India’s New Space Radar More EarthSat Than ReconSat


ISRO says computer graphic is true to 3,900 lb. RISAT-1 design, although it has released no pictures. Imaging radar panel is 6 x 20 ft. while solar arrays span about 40 ft. Photo Credit: ISRO

India’s new imaging radar satellite (above) is undergoing final testing prior to launch in mid April on an Earth resources and military surveillance mission.

The 3,900 lb. RISAT-1 spacecraft is the first C-Band phased array imaging radar spacecraft developed entirely in India by the Indian Space Research Organization (ISRO). It will be one of the heaviest spacecraft ever launched into low Earth orbit from the Satish Dhawan Space Center.

The new spacecraft will be added to India’s existing fleet of 11 Earth resources satellites in polar or geosynchronous orbit, including RISAT-2 launched in 2009 carrying a powerful Israeli built X-band radar. India launched a similar military radar spacecraft for Israel in 2008.

According to ISRO officials, the rocket that will launch RISAT-1 will be an upgraded version of the Polar Satellite Launch Vehicle called the PSLV-XL that has 6 large solid rocket boosters (see picture below).


PSLV-XL rocket like this with 6 large strap-on solids will launch the 2 ton RISAT-1 spacecraft into a 380 mi. sun-synchronous polar orbit. Photo Credit: ISRO

The rocket will be only the third PSLV-XL to be launched by ISRO and the first time it has been needed to carry such a heavy satellite into a low Earth orbit. It was previously only used to send the Chandrayaan-1 lunar orbiter to the moon in 2008 and then launched the Indian GSAT-12 geosynchronous orbit communications satellite in 2011.

The RISAT-1 radar will be capable of 3-20 ft. imaging resolution day or night and in any weather conditions. In addition to this high resolution mode it can also operate in two lower resolution modes depending on the type of targets being imaged. It is designed to transmit radar data at up to 640 Mbps.

The spacecraft carries a 20 x 6 ft. rectangular radar panel below its main bus that sprouts solar arrays spanning about 40 ft.

Previous Indian remote sensing satellites relied on optical and infrared sensors while RISAT-1 uses an indigenously developed C-band synthetic aperture radar (SAR) operating in multi-polarisation and multi-resolution modes.

The RISAT-2 Israeli radar spacecraft launched in 2009 was rushed into service ahead of the all-Indian RISAT-1.  This is because the Indian military knew that the Israeli radar is more specialized for military imaging and could provide intelligence imagery within a year of the 2008 Mumbai attacks tied to Pakistan. Israel operates an identical reconnaissance satellite called TecSAR (picture below).

Identical to India’s RISAT-2 this Israeli TecStar spacecraft is minus its large solar arrays. Israel’s TecSar has been an important asset for monitoring Iran. The 10 ft. antenna dish can obtain 4-5 in. resolution images day or night and in all weather conditions. Photo Credit: Israel Aerospace Industries.

India built the systems bus for the Israeli RISAT-2 radar but claims political bragging rights for the upcoming RISAT-1 mission simply because the entire spacecraft was built in India.

Numerous news media outlets in India and Europe have opted for blaring “spy satellite!” headlines to draw attention to RISAT-1. Actually the new spacecraft will make a tepid recon but superb land monitoring satellite especially for rapid storm damage assessment that can help save lives at night and when bad weather is still raging.

On the other hand the Israeli built RISAT-2 with its 10 ft. dish antenna is far more suited for intelligence gathering than the satellite about to be launched. RISAT-2 has provided India with meaningful intelligence about Pakistan and potential Al Qaeda threats.

The mesh dish on RISAT-2 can physically focus radar spot beams to obtain images with a resolution as high as 4-5 inches, according to Israeli defense officials. India now has this capability, but it is highly classified.

Another difference between the two spacecraft is that virtually every technical detail about the Indian made RISAT-1 is unclassified and easily available online by simply Goggling RISAT-1. But data on RISAT-2 built in part by the famed Israel Aerospace Industries (IAI), is much more sparse. India even declined initially to release images of the RISAT-2 launch on a PSLV rocket.

Israel obtained the RISAT-2 radar from Israel in exchange for launching Israel’s identical TecSat military imaging satellite now used heavily to monitor Iran especially at night. Iran even chided India over its decision to launch the TecSar.

The reason Israel needed another country’s launch capabilities to launch its military radar satellite is because Israel’s own launchers must be fired retrograde—west— instead of east to avoid dropping stages on Jordan and other countries. Westward launches severely limit the payload mass that can be propelled into orbit from Israel because space launches to the east benefit from the Earth’s rotation, gaining up to about 900 mph toward orbital velocity before leaving the ground.

Both the Israeli TecSar and Indian RISAT-2 radar spacecraft each weighing about 600 lb. were launched on PSLV-CA (core alone) launchers with no strap-on solid rocket boosters (ISRO picture below). Canisters that look like small solids actually contain thrust vector control fluid for steering the solid motor first stage core.

Photo Credit: ISRO

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