This PDF file contains the front matter associated with SPIE Proceedings Volume 10781, including the Title Page, Copyright information, Table of Contents, Introduction, Author and Conference Committee lists

JAXA is now planning GCOM mission which is composed of a series of satellites. They are called GCOM-W and GCOM-C satellites. Both satellites are composed of 3 satellites with 5 year lifetime. Hence, 13 years of continuous observation can be assured with 1 year overlaps. The first satellite of GCOM-W was launched on 18, May, 2012 while the first one of GCOM-C was launched on 23, Dec. 2017. GCOM-W1 carries AMSR-2. AMSR-2 is very similar to AMSR on ADEOS Ⅱ and AMSR-E on EOS-Aqua with some modifications. GCOM-C1 will carry SGLI. The SGLI will be rather different from GLI. The main targets of SGLI are atmospheric aerosols, coastal zone and land. In order to measure aerosols over both ocean and land, it will have an near ultra violet channel, as well as polarization and bidirectional observation capability. For, coastal zone and land observation, the IFOV of SGLI for these targets is around 250m. The instrument will be composed of several components. The shorter wavelength region adopts push broom scanners, while long wave region uses a conventional whisk broom scanner. The orbit of GCOM-W1 is A-train, while the orbit of GCOM-C1 will be similar to ADEOS Ⅱ. GCOM-C L1B product will be distributed from June 2018, and the initial results from GCOM-C will be presented at the Symposium.

Landsat-8 has been operating on-orbit for 5+ years. Its two sensors, the Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS), are continuing to produce high quality data. The OLI has been radiometrically stable at the better than 0.3% level on a band average basis for all but the shortest wavelength (443 nm) band, which has degraded about 1.3% since launch. All on-board calibration devices continue to perform well and consistently. No gaps in across track coverage exist as 100% operability of the detectors is maintained. The variability over time of detector responsivity within a band relative to the average is better than 0.05% (1 sigma), though there are occasional detectors that jump up to 1.5% in response in the Short-Wave InfraRed (SWIR) bands. Signal-to-Noise performance continues at 2-3x better than requirements, with a small degradation in the 443 nm band commensurate with the loss in sensitivity. Pre-launch error analysis, combined with the stability of the OLI indicates that the absolute reflectance calibration uncertainty is better than 3%; comparisons to ground measurements and comparisons to other sensors are consistent with this. The Landsat-8 TIRS is similarly radiometrically stable, showing changes of at most 0.3% over the mission. The uncertainty in the absolute calibration as well as the detector to detector variability are largely driven by the stray light response of TIRS. The current processing corrects most of the stray light effects, resulting in absolute uncertainties of ~1% and reduced striping. Efforts continue to further reduce the striping. Noise equivalent delta temperature is about 50 mK at typical temperatures and 100% detector operability is maintained. Landsat-9 is currently under development with a launch no earlier than December 2020. The nearly identical OLI-2 and upgraded TIRS-2 sensors have completed integration and are in the process of instrument level performance characterization including spectral, spatial, radiometric and geometric testing. Component and assembly level measurements of the OLI-2, which include spectral response, radiometric response and stray light indicate comparable performance to OLI. The first functional tests occurred in July 2018 and spatial performance testing in vacuum is scheduled for August 2018. Similarly, for TIRS-2, partially integrated instrument level testing indicated spectral and spatial responses comparable to TIRS, with stray light reduced by approximately an order of magnitude from TIRS.

Ball’s Compact Hyperspectral Prism Spectrometer is being developed for technology insertion in the Sustainable Land Imaging (SLI) program. NASA’s SLI program aims to develop technologies for future Landsat-like measurements. In support of this, NASA’s SLI-Technology program aims to develop a new generation of smaller, more capable, less costly payloads that meet or exceed current Landsat imaging capabilities. By providing continuous visible-to-shortwave hyperspectral data, CHPS will support legacy Landsat data products as well as a much broader range of land science products. We discuss the development of the CHPS technology, initial performance test results, planned airborne demonstration and data distribution to science collaborators, and path to spaceborne demonstration.

