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Those tracking kharif paddy, among other scenes, can get a clear picture of it this year, thanks to RISAT-1, the all-weather satellite.
The nation's second radar imaging satellite will be put into orbit at dawn on Thursday.
Its specialty is the SAR or synthetic aperture radar which can see through clouds.
Development and other agencies that track objects, people movements, natural features and disasters on ground using satellite images can now get a round-the-year, all-terrain view of these areas.
SAR has been developed by the ISRO's Space Applications Centre, Ahmedabad.
A radar imaging satellite is widely believed to have military uses too - a view that ISRO, a civil space agency, ignores.
“RISAT-1 will help to give sharp and clear images of kharif crop, especially paddy, during the cloudy months of September-November,” said an ISRO official.
“Otherwise, rice estimation would have to wait till December or January.”
It also beams some very sharp imageries of 1-metre resolution: of persons or objects such as cars that are 1m high or broad.
For all-weather data, national agencies relied on Canada's RADARSAT's imageries. That dependence will come down now, the official said.
RISAT-1 will also improve tracking and management during floods, cyclone and other natural disasters. The SAR can also ‘look' back and forth with its ‘ScanSAR' feature.
Other earlier IRSs (Indian remote sensing satellites) used optical and infrared sensors that failed to see below clouds.
RISAT-1 is led by its Project Director, Ms N. Valarmathi, - the second woman to helm a satellite project.
It costs Rs 378 crore – almost double an INSAT communications satellite - due to SAR. The launch adds Rs 120 crore to it.
RISAT-1 was due for launch in early to late 2009 but was urgently replaced by a much smaller RISAT-2. (It was in the aftermath of the Mumbai terror attacks.)
ISRO built the RISAT-2, of April 2009, with the help of Israel Aerospace Industries and launched it on its PSLV vehicle.
Its special uses are disaster management, forest cover, terrain mapping and what is called ‘species representation.'
On Monday morning, launch scientists at ISRO's launch port, Satish Dhawan Space Centre at Sriharikota, began counting down three days ahead of the event.
ISRO will launch it on its workhorse PSLV rocket, this one codenamed C19. The Launch Authorisation Board has cleared the launch for 5.47 a.m. on April 26.
The current remote sensing spacecraft weighs an ISRO-regular 1,850 kg. It operates in the C-band. RISAT-2 was around 300 kg and operates in the X-band.
During the 71-hour countdown, liquid propellant will be filled in the rocket's second and fourth stages. The tracking radar systems, communication networks and a host of ground systems will be checked.
“Mandatory checks on the launch vehicle and spacecraft (... and) charging of batteries and pressurisation of propellant tanks onboard the satellite will be performed.”
The rocket codenamed PSLV-C19 will inject RISAT-1 satellite into an initial pole-to-pole orbit at a distance of 480 km from Earth's surface.
Once in space, it will be nudged into a final orbit 536 km away by firing the thrusters on the satellite.
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