Frank J. De Luccia

Early On-Orbit Performance of the Visible Infrared Imaging Radiometer Suite Onboard the Suomi National Polar-Orbiting Partnership (S-NPP) Satellite

The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of the key environmental remote-sensing instruments onboard the Suomi National Polar-Orbiting Partnership spacecraft, which was successfully launched on October 28, 2011 from the Vandenberg Air Force Base, California. Following a series of spacecraft and sensor activation operations, the VIIRS nadir door was opened on November 21, 2011. The first VIIRS image acquired signifies a new generation of operational moderate resolution-imaging capabilities following the legacy of the advanced very high-resolution radiometer series on NOAA satellites and Terra and Aqua Moderate-Resolution Imaging Spectroradiometer for NASAs Earth Observing system. VIIRS provides significant enhancements to the operational environmental monitoring and numerical weather forecasting, with 22 imaging and radiometric bands covering wavelengths from 0.41 to 12.5 microns, providing the sensor data records for 23 environmental data records including aerosol, cloud properties, fire, albedo, snow and ice, vegetation, sea surface temperature, ocean color, and nigh-time visible-light-related applications. Preliminary results from the on-orbit verification in the postlaunch check-out and intensive calibration and validation have shown that VIIRS is performing well and producing high-quality images. This paper provides an overview of the on-orbit performance of VIIRS, the calibration/validation (cal/val) activities and methodologies used. It presents an assessment of the sensor initial on-orbit calibration and performance based on the efforts from the VIIRS-SDR team. Known anomalies, issues, and future calibration efforts, including the long-term monitoring, and intercalibration are also discussed.

Operational calibration of VIIRS reflective solar band sensor data records

The Visible-Infrared Imaging Radiometer Suite (VIIRS) is an instrument on-board the Suomi National Polar-orbiting Partnership (NPP) spacecraft, which launched on October 28, 2011. VIIRS performs measurements in 14 reflective solar bands (RSBs) spanning wavelengths from 412 nm to 2.25 um, which are calibrated by using solar radiance reflected from a Solar Diffuser (SD). The SD reflectance degrades over time, and a Solar Diffuser Stability Monitor (SDSM) is used to track the changes. The ratio between the calculated solar radiance reflected from the SD and the VIIRS measurement of this radiance using the pre-launch calibration coefficients is known as the “F factor.” The F factor is applied in the ground processing as a scale correction to the pre-launch calibration coefficients used to generate the calibrated radiances and reflectances comprising the Sensor Data Records (SDRs). The F factor is trended over time to track instrument response degradation. The equation for calculating expected solar radiance, and the coefficients used to convert the raw digital numbers measured by the detectors into radiance and reflectance values, are based on parameters stored in various Look-Up Tables (LUTs). This paper will discuss on-orbit RSB calibration for VIIRS, along with a description of the processing methodology, which includes operational LUT updates based on off-line calculations of F factor trending behavior.

JPSS-1 VIIRS Pre-Launch Response Versus Scan Angle Testing and Performance

The Visible Infrared Imaging Radiometer Suite (VIIRS) instruments on-board both the Suomi National Polar-orbiting Partnership (S-NPP) and the first Joint Polar Satellite System (JPSS-1) spacecraft, with launch dates of October 2011 and December 2016 respectively, are cross-track scanners with an angular swath of ±56.06°. A four-mirror Rotating Telescope Assembly (RTA) is used for scanning combined with a Half Angle Mirror (HAM) that directs light exiting from the RTA into the aft-optics. It has 14 Reflective Solar Bands (RSBs), seven Thermal Emissive Bands (TEBs) and a panchromatic Day Night Band (DNB). There are three internal calibration targets, the Solar Diffuser, the BlackBody and the Space View, that have fixed scan angles within the internal cavity of VIIRS. VIIRS has calibration requirements of 2% on RSB reflectance and as tight as 0.4% on TEB radiance that requires the sensor’s gain change across the scan or Response Versus Scan angle (RVS) to be well quantified. A flow down of the top level calibration requirements put constraints on the characterization of the RVS to 0.2%–0.3% but there are no specified limitations on the magnitude of response change across scan. The RVS change across scan angle can vary significantly between bands with the RSBs having smaller changes of ~2% and some TEBs having ~10% variation. Within a band, the RVS has both detector and HAM side dependencies that vary across scan. Errors in the RVS characterization will contribute to image banding and striping artifacts if their magnitudes are above the noise level of the detectors. The RVS was characterized pre-launch for both S-NPP and JPSS-1 VIIRS and a comparison of the RVS curves between these two sensors will be discussed.