The increase of atmospheric concentration of anthropogenic greenhouse gases(GHGs), primarily carbon dioxide(CO₂) and methane(CH₄), is concerned as a main cause of the global climate change. From the previous experiences in GHG detecting, satellite imaging spectral remote sensing provides the unique potentials in accuracy, precision, coverage, temporal sampling and spectral resolution, having been developing as an effective and efficient means for monitoring GHGs’ accumulation and emission in the atmosphere. This paper reports a promising optical design of very high spectral resolution imaging spectrometer on LEO satellite with a swath of over 100 km and a spatial resolution of less than 3 km. Its specification satisfies with the requirement of high column concentration retrieval precision of 1ppm for CO₂ and 9ppb for CH₄ within four absorption bands (755-765nm, 1595-1625nm, 2040-2080nm and 2275-2325nm). Above all, up to 23000 spectral resolving power hints us the superiorities of immersed grating in increasing resolution but decreasing volume. A holographic flat plane grating is directly etched on a wedge prism, operating in reflective near-Littrow condition, having optimized diffraction efficiency of over 85%. Additional prisms are introduced to correct the smile distortion of the slit image produced by the grism. This method is crucial for the fidelity of the instrument spectral response function (ISRF) and data processing. Moreover, to desensitize the instrument to the polarization state of the income radiation, four polarization scramblers are adopted after the shared fore-optics, specially designed for each bands. Thanks to the scramblers, the predicted polarization sensitivity is lower than 1% at worst.

One of the scientific instruments aboard the NOAA-20 satellite is the Visible Infrared Imaging Radiometer Suite (VIIRS). The VIIRS regularly performs on-orbit radiometric calibration of its reflective solar bands, primarily through observations of an onboard sunlit solar diffuser (SD). The incident sunlight passes through an attenuation screen (the SD screen) and scatters off the SD to provide a radiance source for the calibration. The on-orbit change of the SD bidirectional reflectance distribution function (BRDF), denoted as the H-factor, is determined by an onboard solar diffuser stability monitor (SDSM). The eight SDSM detectors observe the sun through another attenuation screen (the SDSM screen) and the sunlit SD almost at the same time to measures the SD BRDF change. The products of the SD screen transmittance and the BRDF at t=0 and the SDSM screen transmittance were measured prelaunch. Large undulations in the H-factor were seen when using the prelaunch screen transmittances. Fifteen on-orbit yaw maneuvers were performed to validate and to further characterize the screens. Although significantly improved, the H-factor from the yaw maneuver data determined screen transmittance still has undulations as large as about 0.7-0.8%, revealing that the angular step size of the yaw maneuvers is too large. In this paper, we add regular on-orbit data to the yaw maneuver data to further improve the relative products and the relative SDSM screen transmittance. The H-factor time series derived from the newly determined screen transmittance is much smoother than that derived from using only the yaw maneuver data and thus improves considerably the radiometric calibration accuracy.

The Day/Night Band (DNB) onboard NOAA-20 is a continuation of the heritage nighttime imaging capability on SNPP VIIRS/DNB and supports a wide range of applications such as short-term weather prediction, disaster response and numerous socioeconomic applications. Stray light was observed both in northern and southern hemisphere for SNPP VIIRS/DNB and monthly correction look-up-table has been routinely generated for operational DNB data production. For NOAA-20 VIIRS/DNB, a few changes were introduced such as using Mode 21 to aggregate CCD detectors to form pixels beyond zone 21 due to the nonlinearity in the aggregation with higher mode number. A direct consequence of such aggregation mode change is the extension of the scan angle coverage counter-clockwise beyond that of SNPP, i.e. ~ 4.22 degree into the extended Earth view zone. Evaluation of NOAA-20 DNB performance revealed the appearance of strong and rapidly rising stray light in the extended zone while the overall stray light pattern within the same scan angle range is similar to those of SNPP DNB. This paper characterizes the NOAA-20 DNB stray light. New developments in the DNB stray light correction to address the new stray light features in NOAA-20 DNB are discussed together with the evaluation of the performance of stray light correction.

The NOAA-20 (aka JPSS-1) satellite was successfully launched on November 18, 2017 as the first in the JPSS satellite series, and a follow-on to the Suomi NPP satellite mission. The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard is a major Earth observing instrument with 22 spectral bands covering the 0.41um to 12.5 μm spectral range with spatial resolutions of 375 and 750 meters for the imaging and radiometric bands respectively. Since the VIIRS nadir and cryocooler doors were opened on December 13, 2017, and January 3, 2018 respectively, the instrument has been performing well and producing high quality data. The VIIRS Sensor Data Record (SDR) team has been supporting the postlaunch tests and extensive calibration/validation to ensure radiometric, spectral, and spatial performance.

