Synthetic Aperture Radar (SAR) is the ideal instrument for observing polar regions, with its ability to see through clouds and operate during the long polar nights. Since the launch of ERS-1 in 1991, the international constellation of SARs has enabled great progress in our understanding of sea ice, ice sheets, and glaciers. With its launch in early 2023, NISAR will contribute to the fourth decade of extensive SAR observations of the cryosphere. In contrast to all other missions, it will operate in a permanently south-looking mode, providing complete routine coverage of Antarctica. Here we summarize the NISAR requirements and how the mission will greatly advance our observational capability for the Earth's remote ice-covered regions.