This PDF file contains the front matter associated with SPIE Proceedings Volume 11530, including the Title Page, Copyright information, and Table of Contents.

Rapid advances in small satellite technology is driving an upsurge in the number of space-based applications. Earth Observation has proven to be a well suited to the CubeSat form factor with a large number of missions being successfully delivered over the last few years. The success of these missions is proving that CubeSats are a vital tool to better observe our planet and make decisions on how best to tackle climate change.

Opening remarks by conference chairs for conference on sensors, systems, and next generation satellites XXIV

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, GOSAT-2 carrying TANSO-CAI2 and -FTS2, Shizuku (GCOM-W) carrying AMSR2, Daichi-2 (ALOS-2) carrying PALSAR-2 + CIRC, 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). Super Low Altitude Test Satellite (SLATS) completed its mission successfully. JMA is operating weather satellite Himawari-8 and -9 on geostationary orbit. JSS are operating ASTER on EOS-Terra satellite of NASA and HISUI on ISS. For coming satellites or instruments, JAXA is going to operate CPR on EarthCARE satellite of ESA, ALOS-3 carrying the “wide-swath and high-resolution optical imager”, ALOS-4 carrying PALSAR-3 and GOSAT-GW carrying TANSO-3 + AMSR-3 as follow-on mission for GOSAT-2. In addition to follow-on mission studies, several new studies are underway for near future missions, such as Lidar altimeter mission, Wind Lidar mission and new geostationary missions for land observation and GHG observation.

This paper describes the current status of Advanced Land Observing Satellite-4 (ALOS-4) which will carry L-band SAR system, namely Phased Array-type L-band Synthetic Aperture Radar-3 (PALSAR-3) and SPace based Automatic Identification System for ships Experiment (SPAISE3). In particular, its mission objectives, characteristics and PALSAR-3 draft observation plan.

Global Observing Satellite for Greenhouse gases and Water cycle (GOSAT-GW) is a polar-orbiting satellite carrying two mission instruments, Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3) and Advanced Microwave Scanning Radiometer 3 (AMSR3). TANSO-3 is developed by Ministry of the Environment for the follow-on mission of Greenhouse-gas Observation Satellite 2 (GOSAT-2) launched in 2018. AMSR3 is developed by Japan Aerospace Exploration Agency (JAXA) for the Global Change Observation Mission-Water (GCOM-W) follow-on mission to keep continuity of the passive microwave observation. GCOM-W had completed its nominal mission of five years in 2017 and has transferred to extended operation phase. Continuous observation by the onboard instrument, AMSR2 and early launch of a follow-on instrument are now strongly required both in science community and in operational fields. Specifications of the AMSR3 is almost equivalent to AMSR2. The characteristics and performances of existing 16 frequency channels are secured by making use of heritage design, meanwhile three high frequency channels (166 GHz, 183±3 GHz and 183±7 GHz) and 10-GHz channels with improved Noise Equivalent Delta Temperature (NEDT) will be added for observation of solid precipitation and humidity and improvement in measurement accuracy of sea surface temperature. These additional channels will enhance data utilization in wide fields such as meteorology, polar research and fishery. To produce long-term continuous data record by succeeding to GCOM-W is also one of the most important targets for studies on global climate change. Development of GOSAT-GW and AMSR3 had been officially approved in December 2019 and moved into Phase-B. An overview and current status of the mission and AMSR3 are given in this paper.

Accurate measurements of above ground biomass are important to evaluate its contribution as a CO₂ absorption source. If global canopy height model can be obtained, we can make an appropriate evaluation. This is MOLI’s mission. Moreover, MOLI can improve the accuracy of digital terrain model. In this paper, we will report on the development status of MOLI for LIDAR observation from space by mounting on the Japanese Experiment Module with International Space Station.

An overview will be presented of the Earth Observation missions currently under preparation, development or operations by the European Space Agency (ESA). The presentation will encompass the Earth Explorer missions addressing key scientific issues, the operational missions such as Copernicus Sentinels in partnership with the European Union (EU) and the meteorological missions in partnership with the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and also the preparation of future Earth Observation missions and innovative concepts based e.g. on small satellites.

ESA initiated in 2018 an architectural design study to prepare the development of the next generation of the optical component of the current Sentinel-2 and Sentinel-3 observation functions i.e. Sentinel-3 without the SAR altimeter and related payloads. The aim of this activity was to analyse and trade-off different architectural options for the next-generation of the Copernicus Space Component optical imaging missions, with an implementation in the 2032-time horizon. A holistic approach was taken to assess architectural option to secure the respective observation capabilities in future, not only extrapolating the current scenario, but to openly assess e.g. the merging of observation functions of different instruments as well as to consider potential data flows from third part missions and service providers, institutional as well as commercial. The outcome of the analysis, taking technological as well as programmatic aspects into account, resulted in the conclusion that Sentinel-2 MSI NG as well as Sentinel-3 OLCI NG together with SLSTR NG on the same platform, are most efficiently implemented as free flyers, with dedicated instruments. The data flow of these two missions will be ideally supplemented by the Land Surface Temperature Mission (LSTM) and the Hyperspectral Mission (CHIME), which are going to be implemented in the frame of the High Priority Candidate Missions (HPCMs) of Copernicus. Those operational data flows, building the backbone of the operational services, can benefit significantly by including the data flows of reliable sources e.g. as from the Landsat series of satellites. The needs for very high resolution (VHR) imaging data, can best be served by data from third party missions, as currently implemented in the Copernicus framework; a Sentinel VHR mission is currently not baselined.

