RISAT 1

Spacecraft nº:

Indian spacecraft nº: 65

Launch data: Designation  38248 / 12017A Launch date  26 Apr 2012 - 00:17 UT Launch site  Sriharikota, FLP Launch vehicle  PSLV-XL (#C19) Mission  Military: Earth Observation, radar Sun-synchronous LEO Earth orbit on Apr 28.16: Perigee / Apogee  508 x 530 km Eccentricity  0.002 Inclination  97.60 deg Period  95.00 min

Spacecraft data: Prime manufacturer  ISRO Platform   Operator  Ministry of Defense Mass at launch  1858 kg Dry Mass   kg Basic shape  Triangular box + 2 panels + radar panel Dimension (m)   Equipment  C-Band SAR Solar array  2 deployable solar arrays, 6.10m span Stabilization  3-axis stabilized Propulsion   DC power   Design lifetime  5 yrs

RISAT-1 with one of its solar panel wings in deployed condition at Satish Dhawan Space Centre. Photo: ISRO

Description:

• RISAT 1 (Radar Imaging Satellite 1) is the first satellite imaging mission of ISRO using an active C-band SAR (Synthetic Aperture Radar) imager. The objective of the RISAT mission is to use the all-weather as well as the day-and-night SAR observation capability in applications such as agriculture, forestry, soil moisture, geology, sea ice, coastal monitoring, object identification, and flood monitoring.
• RISAT 1 is developed, manufactured and integrated by ISRO. The 3-axis stabilized spacecraft bus consists of a hexagonal prism shape build around a central cylinder. Most of the spacecraft subsystems and the payload are integrated in the prism structure and the central cylinder. The solar panels and some subsystems are mounted on the cube-shaped section of the spacecraft.
• The 1,858-kg Radar Imaging Satellite features a C-band Synthetic Aperture Radar (SAR) operating at 5.35 GHz in a multi-polarization and multi-resolution mode (ScanSAR, Strip and Spot modes) to provide images with coarse, fine and high spatial resolutions respectively.

Capability:

• The RISAT-1 has a Synthetic Aperture Radar with a 6 x 2 meter planar active array.
• Transmit/Receive modules in the active phased array provide multi-mode capability through electronic agility.
• The satellite provides spatial resolutions of 1 m ( in Spot Mode) to 50 m, and a swath of 10 to 240 km to cater to different applications. (ISRO's optical remote sensing satellites are believed to have a 0.8 meter resolution.)
• The radar will be able to provide day and night imaging through dust, cloud and smoke.
• Some of the new technological elements in RISAT are: 160 x 4 Mbps data handling system, 0.3 Nm (50 Nms) reaction wheels, SAR antenna deployment mechanism, 70 V power bus, thermal control of SAR antenna and phased array antenna (with Dual Polarization).

Mission details:

• Launch delayed from January 2012.
• RISAT-1 mission is not scheduled for March-2012. It may slip further to April or May. Some sources have told that the vehicle is waiting for the satellite to arrive from ISAC center at Bangalore.
• India's Radar Imaging Satellite was launched from the Satish Dhawan Space Center on Sriharikota Island on Apr 26, 2012. The 1858 kg RISAT-1 carries a C-band synthetic aperture radar payload mounted on an IRS-derived bus.
  RISAT-2, launched in 2009, was a smaller Israeli-built radar payload.
• The PSLV-XL rocket's first stage flew eastward to a roughly -5940 x 82 km x 46.6 deg suborbital path, avoiding overflight of Sri Lanka; the second stage then flew southward toward polar orbit, with the third stage reaching perhaps -1940? x 333? km x 96.1 deg and impacting the southern Indian Ocea at 35.5S 74.5E. The fourth stage entered orbit and deployed RISAT-1 to a 465 x 480 km x 97.6 deg initial orbit. RISAT-1's onboard engines raised this orbit to 530 x 549 km x 97.6 deg by Apr 28.63, putting the satellite in a sun-synchronous orbit with 05:51 local time descending node.