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.
Spacecraft and Subsystems
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. Total research, development, launch, and support costs for the Mariner series of spacecraft (Mariners 1 through 10) was approximately $554 million.