Dataset Open Access

Chang'e 5 RF recording at 8471.2 MHz with Allen Telescope Array during LOI-2

Estévez, Daniel

This dataset contains a recording of X-band telemetry signals from the Chinese lunar sample retrieve mission Chang'e 5 done on 2020-11-29 before and during the LOI-2 (lunar orbit injection 2) manoeuvre that circularized the spacecraft's elliptical lunar orbit. The recording was done at Allen Telescope Array using antenna 1h in dual XY (linear) polarization.

The hardware configuration was as follows: antenna 1h was connected to RFCB LO d, which was tuned to a frequency of 8475 MHz and used an output IF of 512 MHz. A USRP N321 was connected to the IF output of the RFCB and digitized both polarizations. The USRP used external 10 MHz reference and PPS coming from the observatory distribution system. The IQ  sample rate of the USRP was 30.72 Msps and a GNU Radio flowgraph was used to channelize four frequencies from the spacecraft (8463.7, 8471.2, 8478.6 and 8486.2 MHz), using an IQ sample rate of 240 ksps for each channel.

The GNU Radio flowgraph stored the IQ data for each channel as 32-bit floats in the GNU Radio metatata file format, with detached headers. After recording, the data was converted to SigMF format.

This dataset contains the IQ data for the channel at 8471.2 MHz, which corresponds to the orbiter, in SigMF format. Each polarization is in a different file. The original metadata headers are also provided.

Note: during the observation, the frequency of the RFCB LO was lowered by exactly 30 kHz in two occasions to prevent the signals from drifting out of the channel passband due to Doppler. The two LO jumps can be easily seen in the residual carrier of the signals and corrected.

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