This paper provides a comprehensive summary of the studies in the postlaunch calibration/validation activities which enables the VIIRS SDR to reach beta, provisional, and calibrated/validation product maturity. The instrument performance is quantified through a large number of tests involving onboard, maneuvers, as well as vicarious calibration/validation. Several issues found in the ground processing are addressed through updating the calibration input parameters known as the lookup tables (LUTs). Instrument performance waivers including the non-standard aggregation mode for the Day/Night band (DNB) and related features are addressed. On-orbit anomalies and mitigations such as the longwave infrared band degradation and saturation in some bands are also discussed. With a local equator crossing time of ~1:30pm with ~50.5 min separation from Suomi NPP achieved since January 2, 2018, NOAA-20 VIIRS provides important Earth observations for generating more than 26 global environmental data records including clouds, sea surface temperature, polar wind, aerosol, vegetation fraction, ocean color, fire, snow and ice for weather, and other environmental applications.

The second VIIRS instrument was launched on-board the NOAA-20 (formerly JPSS-1) satellite on November 18, 2017. It was designed and built with the same performance requirements as the first VIIRS on-board the S-NPP launched on October 28, 2011. Currently, the NOAA-20 is orbiting the Earth in the same plane as the S-NPP but separated in time and space by 50 minutes. The VIIRS observations are made in 22 spectral bands, including a day-night band (DNB) that cover wavelengths from visible to long-wave infrared. The sensor’s on-orbit calibration is provided by a set of on-board calibrators (OBCs), which include a solar diffuser (SD), a solar diffuser stability monitor (SDSM), and a blackbody (BB). After turn-on, the VIIRS instrument conducted a series of post-launch testing (PLT) and intensive calibration and validation (ICV) activities, including those performed via spacecraft maneuvers, designed to verify and establish instrument on-orbit calibration performance baseline. This paper provides an overview of NOAA-20 VIIRS ICV activities and an assessment of its initial on-orbit performance with a focus on several key calibration parameters, such as the detector response (or gain), dynamic range, and signal-to-noise ratio (SNR). Various issues identified and lessons learned from initial instrument operation and calibration are also discussed in support of long-term monitoring (LTM) of NOAA-20 VIIRS calibration and data quality.

The Earth-observing Visible Infrared Imaging Radiometer Suite (VIIRS) on the NOAA-20 satellite (formerly the Joint Polar Satellite System-1) is the follow-on sensor to the early launched VIIRS on the Suomi National Polar-orbiting Partnership (SNPP) satellite. The on-orbit radiometric calibration of its reflective solar bands (RSBs) is regularly performed primarily through observations of an onboard sunlit solar diffuser (SD). The on-orbit change of the SD bidirectional reflectance distribution function (BRDF) value, denoted as the H-factor, is determined by an onboard solar diffuser stability monitor (SDSM). The scene spectral radiance is calculated by a quadratic polynomial of the background subtracted detector digital number for most of the RSBs and a cubic polynomial for the M8-11 bands. A numerical factor, denoted as the F-factor, provides an on-orbit adjustment to the prelaunch polynomial coefficients through observations of the sunlit SD. The accuracy and change in the F-factor directly affect the sensor radiometric performance. The accuracy of the F-factor is proportionally affected by the accuracy in the H-factor. In this paper, we show the time trends of the Hand F-factors and the SDSM detector gain, and also compare the trends with those for the previous VIIRS instrument on the Suomi National Polar-orbiting Partnership satellite. We derive the Earth view signal-to-noise ratio at the typical spectral radiance level and estimate the calibration bias between the two VIIRS instruments through observations of the Moon and pseudo-invariant Earth sites.

The VIIRS instrument onboard the NOAA-20 satellite (launched on November 18, 2017) started to collect Earth-view data after its nadir door opened on December 13, 2017. Seven of the VIIRS bands, I4-5 and M12-16 are thermal emissive bands (TEBs), covering a spectral range from 3.6 to 12.5 μm. They began collecting valid data after the cold focal plane assembly (CFPA) cooled down to its nominal operating temperature on January 6, 2018. This paper will present the performance of each TEB, including calibration coefficients, noise equivalent differential temperature (NEdT), on-orbit calibration coefficient estimates from scheduled onboard blackbody warm-up and cool-down (WUCD) data, as well as related telemetry temperatures. Several methods are tested and compared in the WUCD data analysis for estimating the calibration coefficients. Based on the preliminary results, the NEdT of each band is well below the design specification and very close to that of the VIIRS onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. The detector gains appear stable for bands on the short- and mid-wave infrared CFPA, whereas the detector gains have larger than expected degradation for bands on the long-wave infrared CFPA during the early mission. All TEB related telemetry temperatures are stable. The on-orbit performance of NOAA-20 VIIRS TEB is compared with VIIRS onboard the SNPP.

