The Moderate Resolution Imaging Spectroradiometer (MODIS) is a 36-channel visible to thermal-infrared sensor. It was first launched on 18 December 1999 on the Terra satellite, the flagship of NASA's Earth Observing System (EOS) program. A second MODIS was deployed on the Aqua satellite on 04 May 2002.
The MODIS instruments on Terra and Aqua image the same area on Earth at approximately 10:30 a.m. and 1:30 p.m. (local time), respectively. Working in tandem, these sensors optimize cloud-free surface viewing and provide opportunities to investigate processes that occur on sub-daily time scales. NSIDC archives and distributes a suite of snow cover and sea ice data sets derived from MODIS observations.