Microwave Instrument Geolocation Error Monitoring

Method for Microwave Sounders

The objective of the Geolocation Error Monitoring System is to provide real-time evaluation of the on-orbit geolocation error of ATMS aboard SNPP and NOAA-20 based on a refined coastline inflection point method (CIP). In CIP method, four consecutive observations across a shoreline are fit by a cubic polynomial function. The inflection point of the fit line is regarded as an observed coastline point. The distance from the observed coastline point to the true coastline provided by the high-resolution geography database is estimated to be the geolocation error.

To make the assessment more accurate, several improvements are made in the refined CIP method. Firstly, a separate-domain technique is applied in which the coastline along in-track direction is selected to estimate the cross-track geolocation error while the coastline along cross-track direction is selected to estimate the in-track error. Secondly, only the coastline regions without small islands are selected and VIIRS cloud mask product is utilized to screen out the cloud contaminated observations. Following these strategies, total of 24 regions with smooth coastline are selected, including 12 coastlines aligned with in-track direction and 12 coastlines aligned with cross-track direction. This system has been implemented to NOAA Integrated Calibration/Validation System Long-Term (ICVS) Monitoring, providing scan-angle dependent in-track and cross-track geolocation errors for ATMS onboard SNPP and NOAA-20. Its application can be extended to any transparent window channel of space borne microwave radiometers.

Author: Jun Zhou, University of Maryland, Earth System Science Interdisciplinary Center, 5825 University Research Court, College Park, MD, USA, 20740-3823; jzhou128@umd.edu)

References

• Zhou, J., H. Yang and K. Anderson, 2019: SNPP ATMS On-Orbit Geolocation Error Evaluation and Correction Algorithm. IEEE Transactions on Geoscience and Remote Sensing, vol. 57, no. 6, pp. 3802-3812, doi: 10.1109/TGRS.2018.2887407.
• Zhou, J., H. Yang and F. Weng, 2016: Rebuild the instrument mounting matrix for microwave instrument on-orbit geometric calibration. IEEE GARSS.
• Tang, F., X. Zou, H. Yang, and F. Weng, 2016: Estimation and correction of geolocation errors in Feng Yun-3C microwave radiation imager data. IEEE Transactions on Geoscience and Remote Sensing, vol. 54, no. 1, pp. 407-420.

-- RobbiIacovazzi - 10 Aug 2020