In January 1998, Boeing Satellite Systems (BSS) of El Segundo, CA, working with NASA and NOAA, began development of a unique spacecraft bus design concept for the next-generation Geostationary Operational Environmental Satellites, GOES-N, GOES-O, and GOES-P. The goal of this new design was to substantially improve the quality of NOAA’s GOES weather data. The key features of this design concept included a stellar inertial attitude determination (SIAD) control system which is integrated directly with the imager and sounder on a precision optical bench to have the bus design focus on ‘flying the instruments’ for the next-generations of GOES.

The first of the next generation GOES satellites is planned to be launched in late 2004. This new GOES N-P design enables the precision spacecraft performance that will be support high-resolution ITT instruments. The goal of the GOES program’s design features was to improve the spacecraft performance using SIAD to: · Enhanced instrument accommodation · Significantly improved image navigation and registration (INR) performance · Provide extensive on-board autonomy for reduced ground interaction · Provide ability for the instruments to perform service quickly after orbit control operations (after a 10 minute housekeeping period) · Maintain continuous environmental and storm warning systems with an enhanced ground resolution (1.5 km ground resolution at nadir) and to monitor the Earth’s surface and space environmental conditions.

The BSS developed SIAD system uses star measurements provided by star trackers (3-for-2 redundancies), spacecraft rates measured by Hemispheric Inertia Reference Unit (HIRU), and a 6-states Kalman filter implemented in the spacecraft control processor to determine spacecraft 3-axis attitude. It has the advantage providing never before achieved 10 microradian bus pointing, that is two orders of magnitude improvement in accuracy over existing earth/sun sensor-based attitude determination systems.

This control system has sufficient control authority and precision to allow a single solar array spacecraft configuration, thereby providing a clear field of view for the Imager and Sounder instrument coolers.

The main benefits of improved GOES N-P spacecraft performance include improvements in the ability to detect and locate weather events including flash flood situations, typhoon tracking, valley fog, and hazards to aviation. The present capabilities are not sufficient to distinguish between adjacent valleys in rough terrain, or meet the FAA goals for aircraft safety. The additional objectives of enhanced spacecraft performance includes’ improving weather and flood forecasts. NWS goals for flash floods anticipate improvement with GOES N-P to 60 minutes lead-time with false alarm rates improved. NWS goals for severe storms anticipate improvement with GOES N-P to 20 - 25 minutes lead-time. False alarm rates will improve. Improved air traffic control, separating aircraft from weather thunderstorms and rain cells will also be achieved.