Advanced Land Observing Satellite, ALOS is a Japanese Earth-Observation satellite, developed by JAXA. The objective of the mission is to provide the user community with data of sufficient resolution to be able to generate 1:25,000 scale maps. It is one of the largest Earth observing satellites ever developed. ALOS has a GPS receiver and a laser reflector as tools for orbit determination. ALOS is continuously operating more than 4 years and it works very well. ALOS has three mission instruments i.e. an L-band Synthetic Aperture Radar called PALSAR, and two optical sensors called PRISM and AVNIR-2.