Pioneer 5 (1960 Alpha 1) was a spin-stabilized space probe used to investigate interplanetary space between the orbits of earth and Venus. The spacecraft measured magnetic field phenomena, solar flare particles, and ionization in the interplanetary region. The digital data were transmitted at 1, 8, and 64 bps, depending on the distance of the spacecraft from the earth and the size of the receiving antenna. Weight limitations on the solar cells prevented continuous operation of the telemetry transmitters. About four operations of 25-min duration were scheduled per day with occasional increases during times of special interest. A total of 138.9 h of operation was completed, and over 3 million binary bits of data were received. The major portion of the data was received at the Manchester and Hawaii tracking stations because their antennas provided grid reception. Pioneer 5 performed normally until April 30, 1960, after which telemetry transmission became too infrequent for any significant addition to the data. The spacecraft established a communications link with the earth from a record distance of 22.5 million miles on June 26, 1960, which was the last day of transmission.

Spacecraft and Subsytems


Proportional Counter Telescope
A triple coincidence omnidirectional proportional counter telescope was used to observe terrestrial trapped radiation and solar particles (protons E>75 MeV, electrons E>13 MeV). Measurements were obtained for about 2 months during which a week of quiescent magnetic field conditions followed by two geomagnetic storms closely spaced in time occurred. The date of transmission of the last useful information was May 16, 1960.

Search-Coil Magnetometer
This search coil magnetometer, which was similar to those flown on Pioneer 1 and Explorer 6, was designed to study the interplanetary magnetic field. The detector consisted of a single search coil that was mounted on the spacecraft so that it measured the magnetic field perpendicular to the spacecraft spin axis. The magnetometer could measure fields from 1 microgauss to 12 milligauss. No inflight calibration was provided for. The experiment had both digital and analog outputs. The magnetometer amplitude and phase were sampled continuously for analog transmission and intermittently (every 96, 12, and 1.5 s, depending on satellite bit rate) for digital transmission. Approximately 21,000 digital readings of the magnetic field amplitude were obtained. The last data were taken on May 6, 1960. However, no information was obtained on the phase angle of the field about the spin axis. See Coleman, J. Geophys. Res., v. 69, p. 3051, 1964, for further details.

Ion Chamber and GM Tube
This experiment consisted of a Neher-type integrating ionization chamber and an Anton 302 Geiger counter. The Geiger counter was mounted normal to the spacecraft spin axis. Due to the complex, nonuniform shielding of the detectors, the ion chamber responded quasi-omnidirectionally to protons greater than about 25 MeV while the Geiger counter responded quasi-omnidirectionally to protons greater than about 35 MeV. Energy thresholds fo quasi-omnidirectional responses to electrons were approximately 1.6 and 2.9 MeV for the ion chamber and Geiger counter, respectively. Counts from the Geiger counter and pulses from the ion chamber were accumulated in separate registers and telemetered by both analog and digital systems. The experiment performed normally from launch through May 17, 1960. Telemetry noise limited the timespan of useful data to the period from launch through April 29, 1960.

Micrometeorite Spectrometer
A micrometeorite detector (micrometeorite momentum spectrometer), which consisted of two diaphragm and microphone combinations, was used to measure the number and momentum of meteoritic dust particles at various distances between the orbits of Earth and Venus. The outputs from the piezoelectric microphones were connected in parallel to the electronics so that it was not possible to tell which of the individual detectors was hit. The experiment produced no meaningful data because the data system saturated and failed to operate properly as a counter of impulses from the micrometeorite detector.

Launch-Orbit Information

Launch Information

Launch Date: 1960-03-11
Launch Vehicle: Thor-Able
Launch Site: Cape Canaveral, United States
Mass: 43.0 kg

Trajectory Details

Central Body: Sun
Epoch start: 1960-03-11 00:00:00 UTC

Orbital Parameters

Periapsis Apoapsis Period Inclination Eccentricity
0.71 AU 0.99 AU 311.6 days 3.35° 0.1689