For over 26 years, the MODIS instrument on the Terra platform has generated a broad range of scientific products, enabling the remote sensing community worldwide for the study of many geophysical parameters of the Earth's system. Together with the complementary observations from the MODIS instrument on the Aqua platform, a continuous and consistent data record dating back to the year 2000 has been generated. MODIS, a major advance over its heritage sensors in terms of its spectral, spatial, and temporal resolutions, provides Earth scene imagery via 36 spectral bands ranging from 0.4 to 14.4 mu m at three different spatial resolutions with a wide swath of 2330 km. In addition, significantly enhanced are dedicated calibration efforts to help produce and maintain MODIS data quality through its entire mission. We present a comprehensive summary of Terra MODIS operations, the calibration strategies developed and implemented, and its on-orbit performance over the 26 years of successful operation. Terra MODIS has maintained radiometric uncertainties of less than 2% for reflective solar bands and better than 0.1 K for thermal emissive bands over its 26-year mission, far exceeding its 6-year design life. The mission's success in maintaining long-term data quality demonstrates the critical importance of comprehensive on-board calibration systems and continuous performance monitoring for multiyear Earth observations. This calibration heritage provides essential guidance for designing future multidecadal Earth observing missions.

Following the success of Visible Infrared Imaging Radiometer Suite (VIIRS) instruments currently operating onboard the Suomi-NPP, NOAA-20, and NOAA-21 spacecraft, preparations are underway for the final two VIIRS instruments for the Joint Polar Satellite System 3 (JPSS-3) and 4 (JPSS-4) platforms. To that end, each instrument underwent a comprehensive sensor-level test campaign at the Raytheon Technologies, El Segundo facility, in both ambient and thermal-vacuum environments. Unique among the 22 VIIRS sensing bands is the day-night band (DNB)—a panchromatic imager that leverages multiple CCD detectors set at different gain levels to make continuous (day and night) radiometric observations of the Earth. The results from the JPSS-3 and JPSS-4 VIIRS DNB pre-launch testing are presented and compared against the design specifications in this paper. Characterization parameters include dark offset, gain, linearity, uniformity, SNR, and uncertainty. Performance relative to past builds is also included where appropriate.

The Joint Polar Satellite System (JPSS) is a collaborative program between NASA and NOAA to provide scientific measurements from multiple polar-orbiting satellites. The development, testing, launch, and operation of the satellites is jointly overseen by NASA and NOAA, with NASA responsible for developing and building instruments, spacecraft, ground systems, and launching into orbit. While three VIIRS instruments are currently on-orbit, spacecraft integration of the two VIIRS instruments planned for launch on the JPSS-3 and -4 spacecraft is ongoing. The latest build in the series, set to be launched on the JPSS-4 platform, recently completed its main ground calibration program at the vendor facility. This program covered a comprehensive series of performance metrics designed to ensure that the instrument can maintain its calibration successfully on-orbit. In this paper, we present the results from the radiometric calibration process, which includes metrics such as dynamic range, signal-to-noise ratio, noise equivalent differential temperature, polarization sensitivity, scattered light response, relative spectral response, response versus scan angle, and crosstalk. All key metrics have met or exceeded their design requirements, with some minor exceptions. Also included are comparisons with previous VIIRS instruments, as well as a description of their expected performance once on-orbit.

The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is a key component of the Joint Polar Satellite System (JPSS). VIIRS are currently operating on-board the JPSS-1/NOAA-20 and JPSS-2/NOAA-21 spacecraft in addition to the Suomi-National Polar-orbiting Partnership (SNPP) satellite. Two additional VIIRS instruments, designated for JPSS-3 and JPSS-4 have completed their instrument-level pre-launch testing campaigns. Within the pre-launch characterization program, multiple tests are performed to assess the impact of electronic and optical crosstalk between bands and detectors in both ambient and simulated space environment (thermal vacuum) environments. Though the specific crosstalk behavior of each instrument is unique, the overall crosstalk performance has remained steady or improved with each successive unit. Additionally, performance specifications and test procedures have evolved over the JPSS test program, which has spanned over a decade. We present a comprehensive review of VIIRS crosstalk measured during pre-launch testing along with analysis and direct comparisons between VIIRS sensor builds.

