India Launches RISAT-1 For Remote Sensing, Pakistani Surveillance

A rare image of the full Indian RISAT-1 radar satellite shows technicians unfolding the 20 x 6 ft. radar antenna as viewed from its gold insulated back side. Spacecraft bus with electronics is large box at top here (but aft in flight) that will sprout solar arrays spanning about 40 ft. Compare with graphic further below. Photo Credit ISRO

India’s new RISAT-1 imaging radar satellite in development for 10 yr. is undergoing initial checkout in polar orbit following a predawn launch April 23 from the Satish Dhawan Space Center.

Liftoff of the powerful XL version of India’s nearly 150 ft. 4-stage Polar Satellite Launch Vehicle (PSLV-XL) came at 5:47 a.m. local time.

Liftoff ! The PSLV-XL rocket placed the RISAT-1 imaging radar satellite into an initial 298 mi. Sun Synchronous orbit inclined 97 deg. The spacecraft's own thrusters will propel RISAT-1 to its 333 mi. operational altitude. Photo Credit ISRO

The 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 is one of the heaviest spacecraft launched into low Earth orbit by India.

India had previously only released a graphic drawing of the satellite, but in connection with the launch it has now released detailed images. Compare them with the graphic (below).

The 3,900 lb. satellite will normally fly with the radar panel forward supported by a triangular box that contains propellant for thrusters and avionics for the radar. Large box at rear handles solar arrays and electrical systems. Photo Credit:ISRO

The new RISAT-1 spacecraft adds to India’s existing fleet of 11 Earth resources satellites in polar or geosynchronous orbit, including RISAT-2 launched in 2009 carrying powerful Israeli built X-band radar with a 10 ft. dish antenna to focus energy on the Pakistani border and other targets.  India launched a similar military radar spacecraft for Israel in 2008.

The new RISAT-1 spacecraft (launched second) carries a 20 x 6 ft. rectangular radar panel below its main bus that sprouts solar arrays spanning about 40 ft.

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 moderate resolution mode it can also operate in two lower resolution modes depending on the type of areas being imaged. It is designed to transmit radar data at up to 640 Mbps.

Image shows RISAT-1 lying horizontal in its normal flight mode. The active white side of radar panel will deploy out on either side of triangular core housing propellant tanks and thrusters. At rear, a systems bus has solar arrays attached. Photo Credit:ISRO

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

Numerous news media outlets in India and Europe have opted for blaring “spy satellite!” headlines to draw attention to RISAT-1.

The new spacecraft will make a decent surveillance satellite for images of Pakistan and China. But it should be a superb land and coastal zone monitoring satellite.  This will be especially true for monitoring India’s complex crops, many in paddies and hydrology, especially for rapid storm damage or rescue assessments that can help save lives, day or night when bad weather is still raging.

The RISAT-2 Israeli built 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 dish radar antenna is far 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.

The rocket that launched RISAT-1 is called a PSLV-XL because it uses six larger strap-on motors than those used in the standard PSLV version. Standard Indian strap on solid rocket boosters each carry 9 tonnes of solid propellant, but the extended solids on the XL each carry 12 tonnes. A tonne or long ton equals 2,204 lb. while a short ton equals 2,000 lb.

RISAT-1 with dark colored solar arrays tightly folded against aft systems box, facing up here, and the white radar antenna, folded along two sides of the three sided satellite, is shown ready for placement in launch shroud of PSLV-XL. Photo Credit: ISRO

This is just the third time the Indian Space Research Organization used a PSLV-XL, shown below shortly after liftoff.  It was first used in October 2008 to put Chandrayaan-1 into lunar orbit and again in July 2011 to during the GSAT-12 launch.

The RISAT-1 spacecraft was fired into an initial 298 mi. Sun synchronous orbit inclined 97.5 deg. Later the spacecraft’s thrusters will be used to move it into a 333 mi. orbit.

Photo Credit: ISRO


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