# GFO

> decommissioned American military altimetry satellite

**Wikidata**: [Q1509570](https://www.wikidata.org/wiki/Q1509570)  
**Source**: https://4ort.xyz/entity/gfo

## Summary
GFO (Geosat Follow-On) was a decommissioned American military altimetry satellite launched in 1998 to measure ocean surface topography for military and scientific research. Operated by the 10th Space Operations Squadron, it provided critical data for oceanography and geophysics until its decommissioning in 2008.

## Key Facts
- **Launch Date**: February 10, 1998, at 13:20 UTC from Vandenberg Launch Complex 576 E.
- **Operator**: 10th Space Operations Squadron (U.S. military).
- **Primary Mission**: Radar altimetry and microwave radiometry for oceanographic and geophysical studies.
- **Cost**: $46 million (1992 dollars) for construction.
- **Service Life**: Designed for 5 years, operational for 10.8 years until retirement on November 26, 2008.
- **Launch Vehicle**: Minotaur-C (T2 configuration).
- **Orbit**: Low Earth orbit.
- **Mass**: 410 kg at launch.
- **Power**: 126-watt spacecraft solar array.

## FAQs
### Q: What was the main purpose of the GFO satellite?
A: GFO conducted radar altimetry and microwave radiometry to map ocean surface topography, supporting military operations and scientific research in oceanography and geophysics.

### Q: How long did GFO operate compared to its designed lifespan?
A: GFO was designed for 5 years but operated for 10.8 years, more than doubling its expected service life.

### Q: Who manufactured GFO and its key instruments?
A: The satellite was built by Ball Aerospace & Technologies, with the radar altimeter provided by Raytheon and the microwave radiometer by AIL Systems Inc.

## Why It Matters
GFO played a significant role in advancing oceanographic and geophysical research by providing high-resolution altimetry data. Its extended operational lifespan demonstrated the reliability of its design, and its instruments contributed to understanding ocean currents, gravity fields, and sea-level changes. As a military asset, it supported strategic operations while also serving scientific communities, bridging military and civilian applications. Its decommissioning marked the end of a critical data source, prompting reliance on subsequent satellite missions like Jason-1 and Jason-2.

## Notable For
- **Dual Military-Scientific Role**: Served both U.S. Navy operational needs and civilian scientific research.
- **Extended Mission**: Operated for over a decade despite a 5-year design life.
- **Instrument Suite**: Carried advanced radar altimeters and microwave radiometers for precise ocean surface measurements.
- **Launch Vehicle**: Utilized the Minotaur-C rocket, a solid-fuel launch vehicle derived from intercontinental ballistic missile technology.

## Body
### Mission Overview
GFO was part of the Geosat Follow-On program, succeeding the 1985 Geosat mission. Its primary objective was to collect altimetry data for military applications, such as submarine navigation and oceanographic forecasting, while also contributing to civilian research on ocean dynamics and climate science.

### Technical Specifications
- **Spacecraft Bus**: BCP-600 platform.
- **Instruments**: 
  - Radar altimeter (Raytheon).
  - Microwave radiometer (AIL Systems Inc).
- **Power**: 126-watt solar arrays.
- **Mass**: 410 kg at launch.

### Launch and Operation
- **Launch Vehicle**: Minotaur-C (T2 configuration), a four-stage solid-fuel rocket.
- **Launch Site**: Vandenberg Air Force Base, Complex 576 E.
- **Orbit**: Low Earth orbit with a focus on ocean surface mapping.
- **Design Life**: 5 years (exceeded by 10.8 years of actual service).

### Decommissioning
GFO was decommissioned on November 26, 2008, at 00:18:40 UTC after transmitting data for over a decade. Its retirement was announced by the 10th Space Operations Squadron, concluding a mission that provided continuous oceanographic data since 1998.

### Legacy
GFO’s data supported studies on ocean currents, tides, and geoid modeling, contributing to both military operations and scientific publications. Its extended service life underscored the robustness of its design, and its mission laid groundwork for future altimetry satellites like Jason-1 and the Ocean Surface Topography Mission.

## References

1. [Source](https://space.skyrocket.de/doc_sdat/gfo.htm)
2. [Source](http://www.brookskushman.com/LinkClick.aspx?fileticket=GerNvF0FWFM%3d&tabid=95)
3. Jonathan's Space Report