Earth Observation Satellites are essential for India’s national security

Last month, the Indian Space Research Organisation (ISRO) Earth Observation Satellite (EOS-3) failed to inject into Geo Transfer Orbit (GTO), because of the failure of the Geosynchronous Launch Vehicle’s (GLSV) cryogenic upper stage. This satellite’s ultimate orbital destination was Geostationary Orbit (GEO). Notwithstanding the failure of the mission given the chequered history of the GSLV’s cryogenic stage performance, the EOS-3 was supposed to fulfil an important earth observation mission. Although ISRO did not release details about the payloads aboard the EOS-3, it would not be surprising if the space agency installed electro-optical capabilities that were intended to service the needs of the Indian armed forces. The satellite was expected to be in service or operational for 10 years. ISRO has successfully launched several Earth Observation Satellites (EOS) in the past using its “workhorse” Polar Satellite Launch Vehicle (PSLV) and its variants. Had the EOS-3 been successful, it would have met an important part of the armed services imagery needs. This is a setback not just for ISRO, but the Indian military as well, because they need it given the operational challenges confronting the Indian Army (IA) and the Indian Air Force (IAF) against China. A glance at China’s EO capabilities will give the reader sufficient indication as to why they constitute such an important investment.

ISRO has successfully launched several Earth Observation Satellites (EOS) in the past using its “workhorse” Polar Satellite Launch Vehicle (PSLV) and its variants.

The Indian military needs these EO satellites because the Peoples Republic China (PRC) has several of them. The PRC operates the Gaofen series or constellation of EO satellites. EO satellites are crucial for Imagery Intelligence (IMINT), photo reconnaissance, Synthetic Aperture Radar (SAR), and electro optical functions. These EO Gaofen satellites are at least notionally part of China’s High-resolution Earth Observation System (CHEOS). The latter performs several tasks and functions that help with matters such as land surveying, urban planning, disaster relief, design of road networks, and agriculture. Notwithstanding the utility and purpose behind civilian applications of the CHEOS constellation, the Gaofen series are also integrated with payloads, instruments, and platforms, but with decidedly military reconnaissance missions. China launched the Gaofen-13 satellite in October 2020, which operates from the Geostationary Orbit (GEO). Very little is known about this satellite, because the Chinese have revealed close to nothing about its payloads and instruments. The last occasion the PRC launched a satellite, the Gaofen-4, into the same orbit was in 2004. However, China has not divulged details of other satellites either in the same series such as the Gaofen 11. The Gaofen satellites, believed to be electro-optical remote sensing satellites, are important from a military reconnaissance standpoint. To be sure the PRC has suffered some setbacks as part of its remote sensing satellite programme, such as the failed launch of the Jilin or Gaofen–02C optical earth observation satellite in September 2020. This satellite is believed to have had a 0.76-metre resolution with a swath breadth of 40 kilometres. This satellite was intended for placement in Sun Synchronous Orbit (SSO) or Low Earth Orbit (LEO).

EO satellites are crucial for Imagery Intelligence (IMINT), photo reconnaissance, Synthetic Aperture Radar (SAR), and electro optical functions.

Irrespective of this failure, remote sensing satellites such as the Gaofen series have several advantages. Firstly, remote sensing satellites can provide imaging data about the location and scope of military activities being pursued by adversaries. Secondly, they are also crucial for post-attack damage assessment. The latter enables or creates opportunities for refining attacks against enemy targets for the future. Relying exclusively on drones and reconnaissance aircraft to image the earth’s surface has its disadvantages to the extent that they can be shot down if reconnaissance missions were to be carried out over military installations and facilities whether in China or even Pakistan. Further, movement of troops by an adversary as was the case with the PRC’s Ladakh occupation in 2020 went largely undetected because of the lack of a sufficient number of EOS type or more generally remote sensing spacecraft. For this reason, satellites such as the EOS-3 and the Gaofen-13 are vital to service the imaging and reconnaissance needs of the military. However, satellites in lower orbits are also necessary for remote sensing, but they have limitations as we will see below. The Indian Remote Sensing (IRS) satellites is one of the largest civilian remote sensing constellations in the world, but China’s Ladakh aggression clearly testifies to the need to develop and launch more of them. Other satellites like the CARTOSAT series have dedicated military applications, which ISRO has launched. In addition, the RISAT series spacecraft, which are radar imaging reconnaissance satellites, have also helped meet India’s remote sensing requirements. ISRO has also launched remote sensing satellites as part of the EOS series in years past. For instance, the EOS-1, which was launched from Polar Satellite Launch Vehicle (PSLV) into Low Earth Orbit (LEO)that ISRO has publicly declared to perform applications relating to forestry, agriculture, and disaster management. Nevertheless, this description is no different from what the PRC has done with its Gaofen satellites to conceal the true purpose behind their application.

The RISAT series spacecraft, which are radar imaging reconnaissance satellites, have also helped meet India’s remote sensing requirements.

There are, however, trade-offs involved in launching and operating remote sensing satellites and it is in this context that we must view the failure of the EOS-3. What are these trade-offs? There are time-bound weaknesses in the form of temporal resolution that are compounded by cost and target resolution weaknesses in the form of spatial resolution. The higher the altitude of a spacecraft, the greater the temporal resolution and increased or longer orbital shelf-life of the satellite, but there are also commensurately higher demands for strong spatial resolution in that the spacecraft needs sharper optical payloads to image a target area. Some of these problems can be addressed by launching multiple small satellites into low orbital planes, but only up to a point. Low altitude satellites are susceptible to high atmospheric drag, which reduces the orbital shelf-life of the spacecraft. Thus, imaging satellites such as the EOS-3, which is an expensive space borne platform is durable and necessary and its loss will be felt by the Indian military.

• Defence and Security
• Space
• Internal Security
• China
• India
• CHEOS
• Earth Observation Satellite (EOS-3)
• Earth Observation Satellites
• EOS-3
• Gaofen-4
• Geo Transfer Orbit (GTO)
• Geostationary Orbit (GEO)
• GSLV
• India’s national security
• ISRO
• LEO
• PSLV
• SAR
• SSO

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