TWO FRUSTRATING MISSIONS AT VENUS: 1965

Campaign objectives:

Nineteen months after their frustrating third campaign to Venus, the Soviets were ready with three more spacecraft for the late 1965 launch window. They had tried to reach this planet at every opportunity since February 1961, but after one test launch and seven launches they had nothing to show for it. Only two of the seven spacecraft survived their launch vehicles, and both of these failed in flight rather quickly. But the engineers reckoned they had fixed the problems that crippled Zond 1 and were encouraged by the success of Zond 3 at the Moon and its long interplanetary flight, so they prepared for the second 3MV Venus campaign with confident expectation.

Several 3MV spacecraft were left over from the November 1964 Mars campaign when only one had been launched during the window, flying as Zond 2. Another had been launched in July 1965 as Zond 3 for a test to Mars distance. Three 3MV Mars spacecraft, one configured with an entry probe (3MV-3 No. l) and the other two for flyby observations (3MV-4 No.4 and No.6), were modified for the Venus window in 1965. Their original target. Mars, accounts for their anomalous ‘tail numbers’. Only

Spacecraft launched
First spacecraft:	Venera 2 (3MV-4 No.4)
Mission Type:	Venus Flyby
Country j Builder:	USSR/OKB-1
Launch Vehicle:	Molniya-M
Launch Date: Time:	November 12, 1965 at 05:02:00 UT (Baikonur)
Mission End:	February 10, 1966
Encoun ter Dale і 7 ‘іme:	February 27, 1966
Outcome:	Failed in transit, communications lost.
Second spacecraft:	Venera 3 (3MV-3 No. l)
Mission ‘type:	Venus Atmosphere Surface Probe
Country і Builder:	USSR/OKB-1
Launch Vehicle:	Molniya-M
Launch Date; Time:	November 16, 1965 at 04:19:00 UT (Baikonur)
Mission End:	February 16, 1966
Encoun ter Dale і 7 ime:	March 1, 1966
Outcome:	Failed in transit, communications lost.
Third spacecraft:	3MV-4 No.6 (Cosmos 96)
Mission Type:	Venus Flyby
Country і Builder::	USSR/OKB-1
Launch Vehicle:	Molniya-M
Launch Date: Time:	November 23. 1965 at 03:22:00 UT (Baikonur)
Outcome:	Failed to depart Farth orbit.

two were successfully dispatched. Venera 2 and 3 flew to the vicinity of their target and became the first truly successful interplanetary cruises since Korolev had begun launching planetary spacecraft in 1960. The long interplanetary cruise provided new confidence in the spacecraft, but the fact that they failed at or near their target made them agonizing disappointments. There was a fourth spacecraft, probably with an entry probe, but this was unable to be launched before the window closed.

Venera 2 and 3 were also the last planetary spacecraft to be built and launched by OKB-1 because in late 1965 Korolev had transferred responsibility for robotic lunar and planetary missions to NPO-Lavochkm. The next Venera spacecraft for the 1967 window would be built and launched under the leadership of Gcorgi Babakin.

Spacecraft:

The Venera 2 and 3 spacecraft were basically the same as Zond 2 and 3 but modified for the new target. The Venera 3 entry probe was essentially the same as that carried by Zond 1. By the time the mission was launched, there was strong evidence that the surface of Venus was hot, possibly 400°C. Although the surface pressure was not yet well determined, it was apparent that conditions were beyond the limits to which the 3MV probe was designed (77aC and 5 bar). As it was too late to make changes, Venera 3 was launched in full knowledge that its probe would provide only data on the atmosphere and would not survive the full descent to the surface.

Figure 9.10 Venera 2 (left) and Venera 3 (right).

963 kg (Venera 2)

958 kg (Venera 3)

~ 950 kg (Cosmos 96) 337 kg

Payload:

Venera 2 carrier spacecraft:

1. Lyman-alpha and oxygen spectrometer

2. Triaxial fluxgatc magnetometer

3. Micrometeoroid detector

4. Charged particle detectors

5. Cosmic ray gas discharge and solid state detectors

6. Cosmic radio emission receivers for 20 to 2,200 kl-Iz

7. Decimeter band, radio solar plasma detector

The cosmic ray detectors now consisted of the gas discharge counters and silicon solid-state detectors. The decimeter band radiometer dish antenna was mounted on the ring between the avionics and instrument compartments.

