Recovery Beacon Signals from Kosmos Satellites


First Reception

In early 1966 I was a novice at tracking satellites and listened intently to every signal that I heard. That is why I stumbled upon the recovery beacon signals from the Zenit reconnaissance satellites. On 14 April 1966 I and Geoff Perry both picked up the normal FSK-PDM signals on 19.995 MHz from Kosmos 114 during its last revolution around the earth at 0702.30-0710.08 UT. At Kettering the listeners went 'off watch' after having lost the normal signals. I, on the other hand, not knowing what to expect, kept my radio switched on. This is what I wrote to Geoff Perry six days later:

".... It was not possible to hear any more beacon signals of the usual kind. However, at 0725 a signal of this type started to be transmitted: - -.- The signal continued until at least 1100. ..."


On 6 August 1966 Kosmos 126 was due to be recovered. At Kettering normal FSK-PDM signals on 19.995 MHz were picked up at 0908-0918.20 UT followed by 15 minutes of - -.-  - -.-  - -.-  .... signals starting at 0920 UT. The Morse code interpretation of these signals is TK, and that is what we started to call them - "tee-kays"! They became a normal feature of recoveries of reconnaissance satellites. later, we found variations in that TG's and TF's were transmitted by other versions of the basic Zenit satellite design. (Listen to TG signals here)

The image below shows a short piece of a TK transmission. the ordinate is frequency in Hertz and the abscissa is time in seconds. As can be seen the interval between each TK burst was 2.8 seconds. One can also see that the dash in the "T" is much longer than the dashes in the "K". (Click on the picture to hear the signals)

Basing ourselves on 11 receptions of such recovery beacon signals Geoff Perry and myself published a paper in the BIS Spaceflight magazine (April 1968) where we had calculated that the average delay between the cessation of FSK-PDM signals and the onset of TK's to be 6.75 +/- 0.5 minutes. We speculated in that article that the TK's started when the main parachute of the recovery capsule opened. Sometimes the TK's continued for hours and at other times they ceased in as little as 6.5 minutes. we took this time to indicate the time it took for the recovery forces to reach the landing spot. (Robert Christy has vividly described how he picked up TK's back in 1968).

Location of transmitters

Were the two transmitters for FSK-PDM and TK's in the same part of the satellite? At the time we thought so, because the Vostok re-entry vehicle carried short-wave antennas, but now that design sketches of Zenit satellites have been published, we know that the short-wave antennas were mounted on the instrument module. therefore the cessation of FSK-PDM signals could either represent the detachment of the re-entry vehicle or the destruction of the instrument module. Probably the former explanation is the most probable, since we noted no changes in the telemetry during the last minutes, which one could expect if the re-entry vehicle had been detached.

An even earlier observation!

Was Kosmos 114 the first time that TK's were transmitted? No, I do not think so. On September 9-10, 1978, when I visited space listener Dieter Oslender in Bonn, I ran across a note in Dieter's log for 25 April 1965 that said "Molniya 0632.45-0755.00 UT 19.996 MHz". I asked Dieter to let me listen to the corresponding tape recording and you can understand my astonishment when I heard a steady stream of TK signals coming from the loudspeaker. Dieter had tentatively assigned the signals to Molniya because nothing else fitted the long observation time. I explained about the TK's as recovery beacon signals and the fact that Kosmos-65 was recovered that morning.  So, it seems that the recovery beacon on 19.995 MHz was a regular feature of the Zenit reconnaissance satellites and probably this system was used from the very beginning with Kosmos-4 in 1962.

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