Indian Space Research Organisation (ISRO) chairman S. Somanath said in Mumbai on December 28, 2023 that India aims to launch 50 satellites over the next five years for geo-intelligence gathering.
ISRO plans to create multiple satellite constellations operating in orbits suited to the strategic purpose of the constellation.
The constellations would perform strategic tasks such as tracking adversary movements over land and sea, real time imaging of emerging threats, high resolution surveillance of adversary military assets, all weather radar imaging, missile launch warning, etc.
According to the ISRO Chairman, the number of satellites that India has currently deployed for remote sensing is grossly 40-50.
Speaking at `Techfest', an annual science and technology event organised by the Indian Institute of Technology Bombay, he said that the number should be "ten times what we have today".
The ISRO chief pointed out that satellites are capable of observing a country's borders and neighbouring regions.
"All of it can be seen from satellites. This capability gives us enormous potential. We have been launching satellites to handle this, but there is a different way of thinking now and we need to look at it in a much more critical manner because the power of (any) nation is the ability to understand what is happening around it."
"We have already configured 50 satellites to be realised in the next five years and this is going to be launched for India for supporting this particular geo-intelligence capability over the next five years plus (period)" the ISRO chief added.
Journalists film the live telecast of spacecraft Chandrayaan-3 landing on the moon at ISRO's Telemetry, Tracking and Command Network facility in Bengaluru, India, Wednesday, Aug. 23, 2023.
© AP Photo / Aijaz Rahi
Past Remote Sensing Satellites
ISRO has progressively enhanced its satellite based intelligence gathering capabilities by launching increasingly capable optical, radar and multi/hyperspectral imaging satellites in low earth sun synchronous polar orbit (SSO).
Radar satellites feature a Synthetic Aperture Radar (SAR) that enables them to image the surface of the earth through clouds and in darkness.
Unlike optical satellites, multi and hyper spectral imaging satellites have a limited ability to see through clouds.
ISRO launched its first HysIS (Hyperspectral Imaging Satellite) launched in November 2018.
Cartosat Satellites
Cartosats are dual use satellites. Cartosat-2 series (Cartosat-2B, 2C, 2D & 2E) are capable of imaging a swath (geographical strip) of 9.6 km with a resolution of better than 1-m. The satellites are steerable up to ± 26º along as well as across track to obtain stereoscopic imagery and achieve a four to five day revisit capability.
ISRO is developing a follow-up Cartosat-3 advanced remote sensing satellite series with a resolution of 0.25 m for cartographic applications and high-resolution mapping.
Hysis Satellites
Hysis is the first of a new set of future earth observation satellites called hyperspectral (Hyspex) imaging satellites with an orbital height of about 600 km.
Hyperspectral imaging is a form of multi-spectral imaging that uses much narrower spectral bands providing more detailed information about the specific wavelengths of light reflected or emitted by the Earth's surface.
Hyperspectral sensors capture a large number of narrow and contiguous spectral bands, allowing for more detailed analysis of the electromagnetic spectrum.
While multispectral imaging is suitable for some broad-scale assessments, hyperspectral imaging enables distinct identification of objects from space.
Hyperspectral imaging may provide better insights through certain cloud types or thin cloud cover compared to traditional multispectral imaging, but it does not guarantee complete penetration through thick clouds.
Radar imaging satellites comprise the RISAT series.
GISAT Satellites
In the near future, ISRO plans to launch GEO Imaging Satellites (GISATs) in Geosynchronous orbits (GSO).
ISRO's GISAT will carry a geo-imager with multi-spectral (visible, near infra-red and thermal), multi-resolution (50m to 1.5 km) imaging instruments that will enhance the country’s land mapping capabilities. Gisat has both military and civilian use.
GISAT will facilitate near real-time imaging of large areas of the country under cloud-free conditions. GISAT images, however, would be of lower resolution than the images from satellites in polar orbit.
(File) In this Sept. 18, 2008 file photo, The Chandrayaan 1 spacecraft, India's first unmanned mission to the Moon, is seen as it is unveiled at the Indian Space Research Organization (ISRO) Satellite Center in Bangalore, India
© AP Photo / File
EOS
ISRO's EOS (Earth Observation Satellite) combines radar and optical imaging. ISRO launched EOS-1 on November 7, 2020. The satellite was initially intended to be named RISAT-BR2 because Radar Imaging payloads were traditionally carried by RISAT. Because of the additional optical payload, ISRO chose to spawn a new Earth Observation Satellite series.
Surveillance Satellites
Besides optical and radar imaging remote sensing satellites, space based intelligence additionally requires other specialised satellites such as ELINT (Electronic Intelligence), Missile Launch Warning and Tracking satellites.
EMISAT
EMISAT is a SIGINT satellite jointly developed by ISRO and DRDO, which was launched into orbit in April 2019.
EMISAT was placed in a circular sun-synchronous polar orbit, at an altitude of 749 kilometres and an inclination of 98.4 degrees.
In addition to an ELINT payload the satellite likely also features a COMINT (Communication Intelligence) capability.
Possible uses of the EMISAT satellites include:
Location of adversary surface based radar emitters for targeting by anti radiation missiles;
Analysis of radar signals to determine frequency of carriers and subcarriers, modulation, bandwidth, power level, beam footprint parameters, and emitter location and motion. The information would be used to update signal libraries on combat aircraft in order to immediately identify the nature of the radar illuminating the aircraft. The information would also be useful for developing techniques to jam the radar;
Intercepting communication signals, demodulating them, extracting the original data (audio, video, text) for decryption;
Interception and demodulation of non communication signals such as data links for the purpose of extracting and decrypting the data.
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© Photo : ISRO
Future Satellites
HEO Satellites
Besides more persistent monitoring, HEO satellites have a shorter target area revisit time.
Targeting Satellites
Current ISRO optical and remote sensing satellites capture imagery which is downloaded and studied by photo analysts on the ground. During the course of hostilities, photo analysts analyse the imagery, identify targets and relay their coordinates to military command centres for onward use by field units.
Missile Launch Warning Satellites
Missile launch warning satellites are equipped with powerful Infrared telescopes with cooled sensors to detect the plume of a missile, starting from launch to stage burnout, instantly processing the data to provide coordinates and predict the trajectory of the missiles.
The requirement for such a satellite constellation is acute in the Indian context because our adversaries are across our borders. Relying on radar detection will leave no time to react.
Layered Satellite Constellation
Speaking at the TechFest, the ISRO Chief alluded to multi-layered Earth observation, wherein a satellite in GSO, having observed something of interest, could task a satellite in polar orbit to perform higher resolution observation.
Communication Satellites for Satellite Communication
Indian Earth Observation Satellites operating beyond radio horizon may need to communicate with other Indian satellites in orbit in order to relay their data to a satellite control centre in India. ISRO would need to add communication relay features to its future satellites, or create a dedicated communication satellite constellation to facilitate satellite network communication.
Such satellites would also facilitate communication between layered communication discussed above.
"We have found out a way by which a layer of satellites can be launched starting from GEO (geostationary equatorial orbit) to LEO (lower earth orbit) and also (in) very low earth orbit where we need very critical assessment of some situation," said the ISRO Chief.