Geometric calibration of the Multi-Angle Imager for Aerosols (MAIA)

The Multi-Angle Imager for Aerosols (MAIA) instrument is currently scheduled for launch into polar Earth orbit in 2023. MAIA uses a single camera on a 2-axis gimbal for multi-angle viewing of Earth scenes, with the objective of making radiometric and polarimetric measurements. The data will then be used to determine aerosol size, type, and density. Health records will be collected in parallel as part of the MAIA investigation to enable correlation of adverse health effects with the aerosol data. The MAIA camera includes one visible and one SWIR detector, comprising a total of 14 wavelength bands from the UV to SWIR. Three of the bands are polarimetric. The MAIA telescope is a four-mirror anastigmat and has significant distortion of the field-of-view. Each channel in the camera comprises one or two rows of pixels, and each row has a total of 1216 pixels dedicated to imaging. Different channels must be co-registered to each other and each pixel must be geolocated to a fraction of the pixel size prior to determination of polarimetry and subsequent derivation of aerosol data. This requires, among other items, an accurate model of the camera internal geometry. This paper summarizes the geometric calibration performed during pre-flight testing to measure the transformation from pixel positions in the focal plane to angles in object space, i.e., the pointing angle of each pixel, and vice-versa.