Pioneer 4

Launch data: Designation 00113 / 1959 Nu 1 / 59004A Launch date 03 Mars 1959 - 05:10:45 UT Launch site CC, LC-5 Launch vehicle Juno II (AM-14) Mission Lunar flyby Heliocentric orbit (Solar orbit) Perihelion x Aphelion 0,987 x 1,142 A.U. Incl. to ecliptic 1,3° Excentricity 0.07109 Period (around the Sun) 398 days

Pioneer 4 - Credit: NASA.

Spacecraft data: Prime contractor  Jet Propulsion Laboratory (JPL) Operator  NASA Mass at launch 5,9 kg Dry Mass   kg Dimension 0,56 dia - 0,51 long Basic shape cone Solar array  none Stabilization  Spin stabilized DC power

Installing Pioneer IV, payload for AM-14 (Juno II) onto the fourth stage on the cluster before a spin test, February 16, 1959. The Pioneer IV, lunar and planetary exploration satellite, was the first U.S. satellite to orbit the Sun. - Credit: NASA

Description:

• Pioneer 4 was a cone-shaped probe 51 cm high and 23 cm in 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 spooled out to the end of two 150 cm wires when triggered by a hydraulic timer 10 hours after launch. The weights were designed to slow the spacecraft spin from 400 rpm to 6 rpm and then weights and wires were released.
• Scientific Instruments:
  1) photoelectric sensor trigger
  2) two Geiger-Mueller counters

Mission details:

• After a successful launch Pioneer 4 achieved its primary objective (an Earth-Moon trajectory), returned radiation data and provided a valuable tracking exercise. The probe passed within 60,000 km of the Moon's surface (7.2° E, 5.7° S) on 4 March 1959 at 22:25 UT (5:25 p.m. EST) at a speed of 7,230 km/h. The distance was not close enough to trigger the photoelectric sensor. The probe continued transmitting radiation data for 82 hours, to a distance of 658,000 km, and reached perihelion on 18 March 1959 at 01:00 UT. The cylindrical fourth stage casing (173 cm long, 15 cm diameter, 4.65 kg) went into orbit with the probe.