Gabriel Moy

Mission history of reflective solar band calibration performance of VIIRS

Environmental Data Records (EDR) from the Visible Infrared Imaging Radiometer Suite (VIIRS) have a need for Reflective Solar Band (RSB) calibration errors of less than 0.1%. Throughout the mission history of VIIRS, the overall instrument calibrated response scale factor (F factor) has been calculated with a manual process that uses data at least one week old and up to two weeks old until a new calibration Look Up Table (LUT) is put into operation. This one to two week lag routinely adds more than 0.1% calibration error. In this paper, we discuss trending the solar diffuser degradation (H factor), a key component of the F factor, improving H factor accuracy with improved bidirectional reflectance distribution function (BRDF) and attenuation screen LUTs , trending F factor, and how using RSB Automated Calibration (RSBAutoCal) will eliminate the lag and look-ahead extrapolation error.

SNPP VIIRS thermal emissive band performance after three years on-orbit

The Suomi National Polar-orbiting Partnership (SNPP) spacecrafts primary sensor is the Visible-Infrared Imaging Radiometer Suite (VIIRS) which launched on October 28, 2011. It has 22 total bands with 7 thermal emissive bands (TEBs), a high dynamic range monochromatic Day Night Band (DNB) and 14 reflective solar bands (RSBs). The TEB gain and noise performance is tracked on-orbit using an On-Board Calibrator BlackBody (OBCBB) as a thermal source. The TEBs view the OBCBB every scan allowing gain correction roughly every 1.7 seconds. Long term trending of the F factor (inversely proportional to gain) and Noise Equivalent delta Temperature (NEdT) allows the stability and uncertainty in the TEB thermal model to be evaluated. This paper will discuss the impacts of the thermal model uncertainties on the VIIRS calibration and how those impact the long term performance of VIIRS. It will also show the stability of the TEBs over 3 years on-orbit.

S-NPP VIIRS thermal emissive band thermal calibration errors and their impact on blackbody warm up and cool down f factors

The Visible-Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft as a primary sensor was launched October 28, 2011. There are 22 VIIRS bands: 7 thermal emissive bands (TEBs), 14 reflective solar bands (RSBs) and a Day Night Band (DNB). An on-orbit On-Board Calibrator BlackBody (OBCBB) is used as the TEB calibration source that tracks the detector gain change on a scan-by-scan basis. A thermal model to account for internal sensor emission is used in both the OBCBB derived gain calibration and Earth View (EV) radiance and brightness temperature retrievals. This thermal model uses pre-launch calibration coefficients to convert detector response into radiance and internal VIIRS cavity thermistors to estimate the sensors internal emission from various optical surfaces. The inputs to the thermal model have uncertainties which introduce errors in both the gain correction and the EV retrievals. This paper will discuss the impacts of the thermal model uncertainties on the VIIRS calibration.

SNPP VIIRS thermal emissive band thermal calibration errors and their impact on radiance and brightness temperature retrieval

The Visible-Infrared Imaging Radiometer Suite (VIIRS) on-board the Suomi National Polar-orbiting Partnership (SNPP) spacecraft as a primary sensor was launched October 28, 2011. It has 22 bands: 7 thermal emissive bands (TEBs), 14 reflective solar bands (RSBs) and a Day Night Band (DNB). The TEBs are calibrated on-orbit using the On-Board Calibrator BlackBody (OBCBB) as a thermal source every scan to track the detector gain change. A thermal model is used in both the OBCBB derived gain calibration as well as in other corrections to the Earth View (EV) radiance and brightness temperature retrievals. This thermal model uses prelaunch calibration coefficients to convert detector response into radiance as well as VIIRS cavity thermistors to estimate the sensors internal emission contributions. The inputs to the thermal model have uncertainties which introduce errors in both the gain correction and the EV retrievals. This paper will discuss the impacts of the thermal model uncertainties on the VIIRS calibration.

Fusion of radar and satellite target measurements

A potentially high payoff for the ballistic missile defense system (BMDS) is the ability to fuse the information gathered by various sensor systems. In particular, it may be valuable in the future to fuse measurements made using ground based radars with passive measurements obtained from satellite-based EO/IR sensors. This task can be challenging in a multitarget environment in view of the widely differing resolution between active ground-based radar and an observation made by a sensor at long range from a satellite platform. Additionally, each sensor system could have a residual pointing bias which has not been calibrated out. The problem is further compounded by the possibility that an EO/IR sensor may not see exactly the same set of targets as a microwave radar. In order to better understand the problems involved in performing the fusion of metric information from EO/IR satellite measurements with active microwave radar measurements, we have undertaken a study of this data fusion issue and of the associated data processing techniques. To carry out this analysis, we have made use of high fidelity simulations to model the radar observations from a missile target and the observations of the same simulated target, as gathered by a constellation of satellites. In the paper, we discuss the improvements seen in our tests when fusing the state vectors, along with the improvements in sensor bias estimation. The limitations in performance due to the differing phenomenology between IR and microwave radar are discussed as well.

