This PDF file contains the front matter associated with SPIE Proceedings Volume 10785, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

There has been much recent progress with CubeSat-hosted microwave instrumentation for atmospheric sensing. The Microsized Microwave Atmospheric Satellite Version 2a (MicroMAS-2a), launched on January 11, 2018 and has demonstrated temperature sounding using channels near 118 GHz and humidity sounding using channels near 183 GHz. A second MicroMAS-2 flight unit (MicroMAS-2b) will be launched in late 2018 as part of ELANA-XX. The TimeResolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission was selected by NASA in 2016 as part of the Earth Venture–Instrument (EVI-3) program. The overarching goal for TROPICS is to provide nearly all-weather observations of 3-D temperature and humidity, as well as cloud ice and precipitation horizontal structure, at high temporal resolution to conduct high-value science investigations of tropical cyclones. TROPICS will provide rapid-refresh microwave measurements (median refresh rate of approximately 40 minutes for the baseline mission) over the tropics that can be used to observe the thermodynamics of the troposphere and precipitation structure for storm systems at the mesoscale and synoptic scale over the entire storm lifecycle. TROPICS comprises a constellation of six CubeSats in three low-Earth orbital planes. Each CubeSat will host a high performance radiometer to provide temperature profiles using seven channels near the 118.75 GHz oxygen absorption line, water vapor profiles using three channels near the 183 GHz water vapor absorption line, imagery in a single channel near 90 GHz for precipitation measurements (when combined with higher resolution water vapor channels), and a single channel at 206 GHz that is more sensitive to precipitation-sized ice particles. TROPICS spatial resolution and measurement sensitivity is comparable with current state-of-the-art observing platforms. TROPICS flight hardware development is on track for a 2019 delivery.

The Jet Propulsion Laboratory (JPL) is best known for planetary exploration but is also heavily involved in Earth science and has in recent years become one of the premier centers for atmospheric science related to infrared and microwave satellite sounders such as the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU) and the Advanced Technology Microwave Sounder (ATMS), as well as aircraft based microwave sounders such as the High Altitude MMIC Sounding Radiometer (HAMSR) and the development of future sounders such as an infrared CubeSat system (CIRAS) and a geostationary microwave sounder (GeoSTAR). We give a brief overview of these sensors and focus on the development and assessment of sounder data products, which include vertical profiles of temperature and water vapor, cloud and surface parameters, and in the case of infrared sounders also trace gas estimates and for microwave sounders precipitation as well. The baseline AIRS data product “retrieval system” was developed by the AIRS science team and has been undergoing continuous maintenance and upgrade in close collaboration with the sounder team at JPL. To support that process, the JPL team has developed a broad range of assessment tools and techniques, which can be applied to data from other sounders as well and can range from simple “sanity check” analysis to thorough “validation” analysis. An example of the less complex testing is the preliminary assessment of products generated by new retrieval systems operating on data from the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS) flying on the Suomi NPP and JPSS satellites. These retrieval systems are developed by individual investigators funded by NASA research grants and are delivered to a Sounder “Science Investigator Processing System” (SIPS) located at JPL for integration, testing and delivery to a NASA data processing center and eventual release to the public, but only limited resources are available to the SIPS for the assessment, which therefore must be relatively superficial. An example of thorough assessment is the quantification of the impact on AIRS products of the failure of the AMSU-A2 microwave sounder 2 years ago. The baseline AIRS retrieval system used initially data from the companion microwave sounders, the Humidity Sounder for Brazil (HSB), AMSU-A1 and AMSU-A2, to provide a “first guess” and support “cloud clearing”. As these instruments suddenly failed (HSB) or gradually deteriorated (AMSU), some effort was devoted to develop a version that did not depend on microwave data. It was considered somewhat inferior to the baseline system and was kept in reserve and therefore not fully assessed. When AMSU-A2 failed, this AIRS-only system became the primary version, and a substantial effort was undertaken to fully assess its performance. We discuss details of that assessment. These capabilities have resulted from substantial investments NASA has made over the years in support of AIRS and can now be applied to next-generation systems as well.

The Active Sensing of CO₂ Emissions over Nights, Days, and Seasons (ASCENDS) CarbonHawk Experiment Simulator (ACES) is a NASA Langley Research Center instrument funded by NASA’s Science Mission Directorate that seeks to advance technologies critical to measuring atmospheric column carbon dioxide (CO₂) mixing ratios in support of the NASA ASCENDS mission. The ACES instrument, an Intensity-Modulated Continuous-Wave (IM-CW) lidar, was designed for high-altitude aircraft operations and can be directly applied to space instrumentation to meet the ASCENDS mission requirements. Airborne flight campaigns have been used to demonstrate ACES’ advanced technologies critical for a spaceborne instrument with lower platform consumption of size, mass, and power, and with improved performance. ACES recently flew on the NASA DC-8 aircraft during the 2017 NASA ASCENDS/Arctic-Boreal Vulnerability Experiment (ABoVE) airborne measurement campaign to test ASCENDS-related technologies in the challenging Arctic environment. Data were collected over a wide variety of surface reflectivities, terrain, and atmospheric conditions during the campaign’s eight research flights. ACES also flew during the 2017 and 2018 Atmospheric Carbon and Transport – America (ACT-America) Earth Venture Suborbital - 2 (EVS-2) campaigns along with the primary ACT-America CO₂ lidar, Harris Corporation’s Multi-Frequency Fiber Laser Lidar (MFLL). Regional CO₂ distributions of the lower atmosphere were observed from the C-130 aircraft during the ACT-America campaigns in support of ACT-America’s science objectives. The airborne lidars provide unique remote data that complement data from more traditional in situ sensors. This presentation shows the applications of CO₂ lidars in meeting these science needs from airborne platforms and an eventual spacecraft.

Constellations have proven to be an effective and efficient way to acquire earth science data. By flying together, sensors on all satellites in a constellation take measurements of the same air, water, or land mass at essentially the same time. The sensors form a single “virtual satellite”. The key to making a constellation effective and efficient is keeping the operations as independent as possible in order to minimize the operational burden and costs. The Earth Science Constellation (ESC) has been successful on all counts and continues to welcome new missions to continue its 18+ year record of coincidental earth science observations. The ESC also serves as a model for future constellation designs. This paper describes the ESC and its evolution from its initial launches in 1999 through the present and how new missions might benefit from joining the ESC.

We have developed the P-band Signals of Opportunity (SoOp) sensor based on the Unmanned Aircraft System (UAS) to remotely sense Snow Water Equivalent (SWE) and Root Zone Soil Moisture (RZSM). The P-band UAS SoOp sensor for Hydrology (UASHydro) would operate on the S2 aircraft developed by Black Swift Technologies for sensing of SWE and RZSM with a spatial resolution of about 10m. Root-zone soil moisture and snow water storage in land are critical parameters of the water cycle. The long-term goal of our development would be to use small UAS to perform regional high resolution observation of two key hydrological measurements to improve the estimation of terrestrial water storage for water management, crop production and forecasts of natural hazard. The UASHydro concept utilizes passive receivers to detect the reflection of strong existing P-band radio signals at the 360-380 MHz band from geostationary Mobile Use Objective System (MUOS) communication satellites launched by the US Navy. The SWE remote sensing measurement principle using the P-band SoOp is based on the propagation delay (or phase change) of radio signals through the snowpack. The time delay of the reflected signal due to the snowpack with respect to snow-free conditions is directly proportional to the snowpack SWE, while the soil moisture can be retrieved from the reflectivity at the P-band frequencies for MUOS. We have been conducting ground-based campaigns to test the instrumentation and data processing methods at the Fraser Experimental Forest in Colorado since February 2016. The field campaign data has provided support to the measurement concept. To install the SoOp technologies on the UAS, a lightweight antenna has been built and interfaces with the S2 built by Black Swift Technologies have been completed. A set of flights have been planned starting April 2018 through the end of 2018 in Colorado.