The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on May 4, 2002. The AIRS was designed to measure atmospheric temperature and water vapor profiles and has demonstrated exceptional radiometric and spectral accuracy and stability in-orbit. The accuracy is achieved by transferring the calibration from a Large Area Blackbody (LABB) to the On-Board Calibrator (OBC) blackbody during preflight testing and frequent on-board calibration. The LABB theoretical emissivity is in excess of 0.9999 and temperature uncertainty is less than ±60 mK. The LABB emitted radiance is NIST traceable through thermistors located on the internal surfaces. The AIRS also provides a full aperture space view every scan for offset calibration. AIRS nonlinearity and polarization calibration coefficients were based on pre-flight testing and have been among the highest uncertainty sources in the calibration. A recent method using on-board space view data has reduced the uncertainty of the polarization coefficients and use of separate A side and B side data from pre-flight testing has reduced the uncertainty of the nonlinearity estimates. An update to the system radiometric uncertainty is made based on the new data and includes other refinements and is presented in this paper. This paper does not address the stability of the AIRS radiances in orbit that is usually determined by comparison with surface observations.

JAXA's Global Change Observation Mission for Climate (GCOM-C) spacecraft called "SHIKISAI", which means colorfulness in Japanese, was successfully launched on December 23, 2017 by H-IIA launch vehicle, Flight 37 (F37). GCOM-C is sun-synchronous polar orbit satellite with wide field of view (FOV) and 19 channels optical imager, Second Generation Global Imager (SGLI). The essential satellite operation to establish the satellite basic function to be used for the house keeping was successfully completed after the one day critical phase operation. The three months initial commissioning activities for the both satellite bus and sensor has been conducted before the calibration and verification phase to ensure the sensor observation product accuracy. This paper describes the commissioning of SGLI that we have performed during the first several months of in-orbit operation to confirm the system integrity. The technical aspects to the lunar calibration and the thermal infrared performance are specially described.

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 Geostationary Environmental Monitoring Spectrometer (GEMS) and the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instruments will provide a new capability for the understanding of air quality and pollution. Ball Aerospace is the developer of these UV/Vis Hyperspectral sensors. The GEMS and TEMPO instrument use proven remote sensing techniques and take advantage of a geostationary orbit to take hourly measurements of their respective geographical areas. The high spatial and temporal resolution of these instruments will allow for measurements of the complex diurnal cycle of pollution driven by the combination of photochemistry, chemical composition and the dynamic nature of the atmosphere.

The GEMS instrument was built for the Korea Aerospace Research Institute and their customer, the National Institute of Environmental Research (NIER) and the Principle Investigator (PI) is Jhoon Kim of Yonsei University. The TEMPO instrument was built for NASA under the Earth Venture Instrument (EVI) Program. NASA Langley Research Center (LaRC) is the managing center and the PI is Kelly Chance of the Smithsonian Astrophysical Observatory (SAO).

The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellite system for the Radio Occultation (RO) mission provides advances in meteorology, ionospheric research, climatology, and space weather by utilizing the readily available Global Navigation Satellite System (GNSS) signals in conjunction with GNSS receivers in low Earth orbiting (LEO) satellites. COSMIC was launched in 2006 with six satellites in a constellation known as FORMOSAT-3 in low inclination orbits to provide global coverage. RO relies on the calculation of GNSS signal time delay in carrier phase due to the atmosphere in the L1 and L2 signals transmitted between the GNSS and receiving satellites in the LEO orbit, from which the bending angle, refractivity, and atmospheric profiles can be retrieved. Since the Atomic Frequency Standard (AFS) based GNSS signal is International System of Units (SI) traceable, is actively maintained, and the precise orbit of both the GNSS and the LEO satellites can be determined accurately, RO data from COSMIC have been recognized as stable references for data assimilation (DA) in Numerical Weather Prediction (NWP) models. Currently, NWP customers are eager to obtain similar data from COSMIC2 which will be launched in the next few months to mitigate the aging COSMIC constellation and diminishing number of ROs.

Meanwhile, the calibration of the hyperspectral sounders such as Cross-track Infrared Sounder (CrIS) on NOAA-20 relies on a high quality onboard blackbody which is also traceable to SI through prelaunch characterization relating to the laboratory blackbody with traceable calibration to NIST, and hyperspectral sounders have been recognized as onorbit calibration references for other broad- or narrow-band infrared (IR) observations. In this paper we analyze the traceability of both systems in their raw measurements as well as retrieved geophysical variables. Comparisons are also made in spectral radiance/brightness temperature derived from the two systems. The objective is to gain a better understanding of the different paths of traceability to SI and ensure the consistency of the products for numerical weather prediction and other applications. This study directly supports the COSMIC2 verification and validation, as well as postlaunch calibration/validation of NOAA-20 CrIS.

