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GSAT-6: India’s Second Military Satellite Launched

Gp Capt Ajey Lele (Retd.) is a Consultant at the Manohar Parrikar Institute for Defence Studies and Analyses, New Delhi. Click here for detailed profile.
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  • August 31, 2015

    On August 27, 2015 the Geosynchronous Satellite Launch Vehicle (GSLV) successfully placed in orbit the communication satellite GSAT-6. This launch was important for two main reasons: one, India gaining mastery in launching heavy satellites into geostationary orbit (36,000 km above sea level); and, two, the rationale behind launching GSAT-6, which is also designated as INSAT-4E.

    For many years, success had evaded the Indian Space Research Organisation (ISRO) in the field of the highly complex cryogenic rocket propulsion technology. But not anymore. The successful launch of GSLV D-6, outfitted with the indigenous Cryogenic Upper Stage (CUS), demonstrates that ISRO has succeeded in mastering the cryogenic rocket technology required for such launches. In early January 2014, ISRO had conducted the first successful launch of a rocket (GSLV D-5) using indigenous cryogenic technology. The first ever attempt made by ISRO to undertake a GSLV launch using an indigenous cryogenic upper stage had failed in 2010. Now, with the consecutive second successful launch of the GLSV, ISRO has proved the reliability of its cryogenic rocket technology. This success has come after more than two decades of effort beginning in the early 1990s.

    With GSAT-6, ISRO is also for the first time experimenting with an antenna having a diameter of six metres. Communication satellites require huge antennas for appropriate transmission. According to ISRO, this S-Band unfurlable antenna would be utilised for five spot beams over the Indian mainland and very small handheld devices would be required to be used for data, video or voice transfer. The spot beams would exploit the frequency reuse scheme to increase frequency spectrum utilisation efficiency.

    GSAT-6 is the second satellite launched by ISRO for strategic requirements. In 2013, it has launched GSAT-7, a dedicated communications satellite for the Navy. GSAT-6 is a 2117 kg satellite and would be mainly used by the armed forces. Indian soldiers operate in diverse terrain and topographic conditions, from peninsular region to desert to snow-clad mountains. Owing to topographical challenges, soldiers on many occasions encounter breaks in commutations. GSAT-6 is expected to provide quality and secure communication. This new system also frees the soldier from carrying bulky communication equipment since very small handheld devices would be put in use.

    Rocket technology is tough to master. Designing and developing a cryogenic stage in particular is technically challenging. A normal rocket usually has solid and/or liquid propellant stages, which help to lift the payload from the ground (or water surface) into outer space. A cryogenic rocket stage is more efficient and requires less propellant to lift payloads to greater heights in space. It uses liquid hydrogen and liquid oxygen, which have extremely low temperatures: oxygen liquefies at -183 deg C and hydrogen at -253 deg C. Because of these low temperatures and the associated thermal and structural problems, designing a cryogenic engine is an extremely challenging task.

    While ISRO’s success in mastering cryogenic technology (GSLV-Mark II) is an extremely important achievement, its job is only half done. At present, ISRO is in a position to launch only satellites weighing between two and 2.5 tons into geostationary orbits. But most contemporary communications satellites are normally in the weight category of four to five tons and therefore require a more powerful launcher. India’s future missions to the Moon, Mars and Venus are also expected to involve the launch of satellites in the same weight category. Appreciating this need, ISRO has already started working towards the development of GSLV-Mark III, a vehicle capable of placing four ton satellites in geostationary orbit. In fact, work on this project had started almost a decade back and some noticeable progress has already been made. In December 2014, a suborbital flight test of the GSLV-III launcher was undertaken with a passive cryogenic third stage. This test was successful and it is expected that by 2017 ISRO may start using the GSLV-Mark III launcher.

    Along with GSLV-Mark III, ISRO has been working on another critical technology programme: the development of a semi-cryogenic stage, which is expected to double the lifting power of the GSLV. Such vehicles could carry six to ten tons of weight (heavy communication satellites). They could also be used for a human space mission, development of space station, etc.

    The launch of the military satellite GSAT-6 needs to be analysed in the backdrop of India’s overall military space capabilities. India has announced that the GSAT-7 and GSAT-6 satellites have been developed for strategic purposes. Earlier, some remote-sensing (sub-metre resolution, matching with the best in the world) satellites were also launched by ISRO as dual-purpose satellites like the technology experimental satellite (TES, 2000) and the four cartographic satellites (CARTOSAT-1, 2, 2A and 2B in 2005, 2007, 2008, 2010). India has also launched (with Israeli assistance) two Synthetic Aperture Radar (SAR) satellites called RISAT II (2009) and RISAT I (2011) essentially to address terrorism related threats.

    Satellite based navigation is another important arena which has significant military utility. ISRO is developing a programme called Indian Regional Navigation Satellite System (IRNSS) to provide accurate position information services to civilian and military users. A position accuracy of better than 10 metres is expected to be provided to military users. IRNSS would have seven satellites, out of which four have already been placed in orbit and the system is expected to become operational shortly. All these satellites together constitute India’s military space investments.

    India’s increasing investments in space for strategic purposes clearly indicates the rising relevance of space assets for the armed forces. Space technologies have been considered a force multiplier for militaries for some time. Now, space technologies are fast becoming important constituents of war fighting itself. Various modern day weapon systems and military platforms have significant dependence on satellites systems for their operations. Hence, limiting the adversary’s access to its own satellite systems is fast becoming a critical component of military strategy. Under such circumstances there is a need to look beyond merely developing a capability for network centric warfare. The launch of satellites like GSAT-6 indicates that India has started factoring satellite technology as an important constituent for achieving net centricity.

    Views expressed are of the author and do not necessarily reflect the views of the IDSA or of the Government of India