The objective of ESA’s Next Generation Gravity Mission (NGGM) is long-term monitoring of the temporal variations of Earth’s gravity field at high resolution in time (down to 3 days) and space (100 km). Such variations carry information about mass transport induced by the water cycle and the related mass exchange among atmosphere, oceans, cryosphere and land, and will complete our picture of Global Change with otherwise unavailable data. The observable is the variation of the distance between two satellites measured by a laser interferometer; accelerometers measure the non-gravitational accelerations to be separated from the gravity signal in the data processing. The optimal satellite system comprises two pairs of satellites on low (around 340 km) circular orbits, at 100 km mutual distance, one pair near-polar and the other around 65° inclination. The technique of satellite-to-satellite tracking for detecting the temporal variations of gravity was established by GRACE, which reached 300-400 km spatial resolution at monthly intervals, using tracking in the microwave band. Today, GRACE is being continued by GRACE-Follow-On, with similar objectives, where the laser interferometry has improved the measurement resolution by a factor of 100 (in the upper MBW) which however cannot be fully exploited due to other system limitations. At 150 km spatial resolution, mass change would become observable in 80% of all significant river basins, up from 10% achieved with GRACE. High temporal resolution will reveal large-scale daily mass variations, with applications in water management and operational prediction. Currently, the NGGM is a candidate Mission of Opportunity for ESA-NASA cooperation. Over the last decade, numerous system and technology activities have advanced the maturity of the system and the key subsystems, and the mission can now be proposed for launch around 2028. The paper focusses on the latest design and test achievements, with a discussion on alternative drag compensation scenarios.

The Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission has been selected in September 2019 as the 9th Earth Explorer mission of the European Space Agency. The mission aims to measure the Earth’s Top-Of- Atmosphere (TOA) emission spectrum in the spectral region from 100 to 1600 cm^-¹ (i.e. 6.25 to 100 μm). This will fill the current observational gap from space in the far-infrared region (FIR) from 100 to 667 cm^-¹ (i.e. from 15 to 100 μm). FORUM measurements will improve the understanding of the climate system by providing, for the first time with high resolution, the spectral features of the far-infrared emission of the Earth with a focus on the contribution to the radiation budget of the continuum absorption of the water vapour rotational bands, on cirrus cloud properties, and on ice/snow surface emissivity. The FORUM mission requires a payload able to spectrally-resolve the Earth's outgoing longwave radiation across the Far-InfraRed (FIR) spectral range with high absolute radiometric accuracy. Characterisation of the surface, atmospheric and cloud/surface heterogeneity in the observed field-of-view is also required to help interpret the measured spectral radiance. These needs dictate the use of two instruments: a spectrometer and an infrared imager. The concepts of both instruments, thoroughly studied in phase A preparatory activities by two independent industrial consortia, are presented in this paper.

Jena-Optronik has been contracted to develop and build the core main optics of the Sentinel-4/Ultra-violet/Visible/Near-Infrared (UVN) instrument, which comprises a telescope, a UV-VIS spectrometer and a NIR spectrometer. Due to its geo-stationary orbit and its compactness the photon flux seen by the instrument is low. Simultaneously the lens based optics of the instrument set new standards concerning performance. In consequence straylight levels within the instrument need to be reduced to the bare minimum including high quality polishing of the optics as well as manufacturing facilities as well as processes, which reduce the overall allowed contamination of the optical surfaces to be <50ppm for particular and <50ng/cm² molecular contamination.

This paper presents an overview of an optical instrument for disaster and security monitoring from the geostationary orbit. The described instrument is the payload of the GEOBS (GEOstationary OBServatory) concept, which is the result of an ESA exploratory activity conducted at the ESA-ESTEC Concurrent Design Facility (CDF) in early 2020 in order to assess the technical and programmatic feasibility of optical mission concepts from GEO. Recent improvements in the maturity of critical technologies (e.g. adaptive optics, large CMOS detector arrays, ultra-stable materials,…), together with the development of adequate manufacturing facilities and the required manufacturing techniques in Europe and Japan, have provided the ground for further investigation of the current technical and programmatic feasibility of a geostationary observation system for disaster and security monitoring. The instrument on-board the GEOBS satellite provides medium spatial resolution imagery (10-20 m Ground Sampling Distance at equator) in three visible narrow bands (Red, Green and Blue - RGB), one Panchromatic band and one band in the Near Infrared (NIR). The instrument acquires images using a step-and-stare observation technique, enabling persistent monitoring of selected areas. The instrument is sized to provide a footprint >100 km at Equator and observe the area from 30° to 55° North in Latitude and from 10° West to 36° East in Longitude, with observations possible from 4:00 a.m. to 8 p.m. local solar time. The instrument architecture is based on a Korsch telescope, with an active optics correction loop (wavefront sensor, deformable mirror, 5 degrees-of-freedom mechanism on the secondary mirror), and a focal plane based on multiple CMOS detectors, assembled in either 1D or 2D large arrays to cover the full field of view. The instrument concept also includes ultra-stable structures and light-weight sun-shields to reduce straylight and thermos-elastic effect.

In this presentation, we will report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture. The initial BIRD devices (such as the nBn and the XBn) used either InAs absorber grown on InAs substrate, or lattice-matched InAsSb alloy grown on GaSb substrate, with cutoff wavelengths of ~3.2μm and ~4μm, respectively. While these detectors could operate at much higher temperatures than existing MWIR detectors based on InSb, their spectral responses do not cover the full (3 – 5.5μm) MWIR atmospheric transmission window. The T2SL BIRD devices not only covers the full MWIR atmospheric transmission window, but the full LWIR atmospheric transmission window and beyond. The LWIR detectors based on the BIRD architecture has also demonstrated significant operating temperature advantages over those based on traditional p-n junction designs. Two 6U SmalSat missions CIRAS (Cubesat Infrared Atmospheric Sounder) and HyTI (Hyperspectral Thermal Imager) are based on JPL’s T2SL BIRD focal plane arrays (FPAs). Based on III-V compound semiconductors, the BIRD FPAs offer a breakthrough solution for the realization of low cost (high yield), high-performance FPAs with excellent uniformity and pixel-to-pixel operability.

SAPHIRA (320x256/24μm) is the first of a family of HgCdTe APD infrared sensors for NIR/SWIR sensing in low flux conditions for scientific applications. The paper will present the status of the latest developments of detectors suitable for a range of ground and space applications including wavefront sensing, low flux imaging, Lidar and high speed optical communications. The next generation SAPHIRA (512x512/24μm) array has an architecture specific to pyramid wavefront sensors, supported by a consortium comprising European Southern Observatory, Max Planck Institute, NRC Herzberg Institute and Potsdam University. A 1kx1k/15μm, 3-side buttable sensor called Ike Pono after the Hawaiian for ‘far-vision’ is aimed at extreme, low-flux imaging, supported by NASA through the University of Hawaii, Institute of Astronomy. A large area device suitable for LIDAR and supported by NASA also demonstrates a performance suitable for high speed optical communication applications. Most recently the development of a 2k x 2k/ 15μm device for scientific imaging has started with the support of ESA.

