|Launch Date||March 3, 1959 | 05:10:45 UT|
|Launch Site||Cape Canaveral, Florida, USA | Launch Complex 5|
|Alternate Names||00113, 1959-013A|
Photograph the Moon during a flyby. It also carried sensors to study radiation in space.
A navigation malfunction send the spacecraft flying past the Moon at twice the planned distance and its camera sensor was not triggered. It did send back 82 hours of valuable scientific data on radiation in space.
Although it did not achieve its primary objective to photograph the Moon during a flyby, Pioneer 4 was the first U.S. spacecraft to reach escape velocity.
During the launch, the Sergeants of the second stage did not cut off on time and caused the azimuths and elevation angles of the trajectory to change. The spacecraft thus passed by the Moon at a range of 37,000 miles (59,545 kilometers (instead of the planned 20,000 miles, or 32,000 kilometers) not close enough for the imaging scanner to function.
The closest approach was at 10:25 UT on 4 March 1959.
The spacecraft's tiny radio transmitted information for 82 hours before contact was lost at a distance of 655,000 kilometers from Earth, the greatest tracking distance for a human-made object at the time. The probe eventually entered heliocentric orbit and became the first American spacecraft to do so. Scientists received excellent data on radiation in space.
Mar. 4, 1959: Lunar Flyby
Launch Vehicle: Juno II (no. AM-14)
Spacecraft Mass: 14 pounds (6.1 kilograms)
- photoelectric sensor trigger
- two Geiger-Mueller counters
Siddiqi, Asif A. Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, NASA, 2002.