BENGALURU: The Indian Space Research Organisation ( Isro ) has witnessed a gradual increase in its revenues even as earnings from satellite launches — an important feather on any space agency’s cap — remain low.In the past three years — April 2015 to March 2018 — the space agency, through its commercial arm Antrix Corporation Limited, has earned Rs 5,600 crore from marketing products and services, including launching of satellites for customers, predominantly from other countries. Of this, Rs 1,932 crore was earned in 2017-18, which was marginally more than Rs 1,872 crore in 2016-17.During the same time frame, Isro spent Rs 7,209 crore on various missions in the areas of space transportation systems, earth observation, satellite communication and navigation, space science and planetary exploration.“The revenue we earn through foreign satellite launches is only 10% to 20% on average, while more than 75% of our revenue comes from satellite communication business. The remaining comes from other services, with transponder leasing and revenue coming from ground station services abroad,” Antrix chairman and managing director S Rakesh told TOI.Isro presently has 84 major clients using its communication services, including big service providers like Reliance and television groups like Sun Network. And, in the said period, Isro launched 99 satellites — 69 of which were foreign satellites — including several student and university satellites.But since Isro’s primary responsibility is to meet national demand and given its heavy dependence on the PSLV class of launch vehicles, all the commercial launches have been micro and nano satellites sharing space with the main Indian satellite.“We are looking to increase dedicated commercial (where the main and only payload will be a client’s) launches, but that’s based on the availability of launch vehicles after internal needs are met,” Rakesh said.A senior Isro official said that the immediate challenge the agency faces in letting Antrix market dedicated launches is the low frequency of launches. “If we want to earn more from such launches we need to be able to build more rockets more quickly and have at least 18 launches a year, for this we are also looking to the industry,” the official said.In September this year, Isro’s PSLV will exclusively launch two UK earth observation satellites weighing 450 kg each. Although Isro does not reveal the cost of the deal, the cost of each PSLV launch is pegged at Rs 350 crore.Isro chairman Sivan K told TOI: "As and when there's demand we can surely make PSLV available for Antrix, but the GSLV class of vehicles will be difficult, given that we still have a lot of things to deal with."