Maik Hermenau in Dresden has picked up unusual signals on 121.75 MHz during the final approach of Progress M1-2 to Mir on 27 April 2000 at 2115-2122 UT. At this time Mir and Progress were well within the coverage zone from Dresden (see map on the right). The docking took place at approximately 2130 UT.
I have tried to receive TORU signals during dockings between Progress and Mir, but never succeeded. However, these dockings occur too far to the east to be visible from Stockholm where I live. The spacecraft are just below my radio horizon. Therefore I was quite excited when Maik Hermenau (check out his web site "SatellitenWelt") contacted me with a sample of a signal received on 121.75 MHz during a Progress approach to Mir. If confirmed by other observations, one can probably conclude that Maik really picked up the TORU signal from Progress. My guess is that the TORU system was switched on to initiate a backout in the event of a Kurs failure, i.e. the Mir crew could take over in case the automatic docking system malfunctioned.
The picture on the left
shows
the spectrum of an extract lasting a little more than one second of the
signal received by Maik Hermenau . A subcarrier at 2603 Hz can be
seen as well as 50 msec tone burst at a rate of 6 Hz. In the
spectrogram
on the right the tone bursts around 800 Hz can be seen as a wide peak
and
the multiple tones in the 1450-1650 Hz range can also been seen as well
as the main subcarrier. Listen here
(mp3) for a recording of the signal.
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