High performance detector technology is being developed for sensing over the mid-wave infrared (MWIR) band for NASA Earth Science, defense, and commercial applications. The graphene-based HgCdTe detector technology involves the integration of graphene with HgCdTe photodetectors that combines the best of both materials, and allows for higher MWIR (2-5 μm) detection performance compared with photodetectors using only HgCdTe material. The interfacial barriers between the HgCdTe-based absorber and the graphene act as a tunable rectifier that reduces the recombination of photogenerated carriers in the detector. The graphene layer also acts as high mobility channel that whisks away carriers before they recombine, further enhancing detection performance. This makes them much more practical and useful for MWIR sensing applications such as remote sensing and earth observation, e.g., in smaller satellite platforms (CubeSat) for measurement of thermal dynamics with better spatial resolution. The objective of this work is to demonstrate graphene-based HgCdTe room temperature MWIR detectors and arrays through modeling, material development, and device optimization. The primary driver for this technology development is the enablement of a scalable, low cost, low power, and small footprint infrared technology component that offers high performance, while opening doors for new earth observation measurement capabilities.

NASA’s Earth Science Division (ESD) unlocks the mysteries of our planet, exploring, discovering, and responding to the need to understand our planet’s interconnected systems, from a global scale to minute processes. This knowledge and understanding serves the fundamental need to improve our lives on Earth, advancing this frontier for all humanity. NASA pursues both curiosity-driven and practically focused Earth science because our ability to thrive on our home planet is undeniably tied to our scientific understanding and predictive capability of its dynamics and phenomena. ESD explores our rapidly changing world, where natural and human factors interact, following an interdisciplinary, Earth systems approach that examines the interplay among the atmospheric, ocean, land, and ice systems. Using the recommendations of the 2017 NASA Earth Science Decadal Survey, Thriving on Our Changing Planet a Decadal Strategy for Earth Observation from Space, as a compass, ESD is developing the observing systems that will answer the most important science and application questions of the next decade across the following focus areas: • Coupling of the water and energy cycles • Ecosystem change • Extending and improving weather and air quality forecasts • Reducing climate uncertainty and informing societal response • Sea-level rise • Surface dynamics, geological hazards and disasters The ESD Flight Program develops and operates the observing systems required to address these focus areas. It consists of a coordinated series of satellite and airborne missions for long-term global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans. The Flight Program also encompasses infrastructure for operating these missions, processing their scientific data, and distributing them on a free and open basis to researchers, operational users, and the public. The Flight Program currently has 24 operating Earth observing space missions and instruments. There are 18 more missions and instruments in development. These comprise missions recommended by the 2017 NASA Earth Science Decadal Survey, missions and selected instruments to ensure availability of key climate data sets, operational missions to sustain land imaging provided by the Landsat system, and small-sized competitively selected orbital and instrument missions of opportunity belonging to the Earth Venture (EV) program. Projects in development include the Sentinel-6 Michael Freilich/-B dual satellite altimetry mission; with its first launch scheduled for November 2020 and the recently selected Libera Earth radiation budget (ERB) instrument planned to be hosted on the National Oceanic and Atmospheric Administration’s (NOAA) Joint Polar Satellite System-3 (JPSS-3) spacecraft. Libera is the first of the new Earth Venture Continuity class of missions promoting innovative, capable approaches to acquiring existing Climate Data Record (CDR) measurement sets at lower cost. The 2017 Earth Science Decadal Survey recommended four new Flight Program elements (Designated, Explorer, and Incubation Targeted Observables) in addition to the legacy missions that comprise the Program of Record (POR). Multi-Center architecture studies for the Designated Targeted Observables and plans to address the other new Flight Program elements are underway. An overview of Flight Program plans and current status will be presented.

The NASA Engineering & Safety Center (NESC) was established in 2003 to provide an independent technical resource for the resolution of challenging technical problems (through the use of studies, analysis, tests, etc.). Since its inception, NESC has completed nearly 1000 technical assessments for NASA’s Human Exploration and Operation Mission Directorate (HEOMD), Science Mission Directorate (SMD), Space Technology Mission Directorate (STMD), and Aeronautics Research Mission Directorate (ARMD). Of the SMD related assessments, several were for the resolution of technical problems, analysis, or studies related to NASA’s Earth science missions in various phases of the project from design to operation. Some of the recent examples of NESC technical support for NASA (or NOAA) Earth science missions have been for: Soil Moisture Active Passive (SMAP), Deep Space Climate Observatory (DSCOVR), Cyclone Global Navigation Satellite System (CYGNSS), Ice, Cloud, and Land Elevation Satellite (ICESat-II), Joint Polar Satellite System (JPSS), and the soon to be launched collaboration mission with India, NASA-ISRO Synthetic Aperture Radar (NISAR). In this paper, we outline some of the technical challenges faced by these Earth science missions and describe how NESC contributed to their resolution. The case studies cover a wide range of disciplines involving space lidars, radars, electronics, attitude control systems, as well as Micrometeoroid Orbital Debris (MMOD) risk assessment impact to NASA missions. The efforts include strategies for risk mitigation, technical resolution of challenging problems, and failure root cause investigations combined with lessons learned reports to advance discipline knowledge, enhance NASA capabilities, and avoid future problems.

The GOES-17 Advanced Baseline Imager (ABI) has an anomaly with its on-board cooling system that prevents it from maintaining its Focal Plane Modules (FPMs) at cold, optimal temperatures. Because of this, during certain times of the year the FPMs and their detectors warm and cool throughout the day. Changing the detectors’ temperature changes their response to incoming radiance, which leads to calibration errors over time and degrades the imagery. Numerous mitigation strategies have been implemented to reduce the solar insolation on the instrument and to mitigate image degradation, including semi-annual yaw flips and changing the integration time of the detectors twice daily. These and other mitigations all work with the baseline calibration algorithms currently in place on the GOES-R Ground System. In an attempt to reduce the image degradation even further, the ABI vendor designed a new calibration scheme that predicts key parameters forward in time to account for the drifting FPM temperatures. These parameters, the linear gain term and dark current scene, are nominally updated on orbit every 5 minutes and 30 seconds, respectively. However, even at these relatively short cadences the detectors can change temperature, thereby rendering the parameters invalid for accurate calibration. By projecting these parameters forward in time the radiometric bias is reduced and image quality improves. This Predictive Calibration modification was deployed to operations on July 25, 2019, following several months of extensive testing and optimization by the GOES-R science teams. During this time several parameters and thresholds were tuned to ensure Predictive Calibration was turning on and off at the optimal times. Since going into operations users have seen noticeable improvement to the imagery and its calibration. This paper will discuss the fundamental assumptions behind the baseline equations and highlight the changes introduced by Predictive Calibration. Results will show the improvements to the calibration of the operational L1b products and reduction in image degradation.