This manuscript presents the improvements implemented on the future Sentinel-1C/D spacecraft, which will eventually replace the current in-orbit Sentinel-1A/B satellites. Changes are based on the Sentinel-1A/B lessons learnt and on the addition of new functionalities to improve the system performance. More specifically, the modifications that will be covered in this paper are those that will enhance the performance of the mission. The addition of an Automatic Identification System (AIS) will provide ship position and identification while operating the SAR instrument. The Attitude and Orbit Control System (AOCS) will be upgraded to improve the pointing stability and to be compatible with the new Galileo signals. A novel mechanical bracket interfacing the SAR central panel and the platform has been designed to facilitate the disintegration during the re-entry. The propulsion system has also been modified to allow a faster orbit acquisition. The upgrades done on the SAR instrument to improve the radiometric stability will be also detailed.

The impact of NO2 and other atmospheric trace gases on health and the environment is now acknowledged by governments around the world. The sources, both natural and anthropogenic, have been shown to affect the quality of life due to low air quality in densely populated areas. Consequently, the need for accurate global NO2 measurements with high spatial- and temporal resolution to monitor NO2 is becoming ever more important. Through an ESA study, TNO and KNMI have been evaluating measurement requirements and an instrument design for a ‘Compact NO2 Spectrometer’, based on a hyperspectral imaging instrument operating in the VIS (405-490nm] spectral range and aimed at combining the performance of state-of-the-art instruments with fine spatial sampling (0.5x0.5 km²). By use of a novel free-form optics a very compact low volume and low mass design has been achieved. Combining this with other small satellite design approaches for components the aim is to create a low cost instrument capable of being flown on a wide variety of space platforms. Global daily coverage can then be achieved with a relatively small constellation of instruments. The key design features are described for a ‘Compact NO2 Spectrometer’, such as the optical design approach, the use of free-form optics, an ‘athermal’ all aluminium approach. An overview of the development and airborne results from a breadboard of a small prototype system (Spectrolite) developed by TNO which uses many of the design features envisaged for this new instrument is given.

The Multi-Viewing -Channel -Polarisation Imager (3MI), planned to fly on the Metop-SGA satellites as part of the EUMETSAT Polar System - Second Generation (EPS-SG) programme in the timeframe beyond 2020, is a radiometer dedicated to aerosol and cloud characterisation for climate monitoring, atmospheric composition, air quality and numerical weather prediction. The purpose of the 3MI is to provide multi-spectral (12 channels between 410 nm and 2130 nm), multi-polarisation (-60°, 0°, and +60°), and multi-angular (10 to 14 views) images of the Earth top of atmosphere outgoing radiance. The 3MI concept is based on the PARASOL mission heritage. This heritage allows adapting techniques developed for PARASOL e.g. for the vicarious calibration methods. As PARASOL, 3MI does not have an onboard calibration facility and its radiometric and geometric performances will rely on vicarious calibration. However the monitoring of the SWIR (short wave infrared) channels will be the new challenge for the 3MI calibration as this spectral range was not present on PARASOL. Because the vicarious methods may have less accurate performance for absorption bands (763 nm, 910 nm, and more specifically the SWIR 1370 nm), the access to a moon observation during commissioning would be very beneficial, in addition to the characterization of many other radiometric aspects. The Metop-SGA satellite will also allow simultaneous temporal and geometrical acquisitions between the payload instruments. This synergy will be beneficial to support 3MI with cross-calibration (radiometric, spectral, and geometric). Indeed the Visible-Infrared Imager (METimage) and the UV-VIS-NIR-SWIR Sounder (Sentinel-5), the two other optical instruments covering the similar spectral regions will be both equipped with on-board calibration and provide valuable measurements for cross-calibration with 3MI.

Image calibration and performance assessment activities of the commissioning phase of Venµs EO mission took place in the second semester of 2017 and the first semester of 2018. As for the geometric image quality part, this phase consisted in assessing and correcting the pointing bias, assessing the geolocation performance, calibrating the line of sight (LOS) of each detector, assessing the multi-spectral as well as multi-temporal registration performances, and assessing and setting up reference images. Since the geometric commissioning has been disturbed by attitude restitution errors, this paper gives a feedback on how we adapted the geometric calibration as well as the production processing in order to fulfill the requirements with a minimum of cost. These changes have a non-negligible impact on ~20% of the products. The image registration methodology is presented and discussed. Current registration performances are finally presented.

The DLR Earth Sensing Imaging Spectrometer (DESIS) is a new space-based hyperspectral sensor developed and operated by a collaboration between the German Aerospace Center (DLR) and Teledyne Brown Engineering (TBE). DESIS will provide hyperspectral data in the visible to near-infrared range with high resolution and near-global coverage. TBE provides the platform and infrastructure for the operation on the International Space Station (ISS), DLR has developed the instrument. This paper gives an overview of the design of the DESIS instrument together with results from the optical on-ground calibration. In-flight calibration, stability of dark signal and rolling vs. global shutter analysis will be presented.

The Meteosat Third Generation (MTG) series of future European geostationary meteorological satellites consists of two types of satellites, the imaging satellites (MTG-I) and the sounding satellites (MTG-S). The Infrared Sounder (IRS) is one of the two instruments hosted on board the MTG-S satellites. The scope of the IRS mission is to provide the user community with information on time evolution of humidity and temperature distribution, as function of latitude, longitude and altitude. Regarding time and space sampling, the entire Earth disk will be covered, with particular focus on Europe, which will be revisited every 30 minutes. This paper presents a synthetic overview of the mission and the instrument, and will go through the level 1 processing chain which takes instrument raw data to obtain spectrally and radiometrically calibrated and geolocalised radiances, called level 1b products. Based on the latest information available at instrument level, commonalties and mainly differences with current flying hyperspectral missions will be presented. This will followed by a discussion on the latest specifications on the radiances uniformisation in space, spectral range and time, as well as the spectral sampling, and the apodisation and their impacts for the users community.

Currently, Japan Aerospace Exploration Agency (JAXA), Japan Meteorological Agency (JMA) and Japan Space Systems (JSS) are operating major Earth Observation Satellites. Ibuki (GOSAT) carrying TANSO-CAI and -FTS, Shizuku (GCOM-W) carrying AMSR2, Daichi-2 (ALOS-2) carrying PALSAR-2, DPR on GPM-core satellite of NASA and Shikisai (GCOM-C) carrying SGLI, are being operated by JAXA under cooperation with some domestic agencies, such as Ministry of Environment (MoE), National Institute of Information and Communications Technology (NICT). JMA is operating weather satellite Himawari-8 and -9 on geostationary orbit. JSS are operating ASTER on EOS-Terra satellite of NASA. For coming satellites or instruments, JAXA is going to operate CPR on EarthCARE satellite of ESA, GOSAT-2 carrying TANSO-CAI2 / -FTS2, ALOS-3 carrying the “wide-swath and high-resolution optical imager” and ALOS-4 carrying PALSAR-3. JSS is going to have HISUI on ISS. JAXA is restructuring its program along with new mid-term plan which started from April 2018 for seven years. Adding to follow-on mission studies, several new studies are underway for near future missions, such as Lidar missions, Super low orbit missions and new geostationary missions with large segmented telescope for land observation.

The Japan Aerospace Exploration Agency (JAXA) is pressing forward with Global Change Observation Mission (GCOM) for long-term monitoring of earth environment. GCOM consists of two series of medium-size satellites, GCOM-W (Water) and GCOM-C (Climate). The first satellite, GCOM-W with Advance Microwave Radiometer -2 (AMSR-2), was already launched in 2012 and has been observing continuously. GCOM-C which carries the optical radiometer, Second Generation Global Imager (SGLI), was launched on December 23, 2017. SGLI observation data will produce more than 20 scientific products such as cloud, aerosol, ocean color, vegetation, ice field and so on, and will contribute to improve the understanding of the global mechanism of carbon cycle and radiation budget. SGLI includes two radiometer units of Visible and Near Infrared Radiometer (VNR) and Infrared Scanning Radiometer (IRS), which perform a wide-spectral (380 nm-12 μm) optical observation with relatively high (250 m) spatial resolution. After the launch, the satellite and SGLI instruments were initialized and commissioned for routine operations during a threemonth period called in-orbit checkout. SGLI-VNR performance tests included internal light calibration, solar diffuser calibration, dark signal calibration and electrical calibration. In addition to that, solar angle correction maneuvers were performed within L+2 weeks and lunar calibration maneuvers were performed each synodic period. 90-deg. yaw maneuvers were also performed. In this paper, the in-orbit commissioning activities of SGLI-VNR will be described. Especially we focus on the internal light calibration and solar diffuser calibration results during a commissioning phase.

