The potential for `store-and-forward´ communications using small satellites in low Earth orbits

The UoSAT Spacecraft Engineering group at the University of Surrey has investigated the use of low Earth orbits for electronic mail or `store and forward´ systems. the launch of UoSAT-2 in 1984 as an auxiliary payload alongside LANDSAT-5 pioneered the use of electronic mail via low Earth orbit. The experience gained in experimenting with UoSAT-2, still operational in 1993, has led to a new generation of operational store and forward transponders. The first operational network Health Net, operated by SateLife (a US medical aid agency) has been established using the store and forward transponder on UoSAT-3 alongside its sister network operated by Volunteers in Technical Assistance (VITA,USA). The HealthNet network ties together medical centres and schools within rural and developing areas with those in developed areas. The store and forward system provides for the exchange of messages and files containing a range of medical information allowing health workers more immediate access and the ability to request recent information. The UoSAT networks show that a complementary role can be played by cost effective microsatellites in low Earth orbit carrying digital store and forward transponders. The users of these systems have a requirement for regular low volume data transfer which cannot be satisfied by the use of conventional satellite links and for which terrestrial links are unavailable