The Pioneer (to) Venus program consisted of an orbiter mission and a multiprobe mission. The orbiter was launched from Cape Canaveral Air Force Station on May 20, 1978. The multiprobe soon followed on August 8, 1978. Both missions were launched atop Atlas-Centaur launch vehicles. The orbiter spacecraft was designed to remotely sense the clouds and surface of Venus and to collect data on gravitational and magnetic fields, the upper atmosphere, and the ionosphere of Venus from a 75 degree inclined orbit. The orbiter was designed to return data from 243 days of Venus orbit but continued to return abundant data for several years. The multiprobe mission consisted of five spacecraft - a bus, three small probes, and a large probe - that were designed to enter the Venus atmosphere and transmit atmospheric data directly to Earth while descending to the surface. All four of the probes transmitted data until impact with the surface of Venus and one of the small probes continued to transmit data for 67 minutes after impact. Both missions approached Venus in early December 1978 and have been regarded as highly successful.
Orbiter Subsystems
The orbiter has eight major subsystems and supports twelve scientific instruments. The configuration of the orbiter spacecraft is shown in Figure 1. The total mass of the orbiter was 549 kilograms.
Structure
The orbiter structure consists of seven major assemblies: despun antennas, bearing and power transfer (BAPTA), BAPTA support structure, equipment shelf, solar panel and substrate, orbit insertion motor (OIM), and a thrust tube. The shape and mass of the structure was designed to maintain a roll-to-pitch inertia ratio greater than 1.2 for spin stabilization. Overall spacecraft stiffness was designed so that the fundamental frequencies were greater than 4 Hz to avoid any coupling with the low booster resonant frequencies.
Thermal
The thermal control subsystem was designed to withstand a solar intensity increase from 0.89 sun near Earth to 1.98 suns at Venus. This design was also complicated by a 3.8 hour eclipse that occurred after six months in Venus orbit. The main thermal control of the probe is accomplished by 15 thermostatically controlled louvers mounted underneath the equipment shelf. The thermal control system is also composed of various heaters, Kapton thermal blankets, thermal finishes and paints, and structural elements for conduction.
Sunday, 01-Aug-2004 00:36:47 CDT
CSR/TSGC Team Web