The Visible Infrared Imaging Radiometer Suite (VIIRS), a key instrument in the Joint Polar Satellite System constellation, generates high fidelity land, ocean, and atmospheric data for a suite of science products that include monitoring of vegetation, algal blooms, wildfires, drought, flooding etc. There are three VIIRS instruments on orbit, one on each of the following: Suomi National Polar-orbiting partnership, NOAA-20 (formerly JPSS-1), and NOAA-21 (formerly JPSS-2) spacecraft. Starting March 2024, NOAA-21 and NOAA-20 are the primary and secondary satellites of the constellation and providing meteorologists detailed information on severe weather events. In addition to the 21 spectral bands, covering the wavelength range from 0.41 to 12.2 mu m, VIIRS has a day-night band (DNB) that collects valuable daytime and nighttime measurements at three different gain stages. The VIIRS instrument on the JPSS-4 spacecraft, scheduled to launch in 2027, recently (in Fall 2023) underwent sensor thermal vacuum (TVAC) environmental testing. Several key performance parameters such as the instrument gains, detector SNR or NEdT, dynamic range, relative spectral response, response versus scan angle, polarization sensitivity, stray light, and near-field response were characterized during the various testing phases. In this paper, we provide an overview of the JPSS-4 VIIRS prelaunch calibration activities, with a focus on radiometric performance assessments and their comparisons with previous VIIRS instruments.

The Joint Polar Satellite System 4 (JPSS-4) Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is the fifth in a series (S-NPP VIIRS, JPSS-1,2,3 VIIRS) of highly advanced polar- orbiting environmental satellites. JPSS-4 VIIRS underwent a comprehensive sensor-level Thermal Vacuum (TVAC) testing at the Raytheon Technologies El Segundo facility in the fall of 2023. While the test program provided characterization for many spatial, spectral, and radiometric aspects of the VIIRS sensor performance, this paper focuses on the radiometric performance of the 14 reflective solar bands (RSB) that cover the wavelength range from 0.41 to 2.3 mu m. Key calibration parameters, such as the instrument gain, signal-to-noise ratio (SNR), dynamic range and radiometric uniformity, were derived in a TVAC environment for both the primary and redundant electronics at three instrument temperature plateaus: cold, nominal, and hot. This paper shows that all the JPSS-4 VIIRS RSB detectors have been well characterized, with the key performance metrics being comparable to those of the previous VIIRS instruments. Comparison of radiometric performance to sensor requirements, as well as a summary of key sensor testing and performance issues, will also be presented.

The Joint Polar Satellite System 3 (JPSS-3) and -4 (JPSS-4) Visible Infrared Imaging Radiometer Suite (VIIRS) instruments are the last in the series (S-NPP VIIRS launched in October 2011, JPSS-1 VIIRS launched in November 2017, and JPSS-2 VIIRS launched in November 2022) of highly advanced polar-orbiting environmental satellites. Both instruments underwent a comprehensive sensor-level thermal vacuum (TVAC) testing at the Raytheon Technologies El Segundo facility to characterize the spatial, spectral, and radiometric aspects of the VIIRS sensor performance. This paper focuses on the radiometric performance of the 14 reflective solar bands (RSBs) that cover the wavelength range from 0.41 to 2.3 µm. Key instrument calibration parameters such as instrument gain, signal-to-noise ratio (SNR), dynamic range, and radiometric calibration uncertainty were derived from the TVAC measurements for both the primary and redundant electronics at three instrument temperature plateaus: cold, nominal, and hot. This paper shows that all the JPSS-3 and -4 VIIRS RSB detectors have been well characterized, with key performance metrics comparable to the previous VIIRS instruments on-orbit. The radiometric calibration uncertainty of the RSBs is within the 2% requirement, except in the case of band M1 of JPSS-4. Comparison of the radiometric performance to sensor requirements, as well as a summary of key instrument testing and performance issues, is also presented.