The observation from spaceborne precipitation radar has been contributed to better understanding of earth climate system. Global Precipitation Measurement (GPM) core satellite Dual-frequency Precipitation Radar (DPR) provides us 3- dimentional information of precipitation by the scan width of about 250 km, but there has been an argument that to bring systematic impact on the weather forecasting and monitoring, wider swath observation is necessary. Based on those discussions, the scan pattern of GPM/DPR was experimentally changed for 1 day from 13UTC on September 26th. In this experiment, the scan angle was changed to observe from nadir to about +34° assuming future spaceborne precipitation radar with wider swath width, while in the normal observation DPR scans ±17°. The height and strength of the surface echo clutter with larger incident angle were assessed statistically to examine the possibility of the rainfall retrieval with wide swath observation by DPR. For the observation with the Ku band, the result shows that the clutter top height at the larger incident angle over ocean is somehow suppressed at around 4 km while over land it increases almost linearly up to around 5 km. The same tendency is found on the Ka band observation, but it has lower clutter top height of around 2.5 km and 3.5 km, over ocean and land respectively. The results also indicate that relatively intense rainfall can be retrieved while shallow rainfall with weak echo power may not be acceptable for retrieval because it should be masked by the surface clutter.

JAXA has continued to develop the Advanced Optical Satellite (called “ALOS-3”) since FY 2016, as a successor of the optical mission of the Advanced Land Observing Satellite (ALOS) “DAICHI” (2006-2011). The wide-swath and highresolution optical imager (WISH) is a main sensor of ALOS-3. It has capabilities to collect high-resolution (0.8m Pan / 3.2m MS at nadir) and wide-swath (70 km) images with a high geo-location accuracy to meet the mission objectives of ALOS-3. WISH has a Pan band and 6 MS bands. The MS equips the basic four bands (R, G, B and NIR) and 2 additional bands of "coastal" and "RedEdge" expected to use for the various applications. The development of WISH is in the final stage of the critical design phase. We have finished the test of engineering model of the primary mirror assembly with no critical problem. In addition, the mechanical environmental tests using the structure model was completed, and the demonstration for high accuracy assembling of the large off-axis telescope is undergoing. For the detector system, the evaluation of the engineering model of the CCDs was completed in early phase, and assembly of the flight CCDs has been started in advance. In the current schedule, PFM manufacturing and subsequent proto-flight tests would be conducted within about a year and WISH would be delivered to the satellite system by the middle of FY 2019. ALOS-3 equipped with WISH would be launched by H-IIA rocket in FY 2020.

Accurate measurements of forest biomass are important to evaluate its contribution to the global carbon cycle. Forest biomass correlates with forest canopy height; therefore, global measurements of canopy height enable a more precise understanding of the global carbon cycle. A vegetation lidar named “MOLI” which is designed to measure accurate canopy height has been studied by the Japan Aerospace Exploration Agency (JAXA) in cooperation with some researchers. MOLI stands for Multi-footprint Observation Lidar and Imager. The feature of MOLI is to set multi-footprints for improving the precision of canopy height, and we can find out whether ground surface is flat or slope because an angle of inclination affects the estimation of canopy height. MOLI is going to be mounted on the Exposed Facility (EF) of the Japanese Experiment Module (JEM, also known as “Kibo”) on the International Space Station (ISS). Now, we are carrying out a feasibility study and some experiments. We introduce an overview and a status of MOLI.

SPOT 1→5 satellites have collected more than 30 million images all over the word during the last 30 years which represents a unique historical dataset. SWH (SPOT World Heritage) is the CNES initiative to preserve and valorize this SPOT archive by providing new enhanced products in order to allow the use of past data to extend current temporal analyses. Indeed, this archive, hosted in CNES, is composed of raw binary data only accessible through commercial partner Airbus processing. A first step has begun in 2015 with a major update of this archive by repatriating as much data as possible from remote SPOT stations. Since 2016, SWH has become a dedicated CNES project including first developments. CNES has then started the data extraction from the current archive in order to build a new more useable archive at L1A image level. Meanwhile, data processing chains are being set-up to provide L1A, L1B and L1C products. L1A is the current SPOT 1A format including basic radiometric corrections due to instruments distortions. L1B and L1C will include additional radiometric and geometric corrections in line with Sentinel-2 references (L1C being the orthorectified product in Top Of Atmosphere reflectance). Specific SPOT 5 THR products will also be provided with a new optimized denoising algorithm. Finally, the last part of valorization will consist of providing freely these products to users (licensed). SWH processing will take place on CNES High Performance Computing Centre and will use Big Data technologies such as Elastic Stack for production monitoring.

The Carbon Observatory Instrument Suite, or CARBO, consists of four carbon observing instruments sharing a common instrument bus, yet targeted for a particular wavelength band each with a unique science observation. They are: a) Instrument 1, wavelength centered at 756 nm for oxygen and solar-induced chlorophyll fluorescence (SIF) observations, b) Instrument 2, centered at 1629 nm, for carbon dioxide (CO₂) and methane (CH4) observation, c) Instrument 3, centered at 2062 nm for carbon dioxide and d) Instrument 4, centered at 2328 for carbon monoxide (CO) and methane. From low-Earth orbit, these instruments have a field-of-view of 10 to 15 degrees, and a spatial resolution of 2 km square. These instruments have a spectral resolving power ranging from ten to twenty thousand, and can monitor columnaverage dry air mole fraction of carbon dioxide (XCO2) at 1.5 ppm, and methane (XCH4) at 7 ppb. These new instruments will advance the use of immersion grating technology in spectrometer instruments in order to reduce the size of the instrument, while improving performance. These compact, capable instruments are envisioned to be compatible with small satellites, yet modular to be configured to address the particular science questions at hand. Here we report on the current status of the instrument design and fabrication, focusing primarily on Instruments 1 and 2. We will describe the key science and engineering requirements and the instrument performance error budget. We will discuss the optical design with particular emphasis on the immersion grating, and the advantages this new technology affords compared to previous instruments. We will also discuss the status of the focal plane array and the detector electronics and housing. Finally, we report on a new approach – developed during this instrument design process - which enables simultaneous measurement of both orthogonal polarization states (S and P) over the field-of-view and optical bandpass. We believe this polarization sensing capability will enable science observations which were previously limited by instrumental and observational degeneracies. In particular: improved sensitivity to all species, better sensitivity to surface polarization effects, better constraints on aerosol scattering parameters, and superior discrimination of the vertical distribution of gases and aerosols.

Earth observation (EO) is a rapidly expanding area of space science and technology, fueled by the demands for timely, comprehensive and informative data for an increasing number of applications. With the increased affordability of satellites EO is becoming accessible to a larger pool of commercial developers and users. Presently there does not exist in the market a low cost payload with the performance required to meet the growing demands of the commercial ‘New Space’ EO market (very high resolution, good quality image, low mass and low recurrent cost). The presentation will discuss the characterization results of a novel TDI-CMOS silicon prototype as well as a description of the current flight model design currently being developed under the CEOI EO technology and Instrumentation program funded by the UK Space Agency. This sensor will be a key enabling technology for the high resolution new space payload.

