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Human Spaceflight Telemetry

By Geoffrey E. Perry*



The vast size of the Soviet Union enabled a network of ground-stations to be established providing a good degree of coverage for low Earth-orbit flights but, from the earliest days, the Soviet Union has placed great reliance on the use of short-wave communications to compensate for the lack of ground stations outside the territory of the U.S.S.R. As time went by, ships of the U.S.S.R. Academy of Sciences were deployed to supplement the coverage from home-based stations but, even today, their manned spacecraft are out of range of direct communication for long periods.

The value of long-distance propagation of high frequency radio waves by "whispering gallery" modes within the ionosphere became apparent when the signals from the first Sputniks were received at times when the satellites were well below the horizon of the receiving station. Consequently all Soviet man-related flights have transmitted either telemetry, voice or both on frequencies close to 15, 18, or 20 MHz for at least part of the time.

The first Korabl Sputnik used a pulse-duration modulated (PDM), 15-word telemetry frame on 20.005 MHz in May 1960. The Vostok's and Voskhod's transmitted keyed C/W (continuous wave) and voice on a variety of frequencies.

PDM (pulse duration modulation) telemetry from Kosmos 140, the second unmanned Soyuz precursor, was detected in 30-second bursts at 2-minute intervals at Aberystwyth and hindsight suggests that the intervening 90 seconds were occupied by a continuation of the trans-mission on each of three other frequencies. This provided valuable data on which to base the choice of frequency for the manned Soyuz missions to follow.

The only recording of transmissions from the ill-fated Soyuz 1, known to the Kettering Group, is on one of Flagg's tapes. Although un logged, it comes between two identifiable recordings made on dates falling either side of the Soyuz 1 flight. This shows that the frame format was the same as for Kosmos 140 and all subsequent Soyuz flights.

Thirty-second bursts of this type of telemetry received in Kettering on October 27, 1967, indicated to Perry that Kosmos 186 (not announced until the afternoon following the Kettering disclosure) was the first unmanned test of Soyuz since the Komarov fatality.

The Soyuz 3 flight confirmed that the same telemetry format was still being used for the Soyuz program. Up to the launch of Soyuz 4, word 8 of the telemetry frame was always observed to be of medium length. However, when Soyuz 5 was launched on the following day, word 8 was seen to take one of three values which may be termed short, medium, and long. Since this was the first 3-man Soyuz. Perry realized that this word related to the individual crew-members and wont on to show that there was a regular sequence with each state held for one minute.(16) The fact that word 4 exhibited the same periodicity pointed to biomedical sub commutation with word 8 indicating the cosmonaut being monitored at the time and word 4 probably relating to respiration-rate. Supporting evidence for this was later obtained at intervals from TASS reports of values for such rates for different crew members. It was thus possible to assign the medium value to the commander in the center seat, the short value to the test-engineer in the left-hand seat and the long value to the flights-engineer seated on the right.

The Soyuz 4 and 5 mission also provided a clue to the function of the very short words 6 and 7. During the time of the EVA transfer of Khrunov and Yeliseyev from Soyuz 5 to Soyuz 4, word 7 became very long and this, together with subsequent observations that it also became very long immediately prior to the separation of modules for reentry, suggested that it was a measure of the degree of pressurization (in terms of vacuum) of the orbital module, which was serving as an air-lock at this time. Word 6 was assumed to refer to the pressure in the reentry module. After the EVA transfer had been completed, word 8 of the Soyuz 4 telemetry frame took on the short-medium-long sequence whereas that of Soyuz 5 remained medium until recovery. (17)

Word 13 of the Soyuz 9 frame took a minimum value that sounded like a "blip". This was presumed to refer to the rendezvous system which was not carried on this solo flight —a fact confirmed by the Soyuz 9 commemorative stamp.

Such considerations of short-wave telemetry from Soyuz 11 showed nothing untoward up to the moment of separation of the modules immediately prior to reentry —the instant of tragedy. (18)

No obvious biomedical sub-commutation has been observed in Soyuz flights after this time but support for the hypothesis of pressurization information being carried on words 6 and 7 came during the Soyuz 16 flight. These words were both observed to lengthen during the 5 th orbit but neither reached the very long state associated with complete depressurization. This suggested that pressure-dumping to the level planned for Apollo-Soyuz Test Project (ASTP) had been practiced. This was confirmed during the ASTP mission and published data from that flight may be used to provide calibration for the telemetry.

The short words 6 and 7 are characteristic of Soyuz and observations in Kettering and Akrotiri showed that Kosmos 772, with the short words, was an unmanned test of Soyuz. In this instance, words 4, 12 and 13 were all blips.

The first Salyut transmitted C/W PDM telemetry, similar to that of Soyuz, on 15.008 MHz. Here the characteristic short words appeared at 3 and 7 in the frame. Toward the end of the manned phase of its operation it transmitted its own format on the Soyuz 11 frequency of 20.008MHz.

