Clouds Handling for Planning of Optical Space Missions

Kurzfassung

Every space mission which uses optical band, e.g. ground-satellite/satellite-ground laser telecommunication, optical earth observation, on-ground optical space debris tracking system, is drastically affected by the clouds in the troposphere of the Earth. Mission planning group (MPS) of the German Space Operations Center (GSOC) is investigating the possibility to achieve the maximum performance of future optical space missions. Planning of an optical space mission should be fulfilled by involving the cloud coverage data. Short-term predicted future data are helpful for operational planning of an on-ground station and the relevant satellite. Long-term past data can be used to design a optimal network of on-ground stations and to assess the performance of the whole mission. Such data is distributed by DWD (Germany), ECMWF (UK), NOAA (USA), Weatheroffice (Canada) in the GRIB standard format. During the preliminary investigation data from ECMWF for the past period between 01.01.1992 and 31.12.1996 and some forecasted data for future periods from NOAA were used. Several methods of time-interpolation of the cloud coverage data were compared with and without using wind information and at least two criteria of on-ground stations network designing were applied. As a result a software tool was developed which takes GRIB files, orbit of the mission-satellite and some design restrictions as input and calculate an optimal list of on-ground stations with their coordinates and assessed performance. The performance is expressed in time during which a cloudless link can be established between an on-ground station and the satellite. The results of the work can be compared with some similar research, e.g. [1], [2]. [1] Kenta Ogawa et al., Usage of Cloud Climate Data in Operation Planning for Japanese Future Hyperspectral and Multispectral Senor: HISUI, GFZ Meeting, 23.09.2011 [2] C. Fuchs et al., Verification of Ground Station Diversity for Direct Optical TTC-downlinks from LEO Satellites by Means of an Experimental Laser-source, 5th ESA International Workshop on Tracking, Telemetry and Command Systems for Space Applications, 21 – 23 September 2010.