Abstract
Abstract. Significant in-band stray light (IBSL) error at solar zenith angle (SZA) values larger than 77° near sunset in 4 SBUV/2 (Solar Backscattered Ultraviolet) instruments, on board the NOAA-14, 17, 18 and 19 satellites, has been characterized. The IBSL error is caused by large surface reflection and scattering of the air-gapped depolarizer in front of the instrument's monochromator aperture. The source of the IBSL error is direct solar illumination of instrument components near the aperture rather than from earth shine. The IBSL contamination at 273 nm can reach 40% of earth radiance near sunset, which results in as much as a 50% error in the retrieved ozone from the upper stratosphere. We have analyzed SBUV/2 albedo measurements on both the dayside and nightside to develop an empirical model for the IBSL error. This error has been corrected in the V8.6 SBUV/2 ozone retrieval.
Highlights
Stratospheric ozone shields Earth’s biosphere from solar ultraviolet radiation (DeFabo, 2000), while tropospheric ozone as a pollutant impacts global health and economy (Selin et al, 2009)
During thermal vacuum testing of NOAA-16 SBUV/2 (N16) in 1987, We have identified the in-band stray light (IBSL) error in Fig. 2 using direct comtwo of the quartz crystal surfaces separated causing a sharp parison of N16 and NOAA18 SBUV/2 (N18) albedo measurements at 273 nm
IBSL is found in the earth radiance measurements from the last 4 Solar Backscattered Ultraviolet (SBUV)/2 instruments, which were flown on the NOAA14, 17, 18 and 19 satellites, at a solar zenith angle (SZA) larger than 77◦ when approaching terminator at sunset
Summary
Stratospheric ozone shields Earth’s biosphere from solar ultraviolet radiation (DeFabo, 2000), while tropospheric ozone as a pollutant impacts global health and economy (Selin et al, 2009). Detecting a 2 % ozone density change in Umkehr layers in the stratosphere requires the calibration of SBUV/2 albedo measurements at the short wavelengths to be accurate to within 1 % With such a large dynamical signal range and stringent accuracy requirement, stray light often becomes a difficult issue in optical design and characterization of a spectrometer. These plates are designed to shield the aperture from both direct solar incident radiation and spacecraft surface reflections of both solar light and earth shine.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