Two flight models of the Advanced Baseline Imager (ABI) are in-orbit on the GOES-16 and GOES-17 geostationary satellites, with two more planned to be launched on GOES-T (2021) and GOES-U (2024). The ABI is the primary Earthviewing weather imaging instrument on the GOES-R Series, producing Level 1b (L1b) radiances and Cloud and Moisture Imagery (CMI) data products. The ABI L1b product is the source for all the ABI Level 2+ (L2+) products, including CMI, which makes the maturity process for these two products important. CMI is the only key performance parameter (KPP) of the GOES-R Series mission and thus CMI takes precedence over other ABI L2+ products. As the only KPP, CMI follows the same maturity schedule as the ABI L1b product. For the ABI L1b and CMI data products to be declared operational, they must pass through a series of calibration and validation tests and analyses, with the peerreviewed results showing that the instruments and products have achieved each level of maturity consistent with mission success. This paper describes the assessment process, the definitions of the product validation maturity levels, and an overview of the product performance for each instrument at each validation level. Additionally, this paper will describe planned programmatic changes aimed at streamlining the maturity process for the upcoming GOES-T and GOES-U satellites.

Detection of ultraviolet (UV) bands offers increased spatial resolution, small pixel sizes, and large format arrays, thus benefitting a variety of NASA, defense, and commercial applications. Al_xGa_1-xN semiconductor alloys, which have attracted much interest for detection in the UV spectral region, have been shown to enable high optical gains, high sensitivities with the potential for single-photon detection, and low dark current performance in ultraviolet avalanche photodiodes (UV-APDs). We are developing GaN/AlGaN UV-APDs with large pixel sizes that demonstrate consistent and uniform device performance and operation. These UV-APDs are fabricated through high quality metal organic chemical vapor deposition (MOCVD) growth on lattice-matched, low dislocation density GaN substrates with optimized material growth and doping parameters. The use of these low defect density substrates is a critical element to realizing highly sensitive UV-APDs and arrays with suppressed dark current and jitter under high electric fields. Optical gains of 5×10⁶ and greater with enhanced quantum efficiencies over the 320-400 nm spectral range have been demonstrated, enabled by a strong avalanche multiplication process. We are additionally using device technology developed for high voltage GaN p-i-n rectifier devices to enable advanced Geiger-mode UVAPDs with single-photon counting capability. This technology provides extremely low leakage currents in the reverse bias range near avalanche breakdown, a necessary requirement for stable Geiger-mode operation. The variable-area GaN/AlGaN UV-APD detectors and arrays being developed enable advanced sensing performance over UV bands of interest with high resolution detection for NASA Earth Science applications.

Broadband antireflection (AR) optical coatings covering the ultraviolet (UV) to infrared (IR) spectral bands have many potential applications for various NASA systems. The performance of these systems is substantially limited by signal loss due to reflection off substrates and optical components. Tunable nanoengineered optical layers offer omnidirectional suppression of light reflection/scattering with increased optical transmission to enhance detector and system performance. Nanostructured AR coatings enable realization of optimal AR coatings with high laser damage thresholds and reliability in extreme low temperature environments and under launch conditions for various NASA applications. We are developing and advancing high-performance AR coatings on various substrates for spectral bands ranging from the UV to IR. The nanostructured AR coatings enhance the transmission of light through optical components and devices by significantly minimizing reflection losses, providing substantial improvements over conventional thin film AR coating technologies. The optical properties of the AR coatings have been measured and fine-tuned to achieve high levels of performance. In this paper, we review our latest work on high performance nanostructure-based AR coatings, including recent efforts in the development of the nanostructured AR coatings for UV band applications.

ESA Directorate of Earth Observation Programmes (ESA-EOP) have seized the opportunity to support the development of small and nano-satellites to complement the EOP scientific and application-driven flagship missions. These developments include new science driven missions and constellations which enable a significant increase in temporal resolution leading to new applications. This paper presents an overview of the NewSpace paradigm, describes the overall ESA-EOP small mission strategy and provides a brief insight into some of the small satellites being developed at ESA across three programmatic lines: Scout Missions, Φ-sat Missions and the Investing in Industrial Innovation (InCubed) Programme. The paper focuses on optical missions.

Some aspects of the CubeMAP mission (also known as ESP-MACCS) are presented: its science objectives, and the primary choices made to address them from small satellite platforms. The science case, addressing some key scientific questions related to global change, is elaborated in four objectives focused on upper troposphere and stratospheric composition and its change. The sounding methodology and the associated observation concept retained is a constellation of miniature limb solar occultation thermal infrared sounders, offering the advantages of limb solar occultation, whilst mitigating the inherent lack of coverage of this geometry. The mission focuses on tropical regions as the gateway to the upper troposphere, and the stratosphere. The miniaturized instrument payloads developed for the mission are briefly presented: the High resolution InfraRed Occultation Spectrometer (HIROS) and the Hyperspectral Solar Disk Imager (HSDI). Lastly, the nanosatellite 12U platform and its subsystem are described, completing the overview of the mission space segment.