Evaluation of geostationary lightning mapper navigation performance with the INR Performance Assessment Toolset (IPATS)

The GOES-R flight project has developed the Image Navigation and Registration (INR) Performance Assessment Tool Set (IPATS) to perform independent INR evaluations of the optical instruments on the GOES-R series spacecraft. In this paper, we document the development of navigation (NAV) evaluation capabilities within IPATS for the Geostationary Lightning Mapper (GLM). We also discuss the post-processing quality filtering developed for GLM NAV, and present example results for several GLM datasets. Initial results suggest that GOES-16 GLM is compliant with navigation requirements.

Viirs rsbautocal refinements to allow DNB dark signals & gain ratios transition to automated operation mode

The Visible Infrared Imager Radiometer Suite (VIIRS) Reflective Solar Band Automated Calibration (RSBAutoCal) Day Night Band (DNB) dark signal and gain ratio calculations exhibit two issues: gain ratio trending instability and gain ratio differences relative to those calculated using the VIIRS Recommended Operating Procedures (VROP) monthly look-up table (LUT) generation tool. These issues have thus far prevented transition of RSBAutoCal to automated mode for these two DNB calibration parameters. In this paper we describe the successful diagnosis of the gain ratio stability issue. We also present a solution to stabilize the gain ratios, thereby clearing the way for their tuning to match the VROP derived gain ratios and transition of RSBAutoCal to automated mode for both dark signals and gain ratios. This solution has been fully and successfully tested with Matlab code developed to simulate RSBAutoCal gain ratio and dark signal calculations and is ready for delivery for operational implementation.

Modification of VIIRS sensor data record operational code for consistency of data product limits

The Visible Infrared Radiometer Suite (VIIRS) sensor data record (SDR) product contains geolocated and calibrated radiances, quality flags, and derived products such as brightness temperature and reflectance. The active fire team reported an inconsistency in the way radiance limits and derived products limits are generated. The quality flags are also independently determined for radiance limits and derived product limits. This paper focuses on operational code modifications to address the inconsistent radiance and derived products and quality flag determination algorithm.

Improved VIIRS offset correction during lunar intrusion into space view

The VIIRS radiometric calibration approach relies on views of space above the earth limb to estimate a “zero offset” which is subtracted from the other instrument views (earth, solar diffuser, on board black body). This zero offset estimation is compromised when the Moon lies within the space view. The current calibration approach has a conservative method to determine when the space view is contaminated or potentially contaminated by the Moon. We outline a new approach to detecting lunar contamination, and for estimating the zero offset for contaminated scans. Our approach offers the potential to greatly reduce the number of scans classified as lunar contaminated and thus of lower quality due to the alternate calibration process used in the current operational approach. Thus, such an alternative approach could increase the number of nominal, high quality VIIRS scans available for science analyses.

S-NPP VIIRS instrument telemetry and calibration data trend study

The Suomi National Polar Orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) employs a large number of temperature and voltage sensors (telemetry points) to monitor instrument health and performance. We have collected data and built tools to study telemetry and calibration parameters trends. The telemetry points are organized into groups based on locations and functionalities. Examples of the groups are: telescope motor, focal plane array (FPA), scan cavity bulkhead, radiators, solar diffuser and Solar Diffuser Stability Monitor (SDSM). We have performed daily monitoring and long-term trending studies. Daily monitoring processes are automated with alarms built into the software to indicate if pre-defined limits are exceeded. Long-term trending studies focus on instrument performance and sensitivities of Sensor Data Record (SDR) products and calibration look-up tables (LUTs) to instrument temperature and voltage variations. VIIRS uses a DC Restore (DCR) process to periodically correct the analog offsets of each detector of each spectral band to ensure that the FPA output signals are always within the dynamic range of the Analog to Digital Converter (ADC). The offset values are updated based on observations of the On-Board Calibrator Blackbody source. We have performed a long-term trend study of DCR offsets and calibration parameters to explore connections of the DCR offsets with onboard calibrators. The study also shows how the instrument and calibration parameters respond to the VIIRS Petulant Mode, spacecraft (SC) anomalies and flight software (FSW) updates. We have also shown that trending studies of telemetry and calibration parameters may help to improve the instrument calibration processes and SDR Quality Flags.