# TERRIERS

> NASA mission to study the ionosphere

**Wikidata**: [Q54379](https://www.wikidata.org/wiki/Q54379)  
**Source**: https://4ort.xyz/entity/terriers-q54379

## Summary
TERRIERS (Topographic Experiment using Radiative Recombinative Ionospheric EUV and Radio Sources) was a NASA mission designed to study the Earth's ionosphere. Classified as an Earth observation satellite, it was launched on May 18, 1999, using a Pegasus air-launched rocket. The mission is identified by the COSPAR ID 1999-026A.

## Key Facts
- **Full Name:** Topographic Experiment using Radiative Recombinative Ionospheric EUV and Radio Sources.
- **Mission Type:** Earth observation satellite specifically designed to observe Earth from orbit.
- **Launch Date:** May 18, 1999.
- **Launch Vehicle:** Pegasus (an air-launched rocket).
- **COSPAR ID:** 1999-026A.
- **NSSDCA ID:** 1999-026A.
- **Satellite Catalog Number (SCN):** 25735.
- **Operator:** NASA.
- **Mission Sequence:** Preceded by the Wide-Field Infrared Explorer (former NASA space observatory).
- **Official Website:** http://www.bu.edu/satellite/

## FAQs
### Q: What was the primary purpose of the TERRIERS mission?
A: TERRIERS was a NASA mission specifically developed to study the ionosphere. As an Earth observation satellite, its goal was to observe and analyze this upper layer of Earth's atmosphere.

### Q: How was TERRIERS launched into orbit?
A: The satellite was launched on May 18, 1999, using a Pegasus rocket. The Pegasus is a specialized air-launched rocket system.

### Q: What does the acronym TERRIERS stand for?
A: The acronym stands for "Topographic Experiment using Radiative Recombinative Ionospheric EUV and Radio Sources."

## Why It Matters
TERRIERS represents a specific class of scientific endeavor focused on understanding the Earth's ionosphere through targeted observation. As an Earth observation satellite, its role was to gather data on the ionospheric environment, which is critical for understanding space weather and its effects on radio communications and terrestrial systems. The mission utilized specific techniques implied by its name—employing Extreme Ultraviolet (EUV) and Radio Sources—to map and analyze ionospheric densities.

Launched in the late 1990s, TERRIERS utilized the Pegasus launch system, demonstrating the deployment of smaller, specialized payloads into orbit. It formed a part of the broader NASA Explorer program lineage, following missions like the Wide-Field Infrared Explorer. By characterizing the ionosphere, TERRIERS contributed to the foundational knowledge required for modern space-based navigation and communication infrastructure.

## Notable For
- **Specific Focus:** Being a NASA mission explicitly dedicated to the study of the ionosphere.
- **Launch Method:** Deployment via the Pegasus air-launched rocket system.
- **Classification:** Functioning as an Earth observation satellite designed for orbital observation.
- **Naming Convention:** Having a highly technical and descriptive acronym (Topographic Experiment using Radiative Recombinative Ionospheric EUV and Radio Sources).

## Body
### Mission Overview
TERRIERS was an Earth observation satellite operated by NASA. The mission's primary objective was to study the ionosphere. The satellite is technically defined as an artificial satellite specifically designed to observe Earth from orbit.

### Launch and Orbital History
The mission officially launched on May 18, 1999. It was deployed using a Pegasus launch vehicle, which is classified as an air-launched rocket (inception 1987). The launch event is recorded as a significant milestone in the mission's timeline.

### Identifiers and Classification
The satellite is tracked in space catalogs under several identifiers:
- **COSPAR ID:** 1999-026A
- **NSSDCA ID:** 1999-026A
- **Satellite Catalog Number:** 25735

### Mission Context
In the sequence of NASA exploratory missions, TERRIERS was preceded by the Wide-Field Infrared Explorer, a former NASA space observatory. TERRIERS maintains a digital presence via its archival website hosted by Boston University.

### Technical Specifications
- **Instance of:** Earth observation satellite
- **Image Resources:** Visual documentation is available via the Wikimedia Commons category "TERRIERS (spacecraft)."
- **Google Knowledge Graph ID:** /g/1215vs4x

## References

1. Jonathan's Space Report