In pics | Isro readies to launch sixth navigation satellite today

Isro’s sixth navigation satellite IRNSS-1F will be launched on board trusted workhorse -- PSLV C32 -- at 4pm on Thursday.

Indian Space agency Isro’s sixth navigation satellite IRNSS-1F will be launched on board trusted workhorse -- PSLV C32 -- at 4pm on Thursday.

Isro’s navigation satellite IRNSS-1F will be launched at 4pm on Thursday.(Picture courtesy: Isro)

The 54-and-half hour countdown began on Wednesday after the Mission Readiness Review Committee and Launch Authorisation Board cleared it and currently, it was “progressing normal”, Isro officials said.

The Polar Satellite Launch Vehicle-C32, on its 34th mission, would launch the IRNSS-1F from the Satish Dhawan Space Centre at Sriharikota -- about 110km from Chennai.

IRNSS-1F in a clean room during its integration. (Picture courtesy: Isro)

The satellite is aimed at providing navigation services on par with the US-based Global Positioning System.

The space agency had launched five navigation satellites before, under the Indian Regional Navigation Satellite System (IRNSS).

Integration of the third and fourth stage of PSLV-C32. (Picture courtesy: Isro)

While four satellites would be sufficient to start operations of the IRNSS system, the remaining three would make it more “accurate and efficient”, an ISRO official said.

“With the launch of four satellites, we were able to provide navigation for 18 hours. But after the fifth launch, we increased the capacity to 24 hours with an accuracy of 20 metres. The sixth IRNSS-1F and seventh launch (IRNSS-1G) will be accurate and more efficient,” an ISRO official told PTI.

The five satellites already launched are IRNSS-1A on July 1, 2013, IRNSS-1B on April 4, 2014, IRNSS-1C on October 16, 2014, IRNSS-1D on March 28, 2015 and IRNSS-1E on January 20, 2016.

IRNSS-1F being loaded into a thermo vacuum chamber. (Picture courtesy: Isro)

Isro had planned to put all seven navigation satellites into orbit by March 2016. The last in the series is expected to be launched by month end.

For the IRNSS-1F launch, scientists have used the “XL” variant used in previous launches of IRNSS satellites, given its capacity to carry load.

Placement of the nozzle end segment of PSLV-C32 first stage over the Launch Pedestal. (Picture courtesy: Isro)

Occasions where rocket with XL configuration were used were during the launch of Chandrayaan-1, Mars Orbiter Mission and ASTROSAT apart from the five IRNSS satellites.

With the navigation payload and ranging payload, the satellite also carries a “highly accurate Rubidium atomic clock” with it. The payload will transmit navigation service signals to users.

The IRNSS-1F has a lift-off mass of 1,425kg and would be launched in sub-Geosynchronous Transfer Orbit (sub GTO). It has a 12 year mission life (Picture courtesy: Isro)