event in the history of American space exploration and human spaceflight. This was the first crewed launch from the United States in 9 years and the first crewed launch ever by a commercial provider. Amateur radio operators always follow this kind of events with their hobby, and in the hours and days following the launch, several Amateur operators have posted reception reports of the Crew Dragon C206 “Endeavour” signals.
Yesterday I posted about decoding the data in an X-band recording of BepiColombo. I only made a very shallow analysis of the data, which consisted of CCSDS TM Space Data Link frames. However, I showed that most of the data was transmitted on virtual channel 7. A few hours later, Oleg_meteo in Twitter noted that this data in virtual channel 7 was just a 511 bit PN sequence. After some analysis I’ve confirmed what Oleg_meteo said and shown another interesting and unexpected property of this data.
All the Space Data Link frames in virtual channel 7 have a first header pointer field of 2046, which means “idle data only”. When the payload in these frames is concatenated (there are 8792 payload bits per frame) we obtain an infinite sequence that fits the following description.