In a relatively short time, Spire has grown from a small start-up company to the largest commercial producer of satellite-based GNSS Earth observation products. As of May 2020, and after 21 satellite deployments, Spire now has over 80, 3U (10x10x10 cm) Cubesats satellites operating in a variety of orbit planes, third only to Planet and SpaceX in the size of its satellite constellation and growing with each launch. Spire satellites host three primary payloads: a dual-frequency GNSS science receiver, an automatic identification system (AIS) receiver for ship tracking, and an automatic dependent surveillance—broadcast (ADS–B) receiver for aircraft tracking. The Earth observations produced with Spire’s GNSS science receiver include atmospheric profiles performed by radio occultation (RO), space weather observations (slant total electron content (TEC) and scintillation indices), and GNSS reflectometry (GNSS-R) using signals from the GPS, GLONASS, QZSS, and Galileo constellations. Spire was the first commercial company to produce RO observations and has participated in a number of commercial data pilot programs with NOAA, NASA, USAF, and ESA, Over the past few years, Spire has expanded and matured the Earth observation products available and has continued to improve and grow the size and capabilities of its constellation. Spire now produces thousands of low-latency RO profiles and millions of TEC observations each day, with plans for over 100 RO-producing satellites in the full constellation. Additionally, Spire recently added GNSS-R capabilities by launching the first two GNSS-R scatterometer configuration satelliites in December of 2019, with plans for two more GNSS-R satellites to be launched in mid-2020. Due to its agility and rapid launch cycle, averaging launches of four to eight satellites every six weeks, Spire has the unique ability to improve performance and add capabilities on-orbit that are impossible with traditional, risk-averse satellite missions. Spire has provided RO and space weather data to the second NOAA Commercial Weather Data Pilot program, the US Air Force Commercial Weather Data Pilot program, ESA, and numerous NWP centers and research institutions. Spire is also pioneering the provision of Earth observation data to NASA and ESA researchers through unique data purchase programs. In our talk we will present an overview of the status and capabilities of the Spire satellites and describe the collection of GNSS-based Earth observations using the GPS, GLONASS, Galileo, and QZSS constellations. We will additionally outline our plans for expanding and adding products to the Spire Earth observation constellation.

New design concepts for sensors, systems and satellites are crucial to enable innovative and high-performance working modes. In this contest, the concept of distributed aperture is becoming of a strong interest for the future Synthetic Aperture Radar (SAR) systems. It is based on the idea that the signal emitted by the transmitter and scattered from the area of interest is not collected by a single receiver but by many, conveniently distributed, formation flying, receivers, and, thanks to passive operations, can achieve very high performance through a series of very compact, low weight, agile, satellite platforms. The advantages of such system are innumerable and the potentialities of reliability, flexibility and modularity make it a very interesting approach for the future missions. However, a number of technological and operational issues shall be solved. The formation acquisition after launch, control and maintenance are big challenge. Also, a small satellite-based distributed SAR system may pose challenging requirements in terms of electrical power, communication link, and payload synchronization. In this ambit, the recent technology upgrades have led to the development of small platforms with increasing capabilities, thus opening the way for using distributed space systems also for cost-effective operational, public and commercial services. Finally, signal processing related issues shall also be solved to enable high-performance applications, not reachable by existing systems. The paper is focused on the distributed SAR concepts, showing: (a) main design drivers, (b) main issues to be solved and related approaches and (c) main potentialities.

The Integrated Standard Imager for Microsatellites (iSIM) is a new generation of high-resolution optical binocular imagers for Earth Observation satellites developed by SATLANTIS. It is the result of combining a compact and efficient optomechanical design, with the latest advances in electronics (both in detectors and processors), the use of commercialoff- the-shelf (COTS) components, and the incorporation of advanced manufacturing procedures. Through the use of cutting-edge technologies, the design of iSIM significantly reduces build & delivery times and provides a new level of affordability. iSIM-170 is the highest resolution optical payload of the iSIM family. The imager features a binocular camera with an aperture of 170mm offering multispectral capability (R, G, B, NIR, and PAN). At 500 km, iSIM-170 provides a spatial resolution of less than 1m over a swath width of 7.5km thanks to the implementation of superresolution algorithms based on Artificial Intelligence techniques. This spatial resolution is independent of the number of bands and is preserved while the satellite moves not only along but also across its orbit. The mass of iSIM-170 is less than 15kg (for more information please visit https://satlantis.com/isim-170/). Based on the early optical prescription, IDOM performed a thorough optical tolerance analysis and conceived a compact, lightweight and quasi-athermal optical bench aimed at providing optimum stability during observation in orbit while coping with the demanding launching conditions. IDOM’s collaboration with SATLANTIS expanded to the fabrication and testing of the first qualification units and the design of the first electronics box.

The work presents the CubeSat development and selection process of camera subsystem for Earth Observation (EO) using Commercial Off The Shelf (COTS) components. The 3U CubeSat VZLUSAT-2 implementing <30m Ground Sample Distance (GSD) is described in the work. For the GSD below 30m the 5um pixel size camera chip is used with 100 mm fixed focal length optical lenses system. The camera chip electronics, optics and baffle are described in the work together with camera computer, SW and necessary on-board processing. Special deployment system for S-band antenna was developed and implemented onboard to enable the near-real time observation regime. The necessity of high maturity AOCS system is discussed and solutions to reach high GSD are presented.

Craft Prospect and partners are enabling smarter, more responsive small satellite operations through the development of components which enable on-board data processing and information extraction and mission autonomy. Small satellite operations are currently highly reliant on the processing of captured data and telemetry and the creation of command schedules by human operators on the ground. Our responsive operations work involves the transfer of these activities, in part or in full, from the human ground operators to the satellite itself. We present our approach to enabling this assured autonomy in small satellite missions. We have defined a reference architecture for integrating autonomy-enabling components into mature, existing flight software. These components perform a variety of functions, including goal-based planning, dynamic scheduling, real-time and offline data processing, communications management, and autonomy supervision. Autonomous activities enabled by this architecture can be considered as either data autonomy or mission autonomy, with runtime supervision of autonomy supporting rigorous development-time verification and validation to provide mission assurance. Some example remote sensing use cases are presented, and the benefits of onboard autonomy to these use cases highlighted and related to new operations concepts. These use cases can see improvements in data coverage, timeliness, quality and value through the transfer of analysis and decision making from the ground to the satellite.

