By Amit Mukherjee
The declared use made of earth observation satellites (Cartosat Series) for facilitating the surgical strikes conducted across the Line of Control (LoC) in September 2016 represents a new precedent. India’s proactive action caught the infiltrators as well as the supporting Pakistani establishment by surprise, in both military and policy terms. However, with no subsequent change in the Pakistani establishment’s strategy of sponsoring and facilitating cross-border terrorism, sealing the Western border is being seen as the next counter step. The Home Minister has announced the government’s intent to seal the border by 2018.
Although sealing the entire border would be a significant challenge mainly due to variations in the terrain and topography, the use of remote sensing systems provides one of the more effective means to overcome it. Attempts at infiltration could be detected by using low earth orbit surveillance satellites, which would in turn enable the blocking of infiltrators through suitable force deployment. In this regard, the active deployment of Medium Altitude Long Endurance (MALE) Unmanned Aerial Vehicles (UAVs) which were reportedly used in Operation Ginger in 2011, and High Altitude Long Endurance (HALE) UAVs that are currently under consideration for procurement, will improve India’s surveillance and reconnaissance capabilities.
Further, the deployment of high-resolution radar based imaging sensors with all-weather day and night observation capability in the form of the Synthetic Aperture Radar system (SAR sensor platform) would also be advantageous in both the surveillance and active reconnaissance roles. In the aftermath of the November 2008 terror attacks in Mumbai, India had benefited from cooperation with Israel in developing RISAT 2 and especially its SAR system. Today, the RISAT 1 and 2 are the only two declared SAR systems in India’s possession for all weather day and night capability with X band and C band sensor systems. India would need to increase the number of such satellites for continuous observation of the western border. In addition, the CARTOSAT is also available for imaging purposes. In fact, ISRO has acknowledged that CARTOSAT was used for imaging areas where surgical strikes were carried out.
Most of India’s present repertoire of 13 operational remote sensing satellites with earth observation payloads, including the RISAT and CARTOSAT series, are assumed to be capable of providing high-quality earth observation imagery ranging from 50m to sub-meter resolution. These have swath coverage in the panchromatic range, from 10 kilometres on the CARTOSAT Series to 250 km in the RISAT series.
Since satellites travel over an observation area in an elliptically linear manner, the curves of a land border are passed over by the satellite in a direct overhead elliptical orbital motion from north to south descending or south to north ascending direction with their respective inclination, azimuth and elevation settings. At a known velocity of 7.5 km/s, these satellites pass over the entire length of the observed Area of Interest (AoI) over the western border of India in three to four minutes or even less. A shorter target region like the border in Jammu & Kashmir would mean an even lesser time for the satellite’s orbital pass. Added to this is the fact that low earth observation satellites do not provide continuous 24×7 observation of the same AoI. On each of its flights over any surface on the earth, the satellite takes snapshots or close earth observation high-resolution images of the area it is ground tracing and this process occurs 14 to 15 times a day (like in the case of Risat-2 satellite), but it may not pass over the same AoI.
The satellite coverage of an AoI, while making an adjacent orbital pass, is dependent on side looking capability of the sensor, its discernible range and angle of view, and the footprint of the satellite. Then there is the aspect of revisit time that allows surveillance for a given period of time till the satellite passes over the same region again. Therefore, the constant monitoring of the AoI requires a constellation of satellites.
At present, there are no satellite constellations that could form a contiguous chain of observation systems to monitor a designated target continuously. Hence, most scenes are individual or a series of observed images. These observations are then analysed with patterns and feature identification processes using photogrammetry tools and other visual aid and identification and digital image processing methods. This process along with inputs from other systems like ground radars and aerial surveillance platforms like the Airborne Early Warning and Control Systems (AEWACS), manned posts, aerial reconnaissance that render round the clock surveillance capabilities provide confirmation or build the overall picture of the situation.
Given all this, India would need more than one satellite constellation. It would require multiple satellites that repeat their observation of a target area; ideally one after the other in a contiguous form so that one satellite is always present over the AoI. To meet that objective, preferably smaller satellite systems at very low earth orbit to enable short revisits and repeat cycles would be ideal. The construction of nano and pico satellites is within India’s technological capability. It is highly recommended that a range of nano and pico satellites be manufactured and their employment integrated with the border management system.
Views expressed are of the author and do not necessarily reflect the views of the IDSA or of the Government of India. Originally published by Institute for Defence Studies and Analyses (www.idsa.in) at http://idsa.in/idsacomments/role-of-earth-observation-satellites-in-counter-infiltration_amukherjee_301216