Mariner 3, 4

Mariner 3 [NASA]

Mariner 3 and 4 were the first NASA probes to explore the planet Mars. Two probes and a back-up probe were built, but only two were launched.

Mariner 3

Mariner 3 was a 260 kg solar-cell and battery-powered spacecraft designed to make scientific measurements in the vicinity of Mars and to obtain photographs of the planet's surface and transmit these to Earth. It was intended that the spacecraft would encounter Mars after a 325-million mile journey in a little less than 8 months. A protective shield failed to eject after the spacecraft had passed through the atmosphere. None of the instrument sensors were uncovered, and the added weight prevented the spacecraft from attaining its prescribed Mars trajectory.

The experimental payload included six sensors. A solar probe was designed to measure the charged particles making up the solar wind. A trapped-radiation detector was included to measure the Van Allen belts of earth, similar formations around Mars, and related phenomena in space. The ionization chamber and Geiger-Mueller tube were intended to measure the ionization caused by charged particles and to determine the number of particles. A cosmic-ray telescope was mounted on the shadowed side of the spacecraft to detect protons in three energy ranges. A helium magnetometer was mounted high of the spacecraft's low-gain antenna boom to minimize the effect of spacecraft fields. A cosmic dust detector completed the experiment package. It consisted of an aluminum plate perpendicular to the spacecraft vector velocity. Two surface penetration detectors and a microphone attached to the plate were used to indicate the momentum, direction, and number of hits.

Electrical power for all experiments and spacecraft functions was provided by 28,244 solar cells mounted on four collapsed panels designed to deploy in flight. The cells provided 700 W of electrical power, which was converted into various forms to run the spacecraft and recharge the battery. At Mars distance, it would still generate 300 W, which was a safe margin for the payload.

Mariner 4

Mariner 4 was launched on an Atlas-LV3 Agena-D booster. After launch the protective shroud covering Mariner 4 was jettisoned and the Agena D / Mariner 4 combination separated from the Atlas D booster at 14:27:23 UT on 28 November 1964. The Agena D first burn from 14:28:14 to 14:30:38 put the spacecraft into an Earth parking orbit and the second burn from 15:02:53 to 15:04:28 injected the craft into a Mars transfer orbit. Mariner 4 separated from the Agena D at 15:07:09 and began cruise mode operations. The solar panels deployed and the scan platform was unlatched at 15:15:00 and Sun acquisition occurred 16 minutes later.

After 7.5 months of flight involving one midcourse maneuver on 5 December 1964, the spacecraft flew by Mars on July 14 and 15, 1965. Planetary science mode was turned on at 15:41:49 UT on 14 July. The camera sequence started at 00:18:36 UT on July 15 and 21 pictures plus 21 lines of a 22nd picture were taken. The images covered a discontinuous swath of Mars starting near 40 N, 170 E, down to about 35 S, 200 E, and then across to the terminator at 50 S, 255 E, representing about 1% of the planet's surface. The closest approach was 9,846 km from the Martian surface at 01:00:57 UT 15 July 1965. The images taken during the flyby were stored in the onboard tape recorder. At 02:19:11 UT Mariner 4 passed behind Mars as seen from Earth and the radio signal ceased. The signal was reacquired at 03:13:04 UT when the spacecraft reappeared. Cruise mode was then re-established. Transmission of the taped images to Earth began about 8.5 hours after signal reacquisition and continued until 3 August. All images were transmitted twice to insure no data was missing or corrupt.

The spacecraft performed all programmed activities successfully and returned useful data from launch until 22:05:07 UT on 1 October 1965, when the distance from Earth (309.2 million km) and the antenna orientation temporarily halted signal acquisition. Data acquisition resumed in late 1967. The cosmic dust detector registered 17 hits in a 15 minute span on 15 September, part of an apparent micrometeoroid shower which temporarily changed the spacecraft attitude and probably slightly damaged the thermal shield. On 7 December the gas supply in the attitude control system was exhausted, and on December 10 and 11 a total of 83 micrometeoroid hits were recorded which caused perturbation of the attitude and degradation of the signal strength. On 21 December 1967 communications with Mariner 4 were terminated.  

Mariner 5

The Mariner 5 back up was not launched and eventually modified as a Venus flyby probe, which retained its Mariner 5 name.