This PDF file contains the front matter associated with SPIE Proceedings Volume 8866, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Climate change and air quality are the most pressing environmental issues of the 21st century. Despite decades of research, the sources and sinks of key greenhouse gases remain highly uncertain [IPCC¹] making quantitative predictions of atmospheric composition and their impacts. The Geostationary Remote Infrared Pollution Sounder (GRIPS) is a multi-purpose instrument designed to reduce uncertainty associated with atmospheric radiative forcing. GRIPS will measure will measure greenhouse gases and aerosols – two of the most important elements in the earth’s radiation budget. GRIPS will observe carbon dioxide (CO₂), carbon monoxide (CO), methane (CH4), - the carbon gases, nitrous oxide (N₂O), water vapor and aerosols with unprecedented precision through the atmosphere. The GRIPS instrument uses gas filter correlation radiometry (GFCR) to detect reflected and thermal IR radiation to detect the gases and the reflected solar radiation in the visible and short-wave infrared bands for aerosols. GRIPS is designed to have sensitivity down to the Earth’s surface at ~2-8km nadir resolution. GRIPS can resolve CO₂, CO, and CH4 anomalies in the planetary boundary layer and the free troposphere to quantify lofting, diurnal variations and longrange transport. With repeated measurements throughout the day GRIPS can maximize the number of cloud free measurements determining biogenic and anthropogenic sources, sinks, and fluxes. GRIPS is highly complementary to the Orbiting Carbon Observatory, OCO-2, the geostationary Tropospheric Emissions: Monitoring of Pollution (TEMPO) and Advanced Baseline Imager (ABI) and other existing and planned missions.

The MODIS thermal emissive bands (TEB) are radiometrically calibrated on-orbit on a scan-by-scan basis, with reference to an aboard blackbody operated at 290 K for Terra MODIS and at 285 K for Aqua MODIS. The quality of the calibration can be evaluated with independent thermal sources at other temperatures. As a spectrally, spatially and radiometrically stable source, the Moon has become more important to the on-orbit calibration of space-borne spectral sensors that have regular lunar observation capability. MODIS is scheduled to observe the Moon on a nearly monthly basis at approximately the same lunar phase angle through its space view port. In this paper, the long-term stability of MODIS TEB radiometric calibration is assessed through the multi-year trends of the brightness temperatures (BT) of the lunar surface retrieved from the scheduled lunar observation. The highest lunar surface temperature is approximately 390 K, higher than the saturation temperatures of most TEB. For the non-saturated bands, the trending is based on the BT of the hottest area of the Moon. For the partially saturated bands, the trending is based on the BT difference of the unsaturated matching pixels between the band and a non-saturated reference band, given the fact that all MODIS bands are spatially registered. Overall, the trends have been stable throughout MODIS lifetime. The results also prove that the Moon can be used as a source to monitor the stability of the thermal bands.

Bands 13 (667 nm) and 14 (678 nm) of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites are built with a time delay and integration (TDI) circuit and a high-low dual-gain setting intended for the monitoring of the ocean environment. An important on-orbit performance issue for the high-gain output of Terra Band 14 and Aqua Band 13 and 14 is that these three bands saturate during standard on-orbit calibrations using the onboard solar diffuser (SD). Consequently, their calibration procedure requires a derivation different from other reflective solar bands (RSB). A high-low scaling-ratio approach is employed for these bands to obtain the high-gain coefficients via the low-gain output 13L and 14L through a calculated constant ratio derived from other sources. Currently, earth view (EV) scenes over the North Atlantic Ocean are used as the primary sources. As it also has been observed that the response versus scan-angle (RVS) exhibits noticeable changes with time for RSB, a time-dependent RVS calibration algorithm has been implemented based on the SD and lunar calibration results. This paper reviews the electronic design and operation of Band 13 and 14, discusses the SD calibration and the saturation issue of the high-gain output, and the time-dependent RVS algorithms. Long-term performance of the calibration coefficient and RVS are presented. The long-term trend shows that the gain-change for Terra MODIS Band 13 and 14, for both high- and lowgain bands, is significant at 6% and 23%, but is more modest for Aqua MODIS Band 13 and 14 at 6% and 2%. The gain ratios 13H/13L and 14H/14L are very stable at the level of 0.01% for both MODIS instruments. The long-term gain difference due to RVS effect is up to 3% for Terra MODIS and about 2% and below for Aqua MODIS.

Clouds and the Earth's Radiant Energy System (CERES) instruments were designed to measure the reflected shortwave and emitted longwave radiances of the Earth’s radiation budget and to investigate the cloud interactions with global radiances for the long-term monitoring of Earth's climate. The three scanning thermistor bolometer sensors on CERES measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to <100 micrometer) and in 8 - 12 micrometer water vapor window regions. Of the five CERES instruments that are currently in operation, four of the CERES instruments (Flight Models1 through 4) fly aboard Earth Observing System (EOS) Terra and Aqua platforms with two instruments aboard each spacecraft, in 705 KM sun-synchronous orbits of 10:30 AM and 1:30 PM equatorial crossing time.

A rigorous and comprehensive radiometric calibration and validation protocol comprising of various studies was developed to evaluate the calibration accuracy of the CERES instruments. The in-flight calibration of CERES sensors are carried out using the internal calibration module (ICM) comprising of blackbody sources and quartzhalogen tungsten lamp, and a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM calibration results are instrumental in determining the changes in CERES sensors’ gains after launch from the prelaunch determined values and the on-orbit gain variations. In addition to the broadband response changes derived from the on-board blackbody and the tungsten lamp, the shortwave and the total sensors show a spectrally dependent drop in responsivity in the shorter wavelegth region below one micron that were brought to light through validation studies. The spectrally dependent changes were attributed to the instrument operational modes and the corrections were derived using the sensor radiance comparisons. This paper covers the on-orbit behavior of CERES sensors aboard the Terra and Aqua spacecraft and the determination of the sensor response changes utilising the in-flight calibration and the radiance measurement comparisons viewing various targets. The corrections for the sensor response changes were incorporated in the radiance calculations of CERES Edition3 data products.

The Clouds and Earth's Radiant Energy System (CERES) scanning thermistor bolometers measure earth-reflected solar and earth-emitted long-wave radiances, at the top- of-the-atmosphere. The bolometers measure the earth radiances in the broadband shortwave solar (0.3-5.0 microns) and total (0.3->100 microns) spectral bands as well as in the 8->12 microns water vapor window spectral band over geographical footprints as small as 10 kilometers at nadir. December 1999, the second and third set of CERES bolometers was launched on the Earth Observing Mission Terra Spacecraft. May 2003, the fourth and fifth set of bolometers was launched on the Earth Observing Mission Aqua Spacecraft. Recently, (October 2011) the sixth instrument was launched on the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (Suomi NPP) Spacecraft. Ground vacuum calibrations define the initial count conversion coefficients that are used to convert the bolometer output voltages into filtered earth radiances. The mirror attenuator mosaic (MAM), a solar diffuser plate, was built into the CERES instrument package calibration system in order to define on-orbit shifts or drifts in the sensor responses. It followed a similar design as the Earth Radiation Budget Experiment (ERBE) scanners with improvements from lessons learned.

The shortwave and shortwave part of the total-wave sensors are calibrated using the solar radiances reflected from the MAM's. Each MAM consists of baffle-solar diffuser plate systems, which guide incoming solar radiances into the instrument fields of view of the shortwave and total wave sensor units. The MAM diffuser reflecting type surface consists of an array of spherical aluminum mirror segments, which are separated by a Merck Black A absorbing surface, over-coated with SIOx (SIO2 for PFM). Thermistors are located within each MAM plate and the total channel baffle. The CERES MAM is designed to yield calibration precisions approaching .5 percent for the total and shortwave detectors. The Terra FM1 and FM2 shortwave channels and the FM1 and FM2 total channels MAM calibration systems showed shifts in their solar calibrations of 1.5, 2.5, 1.5 and 6 percent, respectively within the first year. The Aqua FM3, and FM4 shortwave channels and the FM3 and FM4 total channels MAM calibration systems showed shifts in their solar calibrations of 1.0, 1.2, 2.1 and .8 percent, respectively within the first year. A possible explanation has attributed the MAM reflectance change to on-orbit solar ultraviolet/atomic oxygen/out-gassing induced chemical changes to the SIOx coated MAM assembly during ram and solar exposure. There is also changes to the sensor telescope shortwave filters as well as the Total channel mirrors and/or sensors. The Soumi NPP FM5 is still after 2.5 years displaying a stability of less than .5 percent. In this presentation, lessons learned from the ERBE MAM and application of knowledge of how the space environment affected the CERES FM1-4 solar calibrations will be presented along with on-orbit measurements for the thirteen years the CERES instruments have been on-orbit.

The Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometer is designed to measure the solar radiation reflected by the earth and thermal radiation emitted by the earth. Four CERES instruments are already in service; two aboard the Terra spacecraft, launched in 1999; and two aboard the Aqua spacecraft, launched in 2002. A fifth instrument, flight model 5 (FM5), launched in October 2011 aboard the NPP satellite, began taking radiance measurements on January 27th, 2012. The CERES FM5 instrument uses three scanning thermistor bolometers to make broadband radiance measurements in the shortwave (0.3 - 5.0 micrometers), total (0.3 - <100 micrometers) and water vapor window (8 - 12 micrometer) regions. An internal calibration module (ICM) used for in-flight calibration is built into the CERES instrument package consisting of an anodized aluminum blackbody source for calibrating the total and window sensors, and a shortwave internal calibration source (SWICS) for the shortwave sensor. The calibration sources are used to define shifts or drifts in the sensor response over the life of the mission. In order to better understand the sensors adaptation to the space environment, daily internal calibrations were conducted on all three channels for the first week after opening the instrument’s main covers. Over the next month, the frequency of internal calibrations was reduced to the standard mission schedule of three total and window channel calibrations per week and one shortwave channel calibration per week. This paper presents the results of FM5 on-orbit internal calibrations, discusses any ground to flight changes, and describes trends in the calibration data.

NASA’s Earth Venture class (EV) of mission are competitively selected, Principal Investigator (PI) led, relatively low cost and narrowly focused in scientific scope. Investigations address a full spectrum of earth science objectives, including studies of the atmosphere, oceans, land surface, polar ice regions, and solid Earth. EV has three program elements: EV-Suborbital (EVS) are suborbital/airborne investigations; EVMission (EVM) element comprises small complete spaceborne missions; and EV-Instrument (EVI) element develops spaceborne instruments for flight as missions-of-opportunity (MoO). To ensure the success of EV, the management approach of each element is tailored according to the specific needs of the element.

The Earth Venture Instrument (EVI) element of the Earth Venture Program calls for developing instruments for participation on a NASA-arranged spaceflight mission of opportunity to conduct innovative, integrated, hypothesis or scientific question-driven approaches to pressing Earth system science issues. This paper discusses the EVI element and the management approach being used to manage both an instrument development activity as well as the host accommodations activity. In particular the focus will be on the approach being used for the first EVI (EVI-1) selected instrument, Tropospheric Emissions: Monitoring of Pollution (TEMPO), which will be hosted on a commercial GEO satellite and some of the challenges encountered to date and corresponding mitigations that are associated with the management structure for the TEMPO Mission and the architecture of EVI.

The Earth System Science Pathfinder (ESSP) Program Office (PO) is responsible for programmatic management of National Aeronautics and Space Administration’s (NASA) Science Mission Directorate’s (SMD) Earth Venture (EV) missions. EV is composed of both orbital and suborbital Earth science missions. The first of the Earth Venture missions is EV-1, which are Principal Investigator-led, temporally-sustained, suborbital (airborne) science investigations costcapped at $30M each over five years. Traditional orbital procedures, processes and standards used to manage previous ESSP missions, while effective, are disproportionally comprehensive for suborbital missions. Conversely, existing airborne practices are primarily intended for smaller, temporally shorter investigations, and traditionally managed directly by a program scientist as opposed to a program office such as ESSP. In 2010, ESSP crafted a management approach for the successful implementation of the EV-1 missions within the constructs of current governance models. NASA Research and Technology Program and Project Management Requirements form the foundation of the approach for EV-1. Additionally, requirements from other existing NASA Procedural Requirements (NPRs), systems engineering guidance and management handbooks were adapted to manage programmatic, technical, schedule, cost elements and risk. As the EV-1 missions are nearly at the end of their successful execution and project lifecycle and the submission deadline of the next mission proposals near, the ESSP PO is taking the lessons learned and updated the programmatic management approach for all future Earth Venture Suborbital (EVS) missions for an even more flexible and streamlined management approach.

A key element of the National Research Council’s Earth Science and Applications Decadal Survey called for the creation of the Venture Class line of low-cost research and application missions within NASA (National Aeronautics and Space Administration). One key component of the architecture chosen by NASA within the Earth Venture line is a series of self-contained stand-alone spaceflight science missions called “EV-Mission”. The first mission chosen for this competitively selected, cost and schedule capped, Principal Investigator-led opportunity is the CYclone Global Navigation Satellite System (CYGNSS).

As specified in the defining Announcement of Opportunity, the Principal Investigator is held responsible for successfully achieving the science objectives of the selected mission and the management approach that he/she chooses to obtain those results has a significant amount of freedom as long as it meets the intent of key NASA guidance like NPR 7120.5 and 7123. CYGNSS is classified under NPR 7120.5E guidance as a Category 3 (low priority, low cost) mission and carries a Class D risk classification (low priority, high risk) per NPR 8705.4. As defined in the NPR guidance, Class D risk classification allows for a relatively broad range of implementation strategies. The management approach that will be utilized on CYGNSS is a streamlined implementation that starts with a higher risk tolerance posture at NASA and that philosophy flows all the way down to the individual part level.

TEMPO was selected in 2012 by NASA as the first Earth Venture Instrument, for launch circa 2018. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian tar sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (~2 km N/S×4.5 km E/W at 36.5°N, 100°W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies.

TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O₃, NO₂, SO₂, H₂CO, C₂H₂O₂, H₂O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O₃ chemistry cycle. Multi-spectral observations provide sensitivity to O₃ in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring together with European Sentinel-4 and Korean GEMS.

Software engineering processes are often seen as anathemas; thoughts of CMMI key process areas and NPR 7150.2A compliance matrices can motivate a software developer to consider other career fields. However, with adequate definition, common-sense application, and an appropriate level of built-in flexibility, software engineering processes provide a critical framework in which to conduct a successful software development project. One problem is that current models seem to be built around an underlying assumption of “bigness,” and assume that all elements of the process are applicable to all software projects regardless of size and tolerance for risk. This is best illustrated in NASA’s NPR 7150.2A in which, aside from some special provisions for manned missions, the software processes are to be applied based solely on the criticality of the software to the mission, completely agnostic of the mission class itself. That is, the processes applicable to a Class A mission (high priority, very low risk tolerance, very high national significance) are precisely the same as those applicable to a Class D mission (low priority, high risk tolerance, low national significance). This paper will propose changes to NPR 7150.2A, taking mission class into consideration, and discuss how some of these changes are being piloted for a current Class D mission—the Cyclone Global Navigation Satellite System (CYGNSS).

An ultra-fast principal component based physical retrieval algorithm has been developed at NASA Langley research center. Works are under way to maximize the application potential of the algorithm in order to generate reliable products from hyper-spectral sensor data for climate studies. The algorithm has been tested using synthetic data for various infrared sensors. This paper describes in detail about retrieval sensitivity study carried out for several hyper-spectral infrared sensors using this physical algorithm. The retrieval accuracy obtained using the algorithm for the atmospheric parameters including trace gases of interests is discussed. Its dependence on the sensor system noise and spectral resolution is illustrated by comparing the retrieval performance achieved for different sensors. PCRTM has been demonstrated to be a reliable tool for end-to-end sensor performance simulations and has great potential for real-time trace gas retrieval applications.

In the construction of three-dimensional (3D) point clouds from multi-view aerial imagery, voids in the point cloud often exist where multiple views of the area were not obtained during collection. A method is presented for identifying these voids. In this work, point clouds are derived from oblique aerial imagery using multi-view techniques from the photogrammetry and computer vision communities. A voxel-based approach is used to partition the 3D space and each voxel is classified as containing or not containing derived points. Using the imagery and the position of the camera, it is possible to analyze what the cameras can and cannot see, thereby making it possible to label the voxels as occupied, free, and non-classified spaces. Voids in the data will manifest themselves in the non-classified voxels. This method has been tested on high-frame-rate oblique aerial imagery captured over Rochester, NY as well as synthetic data sets. Also presented is a unique synthetic dataset for 3D reconstruction. The data set, created with the Rochester Institute of Technology's Digital Imaging and Remote Sensing Image Generation (DIRSIG) software, provides high-fidelity radiometric data in addition to known 3D locations and surface normals for each pixel location in an image scene. This data set is available to the community for use in their related research.

