Wikipedia lists both Hindi and English as the official languages of ISRO. But what language does ISRO use for radio communication? Say they launch a manned mission, which language would they use to communicate with their astronauts?
Most probably english. For technical communication, Hindi is avoided because it lacks technical words and instead borrows them from Sanskrit. Relaying highly technical information in chaste Sanskrit-derived technical language would unwieldly, so for all practical purposes - English.
Hindi may be used for colloquial conversation. Again language in India depends on the mutual comfort of persons involved, if the astronaut is from a state in the Deep South, where Hindi is usually nor spoken nor understood; conversation is probably going to be conducted in english.
India has 22+ national languages which enjoy wide patronage.
There are many other reasons beyond the availability of jargon in Hindi, that contributes to English being used close to 90% in the organisation, officially, not only for radio communication.
One of the reason being, diversity of employees ISRO recruits. There are parts of India, mostly southern and far eastern where Hindi is as rare as any other language and only common way of communication is using English. I do not have a source to cite, but major fraction or atleast a considerable number of the employees in every domain of ISRO's technical branches are from southern parts of India. Considering the ages, they belong to a time, when hindi was quite unpopular in these states. So, Centres in the South-India like VSSC ,Master Control facility , The prime-branch for design, fabrication and testing of all Indian satellites ISAC and centre for ISRO's major launches SDSC-SHAR have communication medium as English upto percentages close to 100%
Other centres, mainly around Northern side have slightly lower usage, but English still dominates officially for communication in and between centres and also for any operation including radio communication.
*Despite the fact, that Hindi has been crowned as a dominating language of use in parliamentary and other government works, it is not exactly taken into use by whole of the country equally, a result of independence given to each state to choose from one of the 22 recognized languages . This confusingly states that English, being not included in the Constitution (being of foreign origin) , is one of the official languages in India. So English might as well be called psuedo-official language of the country.