Explorer 29

Explorer 29 (also called GEOS 1 or GEOS A, acronym to Geodetic Earth Orbiting Satellite) was an American satellite launched as part of the Explorers program, being the first of the two satellites GEOS. Explorer 29 was launched on 6 November 1965 from Cape Canaveral, Florida, United States, with Delta rocket.

Explorer 29

Image of Explorer 29.
Mission type	Earth science
Operator	NASA
COSPAR ID	1965-089A[1]
SATCAT no.	1726
Spacecraft properties
Manufacturer	Applied Physics Laboratory[2]
Launch mass	387 kg (853 lb)
Start of mission
Launch date	6 November 1965, 18:38:43 (1965-11-06UTC18:38:43Z) UTC[3]
Rocket	Delta-E
Launch site	Cape Canaveral LC-17B
End of mission
Last contact	17 December 1967
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Eccentricity	0.07193[1]
Perigee altitude	1,113 kilometers (692 mi)[1]
Apogee altitude	2,275 kilometers (1,414 mi)[1]
Inclination	59.4 degrees[1]
Period	120.3 minutes[1]
Epoch	6 June 1965[1]
Explorers

Explorer 29 was a gravity-gradient-stabilized, solar cell powered unit designed exclusively for geodetic studies. It was the first successful active spacecraft of the National Geodetic Satellite Program. Instrumentation included:

• Optical Beacon System
• Laser Tracking Reflector
• Radio Doppler System
• SECOR Range Transponder
• Radio Range/Rate System.

These were designed to operate simultaneously to fulfill the objectives of locating observation points (geodetic control stations) in a three-dimensional earth center-of-mass coordinate system within 10 metres (33 ft) of accuracy, of defining the structure of the earth's irregular gravitational field and refining the locations and magnitudes of the large gravity anomalies, and of comparing results of the various systems on board the spacecraft to determine the most accurate and reliable system. Acquisition and recording of data were the responsibility of the GSFC Space Tracking and Data Acquisitions Network (STADAN). Ten major observing networks were used.[1]