Geophysical Corrections and Modeling for ICESat-2 Science

NASA's ICESat-2 mission to measure and monitor the heights of ice sheets, sea ice, glaciers, oceans and planetary vegetation is scheduled for launch in 2017. Fundamentally different than the ICESat full waveform lidar (called GLAS); the primary instrument on ICESat-2 is the photon-counting ATLAS instrument. While the primary measurement of the mission is the photon range from the satellite to the Earth's surface, most science applications require converting range into height with respect to a reference ellipsoid. The science-directed data products require systematic removal of various geophysical signals to enhance their scientific utility. We have made assessments of various present-day models of ocean tides, earth tides, atmosphere-ocean interactions, pole tides and ocean loading, among other geophysical phenomena. We present a description and evaluation of models that presently constitute leading choices, as well as an assessment of the relevant spatial and temporal scales for each correction. Our goal is to produce a set of state-of-the-art corrections that will be applied to the ICESat-2 Level 2A data product (which provides latitude, longitude, and elevation for each photon recorded by ATLAS). A design criterion is that these corrections be easily removed for investigations involving improvements to the correction modeling, itself; or for cases when an investigator desires that a different model be applied.