The Joint Polar-Orbiting Satellite System's (JPSS) flagship instrument is the Visible Infrared Imaging Radiometer Suite (VIIRS) which features a panchromatic band with high dynamic range known as the Day Night Band (DNB). The DNB excels over a wide range of lighting conditions and as such is particularly important for nighttime imagery. In this capacity it has been serving the science community since October 2011 as part of the Suomi NPP, NOAA-20, and NOAA-21 satellites. Two more VIIRS instruments have been produced by Raytheon Corporation and are planned to go into service in 2027 and 2032 extending the current generation of polar orbiting environmental satellites into the next decade. The last VIIRS instrument, JPSS-4 VIIRS, has been produced and recently underwent extensive environmental testing at Raytheon's El Segundo test facility in late 2023. Measurements were made in a Thermal Vacuum (TV) chamber at three different instrument temperatures to simulate expected conditions encountered on-orbit. A comprehensive set of calibration coefficients and performance parameters have been generated from these data for both primary and redundant set of electronics. Detailed here is the radiometric calibration of the JPSS-4 VIIRS DNB with its performance in key parameters detailed including Signal-to-Noise Ratio (SNR), dynamic range, and uniformity comparted with the sensor requirement and previous builds.

Since its launch in May, 2002, Aqua MODIS has successfully operated for more than 20 years and has continuously generated a wide range of data products that have enabled and supported the remote sensing community and users worldwide for their studies of the Earth's system by monitoring changes in its key environmental parameters. Although Aqua MODIS, designed with a lifetime requirement of 6 years, is currently operated in its extended mission phase, it continues to make high quality global observations of the Earth's surface via its 36 spectral bands that cover wavelengths from visible to long-wave infrared. To date, all instrument on-board calibrators (OBC) remain capable of performing their design functions, providing various calibration data sets to help monitor on-orbit changes in sensor responses and performance characteristics. In addition to the OBC, regularly scheduled lunar observations and select Earth-view targets are used extensively to support sensor on-orbit calibration, especially for the calibration of the visible channels (or bands). We provide an overview of Aqua MODIS on-orbit calibration activities and methodologies for both reflective solar bands and thermal emissive bands, illustrate its on-orbit performance over the past 20 years using examples derived from OBC measurements, lunar observations, and Earth-view response trends, and describe various calibration improvements made over its entire mission. We focus on key issues identified since launch, such as solar diffuser degradation, electronic crosstalk, and on-orbit changes in sensor response versus scan-angle, along with approaches and strategies developed to mitigate their impact on sensor calibration quality. Also discussed in this paper are some of the key calibration enhancements incorporated recently in the Collection 6.1 and the upcoming Collection 7 Level-1B algorithms.

The NOAA-21 VIIRS instrument has successfully operated since its launch on November 10, 2022. A panchromatic channel onboard VIIRS, referred to as the Day-Night Band (DNB), was designed with multiple gain stages resulting in a large dynamic range and high sensitivity such that its detectors can make observations during both spacecraft day and spacecraft night. An onboard Solar Diffuser (SD) panel provides a well-understood calibration source for the Low Gain Stage (LGS). While there is no direct, onboard calibration source for the Mid Gain Stage (MGS) or High Gain Stages (HGS), measurements of the SD during times of indirect solar illumination can provide relative gain ratios between the LGS/MGS and MGS/HGS. Results from an early mission pitch maneuver and regular new moon observations are used in combination with onboard calibrator trends to determine the DNB dark offset (DN0) levels. In this paper, we present details for the NOAA-21 VIIRS DNB on-orbit calibration and highlight its early mission performance. Calibration coefficients look up tables (LUTs) are calculated by the NASA VIIRS characterization support team (VCST) for the latest NASA Level 1B (L1B) Collection 1 products. DNB straylight contamination has been observed to differing degrees for earlier VIIRS instruments currently on both the SNPP and NOAA-20 spacecraft. We discuss the impact of straylight on the NOAA-21 VIIRS DNB in comparison to the previous instruments and the performance of our current straylight correction for L1B radiance products.

The first two Visible Infrared Imaging Radiometer Suite (VIIRS) instruments, on-board the Suomi National Polar-orbiting Partnership (SNPP) and the NOAA-20 (N20) satellites, have been operating for over 11 and 5 years since their launches on 28 October 2011 and 18 November 2017 respectively. The day-night band (DNB) onboard VIIRS is a panchromatic visible/near-infrared (Vis/NIR) channel designed to detect radiance from the brightest daytime scenes down to very dim nighttime scenes illuminated by a quarter moon. In this paper, we present the SNPP and N20 VIIRS DNB calibration results performed by the NASA VIIRS Characterization Support Team (VCST) to generate the calibration coefficient look up tables (LUTs) for the latest NASA Level 1B Collection 2 products. The differing DNB straylight contamination between VIIRS instruments is discussed along with the correction methodology and performance.

