48-hr countdown begins for launch of IRNSS-1ESriharikota, Jan 18(AZINS) A 48-hour countdown began today for the launch of the fifth satellite of Indian Regional Navigation Satellite System 'IRNSS-1E' on board PSLV-C31 from the spaceport of Sriharikota on January 20.

"The 48-hour countdown activity of PSLV-C31/IRNSS-1E Mission has started at 09.31 hours today," India Space Research Organisation (ISRO) said. ISRO has scheduled the launch of 'IRNSS-1E', from Sriharikota, about 100 kms from here, on January 20 at 9.31 am.

IRNSS-1E, the fifth navigation satellite in the IRNSS space segment, carries two types of payloads navigation and ranging payload. The navigation payload will transmit navigation service signals to the users and operating in L5-band and S-band while the other consists of a C-band transponder that facilitates accurate determination of the range of the satellite.

IRNSS-1E which has a lift off mass of 1,425 kg, also carries Corner Cube Retro Reflectors for laser ranging and a highly accurate Rubidium atomic clock (also part of the navigation payload of the satellite). IRNSS-1E has configuration similar to that of its predecessors IRNSS-1A, 1B, 1C and 1D in which ISRO used the XL version of the rocket.

The constellation of seven satellites was planned by ISRO to constitute IRNSS, which would be at par with US-based GPS once the full complement of spacecraft are launched. While four satellites would be sufficient to start operations of the IRNSS system, the remaining three would make it more accurate and efficient.

ISRO had launched IRNSS-1A on July 1, 2013, while IRNSS-1B was launched on April 4, 2014. IRNSS-1C was launched on October 16, 2014 and IRNSS-1D on March 28, 2015.