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard S-NPP provides global coverage once per day for the reflective solar bands. With the successful launch of NOAA-20, the global coverage of VIIRS has now been doubled. In order to use NOAA-20 VIIRS data for environmental related studies, the radiometric performance of VIIRS needs to be independently validated. In addition, for long term studies that use data from multiple satellites instruments, it is imperative to have radiometrically accurate and consistent data products from all the instruments. This study uses SNO (Simultaneous Nadir Overpass) and extended SNO over Saharan desert to assess the radiometric performance of NOAA-20 VIIRS relative to S-NPP VIIRS. Since direct SNO doesn’t exist between NOAA-20 and S-NPP, the study uses MODIS as a transfer radiometer. Both NOAA-20 and S-NPP have SNOs with MODIS. Double differencing technique is used to estimate the radiometric bias between the two VIIRS instruments. The study suggests that NOAA-20 VIIRS reflective solar bands are consistently lower in reflectance than that from S-NPP VIIRS by about 2%. Larger bias is observed for bands M5 (0.67 μm) and M7 (0.86 μm) bands mainly because S-NPP VIIRS absolute calibration for these bands is biased high by about 2%. The impact on bias due to spectral differences between the two VIIRS instruments is quantified using hyperspectral measurements from Sciamachy.

The newly launched (November 18, 2017) polar-orbiting satellite of the Joint Polar Satellite System (JPSS-1), now transitioned to NOAA-20, is the follow-on mission to the SNPP (Suomi National Polar-orbiting Partnership) satellite, launched six years ago. NOAA-20 leads SNPP by a half orbit or about 50 minutes. The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key sensor onboard both NOAA-20 and SNPP spacecraft with nearly identical band spectral responses. Similar to the heritage sensor MODIS, VIIRS has on-board calibration components including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB), and a space view (SV) as background reference for calibration. This study provides an initial assessment of calibration of the NOAA-20 VIIRS reflective solar bands (RSB) by intercomparison with measurements from SNPP VIIRS using various vicarious approaches. The first approach is based on a double difference method using observations from simultaneous nadir overpasses (SNO) with Aqua MODIS. The second is from the collected reflectances over the widely used Liby-4 desert site from 16-day repeatable orbits so each data point has the same viewing geometry relative to the site. The third approach is to use the frequent overpasses over the Dome C snow site. Results of this study provide useful information on NOAA-20 VIIRS post-launch calibration assessment and preliminary analysis of its calibration stability and consistency for the first 6 months.

On-orbit radiometric calibration of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) visible and near-infrared (VNIR) band involves vicarious calibration using reflectance-based method, onboard lamp calibration, and cross-calibration with Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra. The ASTER calibration was evaluated with reference to MODIS using an improved cross-calibration algorithm in the previous study (Obata et al., Sensors, 2017). In the present study, the evaluation is expanded by using other sensors that are highly calibrated, including the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 Operational Land Imager (OLI). The objective of the present study is to evaluate radiometric calibration of ASTER VNIR band using MODIS, ETM+, and OLI counterparts over Railroad Valley Playa for the period from 2000 to 2018. Results indicate that ASTER bands 1 and 2 are in average 4.2-4.5% and 1.8-3.3% greater than MODIS/ETM+ and that ASTER band 3N agrees well with MODIS/ETM+. The behavior of ASTER surface reflectances along time shows similar trend to that of OLI. The number of sample data for ASTER and OLI comparison should be, however, increased for accurate analysis of statistics. Nevertheless, insights obtained by cross-comparisons provide beneficial information for evaluating ASTER radiometric calibration. The consistency among radiometric calibrations of multiple sensors is of significance importance in the context of data continuity and sensor fusion studies.

