Optical Satellite Downlinks to Optical Ground Stations and High-Altitude Platforms

Abstract

We have calculated the practical advantage of optical downlinks from earth observation (EO) satellites over conventional RF-downlinks in different downlink scenarios, taking into account blockage by cloud cover. The usability of the EO-sensor could be boosted by nearly a factor of forty with a future StORe-System (HAP-Relays) or by a factor four with simple direct downlinks to optical ground stations without RF-backup (and an OGS in a non-optimum location). This performance is offered by low-power transmit terminals with very small apertures in the range of few centimeters and according low mass. It seems favorable to establish a global OGS-network (and later a StORe-Network) based on compatible technology for downlinks from LEO as well as GEO and later possibly for links from deep-space probes.