Landsat 9 Thermal Infrared Sensor 2 (TIRS-2) Stray Light Mitigation and Assessment

The Thermal Infrared Sensor 2 (TIRS-2) payload for the Landsat 9 mission closely follows design of TIRS instrument currently flying aboard 8. TIRS-2 instrument, however, incorporates an important change to mitigate stray light issue that plagued instrument. Shortly after launch 8 in 2013, calibration errors due artifacts were observed Earth imagery from with magnitudes 4% (10.8 μm band) and 8% (12.0 band). Out-of-field scans Moon conducted map angles which off-axis radiance was detected on focal plane arrays. Optical modeling, constrained by reverse ray traces lunar data, identified primary scattering sources within telescope these results informed locations mitigating baffles TIRS-2. effect modifications tested pre-flight through thermal vacuum (TVAC) characterization tests optical models updated be consistent measured data. Preliminary assessments indicated at least order magnitude reduction total signal On-orbit provided final confirmations demonstrated new changes have reduced out-of-field over 40x original bringing 1% or less. More importantly, produced do not show any related artifacts, as prevalent imagery.