This paper describes application of X-doped AlN (X=Sc, Cr and Y) to wideband surface acoustic wave (SAW) sensors in 200–300 MHz range. First, it is shown theoretically that Cr doped AlN thin film has the highest piezoelectric strain constant, accompanied by a lowest mechanical softening compared to Sc doped AlScN and Y doped AlN thin films for transition metals concentrations ranging from 0 to 25%. Next, the impact of transition metals (Sc, Cr and Y) concentration have been carried out for the first time, in terms of surface wave velocity, electrode reflectivity, transduction coefficient and distributed finger capacitance. Finely, the insertion loss of two-port SAW resonator based on AlXN (X=Sc, Cr and Y) deposited on sapphire substrate is obtained using P-matrix model, and it is shown that AlCrN-SAW resonator exhibit lower insertion loss compared to those based on AlScN and AlYN for metal concentrations of 25%. This finding may position Cr doped AlN as a prime piezoelectric material for low loss SAW sensors whose performance can be tuned via Cr composition

Aqua MODIS has successfully operated for more than 18 years since its launch in May 2002 and has generated numerous science products in support of studies of the Earth’s system and its changes via a set of geophysical and environmental parameters. On-orbit calibration and characterization activities have played a vital role in maintaining the quality of MODIS data products. In addition to data collected from sensor on-board calibrators (OBC), near-monthly lunar observations and select earth view targets have been used to monitor and characterize on-orbit changes in sensor responses and to derive and update the calibration look-up tables. In this paper, we provide an overview of Aqua MODIS on-orbit operations, calibration activities and approaches, and algorithm improvements and also illustrate the sensor on-orbit performance using examples derived from various calibration sources and targets. We will focus on issues identified from instrument operations and calibrations, such as solar diffuser degradation, electronic crosstalk, variations in the cold focal plane temperatures, and changes in response versus scan-angle. Also discussed in this paper are remaining challenges and future improvements.

We aim to introduce and demonstrate several improvements that are applied to the on-orbit solar diffuser (SD) calibration of the day-night band (DNB) low gain stage (LGS) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the NOAA-20 satellite. The most important improvement is the expansion of the angular range, referred to “sweet spot”, from 4° to 7.8° in order to increase the number of fully-illuminated scans considered for the SD calculation. The increase in scan number enables the completion of on-orbit calibration using the SD within one orbit, compared with the multiple orbits approach, which is required in the current standard approach applied in operational DNB LGS calibration coefficients look-up tables (LUTs) updates. The NOAA-20 DNB LGS calibration coefficients have been derived with the new methodology and the results show a more stable, smoother, and less noisy trend when compared with the current standard approach. The results also demonstrate that the NOAA-20 VIIRS DNB overall on-orbit performance has been very stable.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on-board the Suomi-NPP (SNPP) and NOAA-20 (N20) spacecrafts is a multi-spectral Earth-observing instrument with spectral channels ranging from the visible to the long-wave infrared. In addition to these spectral channels, the VIIRS instrument features a panchromatic Day/Night band (DNB) with 3 gain stages (low, mid, and high) which allows for Earth-view (EV) radiance retrievals over 7 orders of magnitude. The DNB is able to collect data ranging from dim city lights during nighttime up to reflected sunlight from cloud-tops during daytime. The DNB data collection is divided into 32 aggregation modes, where sub-pixel aggregation is used to maintain a nearly constant pixel footprint on ground during EV data collection throughout each scan. The DNB is also sensitive enough to observe bright stars through the instrument space-view (SV) port. Data from these bright stars can be used to track the temporal stability of the sensor gain and as a method of intercomparison between the two VIIRS instruments. In this work, we will present several sensor performance assessments of the VIIRS DNB using stars. In addition to the sensor gain trending, these assessments will include a comparison of the differences between the daytime and nighttime data due to the effects of stray-light, a comparison of the measured signal as a function of aggregation mode, a comparison between the two high-gain sub-stages, and half-angle mirror side for both the SNPP and N20 VIIRS DNB.

Aboard the next generation of EUMETSAT geostationary satellites, the Flexible Combined Imager (FCI) will continue the current SEVIRI (Spinning Enhanced Visible and Infrared Imager) mission with enhanced temporal, spatial, and spectral capabilities. For monitoring the radiometric stability of the FCI reflective solar bands ranging from 0.4 to 2.2 μm, the Moon acquisitions are planned to be used. The Moon will cross the FCI field-of-view on a regular basis, under different illumination conditions and elevations. The FCI scan mechanism will allow the acquisition of the Moon with two or three consecutive swaths at the most. Two challenges must be resolved to make use of Moon observations. First, consecutive swaths include an overlap region to avoid coverage gaps. It means that some Moon areas are observed twice. Second, the swaths make an angle with respect to the equatorial plane that varies with the elevation. Consequently, it is necessary to reconstruct the full Moon disc from those consecutive swaths before the total lunar irradiance can be calculated and compared to the current lunar calibration reference, the GIRO (GSICS Implementation of the ROLO) model. This paper presents the prototype developed to make use of Moon observations with FCI. It has two components: i) a Moon transit simulator that generates equivalent Level 1b data using Himawari-8/AHI data as an input, and ii) a Moon image-stitching algorithm, which re-builds the Moon image from the simulated Level 1b swaths. In order to assess the efficiency of the stitching algorithm, two methods to reconstruct the Moon image are implemented and compared. The first one makes full use of the information available from the Moon transit simulator. The second one is the stitching method that will be deployed during operations, i.e. using exclusively information from the Level 1b swaths.

Vicarious calibration approaches using in-situ measurements is a key technique applied to on-orbit remote sensors. The in-situ measurements have advantages in terms of traceability and quantifiable accuracy making them ideal for interconsistency studies of on-orbit sensors. The Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV) Infrared Visible Optical Sensors (IVOS) initiated the Radiometric Calibration Network (RadCalNet) to provide automated surface and top-of atmosphere reflectance data from multiple participating ground sites to the world-wide user community. RadCalNet standardizes protocols for collecting data, processing to top-of- atmosphere reflectance, and provides SI-traceable uncertainty budgets for the 4 currently operating sites. RadCalNet data from the Railroad Valley Playa, Nevada site was used to provide an SI-traceable, absolute radiometric calibration of the Enhanced MODIS Airborne Simulator (eMAS) as part of an overflight of opportunity during the FIREX-AQ campaign. The results shown here demonstrate the utility of RadCalNet data for absolute radiometric calibration of airborne imagers making flights of opportunity without the need for coordination with a field validation team.

