NOAA-21 OMPS Nadir Mapper and Nadir Profiler SDR Data on-Board Calibration: Status and Remaining Challenges Towards Meeting the Scientific Requirements

The Ozone Mapping and Profiler Suite (OMPS) on NOAA's latest polar orbiting environmental satellite NOAA-21, which was launched on November 10, 2022, started collecting Earth science data on Feb 8, 2023. The OMPS on the NOAA-21 satellite consists of a set of three sensors: Nadir Mapper (NP), the Nadir Profiler (NP) and the Limb Profiler (LP), which are vital for monitoring the Earth's Ozone layer and tracking its recovery as the amounts of atmospheric ozone-depleting chemicals decline. For example, the NM and NP are two nadir ultraviolet spectrometers used to measure Earth radiance and Solar irradiance spectra from 300-380 nm and 250-310 nm, respectively. In particular, the OMPS NM on NOAA-21 offers significant improvement in the spatial resolution of NOAA operational ozone products -- 12x10 km² (across-track by along-track) resolution versus 50x17 km² on NOAA-20 and 50x50 km² on SNPP.

In NOAA, we have performed or are performing a series of on-orbit calibration/validation analyses for the NM and NP Sensor Data Record (SDR) data towards meeting the JPSS data scientific requirements, particularly after the generation of the first image for the NOAA-21 OMPS NM and NP were successfully generated on 18 February, 2022 [1][2]. This study will present our latest results about the dark current, gain and nonlinearity and SNR features for the NM and NP, the on-orbit wavelength registration analysis for the NM and NP, the wavelength shift features for the NM and NP, the characterization and correction for the NM and NP in-band and out-of-band stray light effects, and the NP solar intrusion correction. The similar results from the SNPP and NOAA-20 will be given as a comparison. In addition, this study will demonstrate the result about the quality assessments for the NOAA-21 OMPS SDR data and their geolocation accuracy. One of the methods to assess the data quality is to conduct the inter-sensor comparison of SDR data among the NOAA-21, SNPP and NOAA-20 to assess the NOAA-21 quality consistency with SNPP and NOAA-20. The results will include the quality consistency analysis of the data between the NOAA-21 NM and NP in the dichroic range from 300 nm to 310 nm. The geolocation of the OMPS NM will be assessed against that of the NOAA-21 VIIRS M1 band, while the geolocation accuracy of the NOAA-21 NP will be analyzed against the nadir observations of the NM. It is expected that the quality of the NOAA-21 OMPS NM and NP SDR data will meet most of the scientific requirements when we present the results. Certainly, we will identify remaining calibration challenges towards meeting all scientific requirements as a final effort of this study.

Disclaimer: the presentation contents are solely the opinions of the authors and do not constitute a statement of policy, decision, or position on behalf of NOAA or the U. S. Government.