JUICE, the Jupiter Icy Moons Explorer, is ESA’s first mission to Jupiter. It will arrive to Jupiter in 2031, and study Ganymede, Callisto and Europa until 2035. The spacecraft was launched on an Ariane 5 from Kourou on April 14. On April 15, between 05:30 and 08:30 UTC, I recorded JUICE’s X-band telemetry signal at 8436 MHz using two of the 6.1 m dishes from the Allen Telescope Array. The spacecraft was at a distance between 227000 and 261000 km.
The recording I made used 16-bit IQ at 6.144 Msps. Since there are 4 channels (2 antennas and 2 linear polarizations), the total data size is huge (966 GiB). To publish the data to Zenodo, I have combined the two linear polarizations of each antenna to form the spacecraft’s circular polarization, and downsampled to 8-bit IQ at 2.048 Msps. This reduces the data for each antenna to 41 GiB. The sample rate is still enough to contain the main lobes of the telemetry modulation. As we will see below, some ranging signals are too wide for this sample rate, so perhaps I’ll also publish some shorter excerpts at the higher sample rate.
The downsampled IQ recordings are in the following Zenodo datasets:
- Recording of JUICE with the Allen Telescope Array on 2023-04-15 (antenna 1a)
- Recording of JUICE with the Allen Telescope Array on 2023-04-15 (antenna 5c)
In this post I will look at the signal modulation and coding, and some of its radiometric properties. I’ll show how to decode the telemetry frames with GNU Radio. The analysis of the decoded telemetry frames will be done in a future post.