The Moderate-Resolution Imaging Spectroradiometer (MODIS) is the key instrument of the NASA’s Earth Observing System (EOS) Terra and Aqua missions, launched in December 1999 and May 2002, respectively. The Visible Infrared Imaging Radiometer Suite (VIIRS) expands the MODIS legacy, launched onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite in October 2011 and NOAA20 satellite in November 2017, respectively. The MODIS and VIIRS sensors have a similar design with spectrally matched reflective solar spectral bands (RSB). Their on-board calibration components include a solar diffuser and a solar diffuser stability monitor for RSB, a V-grooved blackbody for the thermal emissive bands (TEB), and a space view as a background reference. This study evaluates the calibration consistency of the Terra and Aqua MODIS RSB based on the current Collection 6.1 L1B data products generated by the NASA MODAPS, which have used consistent calibration coefficient look up tables (LUT) for the entire data-record. In the case of SNPP and NOAA20 VIIRS, the latest L1B data produced by NASA Land SIPS are used. Several independent vicarious approaches are used to examine the stability and consistency of the at-sensor reflectance among MODIS and VIIRS instruments. Vicarious approaches include observations from simultaneous nadir overpasses (SNO), the Libya-4 desert and Dome C snow sites, as well as deep convective clouds (DCC). Impact of existing band spectral difference on the reflectance is corrected using hyperspectral observations provided by Europe Space Agency’s SCIAMACHY sensor. Results of this study provide comprehensive assessments of calibration performance, radiometric agreement and associated uncertainties.

The Moderate Resolution Imaging Spectroradiometer (MODIS), a key instrument of the NASA Earth Observing System missions, has operated for over 20 years and 18 years onboard the Terra and Aqua satellites, respectively. Sixteen thermal emissive bands (TEBs) are distributed on two cold focal place assemblies with photovoltaic (PV) HgCdTe detectors for bands 20-25 and 27-30 and photoconductive (PC) HgCdTe detectors for bands 31-36. This paper evaluates the performance of the latest MODIS Collection 6.1 (C6.1) Level-1B products with a focus on the relative differences between the Terra and Aqua MODIS TEBs. The Infrared Atmospheric Sounding Interferometer (IASI) onboard the Metop-A satellite serves as a reference. Observations obtained from the simultaneous nadir overpass between the Terra (or Aqua) and Metop-A satellites are used to track the brightness temperature differences between MODIS and IASI. The assessment is based on the temperature differences as a function of scene temperature and their trends in comparison with IASI from years 2007 to 2020. The results confirm that the calibration of Terra MODIS bands 27-30 significantly improved in C6.1 after implementing the electronic crosstalk correction. In spite of these corrections, Terra MODIS shows a larger drift in PV LWIR bands 27-30 than Aqua MODIS when compared to IASI.A sensitivity study is performed, where the center wavelength of the MODIS relative spectral response is shifted, and as a result some of these bands show a significant improvement in scene temperature dependency and their consistency with IASI measurements.

An accurate on-orbit characterization of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Terra and Aqua satellites is essential to satisfy the requirements from the scientific community for high-quality operational and research products. In this study, NASA’s C6.1 L1B data are utilized to assess the stability of the calibrated top of atmosphere reflectance retrieved from individual detectors within a spectral band over deep convective clouds (DCCs) and desert sites. The results from these invariant Earth targets show detector-to-detector (D2D) differences in the L1B reflectance products for select MODIS reflective solar bands. For Aqua MODIS, the D2D differences have no significant change over time for the bands studied. However, the D2D differences exhibit an increase in magnitude over time for Terra MODIS bands 1, 3-7, and 26, which can induce noticeable striping and higher uncertainties in the downstream data products. The D2D stability assessment results over DCCs are consistent with those observed over desert sites. In addition, the view-angle dependence of the D2D differences is investigated by separating the frames along scan into five zones. The D2D assessment is performed for each of the five zones, and the results will further benefit any improvements in the calibration of a detector-dependent response versus scan angle that can be considered for future MODIS Level 1B Collections.

The Moderate-Resolution Imaging Spectroradiometer (MODIS) has been maintained its nominal operations since it was launched in December 1999 on Terra and May 2002 on Aqua spacecraft, respectively. MODIS is a scanning radiometer with a two-sided mirror that scans the Earth over an angular range from -55° to +55° off nadir and covers a wavelength range from 0.4 to 14.4 μm in 36 spectral bands. The sensitivity to polarization was fully characterized during prelaunch characterization for each reflective solar band (RSB), detector and mirror side as a function of scan angle. It was observed that while on-orbit polarization sensitivity for Aqua MODIS has been stable over the course of mission, the Terra MODIS polarization sensitivity at a few short wavelengths showed a significant increase near the end of scan angle after a few years in the mission. Our previous study examined the impact of polarization on the measured top-of-atmosphere reflectances obtained over the pseudo-invariant desert sites. There are up to 25% change in gain and 30% seasonal variation in select Terra RSBs due to the increase in polarization sensitivity. In this study, we examine relative changes in the polarization sensitivity of detectors within a band. Results from prelaunch tests indicate that there is a noticeable detector dependent polarization sensitivity and it is expected that such a dependency could change on orbit, particularly for Terra MODIS. Results of this study provide useful information on polarization impact and implementation of the correction algorithm.

The MODerate resolution Imaging Spectroradiometer (MODIS) instruments on-board the Terra and Aqua spacecrafts were launched on December 18, 1999 and May 4, 2002, respectively. Each instrument has been scheduled to view the Moon through its Space View (SV) port approximately once per month in order to monitor the long-term radiometric stability of their reflective solar bands (RSB). The lunar calibration has played a key role in tracking the change in the response versus scan angle (RVS) of the instrument’s scan mirror, which is an essential part of the RSB calibration. The lunar irradiance observed by MODIS depends on the view geometry and it is crucial to remove the geometric effects in order to derive accurate RSB calibration coefficients. With a scheduled roll maneuver, the lunar phase angles are kept in a narrow range of 1° for each MODIS instrument such that the impact of these geometric effects is minimized. Nevertheless, it remains a challenge to completely remove the impact of geometric effects in the calibration coefficients derived from the lunar observations, considering the high expectations for the accuracy and quality of the results. In the current MODIS lunar calibration, the geometric effects on the lunar irradiance are corrected by the RObotic Lunar Observatory (ROLO) model. The overall relative uncertainty of the ROLO model for the MODIS calibration has been assessed to be about 1% in the selected lunar phase angle range of 1°. It could be as large as 4% beyond this small phase angle range, especially for the shortest wavelengths. This uncertainty induces noticeable oscillations in the calibration coefficients derived from the lunar observations. We developed a simple lunar model, which is based on MODIS lunar measurements, derived from scheduled lunar observations, as well as those obtained from intrusion of the Moon in the SV, referred to as unscheduled lunar observations, in the time period from 2005 to 2012. Here, the scheduled lunar observations for the entire mission are reprocessed with the new lunar model applied to correct the view geometry effects for each MODIS instrument. New calibration coefficients for the RSBs are calculated. We show that oscillations and noise in the derived lunar calibration coefficients are significantly reduced for both MODIS instruments.

