Bangalore: Preparations are underway for this month's launch of an indigenously designed and developed satellite that has the unique capability of imaging during day and night and in all weather conditions.

ISRO is looking at 'lucky April 20' for the blast-off from India's spaceport of Sriharikota.

RISAT-1, a Radar Imaging Satellite with the capability to take images of the earth during day and night as well as in cloudy conditions, is a first of its kind by India and has already reached the spaceport having been transported from here.

India had launched RISAT-2, which it bought from Israel for USD 110 million, on April 20, 2009, and Resourcesat-2 mission took place on the same day last year. Both were successful ventures.

"April 20 is a lucky day for us", an ISRO official said. After back-to-back failures of GSLV -- one with Russian engine and another with homegrown one --, this statement did not come as a surprise.

RISAT-1, weighing around 1850 kg, is slated for launch by ISRO’s workhorse Polar Satellite Launch Vehicle (PSLV-C19 (XL)) into a 536 km orbit. The launch of the spacecraft, the country’s first microwave remote sensing satellite, was put off by at least a couple of months following the ISRO row, the fallout of the punitive action against four former space scientists for their role in the Antrix-Devas deal, that delayed the preparations.

RISAT-2 with all weather capability and ability to penetrate through clouds was realised in association with Israel Aerospace Industries. RISAT-2, primarily a spy satellite, is being used solely for Defence applications, keeping an eye on the borders and the country's neighbourhood.

"This satellite (RISAT-2) can sharply focus on metallic objects", an ISRO official said.

"The RISAT-1 will be useful for monitoring of agriculture and water resources management, among other applications", said the official, who added that this satellite would not be used for defence applications as RISAT-2 is already doing that job.

RISAT-1 carries a C-band Synthetic Aperture Radar (SAR) payload, operating in a multi-polarisation and multi-resolution mode to provide images with coarse, fine and high spatial resolutions respectively.