Pioneer 5
Pioneer 5 was a spin-stabilized space probe in the NASA Pioneer program used to investigate interplanetary space between the orbits of Earth and Venus. It was launched on 11 March 1960 from Cape Canaveral [Air Force Station] Cape Canaveral Air Force Station [Space Launch Complex 17|Launch Complex 17A] at 13:00:00 UTC with an on-orbit dry mass of. It was a diameter sphere with span across its four solar panels and achieved a solar orbit of 0.806 × 0.995 AU.
Data was received until 30 April 1960. Among other accomplishments, the probe confirmed the existence of interplanetary magnetic fields. Pioneer 5 was the most successful probe in the Pioneer/Able series.
The original mission plan was for a launch in November 1959 where Pioneer 5 would conduct a flyby of Venus, but technical issues prevented the launch from occurring until early 1960 by which time the Venus window for the year had closed. Since it was not possible to send the probe to Venus, it would instead merely investigate interplanetary space and an actual mission to the planet would have to wait another three years.
Design and instruments
The spacecraft was a diameter sphere with four solar panels that spanned over and it was equipped with four scientific instruments:- A triple coincidence omnidirectional proportional counter telescope to detect solar particles and observe terrestrial trapped radiation. It could detect photons with E > 75 MeV and electrons with E > 13 MeV.
- A rotating search coil magnetometer to measure the magnetic field in the distant field of the Earth, near the geomagnetic boundary, and in interplanetary space. It was capable of measuring fields from 1 microgauss to 12 milligauss. It consisted of a single search coil that was mounted on the spacecraft in such a way that it measured the magnetic field perpendicular to the spin axis of the spacecraft. It could output its measurements in both an analog and a digital format.
- A Neher-type integrating ionization chamber and an Anton 302 Geiger-Müller tube to measure cosmic radiation. It was mounted normal to the spin axis of the spacecraft.
- A micrometeorite momentum spectrometer that consisted of two diaphragm and microphone combinations. It was used to measure the amount of meteoritic dust particles and the momentum of these particles.
Mission
Booster performance during launch was overall excellent considering the numerous earlier difficulties with the Thor-Able vehicle. There were some minor anomalies with the second stage flight control system that resulted in unplanned pitch and roll motions, however, they were not enough to endanger the mission.The spacecraft returned data collected by the magnetometer on the magnetic field and it measured that the median undisturbed interplanetary field was approximately 5 γ ± 0.5 γ in magnitude. The spacecraft also measured solar flare particles, and cosmic radiation in the interplanetary region. The micrometeorite counter failed to operate as the data system saturated and failed to operate properly.
The recorded digital data were transmitted at 1, 8, and 64 bit/s, depending on the distance of the spacecraft from 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 three megabits of data were received. The major portion of the data was received by the Lovell radio telescope at Jodrell Bank Observatory and the Kaena Point [Satellite Tracking Station|Hawaii Tracking Station] because their antennas provided grid reception. Data was received until 30 April 1960, after which telemetry noise and weak signal strength made data reception impossible. The spacecraft's signal was detected by Jodrell Bank from a record distance of on 26 June 1960, although it was much too weak by then to acquire data.