The document summarizes the history and activities of the Indian Space Research Organisation (ISRO). It discusses key ISRO missions and systems including the Indian National Satellite System (INSAT), the Indian Remote Sensing Satellite System (IRS), the Stretched Rohini Satellite Series (SROSS), the Polar Satellite Launch Vehicle (PSLV) and the Geosynchronous Satellite Launch Vehicle (GSLV). The document outlines ISRO's role in applying space technology to address national needs and its contributions to India's development.

3. Classical satellite systems base station or gateway Inter Satellite Link (ISL) Mobile User Link (MUL) Gateway Link (GWL) footprint small cells (spotbeams) User data PSTN ISDN GSM GWL MUL PSTN: Public Switched Telephone Network

9. Satellite period and orbits 10 20 30 40 x10 6 m 24 20 16 12 8 4 radius satellite period [h] velocity [ x1000 km/h] synchronous distance 35,786 km

12. Inclination inclination   satellite orbit perigee plane of satellite orbit equatorial plane

13. Elevation Elevation: angle  between center of satellite beam and surface  minimal elevation: elevation needed at least to communicate with the satellite footprint

15. Atmospheric Attenuation Example: satellite systems at 4-6 GHz elevation of the satellite 5° 10° 20° 30° 40° 50° Attenuation of the signal in % 10 20 30 40 50 rain absorption fog absorption atmospheric absorption 

17. Orbits II earth km 35768 10000 1000 LEO (Globalstar, Irdium) HEO inner and outer Van Allen belts MEO (ICO) GEO (Inmarsat) Van-Allen-Belts: ionized particles 2000 - 6000 km and 15000 - 30000 km above earth surface

25. Overview of LEO/MEO Systems