For the earth observation mission, there are some critical environmental requirements including low-light condition, fast moving objects, high scanning rate. In order to meet these requirements, the Time-Delay-and-Integration (TDI) technique is critical and essential for the sensor part to improve the Signal to Noise Ratio (SNR) performance. National space organization (NSPO) collaborates with National Chip Implementation Center (CIC) on the next generation image sensor. In order to increase SNR under the light-starved condition, a 32-stages digital-accumulator Time-Delay-and-Integration (TDI) CMOS image sensor is adapted to improve the image quality. Besides, it could successfully take several pictures under different TDI stages on a dynamic test bench. The experimental results verified that the 32-stage TDI CMOS image sensor could function well.

Physikalisch-Technische Bundesanstalt (PTB) designed a new calibration facility, the Reduced Background Calibration Facility 2 (RBCF2) as the successor of the Reduced Background Calibration Facility (RBCF) [1] and brought it recently into operation. It provides traceable calibrations of space based infrared remote sensing experiments in terms of radiation temperature and spectral radiance. Traceable measurements from space require the use of calibrated stable detector systems and / or source based calibration standards on board of the satellites. In any case they should be calibrated under space like conditions to ensure traceability with the smallest possible uncertainty. The RBCF2 enables therefore the calibration of radiators and detectors and cameras under cryogenic and / or vacuum conditions. The integration of the instruments under test into the RBCF2 can be done under ISO 5 clean room conditions. The general concept of the RBCF2 is to connect different sources in the source chamber and detectors in the detector chamber via a liquid nitrogen cooled beam line. Source and detector chamber also incorporate cooling facilities. Translation units in both chambers enable the RBCF2 to compare and calibrate different sources and detectors with stable comparison instruments at cryogenic temperatures and under a common vacuum. Reference sources for comparisons are dedicated vacuum variable temperature blackbodies, the vacuum medium temperature blackbody (VMTBB, 150 °C to 430 °C), the vacuum low temperature blackbody (VLTBB, -173 °C to 177 °C), the liquid operated blackbody (LBB, -80 °C to 80 °C), the large area heatpipe blackbody (LAHBB, -60 °C to 50 °C) featuring a radiating diameter of 250 mm, the liquid nitrogen blackbody (LNBB, -196 °C) and calibrated vacuum integrating sphere radiators for UV-VIS and SWIR applications. The radiation temperatures of the reference blackbodies and the radiance of the integrating sphere radiators are traceable to the ITS-90 via the primary standards of PTB. Using the calibrated vacuum infrared standard radiation thermometer (VIRST) [2] direct calibrations of sources in terms of radiation temperature in the wavelength range from 8 µm to 14 µm can also be performed. The radiation of the reference sources and the sources under test can also be imaged on a vacuum Fourier-Transform Spectrometer (FTS) to allow spectrally resolved measurements. The FTS covers the wavelength range from 0.4 µm to 1000 µm. Here several detectors are employed, ranging from photomultipliers to liquid helium cooled bolometers. The different reference blackbodies enable measurements with respect to at least two reference temperatures, simultaneously. Hereby disturbances in the IR by background radiation resulting from inside the FTS can be effectively compensated. Sources can be also spatially mapped and characterized for the lateral distribution of their spectral radiance [3]. The flexible design of the facility allows also large aperture camera characterizations and modifications for customer needs and the measurement of directional spectral emissivities over a wide temperature and wavelength range [4]. [1] C. Monte, B. Gutschwager, J. Hollandt, The Reduced Background Calibration Facility for Detectors and Radiators at the Physikalisch-Technische Bundesanstalt, Sensors, Systems, and Next-Generation Satellites XIII, SPIE, 2009, 7474, 747414 [2] B. Gutschwager, J. Hollandt, T. Jankowski, R. Gärtner, A Vacuum Infrared Standard Radiation Thermometer at the PTB, International Journal of Thermophysics, 29, 330-340, 2008 [3] C. Monte, B. Gutschwager, A. Adibekyan, M. Kehrt, A. Ebersoldt, F. Olschewski, J. Hollandt, Radiometric calibration of the in-flight blackbody calibration system of the GLORIA interferometer Atmospheric Measurement Techniques, 2014, 7, 13-27 [4] A. Adibekyan, C. Monte, M. Kehrt, B. Gutschwager, J. Hollandt, Emissivity measurement under vacuum from 4 µm to 100 µm and from -40 °C to 450 °C at PTB, International Jounal of Thermophysics, 2015, 36, 283-289

The Environmental Mapping and Analysis Program (EnMAP) is a German hyperspectral satellite mission to monitor and characterize the Earth’s environment. The EnMAP payload, the Hyper Spectral Imager (HSI) features an on-board calibration assembly (OBCA) which is designated to provide the optical radiation to monitor the instrument radiometric and spectral ‎stability during the ‎mission lifetime. The assembly comprises two integrating spheres in twin configuration equipped with several different optical radiation sources. The large ‎sphere made of white diffuse reflecting material is dedicated for radiometric stability ‎measurements, while the ‎small sphere, made of rare-earth doped diffuse reflecting material, is dedicated for spectral stability checks. ‎The ‎OBCA utilizes two types of optical radiation sources: ‎tungsten halogen lamps and white light LEDs. Here we report on the spectral and radiometric calibration of the OBCA qualification and flight model in the Reduced Background Calibration Facility 2 (RBCF2) of Physikalisch-Technische Bundesanstalt (PTB) [1]. The demanding requirements were to perform a calibration in air and in vacuum with an uncertainty of less than 2% with a spectral resolution of 0.1 nm over a wavelength range from 400 nm to 2500 nm not exceeding an operating time of 40 h for the halogen lamps and 100 h for the LEDs. Furthermore, a precise mapping of the OBCA exit aperture of size 2 mm by 24 mm with 1 mm sampling diameter had to be performed. For that purposes PTB developed a calibration procedure based on spectral comparisons of the OBCA with respect to dedicated vacuum radiance standards with an FTS in three wavelength ranges which were covered by three beamsplitter detector combinations. A dedicated imaging optics was designed transforming the F:3 opening of the OBCA to the F:8 opening ratio of the FTS and providing also the required small sampling area. Before and after their application, the dedicated vacuum qualified radiance standards were calibrated against the primary standards of PTB and corrected for the transition from air to vacuum and back to account for possible drifts of the sources. By this procedure a spectral and radiometric calibration of the OBCA traceable to the SI was achieved with the aspired uncertainties. [1] C. Monte et al, The new Reduced Background Calibration Facility 2 for Detectors, Cameras and Sources at the Physikalisch-Technische Bundesanstalt, Sensors, Systems, and Next-Generation Satellites SPIE 2018

The JPSS-2 VIIRS instrument much like its predecessors JPSS-1 VIIRS (now renamed NOAA-20) and S-NPP VIIRS has an innovative three gain stage Day-Night Band (DNB) will provide high quality imagery of the Earth over a wide range of illumination conditions. This band uses a set of four CCDs and 32 different aggregation modes of time-delay integration and sub-pixel aggregation to achieve high SNR in low light conditions and maintain roughly constant spatial resolution across scan. In support of at launch readiness, JPSS-2 VIIRS DNB has undergone a series of prelaunch tests to characterize its spatial, radiometric, spectral, and functional performance at the instrument level and additional planned tests once integration with the spacecraft is complete. The DNB radiometric measurements were completed in October 2017 at the instrument level by Raytheon Company and subsequently analyzed by both vendor and government teams. These analyses form the basis of showing compliance with the sensor design specifications as well as the ability of the DNB to produce high quality imagery and radiometry similar to the first two missions. Presented in this work is the radiometric and spectral performance of the DNB including dynamic range, sensitivity, radiometric uncertainty and nonlinearity along with a discussion of the potential impact to on-orbit calibration and SDR performance.

