A study of the geolocation errors of the Special Sensor Microwave/Imager (SSM/I)

Geolocation errors in excess of 20-30 km have been routinely observed in SSM/I data. Potential error sources due to inaccurate spacecraft ephemeris, spacecraft predict ephemeris, and the geolocation algorithm are examined. In addition, the effects of possible misalignment of the SSM/I instrument about its spin axis or to the spacecraft and potential spacecraft attitude errors are considered. It is found that the use of accurate spacecraft ephemerides removes about half of the geolocation error. In the cases studied, the remaining error can be reduced to below 7 km by employing a fixed set of effective spacecraft attitude corrections in the geolocation algorithm; 85-GHz imagery is presented to provide a visual evaluation of the geolocation errors along with the reduction of these errors