Ever since SETI Insitute published the news of a possible signal received from Proxima Centauri in some of the Parkes telescope recordings at 982 MHz, Scott Tilley VE7TIL has taken up the interest to search and catalogue the satellites that transmit on this band (specially old, forgotten and zombie satellites). His idea is to try to see if this candidate signal can be explained as interference from some satellite.
This has led him to discover some signals coming from satellites on a Molniya orbit. After examination with the Allen Telescope Array of these signals, we confirmed that they came from wideband transponders (centre frequency around 995 MHz, 13 MHz width) on some of the Meridian Russian communications satellites (in particular Meridian 4 and 8, but also others).
These transponders show all sorts of terrestrial signals that are relayed as unintended traffic through the transponder. By measuring Doppler we know that the uplink is somewhere around 700 or 800 MHz. We have found some OFDM-like signals that seem to be NB-IoT. Unfortunately we haven’t been able to do anything useful with them, maybe because there are several signals overlapping on the same frequency. We also found a wideband FM signal containing music and announcements in Turkmen, which later turned out to be the audio subcarrier of a SECAM analogue TV channel from Turkmenistan.
A few days ago, Scott detected a pulsed strong signal through the transponder of the Meridians at a downlink frequency of 994.2 MHz. He did an IQ recording of this signal on the downlink of Meridian 8. It turns out that this signal is a BPSK pulse radar. In this post I do a detailed analysis of the radar waveform using this recording.