The EUMETSAT Polar System - Second Generation (EPS-SG) Visible/Infrared Imaging mission supports the optical imagery user needs for Numerical Weather Prediction (NWP), Nowcasting (NWC) and climate in the timeframe beyond 2020. The VII mission is fulfilled by the METimage instrument, to be flown onboard the Metop-SG-A satellite series. The instrument itself is a cross-purpose medium resolution, multi-spectral optical imager, measuring radiation emitted and reflected by the Earth from a low-altitude sun synchronous orbit with a swath width of 2700 km. Measurements will be made in 20 spectral channels ranging from 443 nm in the visible up to 13.345 μm in the thermal infrared at a spatial sampling distance of 500 m at nadir. This paper focuses on the Calibration and Validation (Cal/Val) activities planned for the METimage level 1B products to ensure that the calibrated and geolocated radiances meet the performance specifications for the lifetime of the mission. Such methods include cross-calibration with instruments on the same platform e.g. IASI-NG and Sentinel-5 measurements, inter-comparisons with other missions during simultaneous nadir overpasses, comparisons with ground based observations and lunar calibration. The level 1B product performance will be validated with respect to geometric, spectral, and radiometric requirements for all geographic regions including their seasonal variability. In particular the following specific activities are described: • Calibration verification • Validation of radiometry • Geometric verification • Image quality verification As the commissioning phase is limited in time, the products from METimage have to be confidence checked and validated with a concise focus on essential tests. The Cal/Val activities will extend to routine operations in order to ensure long term stability of the calibrated radiances and continually improve the calibration throughout the lifetime of the mission.

For Venµs satellite, launched August 2 nd, 2017, the calibration and performance assessment activities of the commissioning phase took place in the second semester of 2017. In particular, the radiometric calibration includes fine tuning of the dynamic, identification of defective pixels, equalization of the detectors, absolute calibration, viewing parameters tuning. A special focus is made on specificities of the mission concerning level-1 radiometric calibration. As far as equalization is concerned: an unusual behavior has been observed on numerous pixels, called “radiometric spikes”, on Venµs images. An improvement of the Venµs radiometric model has been implemented to remove these spikes. Absolute calibration using the moon consists in comparing the global irradiance of the Venµs moon image with the reference from ROLO radiometric model. Absolute calibration using simultaneous nadir observations with Sentinel-2 is also a specificity of the mission: since Sentinel-2A and Sentinel-2B are currently in orbit with very similar spectral bands, it is possible to use Simultaneous Nadir Observations of Venµs and Sentinel-2. The cross-calibration results will be presented and compared to other vicarious calibration methods. About stray-light modelling and correction: the optical stray-light level exceeds the requirements by far. Two types of stray-light are observed: local ghost and cross-talk ghost. Local stray-light model is computed as a global system MTF, whereas the estimated cross-talk contribution is subtracted from the image. The specific correction model and the in-flight results will be presented.

The first Visible Infrared Imaging Radiometer Suite (VIIRS) instrument has been in operation for more than 6 years on-board the S-NPP satellite and the second instrument, with the same design and performance requirements, was launched in November, 2017 on-board the JPSS-1 satellite (named NOAA-20 after reaching its orbit) and is currently in normal operation conditions. This paper provides a brief description of VIIRS on-orbit calibration and characterization activities and presents performance assessments and comparisons of S-NPP and NOAA-20 VIIRS using data collected from their on-board calibrators (OBC) and regularly scheduled lunar observations. Results show that NOAA-20 VIIRS is performing as well or better than S-NPP VIIRS in all of the key performance metrics. The NOAA-20 reflective solar bands, including the day-night band, have experienced less than 1% change in gain in the first 250 days since launch and did not suffer from the contamination related rapid degradation experienced by S-NPP VIIRS. Some of the NOAA- 20 thermal emissive bands had larger than expected gain degradation after launch due to ice buildup on the dewar window of the long-wave IR focal plane assembly but a mid-mission outgassing operation was able to restore their gains and maintain stable behavior. Though this study is focused on the sensor’s key performance parameters, such as detector responses (gains), signal-to-noise ratios, and noise-equivalent temperature differences, challenges identified and lessons learned through different phases of on-orbit calibration and characterization are also discussed.

The JPSS-1 Visible/Infrared Imaging Radiometer Suite (VIIRS) is a key sensor on the NOAA-20 satellite launched on November 18, 2017 into a polar orbit of 824 km nominal altitude. The NOAA-20 satellite is a weather and climatemonitoring mission for the Joint Polar Satellite System (JPSS) partnership comprised of NASA and NOAA. VIIRS collects radiometric and imagery data of the Earth’s atmosphere, oceans, and land surfaces in 22 spectral bands spanning the visible and infrared spectrum from 0.4 to 12.5 micron. This paper summarizes the radiometric response trending for the 7 VIIRS thermal emissive bands (3.7 to 12.5 μm), covering both pre-launch thermal-vacuum testing and early onorbit checkout period, including the discovery, investigation and resolution of a response degradation anomaly for several long-wave infrared (LWIR) bands. Multiple corrections for response sensitivities based on pre-launch characterizations are applied to significantly improve the precision of the trended response to accurately assess the health of the emissive band radiometric response stability and quickly assess the impact of various experiments on the observed LWIR degradation.

The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NOAA 20 satellite performs radiometric calibration based on the Solar Diffuser (SD) collections for the Reflective Solar Bands (RSBs). The SD Bidirectional Reflectance Function (BRF) degradation (or H-factor) is measured by the Solar Diffuser Stability Monitor (SDSM) which uses Digital Count (DC) ratios between the signals of sunlit to SD and direct Sun illumination through a pinhole screen. The H-factor trends derived using the prelaunch version of the Sun view SDSM transmittance LUT show abnormal oscillations. This problem was not resolved even after applying the updated LUTs from the yaw maneuvers conducted on January 25th and 26th, 2018. As an alternative approach, the NOAA VIIRS team developed a methodology to update the noisy SDSM Sun transmittance function from the regular on-orbit SDSM collections. Initially, the on-orbit SDSM collections were performed each time VIIRS was approaching the night-to-day terminator. The frequency of SDSM collects was reduced to every other orbit starting from Dec. 14th, 2017. It was further reduced to once per day starting from Jan. 5th, 2018. From all the on-orbit SDSM collects, the SDSM Sun view transmittance function is calculated from the DC of the SDSM sun view at the time of SDSM collection, time dependent gain changes of the 8 SDSM detectors, incident Sun angle, Earth-satellite distance and solid angle of the SDSM Sun view. A new Sun transmittance LUT is derived using a combined data set from the yaw maneuver data and the on-orbit SDSM collection data with SDSM detector degradation correction. The new LUT significantly reduces uncertainties of SD degradation estimates (H-factor) from 0.8 percent to 0.2 percent level. Further improvements will be performed once a one-year cycle of SDSM solar azimuth changes will be completed.

The JPSS-1 (now named NOAA-20) VIIRS instrument has been successfully operating on orbit since November 28th, 2017. The Day-Night Band (DNB) is a panchromatic channel covering wavelengths from 0.5 to 0.9 m that is capable of observing the Earth scene in visible/near-Infrared spectral range at spatial resolution of 750 m. The DNB operates at low, mid, or high radiometric gain stages, and it uses an onboard solar diffuser (SD) panel for low gain stage calibration. The SD observations also provide a mean to compute gain ratios between low-to-mid and mid-to-high gain stages. With their large dynamic range and high sensitivity, the DNB detectors can make observations during both daytime and nighttime. This paper provides an early assessment of the DNB on-orbit performance and behavior in the first 90-day post launch test (PLT) period and beyond. The calibration methodology used by the VIIRS Characterization Support Team (VCST) in support of the NASA earth science community will be presented. The trending of OBC dark-offsets, SD gains and gain ratios, and signal-to-noise ratio (SNR) at minimum radiance have been analyzed, especially during key events such as the Nadir and Cryo-cooler doors opening. Furthermore, we performed inter-comparison studies between SNPP and JPSS-1 instruments and evaluated DNB radiometric calibration and characterization, including the SD degradation, detector gains and gain ratios, as well as the calibration comparison between the IDPS LUTs and our VCST delivery results.

