In the early days of space research, and particularly in the case of the Soviet Union, there were numerous HF transmissions. Some were deliberately made at the chosen frequencies for ionosphere research, but in the case of the USSR, it was more to provide 'quick look' data and allow satellite to be tracked when well away from the Asian land mass.
Some classes of satellites transmitted only while above the horizon in the USSR, others transmitted continuously for long periods. This meant two things, First, they could be heard over any point on the globe. Then, from a given location, it was possible to hear a transmission from thousands of miles away.
There were occasions when signals would come in simultaneously by two different routes through the ionosphere. They would have different amounts of Doppler and gave the impresssion that there were two separate transmissions. Only by analysing the signal content was it possible to determine that the source of both transmissions was the same.
From the UK, tracking of Cosmos satellite recoveries and the associated beacons at 19.995 and 20.005 MHz was limited to the period April-October due the seasonal variation of the state of the ionosphere. In winter months, the signal just did not come through. The beacon transmissions usually lasted for about six minutes as the recoverable cabin descended under the parachute. Occasionally, under very favourable ionospheric conditions (usually late spring-summer, weak transmissions would continue for longer periods providing that the aerial had not earthed itself electrically by contact with the ground.
This list is not an exhaustive one - it contains only frequencies that the author was active in tracking.
Freq (MHz) |
Satellite |
Payload |
Signal Type |
Notes |
8.983 |
Orbis-Cal 2
1969-25D
3826 |
Ionospheric studies |
Tones |
Continuous |
15.009 |
Soyuz, Soyuz-T |
Piloted spacecraft |
PDM - 16 data channels - transmitted approx 1 measurement per second (variation on the FSK with PDM transmissions from other satellites) |
Transmissions detected from most Soyuz and Soyuz-T missions, including the test missions orbited under the 'Cosmos' label; specific exceptions were the ASTP-related missions |
15.009 |
Salyut (DOS version) |
Space Station |
PDM - 16 data channels - transmitted approx 1 measurement per second (variation on the FSK with PDM transmissions from other satellites) |
This frequency was used by the Korolyov 'DOS' stations - Salyut 1, Salyut 4, Salyut 6 and Salyut 7 as an alternative to 20.008 MHz
It was also used by Cosmos 557 until it decayed from orbit (it was a failed DOS station - presumably the transmitter was 'stuck' on this frequency) |
19.150 |
Cosmos |
Recoverable satellites - photo-recon |
Morse code |
Simple read-out telemetry without necessity for electronic decoding, changes easily detectable, transmission limited to passes over the Soviet Union |
19.300 |
Cosmos |
Recoverable satellites - photo-recon |
Morse code |
Simple read-out telemetry without necessity for electronic decoding, changes easily detectable - secondary frequency for use when two similar satellites in orbit, transmission limited to passes over the Soviet Union |
19.910 |
Proton 4
1968-103A
3544 |
Science payload - high energy physics |
FSK with PDM - 16 data channels - transmitted approx 1 measurement per second |
19 tonnes satellite orbited as a test of the carrying capacity of the Proton rocket |
19.945 |
Salyut (Almaz version) |
Space Station |
FSK with PDM - 16 data channels - transmitted approx 1 measurement per second |
Chelomei's 'Almaz' reconnaissance platform, flown successfully as Salyut 3 and Salyut 5
The frequency would probably also have been used by Salyut 2 had it not failed on entering orbit |
19.954 |
Cosmos |
Space Station support |
FSK with PDM - 16 data channels - transmitted approx 1 measurement per second |
TKS support vehicles, originally designed for use with the Almaz stations but later trialled with the DOS type Salyut stations - specifically Cosmos 929, Cosmos 1267, Cosmos 1443, Cosmos 1686 |
19.990 |
Cosmos |
Recoverable satellites - mainly photo-recon |
FSK with PDM - 16 data channels - transmitted approx 1 measurement per second |
Easy to detect telemetry variations allowed confirmation that mission was proceeding normally and gave early warning of impending recovery
When two similar satellite were in orbit simultaneously, the first satellite would switch to this frequency from 199.995 MHz to allow a clear channel for use by the second launch
Transmission limited to passes over the Soviet Union |
19.990 |
Cosmos |
Recoverable satellites - photo-recon |
FSK - approx 1s on each frequency |
|
19.995 |
Cosmos |
Recoverable satellites - mainly photo-recon |
FSK with PDM - 16 data channels - transmitted approx 1 measurement per second |
Easy to detect telemetry variations allowed confirmation that mission was proceeding normally and gave early warning of impending recovery
Transmission limited to passes over the Soviet Union |
19.995 |
Cosmos |
Recoverable satellites - mainly photo-recon |
Pseudo morse code |
Recovery beacon while under parachute |
19.995 |
SJ-1(aka China 2)
1971-18A
5007 |
Engineering experiments |
Pulse position data modulation |
Second satellite launch - initial transmissions at 20.006 MHz then changed to this frequency
Transmission was continuous until re-entry in 1979 through natural orbital decay |
19.995 |
Unknown |
Recovery crews? |
AM voice |
Often heard starting soon after transmission from a Cosmos recovery beacon - Russian voices, possibly the recovery crews |
20.005 |
Cosmos |
Recoverable satellites - mainly photo-recon |
Pseudo morse code |
Recovery beacon while under parachute |
20.005 |
Explorer 22
1964-64A
899 |
Ionospheric studies |
CW |
Continuous beacon |
20.005 |
Explorer 27
1965-32A
1328 |
Ionospheric studies |
CW |
Continuous beacon |
20.005 |
Unknown |
Soviet exercises/tests |
Recovery beacon |
Sometimes transmitted for long periods, possible ground simulations or tests of recovery apparatus associated with Soyuz operations and development - morse code letters 'AN' |
20.006 |
DFH-1 (aka China 1)
1970-
|
Technology demonstrator |
Tone-based telemetry plus tune 'The East is Red' |
First satellite launch by the PRC |
20.006 |
SJ-1(aka China 2)
1970-34A
4382 |
Engineering experiments |
Tone-based telemetry |
Second satellite launch by the PRC - transmissions may have been from the final-stage rocket
After a few days, the 200.006 MHz transmission was replaced by one at 19.995 MHz |
20.008 |
Soyuz, Soyuz-T |
Piloted spacecraft |
PDM - 16 data channels - transmitted approx 1 measurement per second (variation on the FSK with PDM transmissions from other satellites)
Occasional voice transmissions |
Transmissions detected from most Soyuz and Soyuz-T missions, including the test missions orbited under the 'Cosmos' label; specific exceptions were the ASTP-related missions |
20.008 |
Salyut (DOS version) |
Space Station |
PDM - 16 data channels - transmitted approx 1 measurement per second (variation on the FSK with PDM transmissions from other satellites) |
This frequency was used by the Korolyov 'DOS' stations - Salyut 1, Salyut 4, Salyut 6 and Salyut 7 as an alternative to 15.009 MHz |
24.912 |
STADAN |
US tracking command and control |
SSB voice |
Useful for 'tracking' Gemini and Earth-orbit Apollo missions - ground stations could be heard talking to each other, giving AOS and LOS times, other NASA satellites could also be tracked |
