The Ice, Cloud, and land Elevation Satellite, whose primary mission was the global monitoring of the polar ice change. ICESat placed in a 91-day exact repeat orbit with 33 days sub-cycles at 600 km altitude and prescribed ground tracks for measuring elevations of ice sheet, sea ice and forest canopy. The global observation systems are being enhanced by ICESat’s precise measurement. With big three missions, it has obvious superiority in pole ice and snow remote sensing. Firstly, ICESat is specifically intended to estimate the change of polar ice-sheet contributions to current and future sea-level rise. ICESat can make different in not only assessing mass balance and mechanisms that driving those changes, but improving predictive ice sheet models. Secondly, as a new and powerful tool, ICESat is designed to measure changes in the spatial patterns of freeboard and thickness of sea-ice by improving narrow lead detection. Finally, it will contribute much to the vegetation and ecosystem science in terms of forest canopy height estimation as well as topographic relief and vegetation vertical structure description. ICESat-2, which is the successor of the ICESat, is a following mission planed by NASA. ICESat-2 will be launched in late 2015 and will follow the ICESat orbit. Compare to the ICESat’s design, ICESat-2 will provide a micro-pulse multi-beam method. ICESat-2 will apply dense cross-track sampling to solve the influence of surface slope. The sensor will have a high laser repetition rate of 10 kHz which are spaced along-track sampling of about 0.7m. The sensor has 9 beams with unequal energy. In contrast to the predecessor, ICESat-2’s elevation measures over high slope areas and very rough areas will be precise.
