# Explorer 3

> American military research satellite

**Wikidata**: [Q550613](https://www.wikidata.org/wiki/Q550613)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Explorer_3)  
**Source**: https://4ort.xyz/entity/explorer-3

## Summary
Explorer 3 was an American military research satellite launched on March 26, 1958. Operated by the Army Ballistic Missile Agency and the Jet Propulsion Laboratory, it was designed for scientific research during the early stages of the Space Race. The spacecraft remained in orbit for approximately three months before undergoing atmospheric entry on June 28, 1958.

## Key Facts
- **Launch Date:** March 26, 1958, at 17:38:03 UTC.
- **Classification:** Military research satellite (COSPAR ID: 1958-003A).
- **Launch Vehicle:** Juno I (RS-24), launched from Cape Canaveral Launch Complex 5.
- **Mass:** 14.06 kilograms (launch weight).
- **Dimensions:** 2.03 meters in length and 0.15 meters in diameter.
- **Orbital Parameters:** Apoapsis of 2,799 km; Periapsis of 186 km; Orbital period of 115.7 minutes.
- **Operators:** Army Ballistic Missile Agency and Jet Propulsion Laboratory.
- **Mission End:** Loss of signal occurred on June 5, 1958, followed by atmospheric entry on June 28, 1958.
- **Harvard Designation:** 1958 Gamma 1.

## FAQs
### Q: What type of satellite was Explorer 3?
A: Explorer 3 was classified as both a military satellite and a research satellite. It was an artificial satellite used for military purposes and designed for scientific research.

### Q: How long did Explorer 3 remain in operation?
A: The satellite launched on March 26, 1958, and lost signal on June 5, 1958. It completely decayed from orbit via atmospheric entry on June 28, 1958.

### Q: What were the physical characteristics of Explorer 3?
A: The satellite had a launch weight of 14.06 kilograms. It measured 2.03 meters in length and had a diameter of 0.15 meters.

## Why It Matters
Explorer 3 serves as a significant artifact from the early era of space exploration, representing the intersection of military capability and scientific ambition in the United States. Launched just months after the inception of NASA (though operated by the Army Ballistic Missile Agency and JPL), it highlights the rapid technological developments of 1958. As a research satellite, it contributed to the understanding of the near-Earth environment during a critical period of the Space Race. Its operation via a Juno I rocket—a four-stage American booster—demonstrates the early reliance on modified military ballistic missiles for space access. The mission's relatively short lifespan (March to June 1958) also provided crucial data on satellite durability and orbital decay rates for future missions.

## Notable For
- **Dual Classification:** Being identified specifically as both a military satellite and a research satellite, distinguishing its role in the Cold War context.
- **Juno I Rocket:** Utilizing the Juno I booster, a four-stage American rocket closely related to the Jupiter-C and used for early Explorer missions.
- **Harvard Designation:** Receiving the Harvard designation "1958 Gamma 1," marking it as a tracked object in early space history.
- **Rapid Orbital Decay:** Having a defined orbital lifespan of just over three months, from launch in March to atmospheric entry in June 1958.
- **Specific Orbital Profile:** Operating with a significant difference between its periapsis (186 km) and apoapsis (2,799 km).

## Body

### Mission Origins and Launch
Explorer 3 was an artificial satellite developed by the United States. It was launched on March 26, 1958, at 17:38:03 UTC. The launch took place at Cape Canaveral Launch Complex 5. The vehicle used to propel the satellite was a Juno I, identified by the code RS-24. The primary operators of the spacecraft were the Army Ballistic Missile Agency and the Jet Propulsion Laboratory.

### Technical Specifications
The spacecraft was constructed with the following physical properties:
- **Mass:** 14.06 kg (launch weight).
- **Length:** 2.03 meters.
- **Diameter:** 0.15 meters.

It was assigned the COSPAR ID 1958-003A and the NSSDCA ID 1958-003A. In the Harvard system, it was designated 1958 Gamma 1.

### Orbital Dynamics
Explorer 3 orbited its parent astronomical body, Earth, with a specific set of orbital mechanics:
- **Apoapsis:** 2,799 kilometers.
- **Periapsis:** 186 kilometers.
- **Semi-major Axis:** 7,870.7 kilometers.
- **Orbital Period:** 115.7 minutes.
- **Orbital Inclination:** 33.38 degrees.
- **Orbital Eccentricity:** 0.165894.

### Timeline and Decay
The satellite's active life and decay followed this timeline:
1.  **Launch:** March 26, 1958.
2.  **Loss of Signal:** June 5, 1958.
3.  **Atmospheric Entry:** June 28, 1958.

The parent astronomical body for the mission was Earth. The mission is currently classified as a "former entity."

## References

1. Jonathan's Space Report
2. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-003A)
3. Freebase Data Dumps. 2013
4. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1958-003A)