The Eaton Smart Transit Hotel in Terminal T3 is now operational. Read
this for a discussion on this facility. You can book a room in the domestic portion of the hotel and it can be booked for an overnight stay or in blocks of a few hours. At present the booking is done by email or calling them and not via the traditional secure web page. This may be a much better option than going to the Radisson as you don't have to leave the airport T3 terminal.
Jet Airways (9W) operates out of terminal T3.