This presentation slide, below, shows Pakistan's Karachi Airport, as viewed using India's RISAT-2, Radar Imaging Satellite.
complete slide link:
International Goals in Space - Indian Space Programme
The choice of using imagery from Pakistan as an example while speaking about the satellite is highly significant. The need for India to fast-track launch of a Satellite, with a Synthetic Aperture Radar [S.A.R.] on-board, arose soon after Pakistani terrorists, under clear directives from the Pakistan Army, undertook a systematic campaign of carnage in the Indian city of Mumbai, that resulted in the death of hundreds of Indians, along with 6 Americans dying in the hands of Pakistan.
Thus, a decision was taken to acquire an Israeli satellite, already equipped with a SAR, the EL/M-2070 TecSAR, and launch it at the earliest. The satellite was named RISAT-2, even while no RISAT-1 was then orbiting, because the Indian Space Research Organisation [I.S.R.O.] had its own programme underway to develop a Radar Imaging Satellite, that had been allocated the RISAT-1 name.
Since then, ISRO has completed work & also successfully launched the RISAT-1 satellite on-board the Polar Satellite Launch Vehicle [PSLV C-19 mission] on April 26, 2012.
Traditional earth observation satellites require an ambient light source [Sun] to illuminate the target [optical reconnaissance]. Hence, these satellites are unable to generate imagery if it is night or cloudy over the region it is passing. Radar imaging satellites, on the other hand, carry their own illuminating source - microwave radiations. Transmitting radiations at frequencies that can penetrate through cloud cover, these satellites can carry out surveillance irrespective of the Sun.
While the RISAT-2 [TecSAR] radiates in the X-Band of the frequency spectrum, the RISAT-1's radar operates a shade lower, in the C-Band. However, since the time the RISAT-1 project was mooted in around 2002, DRDO labs have been successful in developing X-Band T/R modules for use in LCA Tejas's AESA radar,
"According to B.V. Ramesh, project director of LRDE's LSTAR programme, an LRDE-developed X-Band AESA radar could be fitted on the Tejas by 2014. Two modules of the AESA radar have already been launched."
Astra Microwaves has been awarded the contract to productionise the design.
Thus, it would be safe to assume that work on adapting them for use in future RISATs too must be underway. While RISAT-2 has a revisit period of 3-4 days, a constellation of such satellites in similar orbit space would ensure monitoring of any point in its path with less interval of time between successive revisits.
Pakistan under watch - advanced Indian Satellites Eyeballing the country [RISAT-2] - AA Me, IN