A change in climate is not likely captured from any single instrument, since no single instrument can span decades of time. Therefore, to detect signals of global climate change, observations from many instruments on different platforms have to be concatenated. This requires careful and detailed consideration of instrumental differences such as footprint size, diurnal cycle of observations, and relative biases in the spectral brightness temperatures. Furthermore, a common basic assumption is that the data quality is independent of the observed scene and therefore can be determined using clear scene data. However, as will be demonstrated, this is not necessarily a valid assumption as the globe is mostly cloudy. In this study we highlight challenges in inter-calibration and concatenation of infrared radiances from multiple instruments by focusing on the analysis of deep convective or anvil clouds. TRMM/VIRS is potentially useful instrument to make correction for observational differences in the local time and footprint sizes, and thus could be applied retroactively to vintage instruments such as AIRS, IASI, IRIS, AVHRR, and HIRS. As the first step, in this study, we investigate and discuss to what extent AIRS and VIRS agree in capturing deep cloudy radiances at the same local time. The analysis also includes comparisons with one year observations from CrIS. It was found that the instruments show calibration differences of about 1K under deep cloudy scenes that can vary as a function of land type and local time of observation. The sensitivity of footprint size, view angle, and spectral band-pass differenceartmut h. Aumanns cannot fully explain the observed differences. The observed discrepancies can be considered as a measure of the magnitude of issues which will arise in the comparison of legacy data with current data.

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) (SNPP) was launched in October 2011 to continue monitoring the globe in a similar fashion as the heritage sensors, such as the MODerate resolution Imaging Spectroradiometer (MODIS). This paper applies a scene-based technique to examine in-orbit radiometric stability of VIIRS relative to Aqua MODIS. The cross-comparison is made over global deep ocean waters. This cross-comparison allows for a comprehensive examination of the sensors’ radiometric responsivity at relatively low signal levels (over oceanic waters). The study is further extended to L2/L3 products, including remote sensing reflectance and the inherent optical properties (IOPs) of waters under investigation, derived from the top-of-atmosphere (TOA) radiance (L1B). The temporal analyses give insights into the trends in the relative radiometric stability and the resulting discrepancies in the corresponding products.

The CERES observed EBAF 12-year TOA flux dataset are used to monitor the Earth’s climate and in validating climate models. The associated cloud properties are retrieved from a fusion of MODIS and geostationary imagers. The quality of these cloud properties relies on the absolute calibration of these imagers. The geostationary imager radiances are calibrated against the Aqua-MODIS calibration reference in order to retrieve uniform cloud properties both spatially and temporally. Any calibration discontinuity or artifact may be interpreted as a climate trend. CERES record will be extended using CERES fluxes onboard NPP. CERES will need to tie the VIIRS with the Aqua-MODIS calibration in order to provide a seamless record of cloud and flux properties.

This paper will present initial assessment results for interconsistency between VIIRS and Aqua-MODIS calibration of matching visible channels. Empirically derived exoatmospheric VIIRS radiance models for deep convective clouds and deserts invariant targets are used to assess the initial onboard calibration of VIIRS. The VIIRS models are based on characterizing these invariant targets with Aqua-MODIS as an absolute calibration reference in order to tie the VIIRS calibration to Aqua-MODIS. Correction for spectral band differences in the VIIRS and MODIS channels is performed using the SCIAMACHY hyperspectral data.

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi NPP has been undergoing extensive calibration/validation efforts in order to produce high quality weather and climate quality satellite data products. VIIRS absolute radiometric accuracy and consistency can be achieved by inter-comparing its measurements with other well calibrated instruments such as AQUA MODIS. VIIRS moderate resolution bands compared with matching MODIS bands at North African desert has shown that that the radiometric bias for channels M-1 through M-8 is less than 2%. VIIRS is a follow on mission for MODIS and AVHRR. In an effort to evaluate radiometric consistency of VIIRS with multi-decadal global earth observations from AVHRR, this study uses SNO-x approach to inter-compare NOAA-19 AVHRR measurements with VIIRS at North African desert over VNIR region. The radiometric consistency is evaluated and the uncertainty due to spectral differences is quantified using hyperspectral measurements from EO-1 Hyperion. In addition, the Antarctica Dome C site is used to estimate radiometric bias between AVHRR and VIIRS. AVHRR bias relative to VIIRS at Dome C is well within 0.5% for band 1 and 2% for band 2 compared to bias estimated at the desert sites using the SNO-x technique.

Meteorological Operational (METOP)-B spacecraft was launched on September 17, 2012, and the Advanced Very High Resolution Radiometer (AVHRR) visible and near-infrared channels were activated shortly after the launch. Due to the lack of on-board calibrator, the postlaunch calibration update can only be carried out vicariously. Libyan Desert reflectance with seasonal variation consideration has been used as reference since 1995. The initial updates of the calibration are derived using the seasonal oscillations of previous AVHRR measurements. In this paper, this approach is improved using the seasonal curve regression for the MetOp-B AVHRR measurement over Libyan Desert.

A new method is developed using the MetOp-A and MetOp-B inter-comparison with consideration of the Bidirectional Reflectance Distribution Function (BRDF) effect, and applied to the calibration update. Since these two satellites are in the same orbit with half orbit time (~50min) apart, it is feasible to use the inter-comparison of the AVHRR measurement on Libyan Desert between these two instruments. The solar zenith angle and sensor zenith angle are not the same for the collocated measurements, and the BRDF effects on the comparison should be corrected. The zenith angle dependent measurements have been modeled and the comparison of the reflectance with the same solar zenith angle and sensor zenith angle has been derived. The calibrations from these two methods are consistent and the updates are delivered for operational L1B product. This work is also useful to investigate BRDF effect on the inter-comparison for visible and near infrared sensors.

In 2011, three improved ground-viewing radiometers (GVRs) were built and deployed to support the Radiometric Calibration Test Site (RadCaTS) developed by the Remote Sensing Group (RSG) at the University of Arizona. The GVRs are filter-based radiometers with eight spectral channels covering a wavelength range of 400-1550 nm. They are automated, field-deployable instruments capable of long-term, standalone operation. The radiometers are temperature controlled and designed for greater stability and lower noise than their light emitting diode (LED) based predecessors.

This work describes the deployment period of these radiometers with particular attention paid to the in-field performance, reliability, and results from these instruments. Using other RadCaTS inputs including meteorological station data and Aerosol Robotic Network (AERONET) Cimel sun photometer data, select vicarious calibration results are presented. With these results, an assessment of the calibration applications of the RadCaTS during new GVR deployment is discussed. In addition, GVR calibration and characterization results, including solar radiation based calibration (SRBC), are presented as another means of assessing the performance of the radiometers over deployment periods.

The recently launched (October 28, 2011) Suomi NPP (National Polar-orbiting Partnership) satellite has been operating nominally to daily collect global data. The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key NPP sensor onboard the spacecraft. 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) port for background. This study examines VIIRS reflective solar bands (RSB) calibration stability and performance using observed top-of-atmosphere (TOA) reflectance time series collected from two approaches. The first is from comparison with a well-calibrated Aqua MODIS and the second is from overpasses over the widely used Liby-4 desert site. The VIIRS and MODIS comparison data is obtained from simultaneous nadir overpasses (SNO) for their spectrally matched bands. The reflectance trends over the Libya-4 site are extracted from 16-day repeatable orbits so each data point has the same viewing geometry relative to the site. The impact due to the band spectral differences between the two instruments is corrected based on MODTRAN5 simulations. Results of this study provide useful information on NPP VIIRS post-launch calibration assessment and preliminary analysis of its calibration stability and consistency for the first 1.5 years.

The Operational Land Imager (OLI) is one of two instruments onboard the Landsat 8 platform, which was launched on 11 February 2013 from Vandenberg Air Force Base in California. The multispectral bands of OLI retain the 30-m spatial resolution of Landsat 5 TM and Landsat 7 ETM+, but improvements to the system include 12-bit radiometric resolution, eight multispectral bands in the VNIR and SWIR spectral regions, and one panchromatic band. The earlier TM and ETM+ sensors use a whiskbroom configuration, while OLI uses a pushbroom configuration, which allows it to have a higher signal-to-noise ratio than previous Landsat instruments. This also creates challenges in radiometric calibration due to the large number of detectors on the 14 focal plane modules.

