After 16 successful launches of its workhorse rocket Polar Satellite Launch Vehicle (PSLV) in the last 17 years, the Indian space agency is now testing a key component to re-qualify its on-flight performance parameters to avoid any unpleasant surprises.

The Indian Space Research Organisation (ISRO) is testing the gas motor which is fitted in the second stage/engine powered by liquid fuel for high temperature tolerance levels.

The test has forced Isro to postpone the launch of its remote sensing satellite Resourcesat-2 and two other payloads by nearly a month. Remote sensing satellites like Resourcesat send back pictures and other data for various uses. India is a major player in providing such data in the global market.

The rocket was scheduled for launch this week.

According to Isro officials, the gas motor powers the rocket's second stage control actuators for maneuvering the engine's nozzle - the process is called gimballing. The process enables the rocket to maintain a steady course on its way up.

The motor is powered by the hot gases tapped from the rocket.

"During earlier PSLV rocket launches, we had noticed the temperature of the hot gases at the motor inlet being higher by 20-30 per cent while the expected temperature is around or less than 300 degree celsius," an Isro official said.

Isro officials said the space agency's chairman K. Radhakrishnan wanted to be sure about the parameters of the rocket's subsystems as he was of the view that Isro cannot afford another failure and that too involving the PSLV rocket.

Isro's commercial arm Antrix Corporation is earning a sizeable sum, launching third-party satellites using PSLV rockets.

The Indian space agency's last two missions involving its heavy rocket - Geosynchronous Satellite Launch Vehicle (GSLV) - ended in failures, resulting in a total loss of around Rs.600 crore - cost of two rockets and two satellites.

Isro will be using PSLV to launch a communication satellite till the space agency stabilises its GSLV rocket that can sling much heavier satellites into orbit.

According to Isro officials, the temperature tolerance levels of the gas motor is being tested in a power generation company near here.

Isro opted to test the gas motor's heat tolerance limits as that will be quicker than redesigning the rocket's engine to bring down the gas temperature.

"Up to 300 degree celsius we can test the component at Isro's centre in Thiruvananthapuram. We do not have super heated steam generators to test the temperature tolerance levels above that levels," an official said.

According to him, the test results have been satisfactory till now as the motor tolerated temperature up to 370 degree celsius.

The test results will be studied and the final call on the rocket's launch carrying remote sensing satellite Resourcesat-2 is expected to be taken February 28 by Radhakrishnan.

ISRO officials said around 20 days' time is required to test the rocket's subsystems after the launch permission.

If the permission is given on Mar 1, Isro would require 20 days more to make the rocket and the satellite ready for launch.

Meanwhile, the fully assembled PSLV rocket is standing tall at the Sriharikota launch centre, around 80 km from here. All the three satellites are also at the rocket launch pad.

India has the largest constellation of remote sensing satellites in the world providing imageries in variety of spatial resolutions from better than a metre ranging up to 500 metres.

The remote sensing satellites that are operational are - Cartosat-2B, Oceansat-2, RISAT-2, Cartosat-2A, IMS-1, Cartosat-2, Resourcesat-1 and TES.

For some time, Resourcesat-2 and Resourcesat-1 would work together before the latter would go into oblivion.

Launched in 2003, Resourcesat-1 has outlived its original mission life of five years.

Compared to Resourcesat-1, the multispectral swath of Resourcesat-2 has been enhanced from 23 km to 70 km based on user needs.

Suitable changes, including miniaturisation in payload electronics, have also been incorporated in Resourcesat-2.

The other remote sensing satellites that ISRO plans to launch are RISAT, Megha-Tropiques, INSAT-3D, Astrosat - astronomy satellite to observe celestial bodies.