Bangalore. In what has been perceived to be a setback to the Indian space programme, the country's maiden lunar probe Chandrayan-1 has been hit by a snag following the failure of its vital star sensor on April 26.

The loss of the star sensor meant to determine the orientation and position of this lunar orbiter, is known to have been caused by overheating the excessive solar radiation.

However ISRO (Indian Space Research Organisation) has been able to overcome this malfunctionpartly by activating the redundant onboard gyroscopes. In order to conserve the onboard fuel required for orbital maneuvers, on May 19, ISRO also raised the orbit of Chandrayaan-1 to 200 km from 100-km.

In the higher orbit, a spacecraft is known to be less prone to the degrading effects of the space environment.

According to a press note issued by ISRO, “other than the failure of the star sensor and one of the bus management units, health of the spacecraft is normal.”

The loss of one of the bus management units means that Chandrayaan-1 is running on the backup unit. All said and done, the use of gyroscopes along with the antenna information and images of specific location of the lunar surface for determining its orientation is considered a far from safe option. Being an electro mechanical device, gyroscopes are considered far more vulnerable to the environmental rigors of outer space in comparison to the star sensor.

”One cannot predict failures as it can always happen. If some more failures happen, then we have problems,” said ISRO Chairman G Madhavan Nair.

Dismissing the suggestion that the loss of star sensor could reduce the lifespan of the Indian lunar probe, Nair said that the failure though could affect the performance of Chandrayaan-1. “The life of the spacecraft is not dependent on this instrument.”

But to what extent it will affect the various experiments onboard Chandryaan-1, no one is sure as yet, he observed.

The Rs 4,000 million Chandrayaan-1 is carrying six international and five Indian payloads. It is designed for a lifespan of two years, and was launched by means of an augmented version of the fourstage Indian space workhorse, the Polar Satellite Launch Vehicle (PSLV) on October 22, 2008 from the Satish Dhawan Space Centre (SDSC) in Sriharikota island on India’s eastern coast.

This achievement catapulted India to the elite league of space faring nations – USA, Europe, Russia, China and Japan – which have already sent probes to earth’s nearest celestial neighbor.

The Indian designed and developed MIP (Moon Impact Probe), weighing over 30-kg and with miniature Indian flags painted all around, was successfully ejected from the mother spacecraft for its planned crash landing on the lunar surface on the night of Nov 14, 2008.

The Chandrayaan-1 mission, described as the landmark Indian venture beyond the near earth orbit, had as its objectives enhancing our knowledge for the mankind, enhance India’s capability to build more reliable and efficient launch vehicles and spacecraft systems particularly through microminiaturization, and provide opportunities for planetary research for the younger generation.

The scientific focus of the Chandrayaan-1 mission has been on preparing a three dimensional map of the lunar surface showing distribution of chemicals and minerals in addition to looking for signs of water and checking for the presence of Helium-3.

iMr Madhavan Nair drives home the point that during the last eight months of its operations, Chandrayaan-1 has helped collect “almost all the data we needed.” And that most of the misison objectives had been met.

”We had a meeting with the scientific community a month back and they have stated that the quality of data was excellent. We have accomplished 90-95% of objectives set for the mission,” observed Nair.

A press note issued by ISRO noted that Chandryaan-1 had completed 3,000 orbits around the moon and has made available more than 70,000 images of the lunar surface which provided a breathtaking peep into lunar mountains and craters, especially craters in the permanently shadowed polar regions of the moon.

Clearly and apparently, the snag that has hit Chandrayaan-1 is not an isolated phenomenon or an uncommon occurrence. For many high profile lunar probes launched by the leading space faring nations including the USA, Russia and Japan have had their share of “troubles and snags”.

Maneuvering a lunar spacecraft and positioning it around the moon is a very complex operation that can be jeopardized by several space environmental factors including excessive radiation and gravitational deviations.

Interestingly, a third of the moon probes have met with premature ends while being subjected to maneuvers for inserting them into lunar orbit. Moreover, the first nine moon missions had ended up in failures.

As stated by Nair, “Such failures occur in complex missions. We did not have any experience of this kind earlier and we have understood the intricacies of going round the moon. The data obtained so far will help us make the subsequent missions like Chandrayaan-II much more reliable. Our scientists will have to take care of environmental issues for the future.”

Perhaps the biggest achievement of ISRO is the smooth and flawless insertion of Chandrayan-1 spacecraft around the moon after its 3.84 lakh km journey.

Mr Nair also made it clear that Chandrayaan-1 sensor failure would not affect the course of the follow up mission Chandrayaan-II, slated for launch in 2013.

The Rs. 4250-million Chandrayaan-II is planned to be launched by means of the three stage Geosynchronous Satellite Launch Vehicle (GSLV) featuring an upper cryogenic engine stage.

Unlike Chandrayan-1, Chandrayaan-II will feature a rover with robotic arms for landing on the lunar surface to collect samples of rocks and soil.

The soft landing of the lunar probe will be biggest challenge for India’s second moon mission. As there is no atmosphere, parachuting is ruled out.

The collected lunar samples will be subjected to in situ chemical analysis and data transmitted to the mother spacecraft in lunar orbit. The landing platform in tandem with the rover will get separated from the main Chandrayaan-II. Which will be firmly positioned in the orbit around the moon. Like Chandrayaan-1, it is also expected to carry international payloads though they are yet to be finalized.

Russia is a major partner in this venture.

Undeterred by the Chandrayaan-1 sang, ISRO is determined to forge ahead with its plan to sustain its Mission Space, for it is the space which holds the key for the future of humanity.