Abstract
The objective of this paper is to report the improvements in an empirical absolute calibration model developed at South Dakota State University using Libya 4 (+28.55°, +23.39°) pseudo invariant calibration site (PICS). The approach was based on use of the Terra MODIS as the radiometer to develop an absolute calibration model for the spectral channels covered by this instrument from visible to shortwave infrared. Earth Observing One (EO-1) Hyperion, with a spectral resolution of 10 nm, was used to extend the model to cover visible and near-infrared regions. A simple Bidirectional Reflectance Distribution function (BRDF) model was generated using Terra Moderate Resolution Imaging Spectroradiometer (MODIS) observations over Libya 4 and the resulting model was validated with nadir data acquired from satellite sensors such as Aqua MODIS and Landsat 7 (L7) Enhanced Thematic Mapper (ETM+). The improvements in the absolute calibration model to account for the BRDF due to off-nadir measurements and annual variations in the atmosphere are summarized. BRDF models due to off-nadir viewing angles have been derived using the measurements from EO-1 Hyperion. In addition to L7 ETM+, measurements from other sensors such as Aqua MODIS, UK-2 Disaster Monitoring Constellation (DMC), ENVISAT Medium Resolution Imaging Spectrometer (MERIS) and Operational Land Imager (OLI) onboard Landsat 8 (L8), which was launched in February 2013, were employed to validate the model. These satellite sensors differ in terms of the width of their spectral bandpasses, overpass time, off-nadir-viewing capabilities, spatial resolution and temporal revisit time, etc. The results demonstrate that the proposed empirical calibration model has accuracy of the order of 3% with an uncertainty of about 2% for the sensors used in the study.
Highlights
Absolute calibration is a process that converts the voltage recorded by a satellite sensor or digitized counts to an absolute radiance unit
pseudo invariant calibration site (PICS) have been widely used for monitoring temporal stability and cross calibration of optical sensors, but only few have explored the possibility of using PICS to develop absolute calibration model
This paper makes a strong case for the use of these PICS for absolute calibration model development
Summary
Absolute calibration is a process that converts the voltage recorded by a satellite sensor or digitized counts to an absolute radiance unit. Govaerts et al have done the initial work in developing an absolute calibration model using PICS with geostationary satellites [7,8] In these papers, the solar irradiance was used as a forcing function along with a bidirectional surface reflectance model based on a three-parameter bare soil approach. Bhatt et al developed a desert daily exoatmospheric radiance model (DERM) based on a well-calibrated (reference) geostationary Earth orbit (GEO) satellite visible sensor [10]. SpectroMeter for Atmosphere Chartography (SCIAMACHY) instrument onboard the European environmental (ENVISAT) satellite was used to account for the spectral band differences between the reference and target GEO satellites Their results showed that reference Meteostat-9 DERM and ray-matched calibration consistency was within 0.4% and 1.9% for Meteostat-8 and Meteostat-7, respectively, using Libya 4 PICS.
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
