Ranger 4

NSSDC ID: 1962-012A

Description:
Ranger 4 was designed to transmit pictures of the lunar surface to
Earth stations during a period of 10 minutes of flight prior to
impacting on the Moon, to rough-land a seismometer capsule on
the Moon, to collect gamma-ray data in flight, to study radar
reflectivity of the lunar surface, and to continue testing of the
Ranger program for development of lunar and interplanetary space-
craft. An onboard computer failure caused failure of the deploy-
ment of the solar panels and navigation systems, the spacecraft
impacted on the far side of the Moon without returning any
scientific data. 

Ranger 4 was a Block II Ranger spacecraft virtually identical to
Ranger 3. The basic vehicle was 3.1 m high and consisted of a
lunar capsule covered with a balsawood impact-limiter, 65 cm in
diameter, a mono-propellant mid-course motor, a 5080-pound
thrust retrorocket, and a gold- and chrome-plated hexagonal base
1.5 m in diameter. A large high-gain dish antenna was attached
to the base. Two wing-like solar panels (5.2 m across) were
attached to the base and deployed early in the flight. Power was
generated by 8680 solar cells contained in the solar panels
which charged a 11.5 kg 1000 W-hour capacity AgZn launching
and backup battery. Spacecraft control was provided by a solid-
state computer and sequencer and an earth-controlled
command system. Attitude control was provided by Sun and
Earth sensors, gyroscopes, and pitch and roll jets. The tele-
metry system aboard the spacecraft consisted of two 960 MHz