Explorer 6

Infobox Spacecraft
Name = Explorer 6


Organization = NASA
Major_Contractors = Jet Propulsion Laboratory
Mission_Type = Earth science
Satellite_Of = Earth
Launch = August 7, 1959 at 14:23 UTC
Launch_Vehicle = Thor-DM-18 Able-3
Decay = July 1, 1961
Mission_Duration = 60 days
NSSDC_ID = 1959-004A
Webpage = [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1959-004A NASA NSSDC Master Catalog]
Mass = 64.4 kg
Semimajor_Axis = 7,870.7 km
Eccentricity = .758847
Inclination = 47°
Orbital_Period = 754 minutes
Apoapsis = 41,900 km
Periapsis = 237 km

Explorer 6 (1959-004A or S-2) was a United States satellite launched on August 7, 1959. It was a small, spheroidal satellite designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the upper atmosphere, and the flux of micrometeorites. It also tested a scanning device designed for photographing the Earth's cloud cover, and transmitted the first pictures of Earth from orbit. [cite web | url=http://www.esa.int/esaMI/Space_Year_2007/SEMP4FEVL2F_0.html | title=50 years of Earth Observation | work=2007: A Space Jubilee | publisher=European Space Agency | date=October 3 2007 | accessdate=2008-03-20] [The U.S. V-2 rocket mission #12 had taken the first images of Earth from space on October 24, 1946.]

The satellite was launched into a highly elliptical orbit with an initial local time of apogee of 2100 h. The satellite was spin-stabilized at 2.8 rps, with the direction of the spin axis having a right ascension of 217 deg and a declination of 23 deg. Four solar cell paddles mounted near its equator recharged the storage batteries while in orbit. Each experiment except the television scanner had two outputs, digital and analog. A UHF transmitter was used for the digital telemetry and the TV signal. Two VHF transmitters were used to transmit the analog signal. The VHF transmitters were operated continuously. The UHF transmitter was operated for only a few hours each day. Only three of the solar cell paddles fully erected, and this occurred during spin up rather than prior to spin up as planned. Consequently, initial operation of the payload power supply was 63% nominal, and this decreased with time. The decreased power caused a lower signal-to-noise ratio affecting most of the data, especially near apogee. One VHF transmitter failed on September 11, 1959, and the last contact with the payload was made on October 6, 1959, at which time the solar cell charging current had fallen below that required to maintain the satellite equipment.

In 1959 an anti-satellite missile test used Explorer 6 as a target. The missile successfully passed within km to mi | 6.4 | precision = 1 of the satellite. [cite web
url = http://www.astronautix.com/lvs/bolorion.htm
title = Bold Orion
accessdate = 2008-02-03
publisher = Encyclopedia Astronautica]

The satellite's orbit decayed on July 1, 1961. [cite web
url = http://usspaceobjectsregistry.state.gov/registry/dsp_DetailView.cfm?id=12
title = Details of Explorer 6 (S-2)
accessdate = 2008-02-03
publisher = U.S. Space Objects Registry] A total of 827 h of analog and 23 h of digital data was obtained.

Notes and references

See also

* Operation Argus

External links

* [http://nssdc.gsfc.nasa.gov/multi/explorer.html NASA's Explorer Missions]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650012364_1965012364.pdf Scientific findings from Explorer VI]