Mission Type: Orbiter
Launch Vehicle: Thor-Delta E-1 (no. 60 / Thor no. 479 / DSV-3E)
Launch Site: Cape Canaveral, USA / launch complex 17B
NASA Center: Ames Research Center
Spacecraft Mass: 65.36 kg
Spacecraft Instruments: 1) triaxial fluxgate magnetometer; 2) plasma analyzer; 3) cosmic-ray-anisotropy detector; 4) cosmic-ray gradient detector; 5) radio wave propagation experiment; 6) electric field detector; 7) cosmic dust detector and 8) celestial mechanics experiment
Spacecraft Power: solar cells and batteries
Maximum Data Rate: 512 bps
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

Pioneer 9 was the fourth in a series of probes designed to study interplanetary space from heliocentric orbit. In its 297.5-day orbit at 0.754 x 0.990 AU, the cylindrical, spin-stabilized spacecraft obtained valuable data on the properties of the solar wind, cosmic rays, and interplanetary magnetic fields.

The Delta launch vehicle also carried the Test and Training Satellite (TETR-B), which was put into Earth orbit to test ground-based communications systems in support of the Apollo program. NASA maintained contact with Pioneer 9 until 19 May 1983. Subsequent attempts to use Search for Extraterrestrial Intelligence (SETI) equipment to establish contact with the probe on 3 March 1987 failed, and the Agency officially declared the spacecraft inactive.