Long-term data continuity is a crucial component of the 40-year Landsat series of satellites, and ground-based vicarious calibration has played an important role in ensuring that these sensors remain on the same radiometric scale. This work presents the early ground-based in-flight radiometric calibration of OLI, which was determined using the traditional and well-understood reflectance-based approach, as well as the Radiometric Calibration Test Site (RadCaTS), which is an automated suite of instruments located at Railroad Valley, Nevada.

The Atmospheric Infrared Sounder (AIRS) is a grating array infrared hyperspectral sounder with 2378 channels from 3.75 to 15.4 microns with spectral resolution 1200 to 1400 depending on the channel. AIRS was designed as an aid to weather prediction and for atmospheric process studies. It produces profiles of atmospheric temperature and water vapor. Because of its spectral coverage and spectral resolution it is sensitive to a number of trace atmospheric constituents including CO₂, CO, SO₂, O₃, and CH₄. The AIRS sensitivity, stability, and long life have led to its use in climate process studies and climate model validation, both of which place far more stringent requirements on calibration than weather forecasting does. This paper describes results from several special calibration sequences, originally developed for prelaunch testing, that have been used to monitor the AIRS calibration accuracy and instrument health on-orbit, including the scan mirror, space view response, and channel health. It also describes reanalyses of pre-launch calibration data used to determine calibration parameters. Finally, it shows comparisons of AIRS radiometry with two other hyperspectral infrared sounders presently in space—IASI and CrIS.

The Atmospheric Infrared Sounder (AIRS) instrument flies on the NASA Aqua satellite and measures the upwelling hyperspectral earth radiance in the spectral range of 3.7-15.4 μm with a nominal ground resolution at nadir of 13.5 km. The AIRS spectra are achieved using a temperature controlled grating spectrometer and HgCdTe infrared linear arrays providing 2378 channels with a nominal spectral resolution of approximately 1200. The AIRS pre-flight tests that impact the radiometric calibration include a full system radiometric response (linearity), polarization response, and response vs scan angle (RVS). We re-derive the AIRS instrument radiometric calibration coefficients from the pre-flight polarization measurements, the response vs scan (RVS) angle tests as well as the linearity tests, and a recent lunar roll test that allowed the AIRS to view the moon. The data and method for deriving the coefficients is discussed in detail and the resulting values compared amongst the different tests. Finally, we examine the residual errors in the reconstruction of the external calibrator blackbody radiances and the efficacy of a new radiometric uncertainty model. Results show the radiometric calibration of AIRS to be excellent and the radiometric uncertainty model does a reasonable job of characterizing the errors.

The expectation for climate quality measurements from hyperspectral sounders is absolute calibration accuracy at the 100 mK level and stability at the < 40 mK/decade level. The Atmospheric InfraRed Sounder (AIRS)1, Cross-track Infrared Sounder (CrIS), and Infrared Atmospheric Sounding Interferometer (IASI) hyperspectral sounders currently in orbit have been shown to agree well over most of their brightness temperature range. Some larger discrepancies are seen, however, at the coldest scene temperatures, such as those seen in Antarctic winter and deep convective clouds. A key limiting factor for the calibrated scene radiance accuracy for cold scenes is how well the effective radiance of the cold space view pertains to the scene views. The spaceview signal is composed of external sources and instrument thermal emission at about 270 K from the scan mirror, external baffles, etc. Any difference in any of these contributions between spaceviews and scene views will impact the absolute calibration accuracy, and the impact can be critical for cold scenes. Any change over time in these will show up as an apparent trend in calibrated radiances. We use AIRS data to investigate the validity of the spaceview assumption in view of the 100 mK accuracy and 40 mK/decade trend expectations. We show that the space views used for the cold calibration point for AIRS v5 Level-1B products meet these standards except under special circumstances and that AIRS v6 Level-1B products will meet them under all circumstances. This analysis also shows the value of having multiple distinct space views to give operational redundancy and analytic data, and that reaching climate quality requires continuing monitoring of aging instruments and adjustment of calibration.

AIRS was launched on EOS Aqua in May 2002, together with AMSU-A and HSB (which subsequently failed early in the mission), to form a next generation polar orbiting infrared and microwave atmospheric sounding system. AIRS/AMSU had two primary objectives. The first objective was to provide real-time data products available for use by the operational Numerical Weather Prediction Centers in a data assimilation mode to improve the skill of their subsequent forecasts. The second objective was to provide accurate unbiased sounding products with good spatial coverage that are used to generate stable multi-year climate data sets to study the earth’s interannual variability, climate processes, and possibly long-term trends. AIRS/AMSU data for all time periods are now being processed using the state of the art AIRS Science Team Version-6 retrieval methodology. The Suomi-NPP mission was launched in October 2011 as part of a sequence of Low Earth Orbiting satellite missions under the “Joint Polar Satellite System” (JPSS). NPP carries CrIS and ATMS, which are advanced infra-red and microwave atmospheric sounders that were designed as follow-ons to the AIRS and AMSU instruments. The main objective of this work is to assess whether CrIS/ATMS will be an adequate replacement for AIRS/AMSU from the perspective of the generation of accurate and consistent long term climate data records, or if improved instruments should be developed for future flight. It is critical for CrIS/ATMS to be processed using an algorithm similar to, or at least comparable to, AIRS Version-6 before such an assessment can be made. We have been conducting research to optimize products derived from CrIS/ATMS observations using a scientific approach analogous to the AIRS Version-6 retrieval algorithm. Our latest research uses Version-5.70 of the CrIS/ATMS retrieval algorithm, which is otherwise analogous to AIRS Version-6, but does not yet contain the benefit of use of a Neural-Net first guess start-up system which significantly improved results of AIRS Version-6. Version-5.70 CrIS/ATMS temperature profile and surface skin temperature retrievals are of very good quality, and are better than AIRS Version-5 retrievals, but are still significantly poorer than those of AIRS Version-6. CrIS/ATMS retrievals should improve when a Neural-Net start-up system is ready for use. We also examined CrIS/ATMS retrievals generated by NOAA using their NUCAPS retrieval algorithm, which is based on earlier versions of the AIRS Science Team retrieval algorithms. We show that the NUCAPS algorithm as currently configured is not well suited for climate monitoring purposes.

Climate change is expected to be detected first as changes in extreme values rather than in mean values. The availability of data of from two instruments in the same orbit, AIRS data for the past eleven years and AIRS and CrIS data from the past year, provides an opportunity to evaluate this using examples of climate relevance: Desertification, seen as changes in hot extremes, severe storm, seen as a change in extremely cold clouds and the warming of the polar zone. We use AIRS to establish trends for the 1%tile, the mean and 99%tile brightness temperatures measured with the 900 cm^-1 channel from AIRS for the past 11 years. This channel is in the clearest part of the 11 micron atmospheric window. Substantial trends are seen for land and ocean, which in the case of the 1%tile (cold) extremes are related to the current shift of deep convection from ocean to land. Changes are also seen in the 99%tile for day tropical land, but their interpretation is at present unclear. We also see dramatic changes for the mean and 99%tile of the North Polar area. The trends are an order of magnitude larger than the instrument trend of about 3 mK/year. We use the statistical distribution from the past year derived from AIRS to evaluate the accuracy of continuing the trends established with AIRS with CrIS data. We minimize the concern about differences in the spectral response functions by limiting the analysis to the channel at 900 cm^-1.While the two instruments agree within 100 mK for the global day/night land/ocean mean values, there are significant differences when evaluating the1% and 99%tiles. We see a consistent warm bias in the CrIS data relative to AIRS for the 1%tile (extremely cold, cloudy) data in the tropical zone, particularly for tropical land, but the bias is not day/night land/ocean consistent. At this point the difference appears to be due to differences in the radiometric response of AIRS and CrIS to differences in the day/night land/ocean cloud types. Unless the effect can be mitigated by a future reprocessing the CrIS data, it will significantly complicate the concatenation of the AIRS and CrIS data records for the continuation of trends in extreme values.

The paper provides an overview of the radiometric and spectral calibration of MERIS over its 10 years of operations. An overview of the instrwnent, of the radiometric and spectral calibration principles and an outline of the calibration processing chain are presented.

