Missing aircraft Search area has already been mapped by GSI 20 years ago, says top scientist

C Shivakumar
Chennai:
The area where the search and rescue operations are being carried out to locate Indian Air Force’s transport aircraft that went missing with 29 crew on July 22 is not a new terrain for Geological Survey of India scientists as it has been mapped 20 years ago by research institute.

Speaking to Express onboard Samudra Ratnakar, the premier research vessel of Geological Survey of India, chief scientist G Nagendra, who is heading the team of nine scientists to help locate the missing aircraft, said that the area which falls under Economic Exclusive Zone has been mapped in 1990.

“We have been given a search area of 16,000 square kilometres and the operation will take 30 days. It is a familiar territory for us,” said Nagendra, who is based in Chennai.

Since the data of the area is available with GSI, all they have to do is use the multi-beam echo sounder,a type of sonar which is used to map the sea bed. However, the scientists would be focussing more on the back scattered data study employing echo-sounding systems towards the interpretation of seafloor.

“Since we have already surveyed the area the back sacttered data would reflect any variation on the floor of the sea, like the presence of parts of aircraft,” said the top scientist.

He said they would be surveying at a depth of 3,200 to 3,400 metres. “During the search operation, the ship will be going at a speed of 10kmph and if need permits we could also use the Remotely Operable underwater vehicle, which can go to a depth of 2,200 metres,” said Nagendra.

He said that the pressure underwater is such that there is a chance that the aircraft, made of aluminium, could even shrink at such a depth. To a query whether the ship would use side scan sonar, a portable instrument which could give better results if it is towed properly at a depth of 2,500 metres, Nagendran said that his team would try it but the issue is towing it at such a depth. “We will be trying it at the start of the operation,” he said.

Interestingly, the ship also has magnetometer, which could emit signals once it reaches the spot where the aircraft is submerged. But since there has been some issues with the device, the scientists are relying on multi-beam echo sounder. However, the success of the search would also depend on the weather. For the last two days, the sea has been rough, said Nagendran. The ship is likely to leave Chennai Port on Sunday or Monday morning.
Factfile:
1.Geological survey of India’s ship Samudra Ratnakar will be surveying 16,000 square km area
2.They area, which falls under Exclusive Economic Zone,  has been mapped by GSI scientists 20 years ago
3.The ship will use back scattered data study employing echo-sounding systems towards the interpretation of seafloor.
4.The ship will be travelling at a speed of 10kmph while surveying the bottom of sea floor
5.This is the first time the ship is being used for search and rescue operation
6.A team of nine scientists and three coastguard officials along with 25 crew are part of the operation to locate the missing aircraft
7.National Institute of Ocean Technology ship will be joining the search and rescue operation on Sunday evening

How the ship will work:
1.Multi-beam echo sounder will send in the signals from the hull of the ship.
2.Once the signals hit the ground, it will reflect back and will be picked up by the receiver.
3.The receiver will then transmit the image to the computer
4.The operation room has 12 computers each linked to special equipment of the ship
5.The operation room also has plotters which prepares hard copy of sea surface image