GEOSTATIONARY ENVIRONMENT MONITORING SPECTROMETER (GEMS) OVER THE KOREA PENINSULA AND ASIA-PACIFIC REGION
James Lasnik1, Michelle Stephens1, Brian Baker2, Christopher Randall1, Dai Ho Ko3, Seonghui Kim4, Youngsun Kim4, Eung Shik Lee4, Suyoung Chang4, Jong-Moon Park4, Seok-Bae SEO4, Youngchun Youk4, Jong Pil Kong4, Deoggyu Lee4, Seung-Hoon Lee3 and Jhoon Kim5, (1)Ball Aerospace & Technologies, Boulder, CO, United States, (2)Ball Aerospace & Technologies, Boulder, United States, (3)Korea Aerospace Research Institute, Daejeon, South Korea, (4)Korea Aerospace Research Institute, Daejeon, Korea, Republic of (South), (5)Samsung Advanced Institute of Technology, Samsung Particulate Matter Research Institute, Suwon, South Korea
Abstract:
Introduction: The Geostationary Environment Monitoring Spectrometer (GEMS) is one of two instruments manifested aboard the South Korean Geostationary Earth Orbit KOrea Multi-Purpose SATellite-2B (GEO-KOMPSAT-2B or GK2B), which is scheduled to launch in 2018. Jointly developed/built by KARI and Ball Aerospace, GEMS is a geostationary UV-Vis hyperspectral imager designed to monitor trans-boundary tropospheric pollution events over the Korean peninsula and Asia-Pacific region. The spectrometer provides high temporal and spatial resolution (3.5 km N/S by 7.2 km E/W) measurements of ozone, its precursors, and aerosols. Over the short-term, hourly measurements by GEMS will improve early warnings for potentially dangerous pollution events and monitor population exposure. Over the 10-year mission-life, GEMS will serve to enhance our understanding of long-term climate change and broader air quality issues on both a regional and global scale. The GEMS sensor design and performance are discussed, which includes an overview of measurement capabilities and the on-orbit concept of operations.
GEMS Sensor Overview: The GEMS hyperspectral imaging system consists of a telescope and Offner grating spectrometer that feeds a single CCD detector array. A spectral range of 300-500 nm and sampling of 0.2 nm enables NO2, SO2, HCHO, O3, and aerosol retrieval. The GEMS field of regard (FOR), which extends from 5°S to 45°N in latitude and 75°E to 145°E in longitude, is operationally achieved using an onboard two-axis scan mirror. On-orbit, the radiometric calibration is maintained using solar measurements, which are performed using two onboard diffusers: a working diffuser that is deployed routinely for the purpose of solar calibration, and a reference diffuser that is deployed sparingly for the purpose of monitoring working diffuser performance degradation.
