The radio systems of the early Luna probes

The early lunar probes launched by the Soviet Union (Luna 1-3) carried rather simple radio systems. This article is a description of these systems and how they worked, as well as can be determined so long after the actual events. In general the probes carried

• a main radio system for telemetry, tracking and command (only Luna-3 had a command link) working on VHF and with a 9/5 turnaround ratio (RTS-12B).
• simple HF transmitters with FSK or on-off keying for some scientific data (Jupiter).
• at least for the first two Luna probes the last stage of the carrier rocket had HF transmitters sending science data from a package in the stage.
• the last stage of the rocket also carried an S-band transponder (Fakel-S) for trajectory determination during powered flight.
• the last stage also had VHF telemetry systems (RTS-8E, RTS-12A) for use during powered flight.

The S-band radar tracking provided an initial estimate of the state vector and the subsequent trajectory, which was then updated by ranging measurements made through the VHF ranging link (RTS-12B).

Post-Cold War account of Luna 1-3 radio systems

This account is based on information from (12), "Unforgettable Baikonur". The table below summarizes the information in that document.

Vehicle	Radio system	Phase	Pre- December  1958 launch	Luna-1	Luna-2	Luna-3
Probe	Jupiter-1	Cruise	-	19.993 MHz	19.993 MHz	-
	Jupiter-2	Cruise	-	-	39.986 MHz	39.986 MHz
	RTS-12B down	Cruise	183.6 MHz	183.6 MHz	183.6 MHz	183.6 MHz
	RTS-12B up	Cruise	102 MHz	102 MHz	102 MHz	102 MHz
3rd stage	?	Cruise	19.995 MHz	19.995 MHz	19.997 MHz	?
	?	Cruise	19.997 MHz	19.997 MHz	20.003 MHz	?
	RTS-8E	Launch	183.6 MHz	183.6 MHz	-	-
	RTS-12A	Launch	-	-	182.0 MHz	182.0 MHz
	Fakel-S	Launch	2.7-2.8 GHz	2.7-2.8 GHz	2.7-2.8 GHz	2.7-2.8 GHz

The RTS-12B system on 183.6 MHz for flights up to and including Luna-2

The RTS-12B system for probes up to Luna-1 had a complex pulse-position modulation system, where the frequency shift pulses of the “velocity vector” system with the period 0.5 second were somehow transmitted together with the short (10 milliseconds) pulses of the pulse-position modulation (PPM) telemetry (15 ). A complete telemetry frame contained 120 measuring channels and was transmitted in 2 minutes, i.e. one interrogation, or "data word", per second. The frame marker consisted of three pulses. It is unclear how the telemetry pulses were modulated on the carrier.

The "velocity vector" frequency shift pulses are given as 0.5 seconds long. It is unclear if this is the rise time or the total back-and-forth pulse time. Interestingly, the "velocity vector" system worked well on Luna-1, but the telemetry modulation in the RTS-12B system did not work on that flight.

For Luna-2 the flight the RTS-12B system was changed so that the ranging system and telemetry system did not work at the same time, but rather in turn. Also the telemetry part of the system used the same modulation as the “Jupiter” system - i.e. PDM (Pulse-Duration Modulation). A narrow-band filter had to be added to the RTS-12B ground receiver to make up for the fact that a keyed carrier was used for telemetry. The ranging system worked by bursts of pulses with short-term change in the carrier frequency.

The "Jupiter" systems on 20 and 40 MHz

The RTS-12B was evidently causing problems in the early phase of the program, so on the third launch in December 1958 (which failed) the "Jupiter-1" system was added.  That uses two long ribbon antennas on the space probe.   It replicated the same telemetry information as was carried by the RTS-12B system on a frequency of 20 MHz.  Just as with the RTS-12B system 120 parameters were transmitted in a 2 minute cycle. So, the "Jupiter-1" system added in late 1958 saved the scientific mission of Luna-1 in which the RTS-12B system on VHF failed.