The CNES Pleiades-HR satellites have been launched December 17th 2011 and December 2nd 2012. They provide optical images to civilian and defense users with a resolution of 70 cm and a swath of 20 km in false or natural colors. Coverage is almost world-wide with a revisit interval of 24 h.

The new capabilities offered by these satellites agility allowed imagine new methods of image calibration and performances assessment. This paper presents all the operations that were conducted by the CNES Image Quality Team during the commissioning phases and also give the main results for every image quality performance.

PLEIADES is an earth observing system conducted by the French National Space Agency, CNES. It consists of two satellites launched on December 2011 (PHR-1A) and December 2012 (PHR-1B), both designed to provide optical pushbroom imagery on five spectral bands to civilian and defense users, with ground sample distance up to 70 cm. During inflight image quality commissioning, radiometric activities included inter-detector normalization coefficients computation, refocusing operations, MTF assessment and estimation of signal to noise ratios. This paper presents inflight results for both satellites. It focuses on several innovative methods that were implemented, taking advantage of the satellite platform great agility. These methods are based on processing images obtained through dedicated exotic guidance. In particular, slow-motion steering enables an efficient estimation of the instrumental noise model, since during acquisition each detector has been viewing a stable ground target along different time samples. Conversely, rotated retina guidance is used to guarantee that all different elementary detectors have successively viewed the same set of landscape samples during acquisition. Non-uniformity of detector sensitivities can then be characterized, and on-board coefficients used prior to compression can be calibrated in order to prevent vertical striping effects on operational images. Defocus control and Point Spread Function estimation can be easily obtained through processing acquisitions of stars associated to various spectral characteristics, for different adjustments of the refocusing system. All these methods allow an accurate estimation of radiometric performance on the whole range of specified spectral radiances, while drastically reducing the number of required acquisitions on natural targets.

PLEIADES earth observing system consists of two satellites designed to provide optical 70cm resolution images to civilian and defense users. The first Pleiades satellite 1A was launched on December 2011 while the second satellite Pleiades 1B was placed on orbit, one year after, on December 2012. The calibration operations and the assessment of the image of the two satellites have been performed by CNES Image Quality team during the called commissioning phase which took place after each launch and lasted each time less than 6 months. The geometric commissioning activities consist in assessing and improving the geometric quality of the images in order to meet very demanding requirements. This paper deals with the means used and methods applied, mainly the innovative ones, in order to manage these activities. It describes both their accuracy and their operational interest. Finally it gives the main results for geometric image quality performances of the PHR system.

This paper deals with the problem of retrieving attitude perturbances in the framework of the PLEIADES-HR optical satellites. Thus, two complementary methods are compared. The first one uses the high agility capacity of satellites to acquire stars in an inertial steering mode. The second method exploits the fact that multispectral CCD arrays are shifted in the telescope focal plane in the velocity direction: for a same ground point, the resulting images are not affected by the same attitude perturbances. The resulting misregistrations can be exploited to deduce information about the attitude platform. Both methods have been applied to PLEIADES-HR satellites, during commissioning period.

The EUMETSAT Polar System is EUMETSAT’s contribution to the Global Meteorological Satellite Observing System in the polar sun-synchronous orbit and serves, in the frame of the Initial Joint Polar System (IJPS) with the United States, the mid-morning orbit. The space segment is composed of the Metop satellites, of which Metop-A is in orbit since 2006, providing a wealth of Earth Observation data, amongst them data for Atmospheric Sounding, cloud and surface monitoring, ocean observation, including ocean winds, atmospheric composition monitoring. The launch of Metop-B on the 17 September 2013 into the same mid-morning orbit (9:30 LST equator crossing time, descending node, phased 48 min. apart from Metop-A) at 820 km assures the continuity of the system. A third Metop satellite (Metop-C), scheduled for launch early 2018, will assure mission duration of at least 15 years. This paper discusses the status of the EUMETSAT Polar System (EPS) and in particular presents the results from Metop-B commissioning and the actual status of products. Metop-B is out of its commissioning at the time of the conference and is providing its service as the prime satellite together with Metop-A, which is healthy and continues its successful service.

A tunable, intensity-stabilized, quasi-continuous wave (CW) laser system, patterned after the Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS) system at the National Institute of Standards and Technology (NIST) 1, has been installed and is being tested in the NASA Goddard Space Flight Center (GSFC) Code 618 Biospheric Sciences Laboratory’s Calibration Facility. This system is referred to as SIRCUS-G (SIRCUS-Goddard). The tunable output of the laser system is fiber-fed to a 76.2 cm diameter integrating sphere lined with Spectralon. The uniform radiance light emitted from the integrating sphere is used in system-level radiometric responsivity characterizations and wavelength calibrations of remote sensing instruments. The primary radiance reference standards in the responsivity characterizations are a three-element Si trap radiometer for the visible and near infrared and a radiometer employing an InGaAs detector. Both radiometers have been calibrated by NIST. These radiometers are located at the exit port of the Spectralon coated integrating sphere. In addition, a set of three radiometers are mounted on the 76.2 cm integrating sphere’s wall ports to monitor source radiance and to provide real-time sphere radiance data during the calibrations of remote sensing instruments. These monitor radiometers provide spectral coverage from 300nm to near 2500nm. This paper presents the results of our characterization of the performance of these monitor radiometers. Results are presented and discussed on monitor radiometer short- and long-term system stability, noise level, and total measurement uncertainty.

We describe the robotic optical scatter instrument (ROSI), a new robotic arm-based goniometer for in-plane and outof- plane reflectance and bidirectional reflectance distribution function (BRDF) measurements of surfaces. The goniometer enables BRDF measurements to be made at nearly any combination of incident and scattering angles, without obstruction from frames or cradles that occur in traditional goniometers made of nested rotation stages. We present exploratory measurements of in-plane and hemispherically-scanned out-of-plane BRDF on a sintered white polytetrafluoroethylene (PTFE) sample using a supercontinuum fiber laser-based tunable light source operated at a wavelength of 550 nm, in order to demonstrate the capabilities of the system. An initial assessment of uncertainties is presented.

A new type upward-looking airborne double-antenna microwave radiometer (ADAMR) system intended for detecting atmospheric cloud liquid water content (LWC) is developed in this paper. The frequency of this radiometer is 31.65 GHz. For the antenna elevation angle, one is 30°and the other is 90°. In order to detect the signals with low effective noise temperature (<10K) from the LWC, the noise coupling technique is used. Through injecting constant equal noise signal into the two antenna ports respectively, the technique can elevate the small input noise signal power to the detectable range of the square-law detector and thus realize the weak signal detection. Moreover, in order to eliminate the impacts of the system gain fluctuations and obtain a higher sensitivity, an auto-gain compensation method based on the analog-to-digital converter, microcontroller and host computer software techniques is also proposed. Compared with the traditional radiometers, the radiometer topology is greatly simplified and the gain fluctuations can be readily realtime compensated using the compensation method. The laboratory test results show that radiometric sensitivity is better than 0.2 K for 300ms integration time and the instrument is conforming to specifications. Finally, the flight observation experiment results are presented to prove that the designed instrument is able to detect small changes of noise signal in a wide effective range of noise temperature (10-350K) and is a powerful tool for LWC measurement.

Meteosat Third Generation is the next ESA Program of Earth Observation dedicated to Nowcasting and very short term Weather Forecasting (NWC), medium/short range Global and Regional Numerical Weather Prediction (NWP), and Climate and Air Composition Monitoring. The satellites will be operating from the Geostationary orbit using a 3 axes stabilized platform. The main instrument is called the Flexible Combined Imager (FCI), currently under development by Thales Alenia Space France (TAS-F). This instrument will provide full images of the Earth every 10 minutes in 16 spectral channels between 0.44 and 13.3 μm, with a ground resolution from 0.5 km to 2 km. The FCI is composed of a TMA telescope developed by Kayser-Threde (KT), which includes a Scan mirror, and a calibration mechanism with an embedded black body dedicated to accurate in-flight IR radiometric calibration and a Metallic Neutral density for dedicated VNIR Sun calibration. The image produced by the telescope is split into several spectral groups by a spectral separation assembly (SSA) with dichroïc beamsplitters. The output beams are collimated to ease the instrument integration, and reach the cold optics (CO-I) which focalize the optical beams onto the detectors. The cold optics and IR detectors are accurately positioned inside a common cryostat to improve registration between spectral channels. Spectral filters are integrated on top of the detectors in order to achieve the required spectral selection. This article will describe the optical design and the main optical performances of the FCI: image quality, very high line-of-sight stability, and an efficient stray-light rejection thanks to the implementation of dedicated baffles and a stringent control of contamination. The FCI currently under development is expected to exhibit a significant improvement of performances with respect to Meteosat Second Generation satellites.

