Explorer 1
Explorer 1 was the first satellite launched by the United States in 1958 and was part of the U.S. participation in the International Geophysical Year (IGY). The mission followed the first two satellites the previous year; the Soviet Union's Sputnik 1 and Sputnik 2, beginning the Cold War Space Race between the two nations.
Explorer 1 in its orbital configuration, with the launch vehicle's fourth stage attached | |
| Names | Explorer I 1958 Alpha 1 |
|---|---|
| Mission type | Earth science |
| Operator | JPL / Army Ballistic Missile Agency |
| Harvard designation | 1958 Alpha 1 |
| COSPAR ID | 1958-001A |
| SATCAT no. | 00004 |
| Mission duration | 120 days (planned) 111 days (achieved) |
| Spacecraft properties | |
| Spacecraft | Explorer I |
| Spacecraft type | Science Explorer |
| Bus | Explorer 1 |
| Manufacturer | Jet Propulsion Laboratory |
| Launch mass | 13.97 kg (30.8 lb) |
| Dimensions | 203 cm (80 in) length 15.2 cm (6.0 in) diameter |
| Power | 60 watts |
| Start of mission | |
| Launch date | 1 February 1958, 03:47:56 GMT |
| Rocket | Juno I (RS-29) |
| Launch site | Atlantic Missile Range, LC-26A |
| Contractor | Army Ballistic Missile Agency |
| Entered service | 1 February 1958 |
| End of mission | |
| Last contact | 23 May 1958 |
| Decay date | 31 March 1970 |
| Orbital parameters | |
| Reference system | Geocentric orbit |
| Regime | Medium Earth orbit |
| Perigee altitude | 358 km (222 mi) |
| Apogee altitude | 2,550 km (1,580 mi) |
| Inclination | 33.24° |
| Period | 114.80 minutes |
| Revolution no. | 58402 |
| Instruments | |
| Cosmic-Ray Detector Micrometeorite Detector Resistance Thermometers Satellite Drag Atmospheric Density | |
Explorer program | |
Explorer 1 was launched on 1 February 1958 at 03:47:56 GMT (or 31 January 1958 at 22:47:56 Eastern Time) atop the first Juno booster from LC-26A at the Cape Canaveral Missile Test Center of the Atlantic Missile Range (AMR), in Florida. It was the first spacecraft to detect the Van Allen radiation belt, returning data until its batteries were exhausted after nearly four months. It remained in orbit until 1970.
Explorer 1 was given Satellite Catalog Number 00004 and the Harvard designation 1958 Alpha 1, the forerunner to the modern International Designator.