For Luna-2 a second low-frequency telemetry system, "Jupiter-2", operating near 40 MHz, was added. The transmitter “Jupiter-2” worked in the pauses of transmitter “Jupiter-1” (by opposite coding, transferring the same information).The receiving system for “Jupiter” at Baikonur consisted of two troop receivers of R-250 type (see image on right. Thanks to Don P Mitchell for the picture).Recording of information was conducted by tape recorders and photoregistering equipment common with the RTS-12B station.

An antenna field of five rhombic shortwave antennas were erected on wooden posts and were used for both "Jupiter-1" and "Jupiter-2".These wire antennas extended a sector of 150° in azimuth with the center axis to the south. The antennas were switched by hand as the spacecraft moved from the east to the west. In (14) the layout of a rhombic array at the Simferopol tracking station is shown (see image below right). A fan-shaped array of nine rhombic antennas are indicated as being used for space tracking. A pair of rhombic antennas of different size is indicated as being a "day/night pair" for terrestrial communications, most probably with Moscow. The rhombic antennas at Baikonur were modified in 1960 to be bidirectional. This provided around-the horizon coverage. the same is probably true for the Simferopol array. In 1959 the Baikonur rhombic array only had coverage to the south where the Luna probes traversed the sky. The modification of the Baikonur array in 1960 was done to support the shortwave "Signal" beacon on the space vehicles in the Vostok program, the first test vehicle of which was launched on 15 May 1960. 

Luna-3 only supported by Simeiz and far east station in Yelizovo

For Luna-3, the spacecraft that took pictures of the far side of the moon, a new radio system had been developed by NII-885 under the management of Yevgeni Boguslavsky (13 ). The system transmitted the images of the moon, relayed telemetry, measured the range and range rate, and received commands from the ground and acknowledged the reception of these commands. The "Jupiter-1" system was deleted and only the "Jupiter-2" system was retained. 

During the flights of Luna-1 and Luna-2 data reception was performed at Baikonur and the temporary tracking station at Simeiz in the Crimea. During the flight of Luna-3 no reception of signals out to lunar distances was made at Baikonur - only out to 40000 km. Only the stations at Simeiz and Yelizovo on the Kamchatka peninsula communicated with Luna-3 far away from the earth.

RTS-8E system on 183.6 MHz on the carrier rocket used up to and including Luna-1

RTS-12A system on 182.0 MHz on the carrier rocket used on Luna-2 and Luna-3

Sergei Korolev writes about the subject

In a document written in early 1958 (9) Sergei Korolev described plans for the early Luna probes:

 ...."The radio system operates in the wavelength range 1.6 - 2.5 m. The range from the earth to the spacecraft is measured by an active radar. The pulse signal of the range determination is re-sent as a range signal and used on the earth to measure the range from the earth to the spacecraft. From the distance 20.000 - 30.000 km to the Moon, the range from the spacecraft to the Moon starts to be measured simultaneously with the measurements the earth - spacecraft distance. Beside the pulse signals, the on-board radio transmitter sends to the earth a continuous signal with a power of the order of 10 W to determine the spacecraft velocity. This results in the signal power on the earth of the order of 0.1 microwatts only. Receiving such a signal will be made by radio astronomy dishes in Simeiz". .....

Simeiz is a small city near Yevpatoria in the Crimea. In all probability Korolev describes the ranging system operating on approx 102 MHz uplink (probably equivalent to the uplink 101.965 MHz used for Luna-16, 20...) and 183.6 MHz downlink (see Luna 1 or Luna 2 below). The translation of Korolev's text was provided by Dr Stas Barabash, Swedish Institute of Space Physics, Kiruna.

In the Energiya history book (11) the control center for the lunar missions is described as temporary and set up on the Koshka mountain near the city of Simeiz and using the facilities of the Crimean Observatory and the Physical Institute of the USSR Academy of Sciences. In (11) it is also indicated that the radio systems of the early Luna probes were developed by NII-885 under the leadership of Mikhail S. Ryazanskiy, Chief Designer of Radio Control Systems.

