Seamless military satellite communications still have a long way to go
Prasun K. Sengupta
Since mid-2017, the Indian Armed Forces’ over-the-target requirements (OTR), that is, the minimum force level required for any type of weapons configuration to attack a specific type of target within a given period to damage it significantly, have remained works-in-progress, thanks to the tardy progress in the arenas of joint targeting list formulation (during both peacetime and wartime) and extremely slow procurements of over-the-horizon/beyond-line-of-sight intelligence, surveillance and reconnaissance (ISR) capabilities, be they terrestrial or space-based.
It was in 2006 that the Indian Air Force (IAF) established a Directorate of Aerospace in Thiruvananthapuram in South India. This was headed by an Air Commodore rank officer who reported to the IAF Vice Chief’s office through the Directorate of Concepts and Doctrines at IAF HQ. However, it was only in June 2008 that the then Defence Minister A K Antony announced the setting up of the tri-services Integrated Space Cell under the aegis of the HQ Integrated Defence Staff (IDS). This cell was to act as a single window for integration among the armed forces, the Department of Space and the Indian Space Research Organisation (ISRO), and it was to become the precursor to the eventual setting up of a tri-services Aerospace Command to manage India’s military assets in space.
But even this failed to take off and it was only on 18 September 2018 that the creation of the Bengaluru-based Defence Space Agency (DSA) under HQ IDS was approved by the Ministry of Defence (MoD). The DSA became fully operational in November 2019 and has since been the custodian for systems for providing high-quality signals intelligence (SIGINT), communications intelligence (COMINT) and electronic intelligence (ELINT). One such satellite is the Electromagnetic Intelligence Gathering Satellite or EMISAT which was launched into polar orbit in April 2020. It is equipped with an ELINT package called Kautilya that allows the collection of information on ground-based radar as also electronic surveillance across India. The Defence Imagery Processing and Analysis Centre (DIPAC) and Defence Satellite Control Centre (DSCC) have since been merged into the DSA. Alongside the DSA, the Defence Space Research Agency (DSRA) was created. It is the scientific organisation responsible for developing space warfare systems and technologies for the DSA.
Between the three armed services, it was the Indian Navy (IN) that ventured into the space applications domain by deploying its 2.65 tonne GSAT-7 geostationary orbiting (GEO) communications satellite in August 2013. Prior to that, since 2005 the IN had been using the Inmarsat satellite constellation to achieve satellite communication (satcom) networking (known as Rukmini) for real-time positional data provision for its airborne, surface and undersea platforms. The GSAT-7 presently provides the IN with UHF-band, S-band, C-band and Ku-band relay capacity over the Indian landmass and surrounding seas in the Indian Ocean region, thereby strengthening India's maritime domain awareness (MDA) abilities. The succeeding GSAT-7R satellite will be launched in the near future.
The IAF’s GSAT-7A (Angry Bird) communications satellite, with a mission life of eight years in GEO, was launched only in December 2018 and it comes with 10 Ku-band transponders that are used for networking the IAF’s integrated command, control and communications system (IACCCS). The Indian Army (IA) was the last to acquire such a capability last March when the MoD inked a Rs 2,963-crore contract with the state-owned Indian Space Research Organisation’s (ISRO) commercial arm New Space India Ltd (NSIL) for the five tonne GSAT-7B GEO communications satellite, that will provide mission-critical beyond-the-line-of-sight communications to troops and formations as well as weapon and airborne platforms.
Delayed Take-offs
Trying to play catch-up with its regional rival, China’s People’s Liberation Army Navy, the IN, through the DSA, has issued expressions of interest from India’s public sector and private sector enterprises for various space-based ISR solutions, such as the following:
- GEO satellite with modular tracking and data-relay satellite (TDRS) payload for communicating with low-earth orbiting (LEO) satellites along with the pointing assembly and the power electronics. The GEO TDRS module is required to have a high-speed laser-based optical inter-satellite link (ISL) facility. This module should be able to seamlessly integrate with a LEO-ISR satellite and should be able to transmit data at rates greater than 1.5 Gbps. The TDRS must also have a high-throughput system (HTS) for data downlink with networked ground-based earth stations (GES), preferably in Ku-band.
- Development of two highly agile satellites that will provide a significant boost to the imaging capability compared to existing optronic imaging satellites. The challenge is to develop two highly agile platforms that can house an optical and synthetic aperture radar (SAR) payload, respectively. The agility is required to be 7 degrees per second or better and should be compatible with three-axis stabilised satellites. The inter-spot imaging distance derived from this agility rate should be 2 kilometres or less. The weight penalty of the attitude and orbit control system (AOCS) should be approximately 40 kilograms to 60 kilograms while providing this agility rate.
- Developing an RF-based (V-band) inter-satellite link module for small satellites in LEO to communicate with other LEO satellites and GEO satellites as part of the TDRS system. The module should be able to easily integrate with LEO satellites. A compatible receiving system has to be integrated into the GEO satellite. The data rate for this system is proposed to be up to 15 Gbps.
- Development of an autonomous on-board system for small satellites in the LEO. The onboard module would autonomously schedule an inter-satellite link with the nearest available GEO satellite, considering the dynamic link traffic at the GEO satellite end. Scheduling includes all aspects of the datalink, from antenna pointing to the most efficient uplink.
- Developing a laser-based optical inter-satellite link payload for small satellites in LEO to communicate with other LEO satellites and GEO satellites as part of the TDRS system. The system with all its power electronics should be able to easily integrate into LEO satellites. The desired data rate for this system is greater than 1.5 Gbps.
- Developing a beam-steering antenna with high gain and directivity, compatible with high-speed inter-satellite data links between LEO satellites and GEO satellites in a TDRS system.
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