The Landsat Data Continuity Mission (LDCM) with two pushbroom Earth-imaging sensors, the Operational Land Imager (OLI) and the Thermal InfraRed Sensor (TIRS), was launched on February 11, 2013. Its on-orbit check out period or commissioning phase lasted about 90 days. During this phase the spacecraft and its instruments were activated, operationally tested and their performance verified. In addition, during this period, the spacecraft was temporarily placed in an intermediary orbit where it drifted relative to the Landsat-7 spacecraft, providing near simultaneous imaging for about 3 days, allowing data comparison and cross calibration. After this tandem-imaging period, LDCM was raised to its final altitude and placed in the position formerly occupied by Landsat-5, i.e., 8 days out of phase with Landsat-7, with about a 10:10 AM equatorial crossing time. At the end of commissioning, the satellite was transferred to the United States Geological Survey (USGS), officially renamed Landsat-8 and declared operational. Data were made available to the public beginning May 31, 2013. The performance of the satellite and two instruments has generally been excellent as evidenced in the quality of the distributed data products.

Landsat-8, the latest in the Landsat series of satellites, was launched on February 11, 2013 and carries on board the Operational Land Imager (OLI) as one of its payloads. The satellite’s mission is to continue the long history of moderate resolution imaging of the Landsat program. The OLI follows the highly successful Landsat-5 and Landsat-7 in continuing to populate a global archive of Earth images that dates back to 1972.

The design of the Landsat-8 instruments is a significant departure from earlier Landsats. The OLI is a pushbroom instrument; all previous recent Landsat instruments were electromechanical (whiskbroom) instruments. OLI also has two new spectral bands and refined bandpasses; the thermal imaging capability on Landsat-8 is in a separate instrument.

The pushbroom design provides significantly better signal to noise performance than historically available, but at the expense of circa 70,000 detectors versus the 100 or so on previous instruments. The large focal plane and large number of detectors makes detector to detector relative calibration more challenging, increasing the propensity for banding and striping in imagery.

On-board radiometric calibration devices include a shutter to measure the dark levels, a full aperture solar panel for calibration against the sun, and multiple sets of lamps for short-term stability monitoring. Early results from the on-board calibration devices indicate that the OLI is outperforming the Landsat-7 instrument in signal-to-noise ratio by an order of magnitude, consistent with pre-launch measurements. Over the first five months, the instrument is stable to within 0.7%, as measured by the lamps and solar diffuser. A relative calibration (detector-to-detector) and a linearization parameter update have been performed that reduce visible striping; with this update, the residual striping has been reduced by half in all OLI bands.

The Thermal Infrared Sensor (TIRS) on board Landsat 8 continues thermal band measurements of the Earth for the Landsat program. TIRS improves on previous Landsat designs by making use of a pushbroom sensor layout to collect data from the Earth in two spectral channels. The radiometric performance requirements of each detector were set to ensure the proper radiometric integrity of the instrument. The performance of TIRS was characterized during pre-flight thermal-vacuum testing. Calibration methods and algorithms were developed to translate the raw signal from the detectors into an accurate at-aperture spectral radiance. The TIRS instrument has the ability to view an on-board variable-temperature blackbody and a deep space view port for calibration purposes while operating on-orbit.

After TIRS was successfully activated on-orbit, checks were performed on the instrument data to determine its image quality. These checkouts included an assessment of the on-board blackbody and deep space views as well as normal Earth scene collects. The calibration parameters that were determined pre-launch were updated by utilizing data from these preliminary on-orbit assessments. The TIRS on-orbit radiometric performance was then characterized using the updated calibration parameters. Although the characterization of the instrument is continually assessed over the lifetime of the mission, the preliminary results indicate that TIRS is meeting the noise and stability requirements while the pixel-to-pixel uniformity performance and the absolute radiometric performance require further study.

The newly launched Operational Land Imager (OLI) aboard the LDCM satellite has stringent prescription on the levels of ghosting and diffuse stray-light in the reflective bands in order to preserve the mission radiometric requirements. The LDCM project science team and instrument teams wrote the requirements such that they were image based, inclusive of all effects that appear to be ghosts or stray-light, and consequently more directly testable. The OLI Instrument Developer, Ball Aerospace Technology Corporation (BATC), working closely with experts from aerospace, academia, and the NASA/USGS LDCM project were able to identify and mitigate the various contributors to ghosting and stray-light, resulting in outstanding imagery for the wide field-of-view push-broom imaging sensor.

We will describe the ghosting and stray-light requirements and some of the contributing effects such as the leaky pixels that were seen on the EO-1/ALI. We will also highlight some of the technical challenges encountered and the solutions resulting in the substantial reduction of ghosting and stray-light which were verified by ground test. We will compare these ground measurements and analytic predictions with Lunar scan data to, potentially, resolve the question of whether the source of some of the performance outliers was the instrument or the test equipment.

The Visible Infrared Imager Radiometer Suite (VIIRS) instrument onboard the Suomi National Polar‐orbiting Partnership (SNPP) satellite was launched on 28 October 2011. The VIIRS has 5 imagery spectral bands (I-bands), 16 moderate resolution spectral bands (M-bands) and a panchromatic day/night band (DNB). Performance of the VIIRS spatial response and band-to-band co-registration (BBR) was measured through intensive pre-launch tests. These measurements were made in the non-aggregated zones near the start (or end) of scan for the I-bands and M-bands and for a limited number of aggregation modes for the DNB in order to test requirement compliance. This paper presents results based on a recently re-processed pre-launch test data. Sensor (detector) spatial impulse responses in the scan direction are parameterized in terms of ground dynamic field of view (GDFOV), horizontal spatial resolution (HSR), modulation transfer function (MTF), ensquared energy (EE) and integrated out-of-pixel (IOOP) spatial response. Results are presented for the non-aggregation, 2-sample and 3-sample aggregation zones for the I-bands and M-bands, and for a limited number of aggregation modes for the DNB. On-orbit GDFOVs measured for the 5 I-bands in the scan direction using a straight bridge are also presented. Band-to-band co-registration (BBR) is quantified using the prelaunch measured band-to-band offsets. These offsets may be expressed as fractions of horizontal sampling intervals (HSIs), detector spatial response parameters GDFOV or HSR. BBR bases on HSIs in the non-aggregation, 2-sample and 3-sample aggregation zones are presented. BBR matrices based on scan direction GDFOV and HSR are compared to the BBR matrix based on HSI in the non-aggregation zone. We demonstrate that BBR based on GDFOV is a better representation of footprint overlap and so this definition should be used in BBR requirement specifications. We propose that HSR not be used as the primary image quality indicator, since we show that it is neither an adequate representation of the size of sensor spatial response nor an adequate measure of imaging quality.

Right after the opening of the NADIR door of the Visible/Infrared Imager/Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite, it has been observed that the detector gains of the near infrared (NIR) bands have decreased much faster than expected. This large decrease is attributed to the optical reflectance degradation of the Rotating Telescope Assembly (RTA) mirrors. We have established a physical model to describe the degradation. In this Proceeding, we use the model to fit the up-to-date observed data to update the model parameters’ values and the degradation projections. We have adjusted our original model slightly to address the additional optical throughput degradation for the short wave infrared (SWIR) bands, occurred right after the spacecraft Sun Point mode anomaly (orbits 2101-2133; March 24-26, 2012). The RTA optical throughput degradation over the reflective solar bands (RSB) and the additional throughput degradation over the SWIR bands after the Sun Point mode anomaly are not constant across the optical wavelength and therefore impact on a detector’s relative spectral response (RSR). Using the models, we establish the degradation versus wavelength curve at any orbit and use the curve to compute the associated impact on the RSR. We further use this degradation modulated RSR to compute the impact on sensor calibration and the Earth View reflectance at Sensor Data Record (SDR) level.

