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ISRO successfully launches electronic intelligence satellite Emisat

Date: 02 April 2019 Tags: Space

Indian Space Research Organisation (ISRO) successfully launched electronic intelligence satellite Emisat and 28 other third party foreign satellites into their designated orbits. These satellites were launched on board of PSLV-C45 from the second launch pad at Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh.


The main passenger (payload) of this mission was DRDO's electronic intelligence satellite 'Emisat', weighing about 420 kg. The remaining 28 satellites cumulatively weigh about 250 kg included 24 from US, 2 from Lithuania and one each from Spain and Switzerland. Besides this, fourth and final stage of this PSLV rocket (PS4) was carrying three experimental payloads.

Unique features of this mission

PSLV-C45 was new variant of Polar Satellite Launch Vehicle (PSLV) rocket with four strap-on motors instead of six strap-on motors.. This was for first time, four strap-on motors were attached externally to main rocket  to provide additional thrust, energy by firing midway during flight.

ISRO for first time demonstrated its new rocket that injected satellites in three different orbits using multiple burn technology, where engine shut down and restarted multiple times within short period of time allowing rocket to course to the next orbit with the payloads. Second, fourth and last stage of rocket will function as satellite itself for some time, instead of being junk after ejecting payloads.

Launch Sequence

PSLV rocket first placed Emisat Satellite at altitude of 763 km in sun synchronous orbit. Then it was brought down to put 28 satellites into orbit at altitude of 504 km. Following ejection of all satellite, the rocket was brought down further at 485 km where its fourth and final stage of rocket (PS4) was turned into payload platform carrying three experimental payloads.

Fourth stage of rocket (PS4) of PSLV C45

PS4 as experimental payload platform will stay alive in space for the next six months along with three scientific instruments. It will collect data and relay them to the ground station. This is for first time PS4 has been fitted with solar panels.

Its experimental payloads includes (i) Automatic Identification System (AIS): It is from ISRO for Maritime satellite applications capturing messages transmitted from ships (ii) Automatic Packet Repeating System (APRS): It is from AMSAT (Radio Amateur Satellite Corporation), India. It will assist amateur radio operators in tracking and monitoring position data and (iii) Advanced Retarding Potential Analyser for Ionospheric Studies (ARIS): It is from Indian Institute of Space Science and Technology (IIST). It will be used for structural and compositional studies of ionosphere.  

Note: This was for the second time ISRO has converted PS4 of PSLV rocket as satellite-like orbital platform. Earlier in January 2019, PSLV-C44 had carrying student satellite in its PS4 stayed alive for several hours — powered by batteries to help its payload conduct microgravity tests.

Emisat Satellite

  • It has been developed by Defence Research and Development Organisation (DRDO). It is based on ISRO's Indian Mini Satellite-2 (IMS-2) bus platforms.
  • It will be deployed for the task of discovering enemy radars and collecting imagery and communication intelligence.
  • Its objective is to detect low power radar signals, which are typically used to track by low-altitude air-borne vehicles, including aircraft and drones.
  •  It  developed under Kautilya Project, a highly secret project approved by Defence Ministry.
  • Applications: It will help to monitor activities of enemy radars and sensors deployed along the border. It will help to know the exact topography of enemy areas. It will provide communication intelligence to find out how many communication devices are active in an area.
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