NOAA-20 (formerly JPSS-1) is a new polar-orbiting weather satellite launched on 18 November 2017. VIIRS is one of five instruments onboard NOAA-20, and it joints on orbit the previous VIIRS instrument operating on the Suomi NPP spacecraft since November 2011. During post-launch testing, accuracy of VIIRS sensor data record (SDR) geolocation products was evaluated using a ground control point matching program. The control points are based on 30-m Landsat images, and the matchups employ their cross-correlation with the 375-m VIIRS images in band I1. Initial NOAA-20 VIIRS geolocation uncertainty after launch exceeded 2 km and was somewhat larger than the initial uncertainty previously observed for S-NPP. Optimization of processing parameters successfully reduced the uncertainty to less than 200 m (3- sigma or CE95), which is comparable to the current geolocation uncertainty for the S-NPP VIIRS SDR products. The improvement was achieved by adjusting only the instrument-to-spacecraft rotation angles (the “mounting matrix”). While the uncertainty evaluation was based on global matchups collected over the entire 16-day orbit repeat period, the optimization was based on reprocessing a two-day set of VIIRS SDR from North Africa and the Middle East. Geolocation of the 750-m Day/Night Band (DNB), which is not co-registered with the 375-m I-bands and the 750-m M-bands, was evaluated and optimized separately, using observations of point sources and comparisons between DNB and the I1 band. Initial NOAA-20 VIIRS DNB geolocation uncertainty was even larger than that observed for the other bands, but it was successfully reduced to approximately 200 m by adjusting DNB-specific processing parameters.

The Moderate Resolution Imaging Spectroradiometer (MODIS) has been in operation for over 18 and 16 years on the Terra and Aqua spacecrafts, respectively. In order to maintain long-term calibration stability over the life of each mission, MODIS uses a set of on-board calibrators as well as observations of the Moon and selected Earth-view targets. The lunar observations nominally occur in a narrow phase angle range, 55°-56° , and use scheduled spacecraft maneuvers in order to bring the Moon into alignment with the MODIS space-view port. These observations are used to help characterize the MODIS scan-mirror response versus scan-angle. In addition to these scheduled lunar observations, MODIS also views the Moon through the space-view port without a spacecraft maneuver when the geometry is appropriately aligned. This occurs over a wider phase angle range, between 51°-82° degrees, than those of the scheduled moon observations. While the phase angle restriction of our scheduled observations provides consistency between the calibration events, the unscheduled Moon data can provide a valuable assessment of many calibration related investigations that use the Moon. In this paper, we compare the results of unscheduled versus scheduled lunar observations for several sensor calibration and performance assessments. These include the lunar calibration trending used to characterize the scan-mirror response versus scan angle and the electronic crosstalk correction of bands 27-30, which are currently used in the MODIS Level-1B data products, as well as sensor performance assessments such as band-to-band and detector-to-detector spatial registration.

Since April 2011 Communication Ocean Meteorological Satellite (COMS) is under normal operation service for the three missions of meteorological observation, ocean monitoring, and telecommunication service on 128.2° East of the geostationary orbit. The meteorological observation mission is done by the meteorological imager (MI) of the COMS, which observes the Earth to make meteorological images every day. Along with the Earth observation, the MI looks at the Moon every month to get the images of the Moon, which are used to check the variation of radiometric performance of the MI visible channel after the launch of the COMS. The monthly observation of the full Moon can be considered as a good way to avoid the variation of the Moon phase and to improve reliability in the check of optical payload performance using the Moon image. In this paper, the monthly variation of the Moon phase are studied in relation to the design characteristics of the MI and the operational concept for the Moon observation by the MI. And based on the simulation results and the real operation results for the Moon observation of the MI, this paper discusses realistic limit to the monthly observation of the full Moon in the aspect of the mission operation of the COMS.

The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments on board the Terra (EOS AM-1) spacecraft. MODIS has 36 spectral bands ranging in wavelength between 0.4 and 14.2 μm, at three spatial resolutions of 250 m (bands 1 2), 500 m (bands 3 7), and 1 km (bands 8 36). For each 1-km sample, the 250-m and 500-m bands use 4 and 2 detectors with each acquiring 4 and 2 subsamples respectively in order to maintain consistent along-scan and along-track resolutions at nadir. The SWIR bands, 5 - 7 and 26, share the same focal-plane array as the 1-km thermal emissive bands, 20 25. During one of the two 500-m subsamples for bands 5 - 7, sampling of the 1-km bands introduces increased electronic crosstalk contamination, resulting in a subsample difference for both Earth-view and on-board calibrator observations. For this work, we use data from lunar and on-board blackbody observations, which occur at different signal levels for bands 20 - 25, to derive a correction to the contamination. This correction can be applied to reduce the subsample differences in the MODIS Earth-view data over a wide range of scenes. The impact of this correction on the sensor calibration and Earth-view data will be assessed.

Terra MODIS has provided continuous global observations for science research and applications for more than 18 years. The MODIS Thermal emissive bands (TEB) radiometric calibration uses a quadratic function for instrument response. The calibration coefficients are updated using the response of an on-board blackbody (BB) in quarterly warm-up and cool-down (WUCD) events. As instrument degradation and electronic crosstalk of long-wave infrared (LWIR) bands 27 to 30 developed substantial issues, accurate calibration is crucial for a high-quality L1B product. The on-board BB WUCD temperature ranges from 270 K to 315 K and the derived nonlinear response has a relatively large uncertainty for the offset, especially for these LWIR bands, which affects the measurements of low brightness temperature (BT) scenes. In this study, the TEB radiometric calibration impact on the L1B product is assessed using selected cold targets and the measurements during regular lunar rolls. The cold targets include Antarctic Dome Concordia (Dome-C) and deep convective clouds (DCC) for the calibration assessment, focusing on bands 27 to 30. Dome-C area is covered with uniformly-distributed permanent snow, and the atmospheric effect is small and relatively constant. Usually the DCC is treated as an invariant earth target to evaluate the reflective solar band calibration. The DCC can also be treated as a stable target to assess the performance of TEB calibration. During a scheduled lunar observation event with a spacecraft roll maneuver to view the moon through the space view port, the instrument cavity provides a stable reference for calibration assessment. The long-term trending of BT measurements and the relative difference between scan mirror sides and detectors are used for the assessment of the calibration consistency and stability. The comparison of L1B products over the selected targets before and after the calibration coefficients update can be used to assess the impact of a calibration look-up table (LUT) update. This assessment is beneficial for future calibration algorithm and LUT update procedure improvements for enhancing the L1B product quality.

The objective of the Clouds and Earth Radiant Energy System (CERES) scanning radiometer is to measure solar radiation reflected from the Earth, outgoing longwave radiation (OLR) from the Earth and radiation from the 10 to 12 micron longwave window. It has a shortwave channel, a total channel and a window channel. A Shortwave Incandescent Calibration Source (SWICS) is used to calibrate the Shortwave channel and Internal Black Bodies are used for the total and window channels. These three devises make up the Internal Calibration System (ICS) for the instrument. There is no on-board method for checking the shortwave response of the total channel. This response must be deduced by use of vicarious targets such as deep convective clouds. The CERES Flight Models 1 and 2 have been operating in orbit on the Terra spacecraft since 2000 and FM-3 and -4 since 2002 on Aqua. FM-5 flew in 2011 on Suomi-NPP. The last CERES instrument, FM-6, went into orbit in 2017 on the NOAA-20 satellite. There are now adequate data from the in-orbit calibration and validation work to evaluate the efficacy of the Internal Calibration System. After the calibrations are changed and following a period of operation, validation studies are used to produce revised calibrations. Validation methods include comparing measurements among the instruments as they observe the same scenes from the same directions within a short time. Another method is to compute the Tropical Mean, which is the average OLR between 30oN and 30oS. The Tropical Mean has been noted to be constant over the data period. The difference between the revised calibrations and the calibrations indicated by the ICS is a measure of the efficacy of the ICS. The ICS results and the calibrations from the broader study are compared herein. These differences are of the order of 1/4%.

