This PDF file contains the front matter associated with SPIE Proceedings Volume 12264, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

The Suomi National Polar-orbiting Partnership (Suomi-NPP) mission successfully completed ten years of operations since its launch in 2011, and NOAA-20 is in its fourth year of operations since 2017. These two satellites have revolutionized how remote sensing measurements are used in both weather prediction as well as in other applications that serve a variety of users. The third JPSS satellite (JPSS-2) is scheduled to be launched on November 1, 2022. Some major contributions of the mission over the past decade are highlighted here.

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 temporal (down to 3 days) and spatial (100 km) resolution. Such variations carry information about mass change 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; ultra-precise accelerometers measure the nongravitational accelerations to correct the gravity signal in the data processing. The optimal satellite system comprises two pairs of satellites on low (between 396 and 488 km) circular orbits, at 220 km separation, one pair quasi-polar and the other around 65°-70° inclination. The satellite-to-satellite tracking technique for detecting the temporal variations of gravity was established by GRACE (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 (upper MBW). At 150 km spatial resolution, mass change would become observable in 80% of all significant river basins, against 10% achieved with GRACE. High temporal resolution will reveal large-scale sub-weekly mass variations, with applications in water and emergency management. NGGM is a candidate Mission of Opportunity for ESA-NASA cooperation in the framework of MAGIC. The paper focusses on the on-going Phase A system design and technology pre-development activities.

Developed by ADS under CNES responsibility in partnership with Eumetsat, IASI-NG payload on board of METOP-SG satellite will deliver data for operational meteorology, climate monitoring, and atmospheric chemistry in the next decades. In order to improve by a factor two compared to IASI the spectral resolution and radiometric error, the instrument is designed around a Mertz compensated interferometer, whose good spectral performances have been checked at subassembly level in 2020. The PFM is now fully integrated and will go through functional tests, performance tests at ambient and in TVAC through 2022. The aim of this paper is to give an overview on these activities.

The European Space Agency (ESA), in collaboration with the European Commission (EC) and EUMETSAT, is developing as part of the EC’s Copernicus programme, a space-borne observing system for quantification of anthropogenic carbon dioxide (CO₂) emissions. The anthropogenic CO₂ monitoring (CO2M) mission will be implemented as a constellation of identical Low Earth Orbit satellites, to be operated over a period of more than 7 years. Each satellite will continuously measure CO₂ concentration in terms of column-averaged dry air mole fraction (denoted XCO2) along the satellite track on the sun-illuminated part of the orbit, with a swath width of 250 km. Observations will be provided at a spatial resolution < 4 km2 , with high precision (< 0.7 ppm) and accuracy (bias < 0.5 ppm), which are required to resolve the small atmospheric gradients in XCO2 originating from anthropogenic activities. The demanding requirements necessitate a payload composed of three instruments, which simultaneously perform co-located measurements: a push-broom imaging spectrometer in the Near Infrared (NIR) and Short-Wave Infrared (SWIR) for retrieving XCO2 and in the Visible spectral range (VIS) for nitrogen dioxide (NO2), a Multi Angle Polarimeter (MAP) and a three-band Cloud Imager (CLIM). Following the kick-off Mid 2020, the industrial activities have now passed the Satellite PDR allowing to enter the phase C/D. The paper summarises the payload activities performed during the phase B2 culminating with the PDR of the instruments and of the payload. The preliminary design of the CO2M mission’s instruments, the progress of the technological activities and the first results of the development models are presented.

Among future multi-directional polarimetric spaceborne missions that will advance cloud and aerosol studies, the Multiviewing, Multi-channel, Multi-polarisation Imager (3MI) on the MetOp Second Generation – A (MetOp-SG-A) satellite is a direct successor of the classic and successful design of Polarisation and Directionality of the Earth’s Reflectance (POLDER) sensors. The POLDER design comprises of three essential elements: a wide field-of-view lens, a rotating wheel holding spectral and polarizer filters, and a two-dimensional imaging sensor. This presentation demonstrates a new geometric calibration technique for an airborne prototype of the 3MI and other POLDER-like sensors. Geometric calibration is often challenging for an airborne sensor because it is frequently mounted to and dismounted from the aircraft. The rotation of the instrument with respect to the aircraft reference frame must be calibrated every time when the instrument is reinstalled, but the opportunity for a stable flight leg over ground control points is limited because of weather and air-traffic conditions. In addition, the precise aircraft position is often more difficult to obtain than the precise aircraft attitude. To mitigate this difficulty, our new technique derives the instrument rotation by detecting three natural angular features: rainbow, glory, and hot spot. These features are often observed during scientific data acquisitions over clouds and land surface, thus enable the direct validation of the geometric calibration quality for every eligible image under the actual acquisition condition. We present the automatic detection technique of these angular features in in-flight data and derived rotation angles and errors for the AEROCLO-SA field campaign.

