Please let me know how to extract the Earth-Sun Distance and Solar illumination angle for a LISS3 image.? (I opened LISS3 image using ENVI 5.1 - And LISS3 is in Super-Structured Format).
For Sun illumination angle computation u may get a IDL program called solar geometry calculator from Exelis VIS code library. This program opens in Envi IDL and needs Lat long, Day month year and greenwich mean time of your area of interest as input.