The GEOSAT Follow-On satellite altimeter sponsored by the Oceanographer of the Navy was launched 10 February 1998. Several difficult problems including confounding interactions between CPU and compiler versions prevented the satellite from running consistently until they were overcome through the intense work and dedication of NAVSOC (The Naval Space Operational Command), the Cal/Val team, Ball Aerospace (the prime contractor for the spacecraft) , in addition to researchers in academia and government laboratories such as the NOAA Laboratory for Satellite Altimetry.
The GPS receivers onboard never achieved operational use. Fortunately, NASA had provided a laser retro-reflector for the satellite prior to launch and the International Laser Ranging Service (ILRS) provided tracking from its global network of laser ranging stations to support the project. Thus high accuracy orbits were provided for the satellite in addition to the orbit solutions based on the on-board Doppler beacon. (For additional details on ILRS, go to http://ilrs.gsfc.nasa.gov.) Precise time was provided by synchronizing the drift of the on-board Ultra-Stable Oscillator to NAVSOC ground systems.
GFO was accepted by the Navy in 2000. NAVSOC ran the spacecraft during its lifetime, and the data was processed daily at the Naval Oceanographic Office.
In summary, there were several critical failures that would have ended the mission before useful data were provided if not for the passion and dedication of many individuals and organizations that turned the mission into a success.
Through the years, GFO performed extremely well thanks to the continued dedication of the people noted above. The data provided by GFO has been used by operational centers to assimilate into numerical prediction systems that in both research and operational modes provided critical information such as currents and ocean environment structure during many incidents throughout the globe. The data flow was a necessary contributor to moving ocean forecasting from the point of a theoretical possibility on which we could conjecture to a solid demonstration of the feasibility and what the capability can provide and to the point of implementation into operational forecast centers. It has proved a great success especially since the entire mission was accomplished on a total budget of $85M. The continued monitoring and careful guidance from NAVSOC, the Cal/Val team, and Ball Aerospace engineers allowed the satellite to outlive its original predicted life of 8 years. Degradation of battery capability and attitude control sensitivity to heat excursions brought the satellite system to the point where it was no longer maintainable. The decision was made to de-orbit the satellite at the end of 2008. All those who contributed can be proud of what they have achieved.
In memoriam, we would also like to remember the contributions of two individuals who helped make the mission successful: Jimmy Mitchell and Vince Noble -- they are no longer with us, but their names are inscribed on a plaque on the satellite.
Many of us will keep a little space in our hearts and a little space on our disk drives for the GFO data from "the little satellite that could".
Added Note: For those who are not part of DoD: All GFO altimetry data was authorized for unconditional (and unclassified) release by SPAWAR. Hence all GFO data (SDRs, GDRs and raw data over some ice areas) was forwarded to NOAA (and NASA) for distribution and use by the civilian community. NOAA used the SDRs along with the Medium Laser orbit data from NASA to produce an independent set of GDRs known as the IGDRs. For non-DoD users, NOAA is the formal point of contact for data dissemination. If you are not part of DoD and wish access to GFO data, please contact John Lillibridge.
Future Plans -- the Space and Naval Warfare Systems Command in San Diego intends to launch a new version of this satellite to be known as GFO-2. It is expected to be available in 2013.
For reference, the nominal GFO satellite ERO orbit parameters are:
| Semi Major Axis |
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| Eccentricity |
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| Inclination |
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| Argument of Perigee |
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