Earth Radiation Budget sensors, such as the Earth Radiation Budget Experiment (ERBE), the Clouds and the Earth's Radiant Energy System (CERES), and the Radiation Budget Instrument (RBI) have been a crucial part of studying the Earth's radiation budget for the past three decades. These instruments measure the net radiative exchange at the top of the Earth's atmosphere to provide an understanding of the effects of clouds and aerosols within the Earth-atmosphere system. Before launch, these instruments go through several robust design phases followed by vigorous ground calibration campaigns to set their baseline characterization spectrally, spatially, temporally and radiometrically. The knowledge from building and calibrating these instruments has aided in technology advancements and the need for developing more accurate instruments has increased. In order to understand the on-ground instrument performance, NASA Langley Research Center has partnered with the Thermal Radiation Group of Virginia Tech to develop a first-principle, dynamic, electro-thermal, numerical model of a scanning radiometer that can be used to enhance the interpretation of an Earth radiation budget-like instrument on orbit. The modeling tool consists of optical components, calibration targets, detecting elements, and sources that include information on anisotropy of a given earth scene type. The tool allows the designer to simulate the entire science data stream, photons in to bits out, and allows them the flexibility to input various scene types that might be comprised of calibration targets or Earth scenes. As this modeling tool matures, it will allow us to quantify the effects of various anomalous sources of energy, such as stray light, and also run parametric analysis to quantify uncertainties in knowledge of instrument parameters. The current effort presents the capabilities of this tool applied to the design of the Radiation Budget Instrument, demonstrating its optical and radiometric performance at the system level. Furthermore, this complete model was used to investigate stray light impacts on instrument response and calibration, and results from those studies are presented in this paper.

The GOES-16 satellite was launched on 19 Nov 2016, and it became operational as the GOES-East satellite on 18 Dec 2017. The Advanced Baseline Imager (ABI) is one of six instruments onboard GOES-16. It has 16 spectral bands, a spatial resolution of 0.5–2.0 km, and five times the temporal coverage of the previous GOES Imager. ABI has onboard radiometric calibration capabilities that were not available on the previous Imager instrument. The Radiometric Calibration Test Site (RadCaTS) is an automated facility composed of ground-based instruments that measure the surface reflectance and atmosphere throughout the day. It was developed by the Remote Sensing Group (RSG) of the College of Optical Sciences at the University of Arizona, and it is currently used to monitor such low-Earth orbit (LEO) sensors as Landsat-8 OLI, Terra and Aqua MODIS, Sentinel-2A and -2B MSI, SNPP VIIRS, and others. The successful launch of GOES-16, coupled with the improved spectral, spatial, and temporal characteristics of ABI, provide a unique opportunity to intercompare results obtained from a geosynchronous sensor to those obtained from typical LEO sensors. This work describes the recent efforts of RSG to validate the radiometric calibration of ABI, and compare the results with LEO sensors using RadCaTS.

The Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites have successfully operated since their launch in 1999 and in 2002, providing more than 18 and 16 years of continuous global observations, respectively. The inter-comparison between the two MODIS instruments can be very supportive for the instrument calibration and uncertainty assessment. Aqua and Terra MODIS have almost identical relative spectral response, spatial resolution, and dynamic range for each band. Therefore, a site dependent correction for a sensor spectral band pair is not necessary for their comparison. However, Terra is in the morning orbit with an equator crossing time of 10:30 am, and Aqua is in the afternoon orbit with equator crossing time of 1:30 pm. Consequently, there is a dearth of simultaneous nadir overpasses (SNOs) between the two satellites. Major challenges in cross-sensor comparison of instruments on different satellites include differences in observation time, solar angle, and view angle over selected pseudo-invariant sites. In this work, the inter-comparisons of thermal emissive bands are performed over a pseudo-invariant target, using the observations from a sensor onboard a geostationary satellite as a bridge. Himawari8 was launched on October 7, 2014. The Advanced Himawari Imager (AHI) onboard Himawari8 can be used as a reference to bridge the comparison between Terra and Aqua MODIS. AHI has 16 channels; with spatial resolutions from 0.5 km to 2 km at nadir and produces a full disk observations every 10 minutes. The band spectral coverage matchup, comparable spatial resolution and near-simultaneous observation between MODIS and AHI provide feasibility to implement a double difference method. This comparison method minimizes the impact of the difference in observation time and solar angle. The comparison results will be used as an assessment for MODIS instrument calibration and will be helpful for future enhancement of the L1B product.

Planet’s mission is to image the entire Earth, every day, and make global change visible, accessible, and actionable. Planet designs, builds and launches satellites faster than any company or government in history, now operating the largest network of diversified and disaggregated sensors in orbit. Planet relies on quick iterations and space-based testing of satellites, optics, software and systems to create increasingly technology-dense and cost-effective spacecraft. Planet owns and operates fleets of over 100 Dove satellites capturing the whole earth land surface every day at 3.9m with 4 spectral bands (blue, green, red, nir), 5 RapidEye satellites capturing up to 7Mio Sqkm of land surface at 6.5m with 5 spectral bands and 13 SkySat satellites capturing 51k sqkm of earth surface at 0.72m gsd. The proposed presentation will show the full on-orbit radiometric calibration process for the SkySat constellation. This calibration includes the creation of per detector correction gain and offset tables serving the correction of non uniform response of the individual detectors. Additionally the procedures and results for the conversion of raw DN counts into absolute calibrated top of atmosphere radiance products will be shown. The latter shows the application of vicarious calibration methods based on the RadCalNet network of automated calibration sites and cross calibration between the individual satellites of the constellation, other planet owned constellations (especially RapidEye) and other available satellites like e.g. Landsat8

Optical choppers are used in a large range of applications in sensing, from radiometry to telescopes and laser setups. Classical macro-devices comprise of a rotating disk with windows with linear margins. While we have introduced, for the first time to our knowledge, a novel type of chopper disks, with windows with non-linear margins, outward or inward (the latter as a patent), in the present study we approach another type of chopper: with rotating shafts (patent pending). Different types of shafts (cylindrical, spherical, or conical) are possible, in combination with different shapes of slits, but in the present paper cylindrical shafts with a certain profile of slits are considered. The paper is focused on the possibility to reach much higher chop frequencies than with disks choppers. In order to achieve this, a Finite Element Analysis (FEA) is performed on shafts with four slits (two perpendicular channels). A range of geometrical parameters of the shafts and of the slits are considered, as well as two possible materials, i.e. structural steel and an aluminium alloy. A discussion on the structural integrity and of the deformations of the fast rotating shafts is performed, based on the FEA, with regard to the materials used and to the limits of the rotational speed of the device.

The stereoscopic spectral imager combines the space technology and the spectrum technology, which can obtain the three-dimensional information and the spectral information of the target at the same time. A compact stereoscopic spectral imaging system is proposed in this paper. The stereoscopic spectral imaging system works at the wavelength range from 450 to 1000nm. The optical system consists of three telescopes and a spectrometer. The stereoscopic spectral imaging system uses the compact design of the shared spectrometer and detector, which effectively saves the volume weight and the cost of the system, and realizes the requirement of lightweight miniaturization. One of the three telescopes is perpendicular to the earth, the other two observe forward and rear along the direction of the flight. The side angle is 27 degree. The Offner-Chrisp imaging spectrometer based on curved surface prism is used in the system. Curved prism is a special optical element, which can effectively reduce the size of the system, reduce the spectral curvature and improve the performance of the system. The MTF values of all wavelengths at 46lp/mm are greater than 0.6 and the results demonstrated the good performance of the optical design. The stereoscopic spectral imaging system can achieve high-resolution imaging under the condition of wide spectral segment, has the high energy utilization efficiency and can obtain the spectral information in real time.

A novel shortwave infrared imaging spectrometer based on free-form has been presented .The method was proposed for the requirement of lightweight and wide swath for aerospace loads .The theory of aberration was analyzed based on offner structure. Simulations have been performed by software to confirm the methods. The imaging spectrometer was designed with spectrum (950-2500nm), focal length of 70mm, and field view of 20 degrees. The pixel size is 15 microns. The performance shows the spectral resolution is better than 11nm, the spectral keystone is less than 1nm, the MTF< 0.5@33lp/mm .

