GeoSTAR: A New Payload for GOES-R

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new concept for a microwave sounder, intended to be deployed on NOAA's next generation of geostationary weather satellites, GOES-R – due to first launch in 2012. This will fill a serious gap in our remote sensing capabilities of long standing – a key capability that NOAA is book keeping at the top of its list of “pre-planned product improvements” for GOES-R – i.e. the most urgently needed additional payload, which will be added as soon as funding has been allocated and programmatic issues resolved. Although real-aperture GEO microwave sounders have been proposed over the years, only GeoSTAR is capable of meeting the measurement requirements and is therefore now the leading candidate. A ground based prototype has been developed at the Jet Propulsion Laboratory, under NASA Instrument Incubator Program sponsorship, and is currently undergoing tests and performance characterization. Initial tests have been very successful, and images of the sun transiting through the field of view – the first successful imaging using a 2D aperture synthesis system and in effect constituting proof of concept – demonstrate that the system is very stable and that aperture synthesis is a feasible approach. The initial space version of GeoSTAR will have performance characteristics similar to those of microwave sounders currently operating on polar orbiting environmental satellites, but subsequent versions will significantly outperform those systems. In addition to all-weather temperature and humidity soundings, GeoSTAR will provide continuous rain mapping, tropospheric wind profiling and real time storm tracking. With the aperture synthesis approach used by GeoSTAR it is possible to achieve very high spatial resolutions without having to deploy the impractically large parabolic reflector antenna that is required with the conventional approach. GeoSTAR therefore offers both a feasible way of getting a microwave sounder with adequate spatial resolution in GEO as well as a clear upgrade path to meet future requirements. GeoSTAR offers a number of other advantages relative to real-aperture systems as well, such as 2D spatial coverage without mechanical scanning, system robustness and fault tolerance, operational flexibility, high quality beam formation, and open ended performance expandability. The technology and system design required for GeoSTAR are rapidly maturing, and it is expected that a space demonstration mission can be developed before the first GOES-R launch. GeoSTAR will be ready for operational deployment 2-3 years after that. Although the GeoSTAR team has been closely collaborating with the NOAA Office of System Development, which is responsible for overseeing the development of GOES-R, there are programmatic barriers that make it difficult for NOAA to develop new-technology payloads. Traditionally this has been the role of NASA, and both organizations are working on finding ways to implement this “research to operations” model without negatively impacting their other objectives. GeoSTAR is a good candidate for this model, and it is expected to go forward as a space mission within the next decade.