The CERES project utilizes geostationary-derived broadband measurements to infer the regional diurnal flux in between CERES instantaneous measurements to estimate the daily-averaged flux. The geostationary (GEO) imager radiances must be calibrated to the same reference to ensure spatial and temporal consistency of cloud properties and fluxes across the contiguous GEO domains. In order to place all of the GEO visible imagers on the same radiometric scale, the CERES project inter-calibrates the GEO imagers with Aqua-MODIS using multiple independent approaches. The primary inter-calibration approach relies on coincident, ray-matched GEO and MODIS radiance pairs over all-sky tropical ocean scenes (ATO). Another ray-matching approach was recently developed to take advantage of the visible spectral uniformity and near-Lambertian reflectance of deep convective clouds (DCC). The success of the DCC raymatching (DCC-RM) approach has been demonstrated by comparing the calibration with the ATO ray-matching (ATORM) approach for the 0.65-μm GEO and MODIS bands.

Now that many of the recently launched GEO imagers have multiple reflective solar band channels, the DCCRM algorithm is being modified to inter-calibrate those channels as well, especially for the SWIR bands. The spectral uniformity of the DCC over the SWIR bands is not uniform, given that the ice particle absorption is a function of wavelength. New Spectral Band Adjustment Factor (SBAF) strategies will need to be developed. DCC-RM is also wellsuited to inter-calibrate historical near-broadband visible GEO imagers. DCC are spectrally flat across the visible spectrum, which reduces the SBAF uncertainty between two ray-matched sensors. Applying the DCC-RM technique on historical GEO imagers is challenging due to the coarser pixel and temporal resolution of the ISCCP B1U formatted dataset.

The ATO-RM and DCC-RM calibration methods were applied to multiple visible bands on Himawari-8 using MODIS as the calibration reference. The Aqua-MODIS and Himawari-8 calibration difference was less than 0.4% for wavelengths less than 1 µm and for the Terra-MODIS 0.65-μm channel. Other channel combinations would need further examination to obtain consistent ATO and DCC gain results. The ATO-RM and DCC-RM calibration methods were also applied to GOES-8 in the ISCCP B1U format with NOAA-14 AVHRR as the calibration reference. The GOES-8 ATO and DCC calibration gain difference was within 0.15%. The agreement between ATO and DCC gains provides confidence in both methods.

FengYun-4A (FY-4A) is the first three-axis stabilized geostationary meteorological satellite in China, which was launched in the early morning of 11 Dec., 2016. Advanced Geosynchronous Radiation Imager (AGRI) is one of the four payloads onboard FY-4A, and acquired the first image on 20 Feb., 2017. FY-4A AGRI contains 14 spectral bands, in which 6 bands are in reflective solar region, with the nominal wavelengths at 0.47, 0.65, 0.825, 1.375, 1.61 and 2.25μm. The spatial resolution is 0.5 km for 0.65 μm band, 2 km for the shortwave infrared bands and 1 km for others. AGRI is designed with a solar diffuser, however it revealed the insufficient capacity for in-flight calibration mainly due to the partial aperture effect. The first vicarious calibration field campaign was conducted at the Dunhuang site of China Radiometric Calibration Site (CRCS) in Apr. 2017. It revealed the large bias of the AGRI data calibrated using the prelaunch calibration parameters, mostly underestimated. Using multiple land sites in Asia and Oceania, the calibration correction factors were derived combined with the CRCS data. The sensor's on-orbit radiometric response variation and observation bias against the simulated radiation were also monitored. It revealed that the bands at 0.65 μm was most stable, while 0.47 μm band showed the large degradation with an annual rate nearly 17%. In this paper, the calibration status of the FY-4A AGRI solar bands was presented.

In recent years, JAXA has been conducting a technical survey for a geostationary Earth observation satellite using a 3.5 m diameter aperture with a segmented primary mirror. One of the problems associated with such a large optical observing satellite is a reduction in image quality due to thermal deformation of the optical elements and the metering structure. In this paper, we present our first conceptual structural design and thermal analysis of that design. We also propose a solar light incident avoidance maneuver for this satellite and show the validity of that maneuver.

Aqua MODIS is the second MODIS instrument of NASA’s Earth Observation System and has operated for over sixteen years since its launch in 2002. MODIS has sixteen thermal emissive bands (TEBs) located on two separate cold focal plane assemblies (CFPA). The TEBs are calibrated every scan using observations of an onboard blackbody (BB) and a space view port. Low saturation temperatures (Tsat) of Aqua MODIS bands 33, 35, and 36 cause these bands to saturate when the BB temperature is higher than their Tsat values during a BB warm-up cool-down (WUCD) cycle, therefore impacting the ability to perform nominal calibration. In addition, starting from around 2006, the CFPA temperature showed gradual variation from its nominally-controlled operating temperature due to a loss of its radiative cooler margin and the magnitude of its fluctuation reaching a maximum in 2013. The MODIS Characterization Support Team currently uses a correction that is dependent on the CFPA temperature to provide a gain estimate for the saturated scans during the BB WUCD. This gain estimation has been implemented in the Aqua MODIS Collection 6 (C6) and C6.1 L1B products. This paper evaluates the quality of the calibrated radiance of Aqua MODIS bands 33, 35, and 36 using simultaneous nadir observations from the Atmospheric Infrared Sounder (AIRS), which is also onboard the Aqua satellite. Our analysis results show that the differences between AIRS and Aqua MODIS can be controlled well within the fluctuation range compared to the periods when the BB signals for these bands are not saturated.

