Abstract
The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on board the Suomi NPP satellite is a polar-orbiting imager that acquires Earth imagery in 22 spectral bands. Its mechanical design features a rotating telescope that scans the Earth, along with several onboard calibration sources, in sequence. These sources include a blackbody held at a known temperature and a diffuser of known reflectivity that redirects incident solar light of known irradiance. Upon activation of VIIRS in orbit an intensive effort was begun to characterize the performance of the instrument and validate the calibration of the Earth scene data. During the course of this analysis it was critical to have an intuitive understanding of the design of the instrument, as many variables in the calibration equation are dependent on geometry. It is difficult to visualize the precise alignment of the individual components solely using the position and orientation angles reported in the instrument description documents, particularly when there are inconsistencies across multiple sources. A scale model is preferred to allow analysts to visualize and interact with the instrument from various viewpoints. To accomplish this, a three-dimensional model of VIIRS was constructed using the software package Blender. The size and orientation of individual components of the instrument were taken from source documents provided by the instrument vendor, with any disparities between documents being resolved by the VIIRS Sensor Data Record Team. The model has enabled calibration scientists to see the precise location and orientation of the blackbody and solar diffuser, which has helped resolve any anomalous behavior observed from these calibration devices. Visualization has also helped validate solar incidence angle and lunar observation predictions, which are helpful for identifying future calibration events that may warrant specific analysis. A discussion of the model and its creation, as well as instances where it was used to assist in instrument anomaly resolution, will be presented.
A Simplified Three Dimensional Model of the VIIRS On-board Calibration System for Visualization and Anomaly Investigation
The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on board the Suomi NPP satellite is a polar-orbiting imager that acquires Earth imagery in 22 spectral bands. Its mechanical design features a rotating telescope that scans the Earth, along with several onboard calibration sources, in sequence. These sources include a blackbody held at a known temperature and a diffuser of known reflectivity that redirects incident solar light of known irradiance. Upon activation of VIIRS in orbit an intensive effort was begun to characterize the performance of the instrument and validate the calibration of the Earth scene data. During the course of this analysis it was critical to have an intuitive understanding of the design of the instrument, as many variables in the calibration equation are dependent on geometry. It is difficult to visualize the precise alignment of the individual components solely using the position and orientation angles reported in the instrument description documents, particularly when there are inconsistencies across multiple sources. A scale model is preferred to allow analysts to visualize and interact with the instrument from various viewpoints. To accomplish this, a three-dimensional model of VIIRS was constructed using the software package Blender. The size and orientation of individual components of the instrument were taken from source documents provided by the instrument vendor, with any disparities between documents being resolved by the VIIRS Sensor Data Record Team. The model has enabled calibration scientists to see the precise location and orientation of the blackbody and solar diffuser, which has helped resolve any anomalous behavior observed from these calibration devices. Visualization has also helped validate solar incidence angle and lunar observation predictions, which are helpful for identifying future calibration events that may warrant specific analysis. A discussion of the model and its creation, as well as instances where it was used to assist in instrument anomaly resolution, will be presented.