The Ariane Passenger Payload Experiment (APPLE) was ISRO’s first indigenous, experimental communication satellite. It was launched into GTO (Geosynchronous Transfer Orbit) by the third development flight of ESA’a Ariane vehicle from Kourou on June 19, 1981.
Ariane Passenger PayLoad Experiment, APPLE was an experimental communication satellite successfully launched by Ariane-1, from Kourou, French Guiana on June 19, 1981, exactly 35 years back, marking an important milestone in India’s space programme. APPLE was designed and built as a sandwich passenger-carrying Meteosat on top and CAT (Capsule Ariane Technologique) module below. It was boosted into Geo-Synchronous Orbit (GSO) by ISRO’s own apogee motor derived from the fourth stage motor of the SLV-3. APPLE spacecraft was designed and built in just two years with limited infrastructure in industrial sheds. It gave ISRO valuable hands-on experience in designing and developing three-axis stabilized geostationary communication satellites as well as in orbit raising manoeuvres, in orbit deployment of appendages, station keeping, etc.APPLE was used in several communication experiments including relay of TV programmes, and radio networking.
It was used to carry out extensive experiments on time, frequency and code division multiple access systems, radio-networking computer interconnect, random access and pockets switching experiments. It also provided an opportunity to introduce state-of-the-art technologies of the day, such as momentum biased three-axis stabilization techniques, motor driven deployed solar array, earth sensing for attitude control, C-band transponder design, inclusive of composite reflector, orbit raising, station acquisition, station-keeping and a host of mission management and flight dynamic techniques.
APPLE was dedicated to the Nation on August 13, 1981 by then Prime Minister Mrs.Indira Gandhi. The Prime Minister symbolically handed over the model of APPLE to the Minister for Communications and said that APPLE marked the ‘Dawn of India’s satellite communication era’.The Prime Minister’s address to the Nation on August 15 from the Red Fort was carried live by APPLE.A commemorative stamp was released by Indian Posts and Telegraphs Department on the first anniversary of the launching of APPLE satellite on June 19, 1982. APPLE has enabled experimentation in the advanced communications technology and has established expertise in the design; fabrication, launch and complicated post launch mission manoevres for placing and maintaining such a satellite in the geo-stationary orbit.APPLE was used for nearly two years (deactivated on September 19, 1983) to carry out extensive experiments. Though it carried only a single C-band transponder, APPLE yielded rich dividends in technology development and operational experience in communication satellites, thus laying the foundation for the INSAT system.