The Ocean Color Instrument (OCI) is the primary payload on NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission. Its primary purpose is to enable new scientific studies of ocean biology, aerosols, and clouds. This paper describes the design of the instrument and its radiometric performance as measured during the prelaunch characterization campaign. OCI will be the first radiometer to provide hyperspectral (340nm-895nm) daily global coverage of top-of-atmosphere radiances. Seven multispectral bands cover wavelengths from 940nm to 2260nm. The spatial resolution is about 1.2km. OCI performance is optimized for ocean color applications, with a focus on high signal-to-noise ratio (SNR) at low radiance levels and high radiometric accuracy.

The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission [1] will extend and improve the data record of NASA’s satellite observations of global ocean biology, aerosols, and clouds. The Ocean Color Instrument (OCI) is the primary sensor on-board the PACE platform [2]. The OCI is a scanning radiometer with hyperspectral coverage from the ultraviolet (UV) to the near infrared (NIR) wavelength range and a fiber-coupled multiband filter spectrograph in the short-wave infrared (SWIR) spectral region. The OCI Flight Unit completed system level testing in November 2022 at the Goddard Space Flight Center (GSFC).This paper presents the spectral characterization and performance of the OCI Flight Unit. The OCI Flight spectral performance was determined to be within design specifications and the characterization was measured within specified uncertainties.

Scheduled for launch in January 2024, the PACE mission represents NASA’s next investment in ocean biology, clouds, and aerosol data records [1]. A key feature of PACE is the inclusion of an advanced satellite radiometer known as the Ocean Color Instrument (OCI), a global mapping radiometer that combines multispectral and hyperspectral remote sensing. This paper describes the methods used for pre-launch calibration of OCI and considerations to ensure the combination of Ground Support Equipment (GSE) and instrument effects meet uncertainty and performance requirements. General considerations when designing a calibration campaign are also discussed.

Scheduled for launch in January 2024, the Phytoplankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission represents NASA’s next investment in ocean biology, clouds, and aerosol data records [1]. A key feature of PACE is the inclusion of an advanced satellite radiometer known as the Ocean Color Instrument (OCI), a global mapping radiometer that combines multispectral and hyperspectral remote sensing. This paper describes the results of the prelaunch test campaign of the OCI Flight Unit. The measured OCI flight unit performance exceeded requirement thresholds in all critical areas. Overall, the performance of the OCI is excellent, and will allow the PACE science team to meet its science objectives.

The first two flight models of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument continue to operate onboard the Suomi National Polar-orbiting Partnership (S-NPP) and NOAA-20 spacecrafts. The third flight model is set to be launched as one of a complement of instruments onboard the Joint Polar–orbiting Satellite System-2 (JPSS-2) satellite. In addition to its 14 reflective solar bands and 7 thermal emissive bands, VIIRS has a unique Day-Night Band (DNB). The DNB is a panchromatic imager based on CCD detectors, covering a spectral range of about 500 – 900 nm. The DNB is made up of three gain stages, allowing the sensor to operate over a large dynamic range (3×10-9 - 0.02 W/cm2/sr). As part of VIIRS pre-launch ground testing, the DNB has been characterized to determine its functionality and performance under a space-like environment. The results are compared against the design specification and to previous VIIRS flight models when applicable. This paper presents a comprehensive summary of the VIIRS DNB prelaunch testing and the results of radiometric and spectral assessments. The expected impact to on-orbit operations and calibrated data products are also discussed.

The Visible-Infrared Imaging Radiometer Suite (VIIRS) was first launched on-board the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft in October of 2011. There have been three subsequent builds of the VIIRS sensor for the Joint Polar Satellite System (JPSS) program with JPSS-1, -2 and -3 having launch dates of November 2017, March 2022 and 2026 respectively. There is also a JPSS-4 VIIRS, that is in hardware integration during 2020, with a launch date of 2031. VIIRS has 22 bands: 7 thermal emissive bands (TEBs), 14 reflective solar bands (RSBs) and a Day Night Band (DNB). Ocean Color/Chlorophyll (OCC) products use calibrated Science Data Records (SDRs) for bands M1-M7 (0.412-0.865μm) to compute their ocean chemistry products. These bands require accurate polarization sensitivity characterization to compensate for polarized upwelling Rayleigh scatter and produce accurate OCC Environment Data Products (EDRs). VIIRS polarization sensitivity requirement failures have driven hardware modifications to the bandpass filters and dichroic beam splitter over the program. This paper will discuss the preliminary JPSS-3 polarization results and how these hardware modifications, as the JPSS program progresses, have affected the sensor performance. Comparisons of the polarization sensitivities between sensor builds will be discussed along with the hardware modifications that contributed to their differences.

Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) are major instruments for Earth science observations. Nearly 40 MODIS scientific products and a wide range of VIIRS environmental data records are produced using their global observations. The consistency of the MODIS and VIIRS calibrated data is important for the study of Earth science. This article assesses the calibration consistency of the Aqua MODIS and VIIRS thermal emissive band (TEB) data. To remove the impact of the mismatched relative spectral response (RSR) on the comparisons, the simultaneous nadir observation data from the cross-track infrared sounder (CrIS) and the infrared atmospheric sounding interferometer (IASI) are used as references in two different methods to independently verify the consistency. The comparisons of the MODIS and VIIRS TEB calibrated data show that the brightness temperature (BT) differences for comparable bands between MODIS and VIIRS are in general within 0.2 K for BT larger than 230 K. The differences of all comparable MODIS and VIIRS TEBs are consistent over time. MODIS measurements agree better with N20 VIIRS than with Suomi National Polar-orbiting Partnership (S-NPP) VIIRS. The S-NPP VIIRS measurements are higher than N20 VIIRS, within 0.1 K for long-wave infrared (LWIR) bands and 0.3 K for band M13.

The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor aboard the NOAA-20 (previously JPSS-1) spacecraft has successfully operated since its launch in November, 2017. Similar to the first VIIRS instrument on the Suomi-National Polar-orbiting Partnership (SNPP) spacecraft, the data are collected in 22 spectral bands that are calibrated by a set of onboard calibrators. This paper provides an overview of the NOAA-20 VIIRS on-orbit operation and calibration, with a particular focus on the thermal emissive bands (TEBs). The results presented in this paper include the on-orbit changes in the TEB spectral band responses, detector noise characterization, and key calibration parameters, such as the nonlinear coefficients derived from the blackbody warm-up cool-down cycles. Other issues, such as the early mission long-wave infrared (LWIR) response degradation due to icing on the dewar window, and their impact on sensor calibration are also discussed. Since launch, the VIIRS instrument temperature has been stable to within ±0.8 K and the cold focal plane temperatures are well controlled with variations less than 40 mK. With the exception of the early degradation observed in the LWIR bands, the TEB gains have been stable to within 0.04% (except I5 at 0.07%). Based on the current performance, VIIRS is expected to meet its calibration requirements throughout its design lifetime.

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.

This paper evaluates the calibration quality during the blackbody (BB) warm-up cool-down cycle for thermal emissive bands onboard Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS). This evaluation utilizes data from Aqua MODIS Collection 6 Level-1B products and VIIRS Sensor Data Records in 6-min granule format provided by the NASA Land Science Investigator-led Processing System. Nearly simultaneous hyperspectral measurements from the Aqua Atmospheric Infrared Sounder (AIRS) and the S-NPP Cross-track Infrared Sounder (CrIS) are used as references for MODIS and VIIRS, respectively. Each AIRS footprint of 13.5 km is co-located with multiple MODIS pixels while each CrIS field of view of 14 km is co-located with multiple VIIRS pixels. The corresponding AIRS-simulated MODIS and CrIS-simulated VIIRS radiances are derived by convolutions based on sensor-dependent relative spectral response functions. In this paper, the analysis mainly focuses on the bands that are used in sea surface temperature products. The results show that there is virtually no impact for MODIS bands 22 and 23 and bands 31 and 32 for a BB temperature below 290 K; however, when the BB temperature increases above 290 K, the impact is up to 0.3 K for bands 22 and 23 and 0.05 K for bands 31 and 32, respectively. For VIIRS, BB temperature-dependent drifts are observed in M15 and M16, which can reach 0.15 and 0.1 K, respectively, over the operational BB temperature range and the VIIRS brightness temperature range.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key instrument on-board the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft. The S-NPP launched in October 2011 and it has been collecting valuable Earth science data with VIIRS and four other instruments for more than five years. The VIIRS Characterization Support Team (VCST) of the National Aeronautics and Space Administration (NASA) Science Investigator-led Processing Systems (SIPS) is designed to support the VIIRS sensor pre-launch geometric and radiometric characterization and to access on-orbit long-term Level-1B (L1B) calibration and performance. This paper reviews the VIIRS thermal emissive bands (TEB), covering wavelengths from 3.7 to 12.0 μm, L1B radiometric calibration algorithms and presents the calibration uncertainty methodology which will be implanted in the L1B processing software. Discussions will be focused on the key uncertainty parameters and the application in L1B.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) satellite uses its 14 reflective solar bands to passively collect solar radiant energy reflected off the Earth. The Level 1 product is the geolocated and radiometrically calibrated top-of-the-atmosphere solar reflectance. The absolute radiometric uncertainty associated with this product includes contributions from the noise associated with measured detector digital counts and the radiometric calibration bias. Here, we provide a detailed algorithm for calculating the estimated standard deviation of the retrieved top-of-the-atmosphere spectral solar radiation reflectance.

