Before India's space milestone, Isro had to put a 673kg satellite on a bullock cart

DEcades agone, Isro scientists placed the amerindic blank authority’s number one communication satellite on a bullock cart. It was steered into an open field, as an improvised solution to a problem the agency had no facility to solve at the time.The satellite’s antenna had run into trouble. Issues were detected in its Telemetry, Tracking and Control (TT&C) links, crucial for maintaining communication. But testing called for a proper antenna range, with the satellite structure placed under a thermal blanket, a kind of facility Isro did not have then. So, the scientists came up with an indigenous fix — they put the satellite on a bullock cart to ensure a non-magnetic environment and ran the test in the open.That satellite was APPLE.Forty-five years ago, on June 18, 1981, India’s space effort cleared a milestone after the experimental satellite was placed in orbit, taking the country to the doorstep of a domestic satellite communication system.The Ariane Passenger Payload Experiment (APPLE), the Indian Space Research Organisation’s first indigenous and experimental communication satellite, was launched into an elliptical orbit at about 6.20pm (IST) by the European Space Agency’s Ariane rocket from Kourou in French Guiana. The 673-kg satellite, expected to usher in radical changes in India's communication systems once manoeuvred into a geostationary position, soared into space along with the European Space Agency's weather satellite Meteosat and a technological capsule, CAT.About half an hour after blast-off, tracking stations at Sriharikota, Fiji and Kourou began receiving signals from APPLE, providing data on altitude, temperature and the functioning of its various electronic systems.The launch, however, was not without hiccups. Two successive technical snags –– first in the electrical system and then in the radar system –– delayed the take-off by more than an hour. Though the second postponement of the countdown had threatened the launch schedule, senior scientists met hurriedly and decided to go ahead with the mission. It was later revealed that the red signal, which led to the postponement, was caused by cloud cover, while all other systems were functioning normally.Also read: 15 satellites lost, but ‘KID’ made its way out: The outlier in ISRO PSLV C62 mission setbackReports from Kourou said that about 16 minutes after lift-off, the Ariane rocket placed Meteosat in orbit. Forty seconds later, APPLE separated from CAT and was injected into orbit. Scientists at Kourou burst into cheers as the 48-metre-long, three-stage Ariane disappeared into the sky and signals were received confirming the success of the launch. India's Ambassador to France, MK Rasgotra, and a team of Indian scientists led by Isro chief Satish Dhawan were present at Kourou to witness the blast-off.Subsequent reports said that all rocket and satellite systems were working normally, with both Meteosat and APPLE on track. Mission control confirmed that telecommands issued to APPLE after its first pass were successfully received by the satellite.APPLE was designed and built in just two years with limited infrastructure in industrial sheds. It was used for nearly two years to carry out extensive experiments on time, frequency and code division, multiple access systems, radio networking, computer interconnect, random access and packet-switching experiments.APPLE went out of service on September 19, 1983.It gave Isro valuable hands-on experience in designing and developing three-axis stabilised geostationary communication satellites, as well as in orbit-raising manoeuvres, in-orbit deployment of appendages, and station-keeping, among other key technologies.APPLE later led to the development of a large constellation of satellites in the INSAT and GSAT series, which went on to revolutionise the technological and economic growth of the country.