Venera 2 flyby instrument module:

1. Facsimile imaging system

2. Ultraviolet spectrometer at 285 to 355 nm in the imaging system

3. Ultraviolet spectrometer for ozone at 190 to 275 nm

4. Infrared spectrometer at 7 to 20 and 14 to 38 microns

The camera system and ultraviolet spectrometers were identical to those carried by Zond 2 and 3. The camera was provided with a 200 mm lens. The Venus infrared spectrometer was similar to that of Mars 1 but designed to measure thermal radiation from the atmosphere and clouds. It covered two ranges in 150 increments each, the first using an InAn window7 and the second a LiF mirror. The instrument had a mass of 13 to 15 kg, was 50 cm in size, and was mounted outside the instrument module, coaxial with the imaging system, and included a visible photometer for reference. It could also make a spatial scan of the planet at the two fixed wavelengths of 9.5 and 18.5 microns.

Venera.? carrier spacecraft:

1. Lyman-alpha and atomic oxygen photometers

2. Triaxial fluxgate magnetometer

3. Charged particle detectors

4. Cosmic ray gas discharge and solid state detectors

5. Decimeter band radio solar plasma detector

The cosmic ray instrument had an additional gas discharge counter on Venera 3. and both the micrometeoroid detector and the radio emission receivers were deleted.

Venera.? descent I landing capsule:

1. Temperature, pressure and density sensors

2. Atmospheric composition, acidity and electrical conductivity experiments

3. Gamma-ray surface composition detector and cosmic ray detector

4. Visible airglow photometer

5. Mercury level motion experiment

The probe instruments were spares from the 1964 campaign. The photometer was included again since Venera 3 was to be a night-time landing. As with all of the ЗМ V missions, the probe also carried pennants of the Soviet Union.

Mission description:

The Venera 2 flyby spacecraft was successfully launched on November 12, 1965 .It was intended to fly in front of the sunlit hemisphere of Venus and photograph it at a range of less than 40,000 km. The initial trajectory w as so precise that no midcourse maneuver was required. The thermal system did not function well and the spacecraft began to overheat as it neared its target, causing problems with the communications system. An improper coating of the radiation domes was suggested as the cause. By February 10. which proved to be the final interrogation session, the temperature was considerably increased, the quality of communications was seriously degraded, and the command from Harth to initiate flyby observations was not acknowledged. After the flyby Venera 2 failed to respond to commands to download the flyby data, and on March 4 it was declared lost. It may very well have achieved its mission and been unable to transmit its results to Harth. The closest point of approach to the planet was at 02:52 UT on February 27, 1966, at a distance of 23.950 km.

Venera 3 was dispatched towards Venus on November 16, 1965. It performed satisfactorily during cruise and a midcourse correction on December 26 put it on an impact trajectory 800 km from the bull’s-eye. How7ever. the communications system failed on February 16, just seventeen days prior to arrival. The spacecraft may have released its entry probe automatically at 06:56 UT on March 1. 1966, but there was no telemetry from the capsule. Even so. the probe became the first human artefact to reach another planet, near the terminator on the night side somewhere between 20°S and 20 N and between 60 E and 80 E.

The post-mission investigation into the loss of Venera 2 and 3 revealed problems with the thermal control system in both spacecraft which had caused components in the communications system to overheat and fail.

The third spacecraft, 3MV-4 No.6, was launched on November 23. A broken fuel line caused one of the engine chambers in the third stage to explode shortly prior to stage shutdown, with the result that the fourth stage inherited an unstable attitude. It managed to achieve orbit, but the tumbling prevented it from restarting its engine for the escape maneuver. Written off as Cosmos 96, it re-entered on December 9.

A fourth spacecraft (probably 3MV-3 No.2) w as to be launched at the very end of the w indow on November 26, 1965. but was scrubbed w7hen a problem was found in the launch vehicle during pre-flight checks. The launch was abandoned because the vehicle could not be recycled before the window closed.

These were the last robotic interplanetary spacecraft launched by OKB-1. Out of a total of 39 launch attempts in a period of a little more than seven years, only Luna 2, Luna 3, and Zond 3 fulfilled their missions. Twenty lunar launch attempts gave eight successful launches, with only three spacecraft being fully successful. Hlevcn Venus launch attempts gave four successful launches, but unfortunately no spacecraft were successful. Out of six Mars launch attempts only two succeeded, but both spacecraft failed. Two ЗМ V test launches also failed.

Results:

The 1965 campaign produced no data from Venus. Some results were published on micrometeoroids, the interplanetary magnetic field, cosmic rays, low energy charged particles, solar wind plasma fluxes and their energy spectra.