The flight of Sputnik-4

Sven Grahn


Sunday 15 May 1960

Announcement of the flight

I remember quite well the Sunday morning when the news of the launch of Sputnik-4  was announced. It really made big headlines and was seen as a first step to manned spaceflight, despite the fact that TASS clearly stated that the spacecraft would not be returned to earth. Early press reports were quite detailed based on Soviet official announcements. The total mass of 4540 kg was astounding and the airtight cabin was said to weigh 2.5 tons and containing a "dummy" spaceman. It was also clearly stated that the "cabin" would be detached on command and burn up upon re-entry. The orbit was given as having an inclination of 65 degrees and an altitude of 320 kilometres (actually the orbital altitude was 312-369 km).

The TASS communiqué also gave the radio frequency of 19.995 MHz for the radio beacon which also could be used for radiotelephone communications (See below). The existence of solar panels on the spacecraft was also indicated in this first announcement (see figure above).

The news was announced at 0425 UT on Radio Moscow five minutes before the first morning news broadcast after Russian music and party songs had been broadcast. The TASS communiqué was broadcast three times in succession so that nobody would miss its significance. (1)The spacecraft had probably been launched at 0000 UT. (8)

TASS also announced that Sputnik-4 passed Paris at 0438 UT on 15 May.(3) Of course, the significance of this was the fact that the summit between U.S. president Dwight Eisenhower and Soviet leader Nikita Khrushchev was taking place in Paris.

Radio observations on 15 May 1960

UPI's monitoring station at Bickley in Kent picked up signals at 0600 UT on Sunday 15 May 1960 on 19.995 MHz. This was on the spacecraft's forth revolution around the Earth. The signal was described as "plingeling" (in Swedish) or the  Morse letter A with a purring sound at the end (Read here about the character of short-wave signals from Vostok test flights and actual Vostok flights). The Swedish telecommunications Agency monitoring station at Enköping picked a strong CW signal on 19.995 MHz with doppler shift at 0738-0757 UT on 15 May 1960. (2)This station picked up much more signals on 15 May and these are summarized in the table and map below. Interestingly "antipodal" receptions were made and the one on rev 12-13 was actually the strongest during the day. Antipodal receptions were extensively observed during early Soyuz flights.
Receptions of Sputnik-4 in Enköping, Sweden, May 15, 1960
Time (UT)

Monday 16 May 1960

Press reports said that Sputnik-4 passed near Paris at 0325 UT and straight overhead in Stockholm at 0500 UT 16 on May. At  0415-0430 UT on 16 May 1960 the Kettering Grammar School picked up its first signals ever and they came form Sputnik-4. Strangely enough the spacecraft was over the south Pacific during this observation, see map below.

May 18, 1960 - retrofire

In the morning of Friday 20 May 1960 there were reports (6) that radio observations in the UK and Sweden (Swedish telecommunications Agency monitoring station in Enköping) showed that the retro rocket engine had started at about 0300 UT on 19 May. The orbital period had increased from 91.2 to 94 minutes. According to (5) retrofire was indeed planned for early May 19. The retro-rocket actually fired at 2352 UT om May 18. The map below shows the probable location of the retrofire point. Really reliable orbital parameters are not available. Howveer, it is quite evident that the ground track took the spacecraft over the ground station at Yevpatoria.

TASS promptly announced that the retro impulse was directed in the wrong direction causing the spacecraft to enter a higher orbit instead of descending. TASS gave the new orbit as 307-690 km and the period 94.25 minutes. (The RAE table of earth satellites (7) gives the new orbit as 290-675 km). The spacecraft finally re-entered on 15 October 1965.

Retransmitted voice noisy and distorted

In the announcement of the retrofire failure TASS described that the retransmission of voice signals through the short-wave transmitter on 19.995 MHz had been made during the flight but that the retransmitted signal had been noisy and distorted. This quite interesting, because, presumably, the Soviet side wanted to avoid any speculation in case Western tracking stations picked up strange sounds from the spacecraft.

The reason for the retrofire failure

Prior to the firing of the TDU-1 retro engine the controllers at Tyuratam under the command of Boris Chertok had detected problems with the infrared orientation sensor and wanted to perform the retrofire using the backup system based on a solar aspect sensor. However, the designer of orientation system Boris Rauschenbakh, refused to go along and convinced Korolev and Keldysh, the president of the Academy of Sciences. However, the primary system malfunctioned with known results. As a result the IR horizon sensor was dropped for the manned variants of spacecraft, but it was used on Zenit reconnaissance version of the spacecraft.

The orbit of Sputnik-4 and subsequent flights in the Vostok program

The orbits of Sputnik-4 and Sputnik-5 were quite different than those of subsequent flights in the series leading up to the launch of Vostok-1. The low perigee of these later flights permitted natural decay of the spacecraft within ten days, to provide an emergency way of saving the cosmonaut in case the retrorocket failed to fire. The orbital element set (in Two Line Element format) is given below and the following table shows the orbits of Vostok test flights and Vostok-1 itself.

Sputnik 4
1 00034E 60005A 60135.99241567000 .00000000 00000-0 00000-0 0 10
2 00034 64.8900 268.5663 0042419 63.0000 297.4325 15.76722300 00

  Int.Nr       Satellite     Incl   Period    Apogee   Perigee
60-005A        Sputnik 4     64.9     91.3     369.0     312.0
60-011A        Sputnik 5     64.9     90.7     324.0     297.0
60-017A        Sputnik 6     65.0     88.5     232.0     166.0
61-009A       Sputnik 10     64.9     88.4     230.0     164.0
61-012A         Vostok 1     64.9     89.3     315.0     169.0


  1. Swedish evening paper "Expressen", 15 May 1960, p.7
  2. Swedish evening paper "Expressen", 15 May 1960, p.6
  3. Swedish Communist Party daily "Ny Dag", 16 May 1960, p.6
  4. Swedish daily "Svenska Dagbladet", 16 May 1960
  5. Asif Siddiqi, Challenge to Apollo, NASA SP-2000-4408, Washington D.C., 2000.
  6. Swedish daily "Dagens Nyheter", Friday 20 May 1960
  7. The RAE Table of earth satellites, 1957-1989, The Royal Aircraft Establishment, 1989, ISBN 0-9516542-0-9
  8. Sergey A. Voevodin's Reports

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