Pioneer 4

Pioneer 4 was a spacecraft of the U.S. Space Agency NASA as part of the Pioneer program. Pioneer 4 should fly past the moon and thereby transmit pictures of the lunar surface.

Construction

Pioneer 4 consisted of a conical fiberglass structure of 51 cm height and 23 cm in diameter, the tip of which was formed as an antenna, it was slightly smaller than its predecessor. The outside was gold coated in order to render them electrically conductive, and is provided for thermal control with white stripes. The probe was supplied by mercury batteries and wore a transmitter with a power of 0.18 W at 960.05 MHz. To reduce the spin rate of 400 rpm on 6/min two ejectable mass of 7 g each ( " yo-yo masses " ) were attached on the outside.

Mission

Pioneer 4 was launched on March 3, 1959 at 17:11 UTC by means of a four-stage Juno II rocket. The probe should pass the moon and go into a heliocentric orbit. It reached a course to the moon and delivered the desired radiation readings, the approach to the moon of about 60,000 km but not enough to trigger the camera. The probe worked 82.5 hours up to a distance of 658 000 km. It has since been held as well as the fourth stage of the Juno II on a sun orbit with a slightly higher circulation time than the Earth.