The Visible Infrared Imaging Radiometer Suite (VIIRS) plays an important role in Earth observations and climate studies. Multiple VIIRS instruments have been built, including one onboard the Suomi-NPP spacecraft and another onboard the NOAA-20 spacecraft. These instruments have been extensively tested pre-launch in ambient environment and in a thermal vacuum chamber. One of the important tests in the ambient environment provides the characterization of the straylight response of the instrument. The straylight rejection requirement states that for the spacecraft in an operational, nadir-facing attitude, the VIIRS sensor response to any straylight striking the sensor on any surface (except the entrance aperture and within the sensor field of view) from any angle shall be less than 1% of the response to the given typical spectral radiances. It is challenging to replicate the straylight from the operational environment in a clean room; therefore, some modeling plus a special laboratory setup is necessary. The straylight test is briefly summarized and the test results from five VIIRS instruments built in the past 15 years are compared. It is shown that the straylight performance remained consistent among the VIIRS instruments and they meet the requirement by a healthy margin at the beginning of life, which indicates expected low levels of straylight on-orbit.

The Day Night Band (DNB) has been featured on the first two VIIRS instruments aboard the Suomi NPP and NOAA-20 satellites that are both currently in service, and to date prelaunch sensor level testing has been completed for the next two instruments in the series JPSS-2 and JPSS-3 VIIRS. Radiometric testing had found nonlinear behavior in the DNB especially at low radiances. The non-linearity was especially problematic the DNB of NOAA-20 VIIRS which resulted is revisions to the ground test program and operating the instrument in a modified "option 21" configuration on-orbit to mitigate the impacts of the non-linearity. Still, non-linearity remains both in NOAA-20 under option 21 and subsequent VIIRS builds, and this nonlinearity is gain, mode, detectors, and sample dependent. In this analysis we look at results from the most recent three VIIRS builds (NOAA-20, JPSS-2, and JPSS-3) where more extensive prelaunch DNB calibration is available to determine the extent on the non-linearity that remains and its effect on the on-orbit calibration. Especially important is the cross-calibration that transfers the low gain stage calibration coefficients calculated from the solar diffuser to the other gain stages. This process leverages low signal samples where non-linear effects are most significant. Tables have been generated to select the optimal linear samples and improve this process.

The S-NPP and NOAA-20 VIIRS instruments have successfully operated since their launches on October 28, 2011 and November 18, 2017, respectively. A panchromatic channel onboard VIIRS is referred to as the day-night band (DNB), was designed with a large dynamic range and high sensitivity, such that its detectors can make observations during both daytime and nighttime. The DNB uses an onboard solar diffuser (SD) panel for low gain stage calibration, and the SD observations are also carefully selected to compute gain ratios between low-to-mid and mid-to-high gain stages. In this paper, we present the S-NPP and NOAA-20 VIIRS DNB calibration performed by the NASA VIIRS Characterization Support Team (VCST) to generate the calibration coefficient look up tables (LUTs) for the latest NASA Level 1B Collection 2 products. This activity supports the NASA Earth science community by delivering consistent VIIRS sensor data products via the Land Science Investigator-led Processing Systems. The DNB stray light contamination and its different behavior have been highlighted between two instruments. Its estimate and correction methods as well as performance are illustrated.

VIIRS day-night band (DNB) covers a wavelength range from 500 nm to 900 nm, has three gain stages enabling a dynamic range of 7 orders of magnitude, and is calibrated by a solar diffuser. In this paper, the calibration uncertainty of the DNB is analyzed for both SNPP and NOAA-20 VIIRS instruments. It is shown that the uncertainties of the DNB for all gain stages, detectors, half angle mirror sides, and aggregation modes are much smaller than the uncertainty specifications of the band, which is 5%, 10%, and 100% for low, middle, and high gain stage, respectively.