Details of Luna 1-3 radio systems in TASS announcements and foreign tracking reports

Luna 1

• In (2) the last stage of the carrier rocket is said to have carried a radio transmitter operating on two frequencies, 19.997 and 19.995 MHz telegraphic transmissions with 0.8 and 1.6 seconds duration. This transmitter was used to report data from a cosmic radiation counter.
• The only known, but unconfirmed, reception report of the signal on 19.997 MHz is described in (1) . The signal consisted of four pulses lasting 1.6 seconds every 10 seconds.
• According to (2) the last stage was also equipped with a radar transponder. The radar transponder is the S-band (2700-2900 MHz) system mentioned above.
• According to (2)the probe was equipped with a radio transmitter operating on the frequency 19.993 MHz with telegraphic transmissions with varying duration of 0.5-0.9 seconds with which scientific instrument readings were transmitted.
• The probe also had a telemetry transmitter operating on 183.6 MHz which also carried "trajectory measurement". Additionally, the probe carried  a receiver for ranging signals from the ground. This probably operated on 102 MHz (see discussion of radio systems on Luna 20 return craft ).
• JPL director W Pickering said (4) that the telemetry on 183.6 MHz was FSK at 5 Hz keying rate and changing a few kHz in frequency. Recordings released by Moscow showed the repetition rate nearer 1 Hz. JPL picked up the signal from Luna 1 after the probe had passed the Moon.

Luna 2

• The last stage of the carrier rocket was equipped with radio systems analogous to those on Luna 1. According to (2) the radio transmitter operated on two frequencies, 20.003 and 19.997 MHz sending telegraphic transmissions varying in length between 0.8 and 1.5 seconds duration. When there was a pause on one frequency the signals was transmitted on the other frequency.
• In (2) a telemetry system in the probe operating on 19.993 and 39.986 MHz is described. The signals consisted of pulses 0.2-0.8 seconds long sent at a repetition rate of 1 +/- 0.15 Hz."Length of and interval between telegraph pulses transmit essential scientific information". In (3) it is said that the signals on the two frequencies are generated from common crystal-controlled oscillator operated in "telegraph mode" (i.e. on-off). A break in transmission from either one initiated transmission from the other. This system is identical in principle to the system used on Sputnik 1 to transmit pressure and temperature inside the satellite.The same method was also used on the Voskhod series to transmit cosmonaut pulse rate and respiration . 
• On-off telemetry like the signal on 19.993 MHz was also transmitted from the probe on 183.6 MHz according to (5) and this transmitter also carried "trajectory measurements" (2). The trajectory measurements were probably the frequency-shift ranging later observed by me to be used on the Luna 20. I found a fascinating description of this trajectory measuring system in account by L.I Gusev , the director of NII-85 (now known as RNIIKP).

Luna 3

• No radio systems have been described for the last stage of the carrier rocket, although it was indicated in TASS statements (2) that it carried 156.5 kg of scientific instruments.
• Interestingly the probe no longer was equipped with shortwave transmitters near 20 MHz, but only with a transmitter on 39.986 MHz transmitting pulses 0.2-0.8 seconds long sent at a repetition rate of 1 +/- 0.15 Hz.(2).
• According to (10) the picture transmissions from the probe were frequency-modulated on 183.6 MHz which also carried "trajectory measurements".  In (5 ) the modulation is described as "frequency shift modulation".
• In (7) signals from Luna 3 are described as "15 sec on 15 sec off (probably the off period represents a frequency shift). There are two signals in the band with about 5 kHz separation." This is a description that suggests signals like the "frequency sweeps" that I received from Luna 20 . 
• In the Jodrell Bank Archives the signals received on 183.6 MHz from Luna 3 are described in various communications and the descriptions do not contradict the frequency-sweep ranging hypothesis. In one telegram Jodrell bank states "CW at one of several frequencies near 183.6 MHz". "...SIGNALS HAVE BEEN RECEIVED ON SEVERAL CHANNELS IN FREQUENCY BAND 183.600 +/- .01 MHZ...."(8).
• In another message the VHF transmissions are simply described as "signals on 183.600 MHz +/- 0-5 kHz" (6).

