1. The problem statement, all variables and given/known data A geostationary satellite is located at 0'N 0'E (degrees), 36000 km above a spherical Earth with radius R(earth) = 6370 km. To scan the fieldof view, the satellite rotates around its own axis(oriented parallel to the Earth's rotation axis). It records one (constant latitude) scanline per rotation with the scan mirror steering the scanline in latitude with every rotation. A scan of the complete disc from North to South is allowed to take 25 min. With additional 5 min being required for returning the scan mirror back to its start position, one complete scan can be provided every 30 min. When the horizontal resolution of a single scan pixel at the subsatellite point is 7.5 x 7.5 km, what is the rotational speed required to archieve this scan cycle ? 2. Relevant equations αlat,lon = 2tan-1(Resolution/R(geo)) v = wr v = 2H/t 3. The attempt at a solution v = 2H/t = (2*7.5)/(30 min) = 0.5 km/min w = v/r = (0.5 km/min)/(36000 km) = 1.38*10^-5 rad/s Which is wrong. What is it that i dont understand here ?