Abstract
The on-orbit calibration of earth observation satellite sensors with solar diffuser (SD) is significantly of importance to obtain high quality sensor data with low uncertainty for the reflective solar band (RSB). Much effort has been devoted to the pre-launch calibration of SD, and associated components. In those calibrations, the BRDF measurement of SD, as well as the BTDF measurement for associated components, are required to be conducted at different incident angles due to the solar season on-orbit and viewing from various angles based on the instrument geometry with high accuracy. To satisfy different requirements for SD related calibrations, the new diffuser calibration facility is established with two kinds of scatterometer instruments, one is a table-top based goniometer, and the other is a robot-based scatterometer. For the SD calibration in the RSB, the light sources for the system are currently equipped with a 20 W supercontinuum fiber laser with the spectral range from 400 nm to 2500 nm, and two laser diode driven plasma lamp sources covering wavelengths from 200 nm to 900 nm. The detection systems corresponding to the same spectral range of interest are composed of Si and extended InGaAs (EIGA) detectors with low NEP down to 10-15 and 7 × 10-14 W/(Hz)1/2, respectively, which are designed to have two light collection options, with/without input integrating sphere. The development of the table-top based goniometer has reached the final stage of optimization and alignment for sample manipulation and detector rotation, meanwhile the major component, a 6-axis robot-arm, for the robot-based scatterometer was also delivered recently. The light source tests on spectral output and short term stability were carried out, and the preliminary results will be presented together with discussion of practical applications.
New Capabilities of Diffuser Calibration Lab at GSFC NASA to Support Remote Sensing Instrumentation
The on-orbit calibration of earth observation satellite sensors with solar diffuser (SD) is significantly of importance to obtain high quality sensor data with low uncertainty for the reflective solar band (RSB). Much effort has been devoted to the pre-launch calibration of SD, and associated components. In those calibrations, the BRDF measurement of SD, as well as the BTDF measurement for associated components, are required to be conducted at different incident angles due to the solar season on-orbit and viewing from various angles based on the instrument geometry with high accuracy. To satisfy different requirements for SD related calibrations, the new diffuser calibration facility is established with two kinds of scatterometer instruments, one is a table-top based goniometer, and the other is a robot-based scatterometer. For the SD calibration in the RSB, the light sources for the system are currently equipped with a 20 W supercontinuum fiber laser with the spectral range from 400 nm to 2500 nm, and two laser diode driven plasma lamp sources covering wavelengths from 200 nm to 900 nm. The detection systems corresponding to the same spectral range of interest are composed of Si and extended InGaAs (EIGA) detectors with low NEP down to 10-15 and 7 × 10-14 W/(Hz)1/2, respectively, which are designed to have two light collection options, with/without input integrating sphere. The development of the table-top based goniometer has reached the final stage of optimization and alignment for sample manipulation and detector rotation, meanwhile the major component, a 6-axis robot-arm, for the robot-based scatterometer was also delivered recently. The light source tests on spectral output and short term stability were carried out, and the preliminary results will be presented together with discussion of practical applications.