Continuing the successful on-orbit operation of the VIIRS instruments currently on-board the Suomi-NPP and NOAA-20 spacecraft, additional VIIRS instruments are in development to be launched on future JPSS missions. Pre-launch testing of VIIRS, before integration with the spacecraft, is an important step in verifying the performance and operation of the instrument. As part of that testing, investigation into the near-field response (NFR) for each detector is required to assess the detector performance and assure there is no interference due to scattered light that could influence the radiometric measurements. A key element of this test is measuring the detector response of a bright target, followed by viewing the same target through neutral density filters. The measurements are stitched together to quantify the detector response over the entire dynamic range and fit using a Harvey-Shack scatter model. We present our findings for JPSS-4 VIIRS NFR performance evaluated during instrument ambient testing. The results include performance of the VIIRS detectors as compared against their specifications and comparisons against previous flight models.

Satellite imagery and data are playing an increasingly important role in scientific studies of the Earth and its climate. The scientific community has been demanding ever-increasing capabilities and accuracy from the data provided by these satellites. One key instrument on board a series of satellite platforms is the Visible Infrared Imaging Radiometer Suite (VIIRS), which provides high-quality data of the Earth from low Earth orbit covering the visible to long-wave infrared parts of the spectrum. The fourth build in the series, set to be launched on the Joint Polar-orbiting Satellite System 3 (JPSS-3) platform, has recently completed its main ground calibration program and is set to be integrated into the satellite bus in the near future. This calibration program covered a comprehensive series of performance metrics designed to demonstrate the quality of the science data and ensure the instrument can maintain its calibration successfully once on-orbit. The subject of this work covers the radiometric calibration metrics including dynamic range, signal-to-noise ratio/noise equivalent differential temperature (SNR/NEdT), polarization sensitivity, scattered light response, relative spectral response, response versus scan angle, and uniformity, as well as uncertainties; all key metrics met or exceeded their design requirements with some minor exceptions. Comparisons to previous builds will also be provided.

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on-board the Aqua and Terra spacecraft have provided valuable Earth data to the science community for the last 20 and 22 years, respectively. The Spectro-Radiometric Calibration Assembly (SRCA) is an on-board calibrator (OBC) that can characterize the radiometric, spatial, and spectral properties of the MODIS reflective solar bands (RSBs). In radiometric mode, the SRCA is able to monitor the gain trends of the RSBs on a detector level. Nominal radiometric mode measurements are collected during a 10-minute period during spacecraft night using a combination of SRCA halogen lamps. These measurements are intended for deriving on-orbit gains, however due to several 10-watt lamp failures on-orbit, the frequency of SRCA calibrations has been reduced and no longer used in the official L1B LUT algorithm. Once per calendar year the SRCA is operated in radiometric mode over several consecutive orbits using a backup lamp, monitoring the gain changes of the RSBs under unique conditions. This paper will provide insight into the 1W short-term stability of the MODIS RSBs using these calibrations over both the Aqua and Terra missions, along with the long-term trends of these multi-orbit gain observations.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on board the first Joint Polar-Orbiting Satellite System series 1 (JPSS-1) has a panchromatic, three gain stage, day-night band (DNB) capable of imaging the Earth under illumination conditions ranging from reflected moonlight to daytime scenes. The DNB has four charged-coupled devices (CCDs) with 32 different modes of time-delay integration and subpixel aggregation to achieve high SNR in low light conditions while maintaining roughly constant spatial resolution across scan. During the prelaunch testing phase, these 32 different aggregation modes are separately calibrated over a large dynamic range (covering seven orders of magnitude) through a series of radiometric tests designed to generate initial calibration coefficients for the sensor data record (SDR) operational algorithm, assess radiometric performance, and determine compliance with the sensor design requirements. Early in the environmental testing at the Raytheon El Segundo facility, nonlinear behavior was discovered in some DNB edge of scan aggregation modes at low signal levels. In response to this nonlinearity, the test program was altered to characterize the radiometric performance both in the baseline configuration and with a modified aggregation scheme that eliminates the modes used at the end of scan, replacing them with an unaffected adjacent mode and trading off spatial resolution for improved linearity. Presented in this paper is the radiometric performance under both sensor configurations including dynamic range, sensitivity, radiometric uncertainty, and nonlinearity along with a discussion of the potential impact to DNB on-orbit calibration and SDR performance.