Mariner 4 Spacecraft and Subsystems
The Mariner 4 spacecraft consisted of an octagonal magnesium frame, 127 cm across a diagonal and 45.7 cm high. Four solar panels were attached to the top of the frame with an end-to-end span of 688 cm, including solar pressure vanes which extended from the ends. A 116.8 cm diameter high gain parabolic antenna was mounted at the top of the frame as well. An omnidirectional low gain antenna was mounted on a 223.5 cm tall mast next to the high gain antenna. The overall height of the spacecraft was 289 cm. At the bottom center of the spacecraft the television camera was mounted on a scan platform. The octagonal frame housed the electronic equipment, cabling, midcourse propulsion system, and attitude control gas supplies and regulators. Most of the science experiments were mounted on the outside of the frame. Science instruments, in addition to the TV camera, were a magnetometer, dust detector, cosmic ray telescope, trapped radiation detector, solar plasma probe, and ionization chamber/Geiger counter.
Power was supplied by 28,224 solar cells contained in the four 176 x 90 cm solar panels, which could provide 310 W at Mars. A rechargeable 1200 W-hr silver-zinc battery was also used for maneuvers and backup. Monopropellant hydrazine was used for propulsion, via a 4-jet vane vector control 222-N motor installed on one of the sides of the octagonal structure. Attitude control was provided by 12 cold nitrogen gas jets mounted on the ends of the solar panels and three gyros. Solar pressure vanes, each with an area of 0.65 square meters, were attached to the tips of the solar panels. Positional information was provided by four Sun sensors, and an Earth, a Mars, and a Canopus sensor.
Telecommunications equipment consisted of a dual, S-band 7-W triode cavity amp/10-W TWTA transmitter and a single receiver which could send and receive data via the low- and high-gain antennas at 8 1/3 or 33 1/3 bps. Data could also be stored on a tape recorder with a capacity of 5.24 million bits for later transmission. All operations were controlled by a command subsystem which could process any of 29 direct command words or 3 quantitative word commands for midcourse maneuvers. The central computer and sequencer operated stored time-sequence commands using a 38.4 kHz synchronization frequency as a time reference. Temperature control was achieved through the use of adjustable louvers mounted on six of the electronics assemblies, multilayer insulating blankets, polished aluminum shields, and surface treatments.