# Lincoln Experimental Satellite 4

> former American communications satellite

**Wikidata**: [Q28697180](https://www.wikidata.org/wiki/Q28697180)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/LES-4)  
**Source**: https://4ort.xyz/entity/lincoln-experimental-satellite-4

## Summary
Lincoln Experimental Satellite 4 (LES-4) was a former American communications satellite and technology demonstration spacecraft. Launched in 1965, it was part of a series of experimental satellites developed by MIT Lincoln Laboratory for the U.S. Air Force to test advanced telecommunications technologies.

## Key Facts
- **Launch Date:** December 21, 1965, at 14:00:01 UTC from Cape Canaveral Space Launch Complex 41 ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  
- **Mass:** 52 kg (launch weight) ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  
- **Dimensions:** 63 cm height × 79 cm diameter ([Source](https://ntrs.nasa.gov/api/citations/19730022102/downloads/19730022102.pdf)).  
- **Operator:** U.S. Air Force and MIT Lincoln Laboratory ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  
- **Power Source:** Solar cells generating 40 watts ([Source](https://ntrs.nasa.gov/api/citations/19730022102/downloads/19730022102.pdf)).  
- **Orbit:** Highly elliptical orbit ([Source](https://ntrs.nasa.gov/api/citations/19730022102/downloads/19730022102.pdf)).  
- **Mission End:** Signal lost in October 1968; re-entered Earth's atmosphere on August 1, 1977 ([Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1965-108B)).  
- **Preceded by:** LES-3; **Succeeded by:** LES-5 ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  

## FAQs
### Q: What was the purpose of LES-4?  
A: LES-4 was designed to demonstrate advanced communications technologies, including secure military satellite communications, for the U.S. Air Force.  

### Q: How long did LES-4 operate?  
A: It functioned until October 1968 when contact was lost, and it re-entered Earth's atmosphere in 1977.  

### Q: What launch vehicle was used for LES-4?  
A: It was launched aboard a Titan IIIC rocket (mission designation 3C-8) ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  

## Why It Matters  
LES-4 was pivotal in advancing military satellite communications during the Cold War era. As part of the Lincoln Experimental Satellite series, it tested technologies critical for secure, high-reliability transmissions, laying groundwork for modern military and civilian satellite systems. Its highly elliptical orbit demonstrated the feasibility of unconventional orbital paths for continuous coverage. The project also showcased MIT Lincoln Laboratory's role in bridging academic research and defense applications, influencing later satellite designs and operational protocols.

## Notable For
- **Early Military Comsat:** Among the first satellites to test secure U.S. military communications.  
- **Solar Power Pioneer:** Used lightweight solar cells (40W) during an era when power efficiency was a major challenge.  
- **Orbital Innovation:** Validated highly elliptical orbits for extended communication windows.  

## Body
### Technical Specifications  
- **Manufacturer:** MIT Lincoln Laboratory ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  
- **COSPAR ID:** 1965-108B ([Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1965-108B)).  
- **NSSDCA ID:** 1965-108B.  

### Mission Timeline  
- **Launch:** December 21, 1965, alongside LES-3, OV2-3, and OSCAR 4 ([Source](https://space.skyrocket.de/doc_sdat/les-4.htm)).  
- **Operations:** Conducted experiments until signal loss in 1968.  
- **Decay:** Atmospheric re-entry on August 1, 1977 ([Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1965-108B)).  

### Legacy  
Part of the broader Lincoln Experimental Satellite series, which influenced later U.S. defense and commercial satellite programs.  

## Schema Markup
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  "@type": "Thing",
  "name": "Lincoln Experimental Satellite 4",
  "description": "Former American communications satellite and technology demonstration spacecraft.",
  "sameAs": [
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## References

1. [Source](https://space.skyrocket.de/doc_sdat/les-4.htm)
2. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1965-108B)
3. Jonathan's Space Report
4. [Source](https://ntrs.nasa.gov/api/citations/19730022102/downloads/19730022102.pdf)