Post-CDR NPOESS VIIRS sensor design and performance

This paper summarizes post-critical design review (CDR) design refinements and performance estimate updates to the National Polar-orbiting Operational Environmental Satellite Systems (NPOESS) Visible Infrared Imager Radiometer Suite (VIIRS) sensor. The design changes reduced manufacturing and performance risk to meet VIIRS sensor performance specifications. Electro-Magnetic Compatibility (EMC) and Electro-Magnetic Interference (EMI) requirements drove increased shielding and cable modifications. A telescope design modification was also required to remove modulated instrument background (MIB) discovered in the CDR optical design. Performance predictions were then generated from models and demonstration hardware based on the design refinements, and these are also reported here. VIIRS risk-reduction will continue as the Engineering Development Unit (EDU) is assembled and tested over the next year facilitating performance verification and lowering flight unit development risk.

Image Navigation and Registration Performance Assessment Tool Set for the GOES-R Advanced Baseline Imager and Geostationary Lightning Mapper

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.

Results from solar reflective band end-to-end testing for VIIRS F1 sensor using T-SIRCUS

Verification of the Visible Infrared Imager Radiometer Suite (VIIRS) End-to-End (E2E) sensor calibration is highly recommended before launch, to identify any anomalies and to improve our understanding of the sensor onorbit calibration performance. E2E testing of the Reflective Solar Bands (RSB) calibration cycle was performed pre-launch for the VIIRS Flight 1 (F1) sensor at the Ball Aerospace facility in Boulder CO in March 2010. VIIRS reflective band calibration cycle is very similar to heritage sensor MODIS in that solar illumination, via a diffuser, is used to correct for temporal variations in the instrument responsivity. Monochromatic light from the NIST T-SIRCUS (Traveling Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources) was used to illuminate both the Earth View (EV), via an integrating sphere, and the Solar Diffuser (SD) view, through a collimator. The collimator illumination was cycled through a series of angles intended to simulate the range of possible angles for which solar radiation will be incident on the solar attenuation screen on-orbit. Ideally, the measured instrument responsivity (defined here as the ratio of the detector response to the at-sensor radiance) should be the same whether the EV or SD view is illuminated. The ratio of the measured responsivities was determined at each collimator angle and wavelength. In addition, the Solar Diffuser Stability Monitor (SDSM), a ratioing radiometer designed to track the temporal variation in the SD Bidirectional Reflectance Factor (BRF) by direct comparison to solar radiation, was illuminated by the collimator. The measured SDSM ratio was compared to the predicted ratio. An uncertainty analysis was also performed on both the SD and SDSM calibrations.

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.

NPOESS VIIRS: next-generation polar-orbiting atmospheric imager

A new era in atmospheric remote sensing will begin with the launch of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) spacecraft in 2006, and the multiple operational NPOESS launches in sun-synchronous orbital planes (nominally 13:30, 17:30, or 21:30 local equatorial crossing times) starting in 2009. Cloud and atmosphere polar-orbiting environmental satellite data will be profoundly improved in radiometric quality, spectral coverage, and spatial resolution relative to current operational civilian and military polar-orbiting systems. The NPOESS Visible Infrared Imaging Radiometer Suite (VIIRS) will provide Environmental Data Records (EDRs) for day and night atmosphere and cloud operational requirements, as well as sea surface temperature (SST) and many important land EDRs by ground processing of raw data records (RDRs) from the VIIRS sensor. VIIRS will replace three currently operating sensors: the Defense Meteorological Satellite Program (DMSP) Operational Line-scanning System (OLS), the NOAA Polar-orbiting Operational Environmental Satellite (POES) Advanced Very High Resolution Radiometer (AVHRR), and the NASA Earth Observing System (EOS Terra and Aqua) MODerate-resolution Imaging Spectroradiometer (MODIS). This paper describes the VIIRS all-reflective 22-band single-sensor design, following the Critical Design Review (CDR) in Spring 2002. VIIRS provides low noise (driven by ocean color for the reflective visible and near-IR spectral bands and by SST for the emissive mid and long-wave IR spectral bands), excellent calibration and stability (driven by atmospheric aerosol and cloud EDRs, as well as SST), broad spectral coverage, and fine spatial resolution driven by the cloud imagery EDR. In addition to improved radiometric, spectral, and spatial performance, VIIRS features DMSP OLS-like near-constant resolution, global twice-daily coverage in each orbit plane, and direct heritage to proven design innovations from the successful Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Earth Observing System (Terra and Aqua) MODIS.

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.