The Visible/Infrared Imager Radiometer Suite (VIIRS) instrument aboard the Suomi National Polarorbiting Partnership (SNPP) satellite performs its radiometric calibration in the reflective solar bands (RSB) wavelength region primarily through observing the sunlight scattered from the onboard Solar Diffuser (SD). The degradation (over time) of the SD reflectance is determined by the onboard Solar Diffuser Stability Monitor (SDSM). The SDSM detector relative spectral response (RSR) over the out-ofband (OOB) wavelength region leads to a non-negligible bias to the originally determined SD degradation coefficient over wavelengths from 412 nm to 488 nm. In this Proceeding, we consider the out-of-band contribution to determine the bias. Our computation shows that the bias to the degradation coefficient is larger at a shorter wavelength and increases with time. On the 564th day after launch (~ orbit 8000), at a wavelength of 412 nm, the bias (OOB-corrected – not-OOB-corrected) has a mean of -0.021, and at a wavelength of 445 nm, the bias has a mean of -0.009.

The VIIRS instrument on Suomi-NPP performs its primary radiometric calibration using the Solar Diffuser, which degrades with exposure to UV light. The Solar Diffuser is monitored by the Solar Diffuser Stability Monitor. In this paper, we evaluate potential improvements to the algorithms that generate the resulting H-factors, including updates to the screen transmission functions and new methodologies to increase the amount of useful data. We also track the on-orbit degradation of the SDSM detectors and predict the long-term performance of the sensors.

The NASA VIIRS Ocean Science Team (VOST) has developed two independent calibrations of the SNPP VIIRS moderate resolution reflective solar bands using solar diffuser and lunar observations through June 2013. Fits to the solar calibration time series show mean residuals per band of 0.078–0.10%. There are apparent residual lunar libration correlations in the lunar calibration time series that are not accounted for by the ROLO photometric model of the Moon. Fits to the lunar time series that account for residual librations show mean residuals per band of 0.071–0.17%. Comparison of the solar and lunar time series shows that the relative differences in the two calibrations are 0.12–0.31%. Relative uncertainties in the VIIRS solar and lunar calibration time series are comparable to those achieved for SeaWiFS, Aqua MODIS, and Terra MODIS. Intercomparison of the VIIRS lunar time series with those from SeaWiFS, Aqua MODIS, and Terra MODIS shows that the scatter in the VIIRS lunar observations is consistent with that observed for the heritage instruments. Based on these analyses, the VOST has derived a calibration lookup table for VIIRS ocean color data based on fits to the solar calibration time series.

Both VIIRS and MODIS instruments use solar diffuser (SD) and lunar observations to calibrate their reflective solar bands (RSB). A solar diffuser stability monitor (SDSM) is used to track the SD on-orbit degradation. On-orbit observations have shown similar wavelength-dependent SD degradation (larger at shorter VIS wavelengths) and SDSM detector response degradation (larger at longer NIR wavelengths) for both VIIRS and MODIS instruments. In general, the MODIS scan mirror has experienced more degradation in the VIS spectral region whereas the VIIRS rotating telescope assembly (RTA) mirrors have seen more degradation in the NIR and SWIR spectral region. Because of this wavelength dependent mirror degradation, the sensor’s relative spectral response (RSR) needs to be modulated. Due to differences between the solar and lunar spectral irradiance, the modulated RSR could have different effects on the SD and lunar calibration. In this paper, we identify various factors that should be considered for the improvements of VIIRS and MODIS solar and lunar calibration and examine their potential impact. Specifically, we will characterize and assess the calibration impact due to SD and SDSM attenuation screen transmission (uncertainty), SD BRF uncertainty and onorbit degradation, SDSM detector response degradation, and modulated RSR resulting from the sensor’s optics degradation. Also illustrated and discussed in this paper are the calibration strategies implemented in the VIIRS and MODIS SD and lunar calibrations and efforts that could be made for future improvements.

The Suomi National Polar-orbiting Partnership (S-NPP) satellite, carrying the first Visible Infrared Imager Radiometer Suite (VIIRS) was successfully launched on October 28, 2011 with first light on November 21, 2011. The passive cryo-radiator cooler doors were opened on January 18, 2012 allowing the cold focal planes (S/MWIR and LWIR) to cool to the nominal operating temperature of 80K. After an early on-orbit functional checkout period, an intensive Cal/Val (ICV) phase has been underway. During the ICV, the VIIRS SDR performance for thermal emissive bands (TEB) has been under evaluation using on-orbit comparisons between VIIRS and the CrIS instrument on S-NPP, as well as VIIRS and the IASI instrument on MetOp-A. CrIS has spectral coverage of VIIRS bands M13, M15, M16, and I5 while IASI covers all VIIRS TEB. These comparisons largely verify that VIIRS TEB SDR are performing within or nearly within pre-launch requirements across the full dynamic range of these VIIRS bands, with the possible exception of warm scenes (<280 K) in band M12 as suggested by VIIRS-IASI comparisons. The comparisons with CrIS also indicate that the VIIRS Half Angle Mirror (HAM) reflectance versus scan (RVS) is well-characterized by virtue that the VIIRS-CrIS differences show little or no dependence on scan angle. The VIIRS-IASI and VIIRS-CrIS findings closely agree for bands M13, M15, and M16 for warm scenes but small offsets exist at cold scenes for M15, M16, and particularly M13. IASI comparisons also show that spectral out-of-band influence on the VIIRS SDR is <0.05 K for all bands across the full dynamic range with the exception of very cold scenes in Band M13 where the OOB influence reaches 0.10 K. TEB performance, outside of small adjustments to the SDR algorithm and supporting look-up tables, has been very stable through 18 months on-orbit. Preliminary analysis from an S-NPP underflight using a NASA ER-2 aircraft with the SHIS instrument (NIST-traceable source) confirms TEB SDR accuracy as compliant for a typical warm earth scene (285-290 K).

The Visible Infrared Imager Radiometer Suite (VIIRS), a primary sensor on-board the Suomi-National Polar-orbiting Partnership (SNPP) spacecraft, was launched October 28, 2011. It has 22 bands: 7 thermal emissive bands (TEBs), 14 reflective solar bands (RSBs) and a Day Night Band (DNB). The TEBs cover the spectral wavelengths between 3.7 to 12 μm and have two 371 m and five 742 m spatial resolution bands. A VIIRS Key Performance Parameter (KPP) is the sea surface temperature (SST) which uses bands M12 (3.7 μm), M15 (10.8 μm) and M16’s (12.0 μm) calibrated Science Data Records (SDRs). The TEB SDRs rely on pre-launch calibration coefficients used in a quadratic algorithm to convert the detector’s response to calibrated radiance. This paper will evaluate the performance of these prelaunch calibration coefficients using vicarious calibration information from the Cross-track Infrared Sounder (CrIS) also onboard the SNPP spacecraft and the Infrared Atmospheric Sounding Interferometer (IASI) on-board the Meteorological Operational (MetOp) satellite. Changes to the pre-launch calibration coefficients’ offset term c0 to improve the SDR’s performance at cold scene temperatures will also be discussed.

The Day/Night Band (DNB) on the VIIRS sensor is a panchromatic band that can detect very dim nighttime scenes. After launch of Suomi NPP in October 2011 we observed a gray haze in radiance images with offsets up to 5×10^-9 W cm^-2 sr^-1. Overall this impacts about 25% of nighttime scenes. We considered stray light as the likely cause, and studied calibration data from the space view. We concluded that stray light is likely entering the VIIRS scan cavity directly or indirectly through the nadir door and solar diffuser openings. We also studied the darkest earth scenes without any solar, lunar or artificial illumination, and found that the offset is a function of cross-track pixel, solar angle of incidence (AOI) and detector number. We observed a strong detector dependence causing striping. Dividing scenes into 3 or 4 zones in each hemisphere based on solar AOI, we devised an algorithmic correction based on polynomial fits of the medians of the data for each zone. The correction removed almost all the haze and striping and improved dynamic range by 2 orders-of-magnitude, to as low as 1×10^-10 Wcm^-2 sr^-1, but some striping remains in the twilight region due to extrapolation.

