Abstract
The VIIRS instrument on board the S-NPP spacecraft has successfully operated for more than four years since its launch in October, 2011. Many VIIRS environmental data records (EDR) have been continuously generated from its sensor data records (SDR) with improved quality, enabling a wide range of applications in support of users in both the operational and research communities. This paper provides a brief review of sensor on-orbit calibration methodologies for both the reflective solar bands (RSB) and the thermal emissive bands (TEB) and an overall assessment of their on-orbit radiometric performance using measurements from instrument on-board calibrators (OBC) as well as regularly scheduled lunar observations. It describes and illustrates changes made and to be made for calibration and data quality improvements. Throughout the mission, all of the OBC have continued to operate and function normally, allowing critical calibration parameters used in the data production systems to be derived and updated. The temperatures of the on-board blackbody (BB) and the cold focal plane assemblies are controlled with excellent stability. Despite large optical throughput degradation discovered shortly after launch in several near and short-wave infrared spectral bands and strong wavelength dependent solar diffuser degradation, the VIIRS overall performance has continued to meet its design requirements. Also discussed in this paper are challenging issues identified and efforts to be made to further enhance the sensor calibration and characterization, thereby maintaining or improving data quality.
Highlights
The first Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on board the Suomi NationalPolar Orbiting Partnership (S-NPP) satellite has been successfully operated for four years since its launch in October 2011
The F-factor is determined by comparing the known calibration source spectral radiance (LCS) with that retrieved by the sensor (LRET) using the pre-launch calibration coefficients, where c0, c1 and c2 are the instrument temperature-dependent calibration coefficients derived from pre-launch characterization, RVSEV is the detector’s response versus scan angle at the Earth view (EV) half-angle mirror (HAM) angle of incidence (AOI), derived from pre-launch measurements, and F is a calibration scaling factor derived from on-orbit measurements of the solar diffuser (SD) or BB, known as the F-factor [8]
This paper has presented the status of Suomi NationalPolar Orbiting Partnership (S-NPP) VIIRS on-orbit radiometric performance
Summary
The first Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on board the Suomi National. Some of the key characteristics of VIIRS spectral bands are shown, including their wavelength ranges, focal plane location, typical and maximum scene spectral radiances or temperatures and specified signal-to-noise ratios (SNR) or noise-equivalent temperature differences (NEdT) at their corresponding typical radiances or temperatures In this table, radiance and SNR are used for the RSB, while temperature and NEdT are used for the TEB. The list of activities performed to generate VIIRS SDR includes: new RSB calibration coefficients (in LUT form) developed every week to generate the radiance and reflectance in the SDR products [12]; the DNB detector offsets and gain ratios generated on a monthly basis [13]; and the LUTs needed for the DNB stray light correction are updated every month in the operational processing [13].
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