RF recording of Vega-C MEO cubesats 436 MHz telemetry beacons

This dataset contains an IQ recording of the 436 MHz telemetry signals of four of the MEO cubesats launched in the Vega-C maiden flight on 2022-07-13: CELESTA, MTCube2, Greencube and AstroBio Cubesat. The recording was done on 2022-07-24 from 40.5958º N, 3.6991º W, 800 m ASL, near Madrid (Spain). This is a urban location, so the RFI is quite high.

A 7 element yagi antenna built by Arrow and a USRP B205mini were used. The antenna was held on a tripod and aimed manually. The antenna polarization was horizontal with respect to the local horizon (parallactic angle rotation should be taken into account to derive the sky polarization). It was connected to the SDR with a short (~1 metre) piece of coaxial cable.

The signals have rather low SNR, due to the high RFI and the small antenna used. Weak packets from CELESTA and very weak long bursts from Greencube can be seen. Signals from MTCube2 and AstroBio were not detected.

The USRP digitized at 4 Msps IQ with a centre frequency of 436.52 MHz. A GNU Radio flowgraph was used for Doppler correction and channelization. A channel of 40 ksps IQ was recorded around the nominal frequency of each satellite. Two different channels were used for AstroBio Cubesat, due to the uncertainty in its transmit frequency caused by a reset of the satellite's radio to factory settings. Each channel is given in a different file, identified by the name of the corresponding satellite.

The recordings of the satellites are contained in the files identified as 2022-07-24T18_47_38. The files with later timestamps (2022-07-24T19_25_49 and 2022-07-24T19_29_02) are short recordings of a CW carrier injected into the receiver for absolute amplitude calibration.

The data was recorded using GNU Radio metadata format with detached headers and converted to SigMF format in postprocessing. The detached headers of the GNU Radio metadata format are provided with the .hdr extension.

The Doppler correction files are also included in this dataset. These are text files that contain tabulated timestamps in seconds of UNIX time and Doppler frequency in Hz. They were generated using the TLEs from Celestrak and the Skyfield Python library.

More information about this recording, including the details of the absolute amplitude calibration, can be found in the post "Trying to observe the Vega-C MEO cubesats" by the author.