# EPE-D

> former American research satellite

**Wikidata**: [Q1990981](https://www.wikidata.org/wiki/Q1990981)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Explorer_26)  
**Source**: https://4ort.xyz/entity/epe-d

## Summary
EPE-D, also known as Explorer 26, was a former American research satellite launched in 1964 to study energetic particles in space. It was part of NASA's Explorers Program and operated by the Goddard Space Flight Center. The satellite re-entered Earth's atmosphere in 2021 after more than 56 years in orbit.

## Key Facts
- Launched on December 21, 1964, at 09:00:03 UTC from Cape Canaveral Space Launch Complex 17A
- Weighed 45.8 kilograms and was part of the Energetic Particles Explorer series (fourth in the series)
- Operated by NASA's Goddard Space Flight Center, established in 1959
- Used a Delta C launch vehicle (Thor 393/D-027 configuration)
- Had a COSPAR ID of 1964-086A and NSSDCA ID of 1964-086A
- Re-entered Earth's atmosphere on August 25, 2021
- Also known by aliases Explorer 26, Energetic Particles Explorer-D, and S-3C
- Preceded by Injun 4 and succeeded by Beacon Explorer C

## FAQs
### Q: What was EPE-D's primary mission?
A: EPE-D was designed to study energetic particles in space as part of NASA's Explorers Program. It was the fourth satellite in the Energetic Particles Explorer series, focusing on measuring and analyzing particle radiation in Earth's magnetosphere.

### Q: How long did EPE-D remain in orbit?
A: EPE-D remained in orbit for over 56 years, from its launch on December 21, 1964, until its atmospheric re-entry on August 25, 2021. This extended orbital lifetime demonstrates the durability of early space technology.

### Q: Who operated EPE-D and where was it controlled from?
A: EPE-D was operated by NASA's Goddard Space Flight Center, which was established in 1959 as NASA's first space flight center. The satellite was controlled from Goddard's facilities in Greenbelt, Maryland.

## Why It Matters
EPE-D represents an important chapter in the early exploration of space radiation and particle physics. As part of the Explorers Program, it contributed to our fundamental understanding of the space environment around Earth, particularly the behavior of energetic particles in the magnetosphere. This knowledge was crucial for the development of later space missions and the protection of both astronauts and spacecraft from radiation hazards. The satellite's long orbital lifetime also provided valuable data about long-term space exposure effects on spacecraft materials and systems. EPE-D's successful operation for over five decades demonstrates the engineering excellence of early space programs and their lasting impact on space science. Its data helped establish baseline measurements for space radiation that continue to inform current space exploration efforts, from satellite design to human spaceflight safety protocols.

## Notable For
- Fourth satellite in the Energetic Particles Explorer series, advancing our understanding of space radiation
- Operated for over 56 years, making it one of the longest-serving research satellites in history
- Part of NASA's Explorers Program, which has launched over 90 scientific spacecraft since 1958
- Successfully studied energetic particles in Earth's magnetosphere during the early Space Age
- Demonstrated the reliability of Delta launch vehicles for scientific missions

## Body
### Technical Specifications
EPE-D was a compact research satellite weighing 45.8 kilograms, designed specifically for studying energetic particles in space. The satellite incorporated specialized instruments to measure particle radiation and magnetic fields in Earth's magnetosphere. Its small size and focused mission profile were typical of the Explorers Program satellites, which prioritized scientific return over complex engineering.

### Launch and Operations
The satellite launched on December 21, 1964, at 09:00:03 UTC aboard a Delta C rocket from Cape Canaveral Space Launch Complex 17A. The Delta C configuration used a Thor first stage and was designated as Thor 393/D-027 for this particular launch. After reaching orbit, EPE-D was operated by the Goddard Space Flight Center, which managed the satellite's scientific operations and data collection throughout its mission lifetime.

### Mission Context
As the fourth satellite in the Energetic Particles Explorer series, EPE-D built upon the findings of its predecessors to provide more comprehensive data about space radiation. The satellite operated during a crucial period in space exploration when understanding the space environment was essential for planning future missions. Its data contributed to the growing body of knowledge about the Van Allen radiation belts and other radiation phenomena that affect spacecraft and astronauts.

### Legacy and Impact
EPE-D's mission ended with its atmospheric re-entry on August 25, 2021, but its scientific contributions continued to influence space research for decades. The satellite's long operational lifetime provided unique opportunities to study how spacecraft materials and systems degrade over extended periods in the space environment. This information proved valuable for designing more durable spacecraft and understanding the long-term effects of space exposure on orbital debris.

## Schema Markup
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  "description": "Former American research satellite launched in 1964 to study energetic particles in space",
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## References

1. [Source](http://www.astronautix.com/e/explorer.html)
2. Jonathan's Space Report
3. [Source](https://www.space-track.org/#decay)
4. [Source](https://www.n2yo.com/satellite/?s=963)
5. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-086A)