NASA - National Aeronautics and Space Administration

Global elevations are critical to understanding the Earth's dynamic processes and changing climate. These measurements are best acquired from a space‐based vantage point and are most accurate using laser altimetry technology. However, the accuracy associated with the elevation retrievals from laser altimetry relies heavily on the ability to precisely determine the pointing angle of the laser beams from the satellite to the illuminated spot on the surface. The Ice, Cloud, and land Elevation Satellite 2 (ICESat‐2) has a system consisting of instruments that support the determination of the laser pointing direction through a process called Precision Pointing Determination (PPD). In this paper, we describe the PPD conceptual implementation, instrument details, data processing approach, calibration/validation techniques, and performance assessment. We show that the PPD has successfully achieved the allocated accuracy goal essential to meeting the ICESat‐2 geolocation mission requirement.