The NOAA-20 (formerly the Joint Polar Satellite System-1) satellite was launched on November 18, 2017. One of the five scientific instruments aboard the NOAA-20 satellite (N20) is the Visible Infrared Imaging Radiometer Suite (VIIRS). The VIIRS scans the earth surface in 22 spectral bands, of which 14 are denoted as the reflective solar bands (RSBs) with design band central wavelengths from 412 to 2250 nm. The VIIRS regularly performs on-orbit radiometric calibration of its RSBs, primarily through observations of an onboard sunlit solar diffuser (SD). The on-orbit change of the SD bidirectional reflectance distribution function (BRDF) value, denoted as the H-factor, is determined by an onboard solar diffuser stability monitor (SDSM). We have shown that the H-factor for the SD on the VIIRS instrument on the Suomi National Polar-orbiting Partnership (SNPP) satellite is both incident and outgoing sunlight direction dependent. This angular dependence profoundly affects the on-orbit radiometric calibration process and results. Here, we give preliminary results for the angular dependence for the N20 VIIRS SD H-factor, and compare the dependence with that for the SNPP VIIRS.

A feasibility study was conducted for an optical imager system assumed to be mounted on a geostationary orbit satellite for Earth observation. The targeted spatial resolution was less than 10 meters for panchromatic mode at nadir observation conditions, and the observation area was assumed to 100 × 100 square kilometers. The optical system was designed based on a Korsch three mirror anastigmat; the primary mirror was 3.5 meters in diameter, and the focal length was approximately 45 meters. The worst wavefront error was estimated at less than 0.017 λrms in the field of view. As the next step, the primary mirror was segmented, and a trade-off study was conducted on two types of segmented mirror configurations. The optical performance of each configuration was compared in terms of PSF and MTF. Moreover, the deterioration of optical performance due to the misalignment and distortion of the segmented mirror was discussed and numerically estimated by using the Monte Carlo method. The sensitivity of the wavefront error was consequently estimated for the segmented mirror assembly.

The Clouds and the Earth’s Radiant Energy System (CERES) mission is instrumental in monitoring changes in the Earth’s radiant energy and cloud systems. The CERES project is critical in guaranteeing the continuation of highly accurate Earth radiation budget Climate Data Records (CDRs). The CERES Flight Model-5 (FM-5) instrument, integrated onto the Suomi-National Polar-Orbiting Partnership (NPP) spacecraft, joined a suite of four CERES instruments deployed aboard NASA’s Earth Observing System (EOS) satellites Terra and Aqua. Each CERES instrument consists of scanning thermistor bolometer sensors that measure broadband radiances in the shortwave (0.3 to 5μm), total (0.3 to < 200 μm) and water vapor window (8 to 12 μm) regions. In order to ensure the consistency and accuracy of instrument radiances, needed for generating higher-level climate data products, the CERES project implements rigorous and comprehensive radiometric calibration and validation procedures.

This paper briefly describes the trends observed in Edition-1 FM5 flux data products that are corrected for inflight gain changes derived from on-board calibration sources. The strategy to detect artifacts and correct for any sensor spectral response changes is discussed. Improvements and validation results of preliminary FM5 Edition-2 products will be compared with Terra and Aqua data products.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key sensor carried on the newly launched (November 18, 2017) Joint Polar Satellite System-1 (JPSS-1), now transitioned to NOAA-20, and the Suomi National Polar-orbiting Partnership (SNPP) satellite. The two VIIRS sensors are nearly identical in design. Its on-board calibration components include a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB), and a space view (SV) port for background subtraction. These on-board calibrators are located at fixed scan angles. The VIIRS response versus scan angle (RVS) was characterized prelaunch in lab ambient conditions and is currently used to calibrate the on-orbit response for all scan angles relative to the calibrator’s scan angle. A spacecraft level pitch maneuver was scheduled during the initial intensive Cal/Val testing for both the NOAA-20 and SNPP. The pitch maneuver provided a rare opportunity for VIIRS to make observations of deep space over the entire scan angle range, which can be used to characterize the TEB RVS. This study provides our analysis of the NOAA-20 pitch maneuver data and assessment of the derived TEB RVS. A comparison between the RVS determined by the pitch maneuver observations and prelaunch lab measurements is conducted for each band, detector, and mirror side of the half angle mirror.