This paper examines the feasibility and potential benefits of enhancing the spatial resolution of the VIIRS DNB channel for the JPSS-2 mission and beyond, by modifying the on-chip pixel binning recipe used in the DNB CCD to aggregate detector area within the scan swath. Presently the DNB delivers 16 cross-scan samples similar in size to the detectors in the VIIRS Moderate Resolution Bands. The relatively low-cost enhancement proposed would instead bin the pixels of the existing DNB CCD into 32 cross-scan samples, each half as large in track and scan, effectively doubling the spatial resolution of DNB in each dimension to match the VIIRS Imaging Bands at nadir. Other potential benefits include, for unresolved point sources, improved detection sensitivity and SNR. Smaller DNB image pixels would be less spatiallymixed, and therefore better suited to many quantitative analyses. DNB geolocation accuracy would also benefit from the increased spatial resolution, but less so for regions approaching edge-of-scan. To implement the maximum DNB spatial resolution enhancement over the full cross-track scan swath would require design and hardware modifications to the focal plane electronics (FPIE) to increase certain CCD clock rates. This paper explores the performance of this option, alongside other options that (if constrained to use the existing FPIE design with minimal changes) would not provide the enhanced DNB spatial resolution all the way out to the edges of the cross-track scan. These would instead offer other benefits, such as better maintaining SNR to edge-of-scan and, if away from nadir DNB sampling matched the I-bands, better enabling future environmental products merging the enhanced DNB data with existing VIIRS spectral band data.

A new generation of hyperspectral imagers requires a much higher absolute accuracy for reflected solar radiation measurements to further improve climate monitoring capabilities. For example, the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission, a future satellite mission led and developed by NASA and partner organizations, is currently considered to consist of two hyperspectral imagers that cover the reflected solar (RS) and infrared radiation. The design of the CLARREO RS instrument operates from 320 to 2300 nm with 4 nm in spectral sampling and 8 nm in spectral resolution. In this study, the sensitivity of spectral coverage, sampling and resolution of the CLARREO RS type instrument is tested for their impacts on integrated radiances using the relative spectral responses (RSR) of existing broadband sensors. As a proxy, our hyperspectral data is based on MODTRAN simulations and SCIAMACHY observations and the RSR data is from those used in MODIS, VIIRS and AVHRR level 1B (L1B) products. The sensitivity is conducted for ocean, forest, desert, snow and cloud.

The Day Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite provides imagery of clouds and other Earth features over illumination levels ranging from full sunlight to quarter moon. In order to cover this extremely broad measurement range, the DNB employs four imaging arrays that comprise three gain stages. The low gain stage (LGS) gain values are determined by solar diffuser data. In operation, the medium and high gain stage values are determined by multiplying the LGS gains by the medium gain stage (MGS)/LGS and high gain stage (HGS)/LGS gain ratios, respectively. This paper demonstrates a scheme of using DNB observation of ground vicarious sites under lunar illumination at night to independently verify the radiometric accuracy of HGS of DNB. We performed vicarious calibration of DNB when S-NPP flies above the vicarious site such as Dome C in Antarctic and Greenland in northern hemisphere at night and the moon illuminates the site with lunar phase being more than half moon. Lunar spectral irradiance model as a function of Sun-Earth-Moon distances and lunar phase is used to assist the determination of top-of-atmosphere reflectance at the vicarious site. Analysis of the vicariously-derived reflectance from DNB observations show agreement with the reflectance derived from Hyperion observations of the vicarious sites.

MODIS has 20 reflective solar bands (RSB) with a total of 330 individual detectors. Currently, there are two nearly identical MODIS instruments operating in space: one on the Terra spacecraft launched in December 1999 and another on the Aqua spacecraft launched in May 2002. MODIS reflective solar bands (RSB) are calibrated on-orbit by a system that consists of a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). Near-monthly lunar observations are also used to track the sensor response versus scan angle (RVS) change on-orbit. On-orbit observations show that the changes in the detector response are wavelength, scan-angle and mirror side dependent. This paper provides a comprehensive assessment of the detector-to-detector calibration differences in the MODIS VIS/NISR spectral bands using the on-board calibrators and earth-view (EV) level 1B (L1B) data products. Different EV targets are analyzed to accommodate the high-gain ocean bands which tend to saturate over land surfaces. The results from this study highlight the necessity of the constant monitoring of the detector-level gain and its change as a function of scan-angle, as implemented in the MODIS Collection 6 (C6) products.

The paper presents the mathematical technique for calculation of the output radiance of the precise uniform light sources which have a form of several or multiple optically connected integrating spheres. The light source contains several primary integrating spheres of small diameters which are installed on a secondary integrating sphere of bigger diameter. The proposed technique takes into account the fluxes multiple times coming from the secondary integrating sphere to the primary ones and in opposite direction. The proposed light sources can be considered as one of the best candidates for calibration of high level optical instruments working in optical range 0.4 - 2.2 mkm including radiometers for remote sensing.

The moon is a stable source for the on-orbit calibration of the space-borne sensors with regular lunar observation capability, such as MODIS on-board the Terra and Aqua satellites and VIIRS on-board the Suomi NPP satellite. The spectral bands of both sensors are located on multiple focal plane assemblies and spatially co-registered in both the along-scan and along-track directions. Any mis-registration, or the band-to-band registration (BBR) shift, can deteriorate the quality of the science products that are derived from the data of multiple spectral bands. In this paper, the VIIRS spatial performance, mainly focusing on its BBR, is characterized using its lunar observations via an algorithm developed and verified for MODIS. In this algorithm, the centroids of the lunar images of various bands are calculated and the BBR shift between bands is determined by differentiating these centroids. Results show that the on-orbit change of the BBR has been small for VIIRS reflective solar bands (RSB) since its launch in Oct. 2011. The modulation transfer function (MTF), a measure of the image sharpness of an optical system, is also derived for RSB from the same set of lunar images by an algorithm inherited from MODIS characterization. The VIIRS on-orbit MTF in the along-track direction is trended and shown to have been stable.

Atmospheric aerosol play an important role in the climate change, though direct and indirect processes¹. To evaluate the effects of aerosols on climate it is necessary to estimate their spatial and temporal distributions². Since 2000, the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) have been providing global aerosol products³. However, the uncertainties still exist in current satellite aerosol products attributable to the complex surface, cloud contamination, and aerosol models used in the retrieving process⁵. Comparing to AERONET AOD, the larger magnitude and different variation tendency in AOD for both sensors indicate that either individual aerosol product may not be good application over China. Combing multiple sensors is a method to reduce uncertainties and improve observational accuracy. An adaptive weighted estimate algorithm of multi-sensor data fusion was presented, which could adjust the fused sensor’s weight in time according to the variation in sensor’s variance. The combined AOD product using the fusion method is in better agreement with corresponding AOD from AERONET than single sensor, which illustrate the fusion method performs better applicability in China. The fusion method can reduce uncertainties both sensors and expand the scope of the distribution in AOD. Using the latest ten-year (2002-2010) fusion product, we study the trend analysis of the aerosol optical depth over typical regions in China. The increasing trend is found over Jingjintang and Yangtze River Delta, which are highly associated with human activities.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a radiometric sensing instrument currently operating onboard the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft. It provides high spatial-resolution images of the emitted and reflected radiation from the Earth and its atmosphere in 22 spectral bands (16 moderate resolution bands M1-M16, 5 imaging bands I1-I5, and 1 day/night pan band DNB) spanning the visible and infrared wavelengths from 412 nm to 12 μm. Just prior to each scan it makes of the Earth, the VIIRS instrument makes a measurement of deep space to serve as a background reference. These space view (SV) measurements form a crucial input to the VIIRS calibration process and are a major determinant of its accuracy. On occasion, the orientation of the Suomi NPP spacecraft coincides with the position of the moon in such a fashion that the SV measurements include light from the moon, rendering the SV measurements unusable for calibration. This paper investigates improvements to the existing baseline SV data processing algorithm of the Sensor Data Record (SDR) processing software. The proposed method makes use of a Moon-in-SV detection algorithm that identifies moon-contaminated SV data on a scan-by-scan basis. Use of this algorithm minimizes the number of SV scans that are rejected initially, so that subsequent substitution processes are always able to find alternative substitute SV scans in the near vicinity of detected moon-contaminated scans.

Time and frequency transfer is new usage of optical links. Recently, it started to deploy as a service of optical networks. Due to principle of time and frequency transfer, it is not possible implement it over data transport layer. The paper describes optical infrastructure for time and frequency transfer in the Czech Republic. The infrastructure is heterogeneous and utilizes resources of the Czech academic optical network. The paper also shows achieved results and indicates necessary steps for further transmission stability improvements.