The Kettering Group failed to pick up any signals from Salyut 2 but it is probable that it used the same 19.944 MHz frequency which rahn discovered was being used by Salyut 3. Some analysts even doubted that it was a Salyut intended to be visited by a human crew. This was followed by Kosmos 557 which appeared optically brighter, suggesting that it was larger. Its transmissions on 15.008 and 922.75 MHz made some people insist that it was only a Soyuz test rather than a Salyut station which failed early in its mission. However, the telemetry format with short words 3 and 7 was more akin to Salyut 1 than to Soyuz.19 Positive confirmation of its Salyut relationship was provided by the telemetry on 15.008 MHz from Salyut 4 which differed only in respect of word. (18)

Salyut 3 telemetry on 19.944 MHz was f.s.k. like the early recover-able Kosmos satellites instead of the C/W of the Soyuz and Salyut 1. Paul -Rosser, a pupil at Kettering Grammar School has analyzed 70or so transmissions recorded at various stages of its mission. The lengths of words 1, 3, 4, 6, 14 and 15 remained more or less constant throughout the flight. So did word 5 at a half-length until January 5, 1975 when it began to decrease to a very low value by the time the flight ended on January 24. Some of the other words were more interesting. Word 2 showed a steady decrease in length whereas word 7 increased. Word 8 increased in length during the period in which the station was occupied by the Soyuz 14 cosmonauts and words 9 and 10 which were blips during the unmanned phases of the flight became three-valued when the crew was present. It is interesting to note that on the occasions when the cosmonauts returned briefly to the Soyuz, these words reverted to blips. A suggestion of an approximate 40-day periodicity in the length of word 11 might possibly be due to a variation of Sun-angle at the solar panels producing a corresponding variation in battery-charging current. Before the launch of Soyuz 14, word 13 was short but increased to a long state during the time in which the Soyuz 14 crew were in orbit. Immediately prior to the launch of Soyuz 15 it was back in the short state, lengthening once again during the two-day Soyuz 15 flight. However, it remained in the long state until a week after the capsule was returned to Earth in September 1974. Thereafter, it remained in the short state until the end of the flight.

Word 12 was always three-valued taking long, short and medium states reminiscent of the original Soyuz word 8. Perry was able to show that it was in the long state when he first received transmissions and that the change to the short state occurred very shortly after the spacecraft rose above the horizon of the Yevpatoriya tracking facility in the Crimea. After 7 or 8 frames in this state, corresponding to a total time of two minutes, it reverted to the medium state. The transition from medium to long was never observed at Kettering. Perry suggests that this word relates to the onboard tape recorder which is in the record-mode when represented by the long state. After rising above the horizon of the ground stations it plays-back on command, the data stored on the tape. Initially the play-back took two minutes but later in the flight this time became quite irregular. It is also suggested that the medium state indicates re-wind of the recorder.

David Dean, another of Perry's pupils, made a study of the broad-band FM voice transmissions on 121.75, 142.4 and 143.625 MHz. In these, the cosmonauts have been heard reading through a series of numbers prefaced by the words "Form 2" and "Form 3". He has shown that the less frequent Form 2, containing fewer numbers, relates to the medical status of the crew and that Form 3 is concerned with the spacecraft's systems status. There have been indications when a specific time or orbit number has been quoted that the data refer to an earlier period when the spacecraft was out of communication with ground-stations. Dean has been able to correlate certain numbered data points with values for humidity (typically kept constant at around 10 percent), partial pressures of oxygen and carbon dioxide, total pressure and temperature. It appears that the latter are measured at two or three locations corresponding to the Soyuz orbital and reentry modules and the Salyut space station. Dean also has noted that the Soyuz 14 Form 3 contained far more data points than the corresponding forms for Soyuz 16, 17 and 18.

This observation of Dean's, the use of different frequencies and transmission mode and the all-military crew of Soyuz 14 points to the existence of two parallel space station programs within the Salyut label: one military in a low Earth orbit and the other scientific in a higher orbit. Perry has pointed out that no recoverable reconnaissance Kosmos payloads were flown between the recovery of Kosmos 674 on September 7 and the launch of Kosmos 685 on September 20 during which period the Salyut 3 station was passing over Kettering at times normal for the recoverable Kosmos types. Moreover, it was officially announced that a data capsule had been automatically returned to Earth on September 23.



16. Perrv, G. E. and R. S. Flagg, Journal of the British Interplanetary Society, 2S, 4B1- 464. 1970.

17. Ibid.. Fig. 7. p. 459.

18. Perry, G. E. Northampton and County Independent, 60, 24-25 (October 1971).

19. The Kettering Group, Spaceflight, London, 16, 39-40, January 1974.

* The late Mr. Perry was senior science master at the Kettering Grammar School , Kettering , England

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