The Joint Polar Satellite System 2 (JPSS-2) is the follow-on for the Suomi-National Polar-orbiting Partnership (S-NPP) and JPSS-1 missions. These spacecrafts provide critical weather and global climate products to the user community. A primary sensor on both JPSS and S-NPP is the Visible-Infrared Imaging Radiometer Suite (VIIRS) with Earth observations covering the Reflective Solar Band (RSB), Thermal Emissive Band (TEB) and Day Night Band (DNB) spectral regions. The VIIRS Sensor Data Records (SDRs) contain the calibrated Earth observations that are used to generate numerous Environmental Data Record (EDR) products such as Ocean Color/Chlorophyll (OCC), Global Land Cover, Aerosol and Land/Sea Surface Temperature (LST/SST). This SDR calibration is performed using unpolarized sources such as the Solar Diffuser (SD) for the RSBs and an On-Board Calibrator BlackBody (OBCBB) for the TEBs. Therefore, polarized Earth scenes will have radiometric bias errors within the SDRs based on how sensitive VIIRS is to polarized illumination and is corrected in some EDR algorithms. In addition to VIIRS polarization characterization methodology, this paper will discuss the JPSS-2 polarization sensitivity results and compare its performance to its predecessors S-NPP and JPSS-1 VIIRS. Optical modifications to the JPSS-2 VIIRS sensor to address heritage polarization sensitivity issues will be discussed.

The short-wave infrared (SWIR) bands (5-7, 26) of Terra MODIS, co-located with the mid-wave infrared (MWIR) bands (20-25) on the short and mid-wave infrared (SMIR) Focal Plane Assembly (FPA) have a known issue related to 5.3 μm out-of-band (OOB) thermal leak and electronic crosstalk that was identified prelaunch. Intensive efforts were undertaken shortly after launch to mitigate its impacts on the on-orbit calibration and in turn the level 1B (L1B) products. In order to the isolate the OOB contribution among the SWIR bands, special night time day mode (NTDM) operations have been regularly scheduled to collect Earth scene reflective solar bands (RSB) data during spacecraft night time. As MODIS does not have a spectral band centered at 5.3 μm, measurements from the MODIS Airborne Simulator (MAS) spectrometer field campaigns in the early months after Terra launch were used to help identify band 28 (7.325 μm) as the best surrogate to simulate the radiances at 5.3 μm. As a result, band 28 is used as the sending band for the SWIR crosstalk correction for Terra MODIS. In the case of Aqua MODIS, band 25 (4.52 μm) was found to be more effective as the sending band for the SWIR crosstalk correction. In recent years, the Terra MODIS PV LWIR electronic crosstalk (including band 28), has gradually increased, more significantly after the safe-mode event occurred in Feb, 2016. This accentuated degradation in the PV LWIR performance has also impacted the performance of on-orbit SWIR crosstalk correction algorithm and thus the L1B products. In this paper, we examine the use of band 25 as the sending band for Terra MODIS SWIR crosstalk correction and compare its performance with that based on band 28 as the sending band. Results indicate an improvement in the stability of the on-orbit gain for the SWIR bands and a reduced detector-detector and subframe striping in the L1B products, especially during the period when the PV LWIR electronic crosstalk is more severe.

The Electronic Calibration (Ecal) tests are performed during various stages of instrument development to examine the linearity of the instrument electronics. During this process, charges with stepwise increments are injected in the analog electronics circuitry to generate a ramp signal that can be used to characterize any nonlinearities in the electronics. The prelaunch characterization of MODIS (on the Terra and Aqua platforms) and VIIRS (on SNPP, JPSS-1 and JPSS-2) involved a regular evaluation of the electronics linearity using the Ecal tests. On orbit, the Ecal tests have been regularly performed over the mission for both the MODIS instruments to derive the electronics gain and linearity. Unlike MODIS, the Ecal tests on the VIIRS instruments are performed on an as-needed basis. To date, no Ecal tests were performed for S-NPP VIIRS on orbit. The VIIRS instrument on JPSS-1 (now NOAA 20) was launched on November 18, 2017. An Ecal test was performed to support the instruments initial post-launch performance assessment. Shortly after the