The Visible Infrared Imaging Radiometer Suite (VIIRS) instruments onboard 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 late 2016, respectively, have polarization sensitivity, which affects the at-aperture radiometric calibration. This polarization sensitivity is caused by optics within VIIRS having different reflectance and transmission values as a function of at-aperture photon electric field orientation and is spectrally, spatially, and scan angle dependent. Characterization of the instrument's polarization sensitivity for each visible near-infrared (VNIR) band and detector was performed prelaunch at multiple cross-track scan angles. The resultant characterization parameters are VIIRS polarization amplitude and phase that enable the at-aperture radiance to be adjusted based on its polarization characteristics. The sensor requirements are that the polarization amplitude for scan angles within ±45° of nadir be below 2.5%-3% depending on the band and have an uncertainty in both amplitude and phase of less than 0.5%. The S-NPP VIIRS passed these requirements with band M1 (412 nm) having the smallest margin (~8%). Modification to the VNIR bandpass filter designs on JPSS-1 was performed to reduce out-of-band response leaks observed prelaunch on S-NPP. An unintended consequence of the spectral bandpass modification was an increase in the polarization sensitivity by roughly a factor of 2 for some VNIR bands. The degree to which JPSS-1 VIIRS polarization sensitivity characterization results exceed the sensor specifications and comparisons with S-NPP will be discussed.

The Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (S-NPP VIIRS) instrument contains a visible imaging band designed to produce imagery during both daytime and nighttime, which is called the day-night band (DNB). The DNB is a three-gain-stage backside-illuminated charge-coupled device (CCD) with four detector arrays that aggregate the individual CCD pixels into 32 different aggregation modes across scan, yielding imagery with a roughly constant horizontal sampling interval. The highest gain stage is over 100 000 times more sensitive than the lowest gain stage; the combination of the three gain stages allows for imagery with radiances ranging from 10-10to 10-2W · cm-2· sr-1. The initial DNB on-orbit calibration relies on monthly sensor special operations. This offline calibration approach results in discrete calibration and the loss of some science data. In this paper, we will present a new calibration method based solely on VIIRS onboard calibrators (OBCs). The calibrator data collected on the nighttime side of an orbit are used to determine the dark offset and the data collected over the daytime side of the orbit, and the day-night terminators are used to compute the cross-stage gain ratios. The results showed that the dark offset and the gain ratio derived from the initial method could be biased up to ten digital numbers (DN) and 12%, respectively, due to nighttime airglow and Earth scene stray light. The calibration is also continuous as calibrator data are recorded for each scan. Because no special operation and offline analysis are required, this method was approved for VIIRS operational implementation to improve the DNB radiometric calibration and sensor on-orbit operations.

The Suomi National Polar-orbiting Partnership (S-NPP) spacecraft executed a series of yaw maneuvers on February 15 and 16, 2012. Data collected during these maneuvers were used to characterize the transmission functions of the Visible Infrared Imager Radiometer Suite (VIIRS) instrument solar diffuser (SD) and solar diffuser stability monitor (SDSM) views. On orbit, only the product of the attenuation screen transmittance and SD bidirectional reflectance distribution function (BRDF) can be measured for the VIIRS detector and SDSM SD views. For the SDSM solar view, the attenuation screen transmittance was also measured. The angular sampling provided by the yaw maneuver data of this solar view was too coarse to capture the fine structure of the transmission function; a model was developed to include this structure in the vignetting function by combining solar observation data from the first nine months of the mission with the yaw maneuver-derived vignetting function. The derived transmission functions were delivered for implementation in the operational processing stream (the derived VIIRS detector view transmittance produced up to 0.4% difference in the instrument responsivity, and SDSM transmission functions impacted the BRDF tracking by up to 3.0%). An uncertainty analysis was also conducted on all transmission functions delivered.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key instrument onboard the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft that was launched on October 28, 2011. VIIRS is designed to provide top of the atmosphere radiometric measurements and imaging of the entire planet Earth twice daily. It is a wide-swath (3040 km) cross-track scanning radiometer with spatial resolutions of 375 and 750 m at nadir for imaging and moderate bands, respectively. It has 22 spectral bands covering the spectrum between 0.4 and 12.5 μm, including 15 reflective solar bands and 7 thermal emissive bands. VIIRS observations are used to generate 22 environmental data records used by various operational applications and for climate research. This paper describes the prelaunch radiometric calibration and characterization methodologies used by the NASA VIIRS Characterization Support Team, including performance assessments for the reflective and emissive band radiometric calibration, the signal-to-noise ratios, dual gain transition, and dynamic range. Other aspects of the sensor performance such as scattered light response, response versus scan angle, polarization sensitivity, relative spectral response, and crosstalk will also be briefly described. A comprehensive set of performance metrics generated during the prelaunch testing program will be compared to the sensor requirements, and a list of lessons learned will be presented to enhance testing and performance assessment for future Joint Polar-Orbiting Satellite System VIIRS sensors.

