RISAT-1. Radar Imaging Satellite

Modes of Operation
100 km
(UNQUALIFIED)
100 km
(UNQUALIFIED)
608 km
FRS1&2 MODE
200
km
400 km
(QUALIFIED)
CRS MODE
MRS MODE
Radar Imaging Satellite
The active antenna consists of three
panels each of 2m x 2m size, totaling
6x2minall,andisdividedinto12tiles
of 1m x 1m each. Front side of each tile
has a grid of 24 x 24 radiation patches.
Backside of each tile carries 24 T/R
modules, their power supply modules
and controllers. With the help of phase
shifters in the T/R modules, the antenna
beam can be steered in range direction.
Output RF peak power of each T/R
module is 10 watts and the noise figure
of its receiver is 2 dB. The antenna has
its own calibration network to cross
check the performance of its various
elements on ground and in orbit. Input
signals to and output signals from TR
modules are processed using RF and
baseband subsystems. A chirped signal
at 5.35 GHz, having a pulse width upto
20 µ sec is fed to the T/R module for
further amplification and transmission.
The output of the receiver is filtered,
digitised using block adaptive
quantisation and sent to data formatter.
The data from SAR is formatted and
fed to RF transmitter. A solid-state
recorder (SSR) is part of the baseband
data handling subsystem. The payload
data can be transmitted in real time
mode or in playback mode.
It is planned to transmit the SAR
data, with 640 MBPS data rate using X-
band down-link in QPSK mode. A phased
array antenna with dual polarization is
used to overcome the limitation of
available bandwidth. The data rate for
each polarisation is, thus, planned to be
2 x160 Mbps. Data transmitter antenna
will have onboard beam
steering towards the
ground station during
data transmission.