China had conducted a reconnaissance mission with Tupolev Tu153M aircraft prior to its transgression in the Barahoti area in Uttarkhand district.
The aircraft used by Chinese People’s Liberation Army was armed with Synthetic Aperture Radar (SAR) which provides broad-area imaging at high resolutions. The PLA had carried out two to three sorties earlier this year in the middle sector falling in the areas of Uttar Pradesh, Himachal Pradesh and Uttarakhand.
Piecing together intelligence gathered from various sources in the aftermath of Barahoti transgression, officials in the know were quoted as saying by PTI that at least three sorties of the aircraft, which is designed by the Chinese companies on the basis of technology from the erstwhile USSR, was carried out in last three months.
The aircraft flies at an altitude of above 40,000 feet and can go up to 60,000 feet to avoid detection by radars and can click pictures and other cyber and communication signatures at that height.
It has an SAR which can provide high-resolution pictures even in inclement weather or in night time. The systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery.
The information about the flight was shared during exchanges with foreign intelligence agencies, the sources said.
At least 20 to 25 Chinese troops had entered into the demilitarised area in Barahoti pastures in Chamoli district of Uttarakhand earlier this month, besides flying its helicopters in the Indian air space for over five minutes.
The sources said an Indian civilian team was sent back by Chinese People's Liberation Army troops, who claimed it to be their land and recognised it as 'Wu-Je'.
A Chinese helicopter hovered over the ground for nearly five minutes before returning to its side. It was apprehended that it could have carried out aerial photography of the area during its reconnaissance mission. The chopper was identified as Zhiba series of attack helicopter of the PLA.
Barahoti is one of the three border posts in the 'middle sector' comprising Uttar Pradesh, Himachal Pradesh and Uttarakhand where ITBP jawans are not allowed to take their weapons as per the unilateral decision of the then government in June 2000.
In 1958, both the countries listed Barahoti, an 80-square km sloping pasture, as a disputed area where neither side would send their troops. In 1962 war, Chinese PLA did not enter the 545-km middle-sector and focused on Western (Ladakh) and Eastern (Arunachal Pradesh) sectors.
However, after the 1962 Sino-Indian war, the ITBP jawans used to patrol the area with weapons in non-combative manner under which the barrel of the gun is positioned downward.
During prolonged negotiations on resolving border dispute, the Indian side had unilaterally agreed in June 2000 that ITBP troops would not be carrying arms to the three posts -- Barahoti, Kauril and Shipki in Himachal Pradesh.
The ITBP men do patrolling in civil dress and the pasture attracts Indian shepherds from the border villages tending their sheep and people from Tibet bringing their yaks for grazing.