SOLRAD 4

SOLRAD 4
SOLRAD 4 satellite
NamesGRAB 3
SOLar RADiation 4
SR 4
GREB 3
Mission typeSolar X-Rays
OperatorUnited States Naval Research Laboratory (USNRL)
COSPAR ID1962-F02 (SR4GREB)
Mission durationFailed to orbit
Spacecraft properties
Spacecraft typeSOLRAD
ManufacturerNaval Research Laboratory (NRL)
Launch mass25 kg (55 lb)
Dimensions51 cm (20 in)
Start of mission
Launch date24 January 1962, 09:30 GMT
RocketThor-Ablestar
Launch siteCape Canaveral, LC-17B
ContractorDouglas Aircraft Company
End of mission
Decay dateFailed to orbit
Orbital parameters
Reference systemGeocentric orbit (planned)
RegimeLow Earth orbit
Perigee altitude930 km
Apogee altitude930 km
Inclination66.80°
Period103.00 minutes

SOLRAD (SOLar RADiation) 4 was a solar X-rays, ultraviolet, and electronic surveillance satellite. Developed by the United States Navy's United States Naval Research Laboratory (USNRL), it was the fourth in both the SOLRAD and the GRAB (Galactic Radiation and Background) programs.

The satellite was to be orbited along with ionospheric study satellite LOFTI-2, the United States Army's range calibration satellite SECOR, Navy surveillance calibration satellite Surcal, and the University of Iowa's Van Allen radiation belts-studying Injun 2 satellite. This unprecedented five-in-one mission, called "Composite 1" and "Buckshot", ended in failure on 24 January 1962 after its Thor-Ablestar's second stage failed to deliver the payloads to orbit.