Decoding the Artemis I Orion vehicle

On Wednesday 16th, the Artemis I mission was launched from Kennedy Space Center. This mission is the first (uncrewed) flight of the Orion Multi-Purpuse Crew Vehicle that will be used to return humans to the Moon in the next few years. Together with Orion, ten cubesats with missions to the Moon and beyond were also launched.

Seven hours after launch, I used two spare antennas from the Allen Telescope Array to record RF signals from Orion and some of the cubesats. By that time, the spacecraft were at a distance of 72000 km, increasing to 100000 km during the 3 hours that the observations lasted.

I have collected a lot of data on those observations, around 1.7 TB of IQ recordings. I am going to classify and reduce this data, with the goal of publishing it on Zenodo. Given the large amount of data, this will take some time. I will keep posting in this blog updates on this progress, as well as my results of the analysis of these signals.

Today’s post is about Orion’s S-band main telemetry signal, which is transmitted at 2216.5 MHz. This signal has attracted great interest in the spacecraft tracking community because back in August NASA published an RFI giving the opportunity to ground stations belonging to private companies, research institutions, amateur associations and private individuals to track the S-band signal and provide Doppler data to NASA. Some of the usual contributors of the amateur space tracking community, including Dwingeloo’s CAMRAS (see their results webpage), Scott Chapman K4KDR and Scott Tilley VE7TIL (see his Github repository) are participating in this project.

Shortly after Artemis I launched, Amateur observers in Europe, such as Paul Marsh M0EYT, the Dwingeloo 25m radiotelescope, Ferruccio Andrea IW1DTU, Roland Proesch DF3LZ, were the first to receive the signals. They were then followed by those in America.