Wide field of view (FOV) can provide the high efficiency of remote sensing. In this paper, the optical fiber array is used to connect the telescope and the spectrometer, which makes the configuration of the imaging spectrometer flexible and compact with large FOV. In the proposed system, the optical fiber array is coupled with slit, and relay the image of the slit into the several spectrometers with short field or several parallel fields in a single spectrometer. The optical fiber array can avoid the problems of linear array of imaging fiber bundles without slit, such as manufacture difficulty of the single row fiber bundles, breakage of fiber and the difficulty of alignment the fiber with the pixels of detector. The optical design of the telescope based on TMA and the imaging spectrometer based on Fery prism are detailed in this paper. Moreover, the pushbroom scan experiment demonstrates the feasibility of the optical fiber array in the imaging spectrometer.

Advancements in modern technologies, such as remote sensing systems and instruments have led to rapid developments in the field of Earth observation /EO/. As a result, enormous volumes of EO data with various spatial and spectral resolutions are obtained. However, the expected enhancements in the classification accuracy still have not been reached, due to the complexity of the remote sensing measurements and the big volume of data that need to be processed. The last leads to the necessity of development and improvement of methods and techniques for data obtaining and analysis. The methods include the validation multi-sensor systems, the processing technique of big data, and the object identification and classification methods for improving information quality through data fusion. To achieve correct information with highest accuracy in data analyzing and interpreting, researchers have to apply these methods and to create technologies for obtaining and integrating data from different Earth Observation Systems /EOS/. For gathering and using all of the information a local and regional EOS of Systems needs to be established. By creating such local EOS of Systems more extensive information could be collected, analyzed and retrieved. In this paper a local system is presented, focusing on the description of the ground component. The main sensors embedded in the system are spectrometers. The working range of the multi-sensor system is VIS-NIR-SWIR. Thus, by applying the data fusion methods, combining images and spectral information, a more accurate thematic interpretation is achieved. Example illustrating the benefits of a multisensor system data fusing is presented and discussed.

In this paper, we describe the characteristics and performances of monolithic sensord designed for low frequency motion measurement of spacecrafts and satellites, whose mechanics is based on the UNISA Folded Pendulum technology platform. The latter, developed for ground-based applications, exhibits unique features (compactness, lightness, scalability, low resonance frequency and high quality factor), consequence of the action of the gravitational force on its inertial mass. In this paper, we present the general methodology for extending the application of ground-based folded pendulums to space, also in total absence of gravity, still keeping all their peculiar features and characteristics, discussing a tri-axial version in connection with the most recent improvements.

MODIS is the key instrument for the NASA's EOS Terra and Aqua missions, launched in December, 1999 and May, 2002 respectively. The reflective solar bands (RSB) on Terra and Aqua MODIS are calibrated independently using an on-board solar diffuser and a solar diffuser stability monitor. Near-monthly lunar observations are also a major component of the on-orbit calibration strategy facilitating a response-versus-scan angle (RVS) characterization on-orbit. With a few exceptions, the regularly scheduled lunar observations have been performed with the same phase angles ranging from -55◦ to -56◦ for Aqua MODIS and 55◦ to 56◦ for Terra MODIS. Previous efforts have demonstrated that the observations of the Moon serve as an effective mechanism to perform an on- orbit cross-calibration of the two MODIS instruments. In addition to the regularly scheduled lunar observations that require a roll maneuver, both MODIS instruments also view the Moon via its space-view (SV) port for three to four months in a year that covers a wider range of phase angles. In this paper, we expand on the previous effort to provide an assessment of the RSB calibration difference between Terra and Aqua MODIS based on unscheduled lunar observations made over a range of phase angles. Also, discussed in this paper are strategies that could benefit other EOS sensors such as SNPP and NOAA 20 VIIRS.

The National Oceanic and Atmospheric Administration 20 (NOAA-20) operational satellite, also known as the Joint Polar Satellite System 1 (JPSS-1), is the follow-on to the Suomi-National Polar-orbiting Partnership (S-NPP) with launch dates of November 2017 and October 2011, respectively. S-NPP and NOAA-20 provide critical weather and global climate products to the user community. The Visible-Infrared Imaging Radiometer Suite (VIIRS), a primary sensor on both SNPP and NOAA-20, has 22 bands covering a spectral range of 0.412-12.0μm with spatial resolutions of 750m and 375m for moderate and imaging bands, respectively. VIIRS provides calibrated Earth observations within the Sensor Data Records (SDRs) using on-orbit calibration sources such as the Solar Diffuser (SD) for the Reflective Solar Bands (RSBs) and an On-Board Calibrator BlackBody (OBCBB) for the Thermal Emissive Bands (TEBs), combined with pre-launch characterization information. Both the on-orbit calibration sources and pre-launch measurements contain calibration errors that propagate into the SDR radiance retrievals and degrade the performance of the Environmental Data Records (EDRs). This paper will focus on the TEB SDR calibration products and investigate the sources of the on-orbit calibration errors observed. This includes looking at gain drifts during the OBCBB warm-up and cool-down, along-scan temperature biases, and thermal model errors used in the estimation of the sensor’s background thermal emission. The pre-launch errors from the Response Versus Scan angle (RVS), calibration coefficients, and Ground Source Equipment (GSE) will also be included in the discussion. Finally, this paper will compare the differences in calibration errors between the S-NPP and NOAA-20 sensors and how they impact the SDR products in unique ways.

The hyperspectral imageries obtained from dispersive imaging spectrometer often contain significant cross-track spectral curvature nonlinearity disturbances, known as the smile/frown effect, which is due to the change of dispersion angle with field position. The smile effect must be corrected because the across-track wavelength shift from band-center wavelength alters the pixel spectra and reduces the application effect of classification and target recognition. There are several methods to correct the smile effect which don’t take into account the fact that the smile effect is woven together with the sensor radiation characteristic. Individually processing spectra distortion to correct the smile effect would renewably lead to radiometric distortion of the radiometric correction image. A new method is proposed to deal with this problem. An experiment based on the proposed method is conducted. Hyperspectral images are acquired from an UAV airborne Offner Spectral Imager which has a spectral coverage of 0.395~1.028μm. The band of corrected image at 760nm, the absorption peak of O2, has become consistent which shows that the smile effect is effectively removed, and meanwhile the radiometric correction result is finely reserved.

Spectrometers for Earth Observation require inflight radiometric calibration, for which the sun can be used as a known reference. For wide field instruments, a diffuser is placed in front of the spectrometer, scattering incoming sun light into the entrance slit and ensuring a homogenous illumination. As drawback, the diffuser induces a specific radiometric error caused by interference, which is called Spectral Features. The scattering of the incident light at the diffuser induces a random path difference yielding a specific interference pattern at the entrance slit, known as speckle pattern. These speckles are propagated through the disperser to the detector plane and further integrated by the detector pixels. The resulting feature can yield a significant signal error contribution, whose spectral variation is referred to as spectral features. The magnitude of this error is evaluated in terms of the Spectral Features Amplitude (SFA), the ratio of the signal standard deviation with its mean value over a specific wavelength range. There have been several ways implemented to measure the SFA of a spectrometer, e.g. end-to-end measurements with representative instruments. Typically the measurement accuracy is not sufficient to isolate the SFA from other radiometric errors. As a consequence, the instrument layout can hardly be optimized to suppress Spectral Features. We propose a novel characterization technique for Spectral Features based on the direct acquisition of monochromatic speckle patterns at the entrance slit. This allows the observation of Spectral Features below the level of the spectrometer spectral and spatial resolution. The Spectral Features are derived from various observed speckle patterns by properly mimicking the real spectrometer in the data analysis. With this measurement technique we are able to gain insight into the mechanism behind speckle induced Spectral Features. This insight will be used to develop a parameterized model facilitating the design of future space based spectrometers.