IMD operates a network of hundreds of surface and glacial observatories, Upper Air (high altitude) stations, ozone and radiation observatories and meteorological radar stations. Additional data is received from India's constellation of satellites, such as Kalpana-1, Megha-Tropiques and instruments on board the IRS series and the INSAT series of satellites. Data and observations are also reported into the IMD network from meteorological instruments on board Indian merchant marine and Indian Navy ships. IMD was the first organisation in India to deploy a message switching computer for supporting its global data exchange.