Pioneer 3

Launch data: Designation 00111 / 1958Theta 1 / 58008A Launch date 06 Dec 1958 - 5:44:52 UT Launch site CC, LC-5 Launch vehicle Juno II (AM-11) Mission Luner flyby Maximum distance from Earth 102333 km All-burnt velocity 10,5 km/sec

• The US Army mounted the three upper stages of its Redstone satellite launcher on a Jupiter missile. 1e launch of Juno 2 rocket
• The first stage ran with an improper fuel mixture ratio reducing performance, and also cut off 3,7 seconds early.
• Then the second, third and fourth stages fired three degrees off the right angle an the prope failed to reach Earth escape velocity; re-entered from 102.333 km apogee.
• Pioneer 3 discovered a second Van Allen radiation belt around Earth, before falling back over Africa.

Description:

• Pioneer 3 was a cone-shaped probe 58 cm high and 25 cm diameter at its base. The cone was composed of a thin fiberglass shell coated with a gold wash to make it electrically conducting and painted with white stripes to maintain the temperature between 10 and 50 degrees Celsius. At the tip of the cone was a small probe which combined with the cone itself to act as an antenna. At the base of the cone a ring of mercury batteries provided power. A photoelectric sensor protruded from the center of the ring. The sensor was designed with two photocells which would be triggered by the light of the Moon when the probe was within about 30,000 km of the Moon. At the center of the cone was a voltage supply tube and two Geiger-Müller tubes. A transmitter with a mass of 0.5 kg delivered a phase-modulated signal of 0.1 W at a frequency of 960.05 MHz. The modulated carrier power was 0.08 W and the total effective radiated power 0.18 W. A despin mechanism consisted of two 7 gram weights which could be spooled out to the end of two 150 cm wires when triggered by a hydraulic timer 10 hours after launch. The weights would slow the spacecraft spin from 400 rpm to 6 rpm and then weights and wires would be released.

• photoelectric sensor trigger
• two Geiger-Mueller counters

Mission details:

• The flight plan called for the Pioneer 3 probe to pass close to the Moon after 33.75 hours and then go into solar orbit. However, depletion of propellant caused the first stage engine to shut down 3.7 seconds early preventing the spacecraft from reaching escape velocity. The injection angle was also about 71 degrees instead of the planned 68 degrees. The spacecraft reached an altitude of 102,360 km (109,740 km from the center of the Earth) before falling back to Earth. It re-entered Earth's atmosphere and burned up over Africa on December 7 at approximately 19:51 UT (2:51 p.m. EST) at an estimated location of 16.4 N, 18.6 E. The probe returned telemetry for about 25 hours of its 38 hour 6 minute journey. The other 13 hours were blackout periods due to the location of the two tracking stations. The returned information showed that the internal temperature remained at about 43 °C over most of the period.

• While Pioneer 3 did not meet is primary mission objective of a lunar flyby, the data obtained was of particular value to James Van Allen. The Pioneer 3 probe data in addition to the data from the previous Explorer 1 and Explorer 3 satellites led to the discovery of a distinct second radiation belt around the Earth (e.g. characteristics). The trapped radiation starts at an altitude of several hundred miles from Earth and extends for several thousand miles into space. These Van Allen radiation belt surrounding the Earth are named for Dr. James Van Allen, in honor of his discovery.