Two Visible Infrared Imaging Radiometer Suite (VIIRS) instruments are currently operating in space, one onboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite launched on October 28, 2011 and the other onboard the NOAA-20 satellite launched on November 18, 2017. The performance of the seven VIIRS thermal emissive bands (TEBs) is monitored via on-orbit calibration data, the analysis of Earth view observations, as well as inter-comparisons with other sensors. The Moon has been used as a unique invariant target for on-orbit sensor calibration because its surface property is considered extremely stable over time in spectra, radiometry, and geometry with a repeatable lunar phase. This paper presents the assessments of the S-NPP and NOAA-20 VIIRS TEB on-orbit calibration stability using near-monthly scheduled lunar observations over their respective missions. The methodology previously developed for MODIS is now applied to VIIRS to monitor the TEB long-term stability by extracting and trending the lunar brightness temperatures from selected unsaturated pixels. It includes a correction applied to reduce any impact from the Sun–Moon geometry (e.g. Sun-Moon distance variation). The results show that the mission-long brightness temperature trends from the lunar surface are stable for all VIIRS TEBs, despite noticeable seasonal variations in the lunar thermal emissive radiance.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua platforms is a multi-spectral, whiskbroom scanning radiometer with 36 spectral bands covering wavelengths from 0:4 - 14:2 μm. Among these bands, the 20 reflective solar bands (RSB, 0:4 - 2:1 μm) use an on-board solar difuser (SD) and SD stability monitor (SDSM) to track the detector gain changes on orbit. In addition to this, lunar and Earth-view (EV) observations are used in order to characterize the scan-mirror response versus scan angle (RVS), which improves the Earth-view retrieval over the full width of each scan. For the short-wave infrared bands (SWIR, 1:2 - 2:1 μm), the prelaunch RVS has been used for both Aqua and Terra MODIS throughout each mission. While these bands are not expected to have a significant change in the RVS on-orbit, issues such as electronic crosstalk and an out-of-band optical leak have prevented the use of the Moon for deriving the on-orbit RVS for validation. However, recent improvements to the MODIS lunar calibration for the SWIR bands allow us to mitigate the electronic crosstalk impact and derive the RVS for the SWIR bands. In this work, we will assess the impact of this newly derived RVS on the EV data compared to MODIS Collection 6.1. By comparing to EV data obtained from pseudo-invariant calibration sites at different angles-of-incidence on the scan mirror, we can assess the effectiveness of the newly derived RVS from the Moon. We find that while the change in the RVS on-orbit for the SWIR bands is relatively small, applying a correction to the RVS based on the Moon and SD data can provide an improvement for some bands.

The primary mission of the two Lunar Terrestrial Imagers (LUTIs) onboard the Korea Pathfinder Lunar Orbiter (KPLO) is to obtain high-resolution images of the Moon that will enable landing site identification and certification and target observation of interesting places. The two LUTIs are panchromatic push-broom line scanners, with an instantaneous field-of-view (IFOV) of 25-microradians. The two LUTIs are designed to provide 2.5 m scale panchromatic images over a combined 9.75 km swath from the nominal 100 km orbit. Each LUTI utilized a 400 mm focal length Ritchey-Chretien telescope that images onto a 2048-pixel charge coupled device (CCD) line array, providing an IFOV of 25-microradians and a cross-track field-of-view of 2.88° each. The design also incorporates a 131 mm long sunshade to prevent illumination of the primary mirror by rays more than 12.4° off axis. There are key parameters to quantify stray light effects by external sources, i.e., ray paths, irradiance distribution at the focal plane arrays, point source transmittance and radiometric error due to the stray light. All the parameters can be simulated using the forward ray tracing computation with the stray light model and the extended scene integration. The stray light model is the surface-based three-dimensional geometry for ray tracing computation using opto-mechanical design and those optical properties including reflection-, transmission-, absorption-coefficients, and bi-directional scattering distribution function (BSDF) models. After building the stray light model, ray sets are prepared and located at the entrance aperture (EA) to conduct the forward ray tracing computation towards the focal plane (FP). For this, incident angle boundaries are limited in consideration of the viewing geometry and each angle of incidence (AOI) is weighted by the backward ray tracing computation results, then representative AOIs are selected considering sampled regions for extended scene integration. In the ‘Sampling AOIs’ process, weighting factors are to be assigned to each incident angle. The backward ray tracing computation can be also used as possible ray paths investigation from the EA towards the FP. Assuming that a ray leaving from the FP is reflected or transmitted on the optical or mechanical surfaces along the mth and nth ray paths including scattered at an intervening object I and finally arrived at the EA, the mth and nth ray paths combination could be one of stray light ray paths having kth direction at the EA if it is not normal optical ray path. In this case, the ray fluxes can be changed by transmittance between the FP and the intervening object l along the mth ray path, TI_m, that between the intervening object l and the EA along the nth ray path, TI_n, BSDF of the intervening object I, and geometric configuration factor between the intervening object I and other surface illuminated by randomly distributed scatter rays in consideration of the mth and nth ray paths. Total flux with kth direction at the EA can be obtained by iterative backward ray tracing computation and summation of ray fluxes by kth incident angle. The kth incident angle weighting factor is a normalization of kth ray fluxes. Assuming that the single LUTI telescope observes the Moon, which is a spheroid having 3,474 km in diameter, from the nominal 100 km orbit at (0°, 90°) nadir angle, incident angle boundaries are limited less than 70°, latitudes and longitudes of the boundary region on the Moon are ±13.60° and 76.40°~103.60°, respectively. Directional weight distributions within 70° incident angles were obtained with the backward ray tracing computation technique. And then AOIs were sampled by dividing into far- and near-field based on the directional weight map. Each AOI represents each sampled region and summation of directional weights within the region is used a criterion for AOI selection. In this report, we present LUTI stray light rejection performance estimation focusing critical AOI sampling technique in detail.