ISRO's first home-built experimental communication satellite, launched on an Ariane rocket in 1981 and used for about two years of geostationary communication tests.
No longer operational, according to the public satellite catalogue.
APPLE (Ariane Passenger Payload Experiment) was ISRO's first indigenous experimental communication satellite. For nearly two years it was used for experiments in time, frequency and code division multiple access, radio networking, computer links, random access and packet switching. It also relayed TV programmes.
APPLE weighed 670 kg at launch. Its body was a cylinder about 1.2 m wide and 1.2 m tall. Two C-band transponders were connected to a 0.9 m dish antenna, and the satellite had 210 watts of power.
It was three-axis stabilised, using momentum wheels, torquers and hydrazine thrusters. One of its solar panels failed to deploy. ISRO designed and built it in just two years, working in industrial sheds with limited facilities.
The third development flight of the European Ariane rocket carried APPLE from Kourou, French Guiana, on 19 June 1981, into a geosynchronous transfer orbit. An ISRO apogee motor, derived from the fourth stage of SLV-3, then lifted it to geosynchronous orbit at 102° E, over Indonesia.
APPLE gave ISRO hands-on experience with three-axis stabilised geostationary communication satellites. Engineers practised orbit raising, unfolding parts in space and station-keeping. It went out of service on 19 September 1983, when its attitude-control fuel ran out.