RISAT is a series of India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

n radar imaging reconnaissance satellites built by ISRO. They provide all-weather surveillance using synthetic aperture radar

Synthetic aperture radar

Synthetic-aperture radar is a form of radar whose defining characteristic is its use of relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional...

s (SAR).

The RISAT series are the first all-weather earth observation satellites from ISRO. Previous Indian observation satellites relied primarily on optical and spectral sensors which were hampered by cloud cover.

After the November 26, 2008 Mumbai attacks

2008 Mumbai attacks

The 2008 Mumbai attacks were more than 10 coordinated shooting and bombing attacks across Mumbai, India's largest city, by Islamist attackers who came from Pakistan...

, the launch plan was modified to launch RISAT-2

RISAT-2

RISAT-2, or Radar Imaging Satellite 2 is an Indian radar reconnaissance satellite that is part of India's RISAT programme. It was successfully launched aboard a PSLV-CA at 01:15 GMT on April 20, 2009 from the Second Launch Pad at the Satish Dhawan Space Centre...

 before RISAT-1

RISAT-1

RISAT-1 is the first of the RISAT series of Indian remote sensing satellites built by the Indian Space Research Organisation . The satellite uses a Synthetic Aperture Radar for all-weather earth observation.While the RISAT-1 was the first satellite of the RISAT series to be built, it will be the...

, since the indigenous C-band SAR to be used for RISAT-1 was not ready. RISAT-2 used an Israel Aerospace Industries (IAI) X-band SAR sensor similar to the one employed on TecSAR

TecSAR

TecSAR, also known as TechSAR, Polaris and Ofek-8, is an Israeli reconnaissance satellite, equipped with synthetic aperture radar developed by Elta Systems...

.

RISAT 2

RISAT-2 was the first of the RISAT series to reach orbit. It was launched successfully on April 20, 2009 at 0015 hours GMT by a PSLV rocket. The 300-kg satellite was built by ISRO using a X-band SAR manufactured by IAI.

This satellite was fast tracked in the aftermath of the 2008 Mumbai attacks. The satellite will be used for border surveillance, to deter insurgent infiltration and for anti-terrorist operations. It is likely to be placed under the Aerospace Command of the Indian Air Force

Indian Air Force

The Indian Air Force is the air arm of the Indian armed forces. Its primary responsibility is to secure Indian airspace and to conduct aerial warfare during a conflict...

.

No details of the technical specifications of RISAT-2 have been published. However, it is likely to have a spatial resolution of about a metre or so. Ship detection algorithms for radar satellites of this class are well-known and available. The satellite also has applications in the area of disaster management and agriculture-related activities.

RISAT 1

RISAT-1 is an ingeniously developed radar imaging satellite expected to be launched by a PSLV rocket by January 2012. RISAT-1 was postponed in order to prioritize the building and launch of RISAT-2.

The features of RISAT-1 include:

• 160 x 4 Mbit/s data handling system
• 50 Newton-meter-second reaction wheels
• SAR antenna deployment mechanism
• Phased array antenna with dual polarisation