Peter Isaacson, Evan Haas, Frank De Luccia, Gabriel Moy, Brian Porter, Alan Reth, Scott Houchin, Justin Graybill, Philip Slingerland, Christopher Folley
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.
The Joint Polar Satellite System 1 (JPSS-1) is the follow on mission to the Suomi-National Polar-orbiting Partnership (SNPP) and provides critical weather and global climate products to the user community. A primary sensor on both JPSS-1 and S-NPP is the Visible-Infrared Imaging Radiometer Suite (VIIRS) with the Reflective Solar Band (RSB), Thermal Emissive Band (TEB) and Day Night Band (DNB) imagery providing a diverse spectral range of Earth observations. These VIIRS observation are radiometrically calibrated within the Sensor Data Records (SDRs) for use in Environmental Data Record (EDR) products such as Ocean Color/Chlorophyll (OCC) and Sea Surface Temperature (SST). Spectrally the VIIRS sensor can be broken down into 4 groups: the Visible Near Infra-Red (VNIR), Short-Wave Infra-Red (SWIR), Mid- Wave Infra-Red (MWIR) and Long-Wave Infra-Red (LWIR). The SWIR spectral bands on JPSS-1 VIIRS have a nonlinear response at low light levels affecting the calibration quality where Earth scenes are dark (like oceans). This anomalous behavior was not present on S-NPP VIIRS and will be a unique feature of the JPSS-1 VIIRS sensor. This paper will show the behavior of the SWIR response non-linearity on JPSS-1 VIIRS and potential mitigation approaches to limit its impact on the SDR and EDR products.
The GOES-R Flight Project has developed an Image Navigation and Registration (INR) Performance Assessment Tool Set (IPATS) for measuring Advanced Baseline Imager (ABI) and Geostationary Lightning Mapper (GLM) INR performance metrics in the post-launch period for performance evaluation and long term monitoring. For ABI, these metrics are the 3-sigma errors in navigation (NAV), channel-to-channel registration (CCR), frame-to-frame registration (FFR), swath-to-swath registration (SSR), and within frame registration (WIFR) for the Level 1B image products. For GLM, the single metric of interest is the 3-sigma error in the navigation of background images (GLM NAV) used by the system to navigate lightning strikes. 3-sigma errors are estimates of the 99. 73rd percentile of the errors accumulated over a 24 hour data collection period. IPATS utilizes a modular algorithmic design to allow user selection of data processing sequences optimized for generation of each INR metric. This novel modular approach minimizes duplication of common processing elements, thereby maximizing code efficiency and speed. Fast processing is essential given the large number of sub-image registrations required to generate INR metrics for the many images produced over a 24 hour evaluation period. Another aspect of the IPATS design that vastly reduces execution time is the off-line propagation of Landsat based truth images to the fixed grid coordinates system for each of the three GOES-R satellite locations, operational East and West and initial checkout locations. This paper describes the algorithmic design and implementation of IPATS and provides preliminary test results.
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.
The Suomi National Polar-orbiting Partnership (NPP) satellite was launched on Oct. 28, 2011, and began the
commissioning phase of several of its instruments shortly thereafter. One of these instruments, VIIRS, was found to
exhibit a gradual but persistent decrease in the optical throughput of several bands, with the near-infrared bands being
more affected than those in the visible. The rate of degradation quickly increased upon opening of the nadir door that
permits the VIIRS telescope to view the earth. Simultaneously, a second instrument on NPP, the Solar Diffuser Stability
Monitor (SDSM), was experiencing a similar decrease in response, leading the investigation team to suspect that the
cause must be the result of some common contamination process. This paper will discuss a series of experiments that
were performed to demonstrate that the VIIRS and SDSM response changes were due to separate causes, and which
enabled the team to conclude that the VIIRS sensor degradation was the result of ultraviolet light exposure of the
rotating telescope assembly. The root cause investigation of the telescope degradation will be addressed in a separate
paper.
The Visible-Infrared Imaging Radiometer Suite (VIIRS) was launched onboard the Suomi National Polar-orbiting
Partnership (NPP) spacecraft on October 28, 2011. Among the bands on VIIRS are 14 reflective solar bands (RSBs).
The RSBs are calibrated using the sun as a source, after attenuation and reflection of sunlight from a Solar Diffuser (SD).
The reflectance of the SD is known to degrade over time, particularly at the blue end of the visible spectrum. VIIRS
incorporates a separate instrument, a Solar Diffuser Stability Monitor (SDSM), in order to measure and trend the SD
Bidirectional Reflectance Distribution Function BRDF changes over time. Inadequate knowledge of the SDSM screen
transmission as a function of solar geometry and SDSM detector dependent modulation effects require a unique
processing methodology to eliminate unphysical artifacts from the SD BRDF trending. The unique methodology is used
to generate periodic updates to operational Look-up Tables (LUTs) used by the Sensor Data Record (SDR) operational
code to maintain the calibration of the RSBs. This paper will discuss on-orbit SD BRDF behavior along with the
processing methodology used to generate RSB LUT updates incorporating the trended SD BRDF behavior.
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