# Explorer 7

> 1959 research satellite

**Wikidata**: [Q2509028](https://www.wikidata.org/wiki/Q2509028)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Explorer_7)  
**Source**: https://4ort.xyz/entity/explorer-7

## Summary
Explorer 7 is a United States Earth observation satellite launched on 13 October 1959. It was a small, solar-powered low Earth orbit research satellite operated by NASA and manufactured by the Army Ballistic Missile Agency.

## Key Facts
- Explorer 7 was launched 1959-10-13 at 15:30:04 UTC from Cape Canaveral Launch Complex 5.  
- Launch vehicle: Juno II (vehicle designation AM-19A).  
- Operator: National Aeronautics and Space Administration (NASA); manufacturer and launch contractor: Army Ballistic Missile Agency (ABMA).  
- Primary classification: Earth observation satellite (artificial satellite designed to observe Earth from orbit).  
- COSPAR ID: 1959-009A; Harvard designation: 1959 Iota 1; NSSDCA ID: EXP-7X.  
- Mass: approximately 41.5 kilograms.  
- Dimensions: diameter/height approximately 76 centimetres.  
- Power: solar cells; source lists the value "3000" as an approximate qualifier (unit not specified in the provided data).  
- Orbital regime: low Earth orbit; orbital periapsis 573 km (value dated 1959-10-13), apoapsis 1073 km (value dated 1959-10-13).  
- Orbital period: 101.38 minutes (value dated 1959-10-13); orbital inclination: 50.27° (value dated 1959-10-13); orbital eccentricity: 0.034692 (value dated 1959-10-13).  
- Significant events recorded in source: rocket launch (Cape Canaveral LC-5, 1959-10-13) and loss of signal on 1961-08-24.

## FAQs
### Q: What was the mission of Explorer 7?
A: Explorer 7 was an Earth observation satellite—an artificial satellite specifically designed to observe Earth from orbit. Its classification in the source material is "Earth observation satellite."

### Q: When and how was Explorer 7 launched?
A: Explorer 7 was launched on 13 October 1959 at 15:30:04 UTC from Cape Canaveral Launch Complex 5 aboard a Juno II launch vehicle (AM-19A).

### Q: Who built and operated Explorer 7?
A: The satellite was manufactured by the Army Ballistic Missile Agency and operated by the National Aeronautics and Space Administration (NASA). ABMA is also listed as the launch contractor in the provided data.

### Q: How big and heavy was Explorer 7?
A: Explorer 7 had an approximate mass of 41.5 kg and measured about 76 cm in diameter/height.

## Why It Matters
Explorer 7 represents an example of early, purpose-built Earth observation spacecraft. As a compact, solar-powered satellite launched in 1959 and operated by NASA, it illustrates the use of small satellites placed into low Earth orbit to carry instruments intended to observe the planet. The satellite’s design and deployment by the Army Ballistic Missile Agency for NASA demonstrate collaboration between U.S. military and civilian organizations in early space research and operations. Its measured orbital parameters—periapsis, apoapsis, inclination, period, and eccentricity—place it squarely in low Earth orbit, the regime commonly used for Earth observation because of closer proximity to the surface. The recorded loss of signal on 24 August 1961 marks the operational endpoint recorded in the source. For historical and technical reference, Explorer 7’s identifiers (COSPAR, Harvard designation, NSSDCA ID) and catalog numbers make it a traceable object in satellite records and archives.

## Notable For
- Being classified specifically as an Earth observation satellite launched in 1959.  
- Launch on a Juno II (AM-19A) from Cape Canaveral Launch Complex 5 on 13 October 1959.  
- Compact mass and form factor: approximately 41.5 kg and ~76 cm in diameter/height.  
- Manufactured and launched under the Army Ballistic Missile Agency and operated by NASA.  
- Documented orbital parameters in low Earth orbit (periapsis 573 km, apoapsis 1073 km, inclination 50.27°, period 101.38 minutes).

## Body
### Overview
- Name: Explorer 7 (also referenced as NASA S-1a; S-1a; Explorer 7x; S-1 (Explorer); S1-a).  
- Country of origin / country: United States.  
- Instance of: Earth observation satellite.  
- Parent astronomical body: Earth.  
- Satellite catalog number (scn): 00022.  
- Wikimedia Commons category: Explorer 7; image available: https://commons.wikimedia.org/wiki/Special:FilePath/Installing_Explorer_VII.jpg.

### Design and specifications
- Mass: 41.5 kg (approximately).  
- Diameter / height: ~76 cm (approximately).  
- Power: solar cells. The source lists a qualifier value of "3000" as approximate (unit not specified in the provided data).

### Launch and orbit
- Launch date and time: 1959-10-13 at 15:30:04 UTC.  
- Launch site / start point: Cape Canaveral Launch Complex 5.  
- Launch vehicle: Juno II, vehicle designation AM-19A.  
- Orbital regime: low Earth orbit.  
- Orbital parameters (values dated 1959-10-13):  
  - Periapsis: 573 km.  
  - Apoapsis: 1073 km.  
  - Orbital period: 101.38 minutes.  
  - Orbital inclination: 50.27°.  
  - Orbital eccentricity: 0.034692.

### Operations and mission timeline
- Operator: National Aeronautics and Space Administration (NASA).  
- Manufacturer: Army Ballistic Missile Agency (ABMA).  
- Launch contractor: Army Ballistic Missile Agency (as listed).  
- Significant recorded events: launch on 1959-10-13 from Cape Canaveral LC-5; loss of signal recorded on 1961-08-24.

### Identifiers and cataloging
- COSPAR ID: 1959-009A.  
- Harvard designation: 1959 Iota 1.  
- NSSDCA ID: EXP-7X.  
- Freebase ID: /m/04pz0v.  
- Wolfram Language entity code: Entity["Satellite","00022"].

### References and provenance (as listed in source data)
- Trajectory and orbital data referenced to NASA NSSDCA trajectory pages (1959-009A).  
- Spacecraft and mission details referenced to NASA NSSDCA spacecraft pages and space.skyrocket.de documentation.  
- Manufacturer and contractor information referenced to Air and Space Museum collection and related ABMA/NASA documents.

## References

1. [Source](https://space.skyrocket.de/doc_sdat/explorer_s1.htm)
2. [Source](https://airandspace.si.edu/collection-objects/satellite-explorer-7-replica/nasm_A19761109000)
3. Jonathan's Space Report
4. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1959-009A)
5. Freebase Data Dumps. 2013
6. [Source](https://www.nasa.gov/wp-content/uploads/2018/01/explorer_i_boehm_document.pdf)
7. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1959-009A)