Resolution Satellite Imaging Systems – an Overview, PFG 6/2005,pp

More and more high and very high resolution optical space sensors are available. Not in any case the systems are well known and the images are distributed over popular distributing channels or are accessible for any user. Several imaging satellites are announced for the near future. Not every announced satellite finally will be launched and some starts are failing. In most cases the launch has or will be postponed. In the following, mainly the characteristics of systems usable for topographic mapping are shown, limiting it to sensors with a ground sampling distance (GSD) of approximately 15m and better. Not only the GSD of the imaging system is an important value for the characteristics, also the type of imaging with a transfer delay and integration sensor (TDI) or by reducing the angular speed with a permanent rotation of the satellite during imaging is important, like the accuracy of the attitude control and determination unit. The radiometric and spectral resolution has to be taken into account. For operational use the swath width, viewing flexibility and imaging capacity has to be respected. The very high resolution optical satellites can change the view direction very fast, allowing a stereoscopic coverage within the same orbit, but this is reducing the amount of scenes which can be taken from the same orbit. On the other hand stereo combinations taken from neighboured paths are affected by changes in the object space, atmospheric conditions or different length of shadows. In the near future we will have accessible stereo systems like the existing, but restricted SPOT 5 HRS sensor, generating a stereoscopic coverage within some seconds by viewing forward and afterward in the orbit direction. Synthetic Aperture Radar (SAR) sensors with up to 1m GSD are announced for the near future, allowing an imaging independen