Frequencies announced in the West

Several sources have given other frequencies for Luna-1. In Nature (19) 71.2 and 212 MHz were mentioned as frequencies for Luna-1 but without any details.

• In the U.S. Senate hearings about Luna-1 (4) there is a report from Stanford University that mentions that it was alerted to the possible use of the frequency 71.2 MHz by Lunik and that the station tried this frequency by hooking up a six-element Yagi to a Nems-Clarke receiver.
• In (16) it is reported that the USAF station at Hilo, Hawaii picked up signals on 70.2 MHz (not 71.2 - misprint?) 15-20 minutes after launch and that other USAF stations also picked up 70.2 MHz and 212 MHz. These stations were Singapore, Millstone Hill (Mass., USA) and Cape Canaveral.

It is entirely believable that there were signals on these frequencies and that at least Hawaii got them. On the last stage of the A-2 (Vostok-type in Soviet parlance) vehicle there are hairpin shaped antennas very well matching the two frequencies. It is doubtful if these signals could be heard very far out from Earth since they were probably rather broadband containing high speed telemetry from many sensors associated with the propulsion system in the last stage. Also, the batteries for these transmitters probably went dead quickly. 

But why are not these frequencies mentioned in (12) which reveals so much previously secret information? And where does this frequency information in Nature come from ? An unintentional leak from Jodrell Bank?

References

1. "Simplified Tracking Gear Provides Much Data", Missiles and Rockets, March 16, 1959, pp. 29-33.
2. Mastery of Cosmic Space by the USSR, official TASS communiques and materials from the central press 1957-1967, Nauka Publishers, Moscow 1971.
3. V.A. Kotelnikov, .M. Dubrovin, O.N. Rzhiga and A.M. Shakhovsky. "Reception and investigation of the properties of radio signals from Soviet Space Rockets".
4. Hearings before the Committee on Science and Astronautics and Special Subcommittee on Lunik Probe, U.S. House of Representatitives, Eighty-Sixth Congress, First Session, U.S. Governement Printing Office, Washington D.C., 1959. The hearings were held during the period May 11-29, 1959.
5. J.G Davies, A.C.B. Lovell, Observations of the Russian Moon Rockets Lunik II and III, Space Research 1, Proceedings of the first COSPAR conference, 1960.
6. A telegram from Jodrell Bank to SPACE CONN NASA WASH DC dated 4 October 1959
7. A telegram from Jodrell Bank to SPACE CONN NASA WASH DC dated 7 October 1959
8. A telegram sent by Prof. J.B Davies at Jodrell Bank to MEGER, PRAHA on 15 October 1959 describing signal from Luna 3.
9. S.P Korolev (edited by M Keldysh), "The Creative Legacy of Academician S.P. Korolev", Nauka, Moscow 1980, p.402.
10. V.Ye Demidov, "Radio Bridge- 'Earth-Moon-Earth'." Znaniye Press, Moscow 1967.
11. Yu. P Semenov, ed. Raketno-Kosmicheskaya Korporatsiya "Energiya" imeni S.P. Koroleva 1946-1996, 1996, p. 97
12. K.V.Gerchik (ed.), "Nezabyvaemy Baikonur" (Unforgettable Baikonur), 1998.
13. Deputy chief designer of the Scientific Research Institute. of Radio Instrument Building.
14. The Simferopol Space Flight Center, National Photographic Interpretation center, June 1969, Report RCA-03/0017/69 
15. Called pulse-time modulation in (12))
16. Martin Caidin, "Race for the Moon" William Kimber Publisher, London 1960.
17. NATURE, January 10, 1959, page 83.

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