The S-NPP VIIRS was launched on October 28, 2011 and activated on November 8, and then went through a series of intensive functional tests in order to establish the sensor's baseline characteristics and initial on-orbit performance. With the exception of large optical degradation in the NIR and SWIR spectral regions that is due to pre-launch mirror coating contamination, both the VIIRS instrument and its on-board calibrators continue to operate and function normally. With continuous dedicated effort, it is expected that most of the sensor calibration parameters will continue to meet their design requirements and that high quality data products will be continuously generated and used by the operational as well as research community.

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft was launched on October 28, 2011. The S-NPP is orbiting the Earth in a sun-synchronous plane with nominal 13:30 local equatorial crossing time. The VIIRS nadir aperture door was opened on November 21, followed by cryo-cooler door opening on January 18, 2012. The NASA VCST team has carried out a series of VIIRS pre-launch and on-orbit calibration activities and analyses in support of the sensor data records validation and improvement. The sensor and its on-board calibrators have been successfully operated for more than one and a half years.

The Suomi National Polar-orbiting Partnership (S-NPP) satellite, formally the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP), provides a bridge between current and future low-Earth orbiting weather and environmental observation satellite systems. The NASA's NPP VIIRS Characterization Support Team (VCST) is designed to assess the long term geometric and radiometric performance of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument onboard the S-NPP spacecraft and to support NPP Science Team Principal Investigators (PI) for their independent evaluation of VIIRS Environmental Data Records (EDRs). This paper provides an overview of Suomi NPP VIIRS on-orbit calibration activities and examples of sensor initial on-orbit performance. It focuses on the radiometric calibration support activities and capabilities provided by the NASA VCST.

The NPP Instrument Calibration Support Element (NICSE) is one of the elements within the NASA NPP Science Data Segment (SDS). The primary responsibility of NICSE is to independently monitor and evaluate on-orbit radiometric and geometric performance of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument and to validate its Sensor Data Record (SDR) [1]. The NICSE interacts and works closely with other SDS Product Evaluation and Analysis Tools Elements (PEATE) and the NPP Science Team (ST) and supports their on-orbit data product calibration and validation efforts. The NICSE also works closely with the NPP Instrument Calibration Support Team (NIC ST) during sensor pre-launch testing in ambient and thermal vacuum environment [2]. This paper provides an overview of NICSE VIIRS sensor post-launch calibration support with a focus on the use of sensor on-board calibrators (OBC) for the radiometric calibration and characterization. It presents the current status of NICSE post-launch radiometric calibration tool development effort based on its design requirements.

Electronic and optical crosstalk are radiometric challenges that often exist in the focal plane design in many sensors such as MODIS. A methodology is described to assess the impact due to optical and electronic crosstalk on the measured radiance, and thereafter, the retrieval of geophysical products using MODIS Level 1 data sets. Based on a postulated set of electronic and optical crosstalk coefficients, and a set of MODIS scenes, we have simulated a system signal contamination on any detector on a focal plane when another detector on that focal plane is stimulated with a geophysical signal. The original MODIS scenes and the crosstalk impacted scenes can be used with validated geophysical algorithms to derive the final data products. Products contaminated with crosstalk are then compared to those without contamination to assess the impact magnitude and location, and will allow us to separate Out-Of-Band (OOB) leaks from band-to-band optical crosstalk, and identify potential failures to meet climate research requirements.