Vicarious Calibration of Orbiting Carbon Observatory-2

Vicarious calibration methods use well- changes in their response as they age or accumulate contacharacterized surface sites to complement other on-orbit minants. To meet these requirements, many instruments have radiometric calibration techniques. Since 2009, NASA’s Orbiting on-board calibrator (OBC) systems that employ lamps and calCarbon Observatory-2 (OCO-2) and Japan’s Greenhouse gasses Observing SATellite teams have conducted annual campaigns ibration targets. Some also use observations of radiometrically at Railroad Valley, NV, USA, for this purpose. These sensors stable astronomical targets such as the sun, moon, or standard pose special challenges due to their large footprint sizes and stars. These capabilities can be augmented by observations view angles. OCO-2 sweeps the playa surface during a targeted of well-characterized earth targets including pseudoinvariant overpass of the test site, and records data at a number of viewing calibration sites (PICS) and vicarious calibration (VicCal) angles. The smallest of these is selected for processing, thereby minimizing the off-nadir correction. Surface reflectances at nadir targets, which are routinely characterized by SI-traceable are recorded by the field team, and the Moderate Resolution surface and atmospheric measurements [1], [2]. Each of these Imaging Spectroradiometer (MODIS) surface reflectance calibration methodologies has its strengths and weaknesses. product is used to provide the small, off-nadir correction. 1) OBC: OBCs can be observed frequently to track rapid