This paper describes the current status of PALSAR-3, L-band Synthetic Aperture Radar (SAR) boarded on Advanced Land Observing Satellite-4 (ALOS-4). ALOS-4 is the following mission of the ALOS-2 and the fourth generation of Japanese L-band SAR missions. PALSAR-3 has three observation modes same as PALSAR-2 boarded on ALOS-2. The same orbit and observation geometry as PALSAR-2 are selected to enable interferometric SAR (INSAR) time series analysis over 10 years using both of PALSAR-2 and PALSAR-3 data. PALSAR-3 will have the Basic Observation Scenario (BOS), same as PALSAR-2.

The tremendous potential of ALOS-4/PALSAR-3 for further advancements in forest monitoring from local to global scales are discussed on the basis of the groundbreaking achievements made by its predecessor ALOS-2/PALSAR-2, the first long-term L-band SAR forest observation mission in history. The unprecedented seamless and frequent dual-polarization observation of the entire tropical forest belt between 2016 and 2022 has revolutionized the idea of global forest monitoring. In the upcoming ALOS-4 era, wide-area imaging with greatly improved spatial resolution and image quality at shorter revisit times will further boost the reliability for all kinds of forest remote sensing applications including forest classification, biomass estimation and deforestation detection.

Increasing human and economic losses from urban disasters demand synthetic aperture radar (SAR), which has allweather, day-and-night observation capability. The Japan Aerospace Exploration Agency (JAXA) has been operating the Advanced Land Observing Satellite-2 (ALOS-2), carrying PALSAR-2, an L-band SAR, for monitoring disasters and environmental changes. We developed the first fully automated algorithms for detecting flood extents and earthquakeinduced building damage from ALOS-2 data. The algorithms rapidly process ALOS-2 and ancillary data (flood simulation, hazard map, and other geographical information) and provide damage information less than an hour after the input data are entered. The validation results showed that the accuracy of the estimated flood extent was 60 to 94%, depending on the observation conditions, especially the incidence angle of ALOS-2 observation. The accuracy of the damaged building detection was 72% for buildings with a footprint larger than 200 m² in the area. We implemented these algorithms in an operational disaster response system. We launched a one-stop operation that automatically processes ALOS-2 data after emergency observation and provides the damage maps rapidly via email for disaster response workers.

Advanced Land Observing Satellite-3 (ALOS-3) is one of the follow-on missions of ALOS, also called “DAICHI” (2006−2011), and it takes over the optical mission from ALOS. The goal of the ALOS-3 mission is to contribute to the disaster monitoring and updating of geo-spatial information, as well as the environmental monitoring of coastal and vegetation areas. The main payload of ALOS-3 is an optical camera, named wide-swath and high-resolution optical imager (WISH). It has a resolution of 80 cm (panchromatic) and 3.2 m (multispectral) at nadir together with a wide-swath of 70 km by employing an off-axis large FMA (Four Mirror Anastigmat) telescope. The detectors on the focal plane are TDI-CCDs, with observational bands of panchromatic and six multispectral bands, including “coastal (0.40 - 0.45 μm)” and “RedEdge (0.69 - 0.74 μm)” in addition to red, green, blue, and near-inferred. In order to achieve high optical performance, the technical challenges specific to this satellite telescope have been required in all the processes of design, manufacturing, and testing. This paper presents an overview of the WISH and the development result of each process. All the processes have been completed without critical problems, and all the required pre-flight performance has been verified and reviewed.

Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW) is a Japanese Earth observation satellite to be launched in FY2023 and jointly funded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) and the Ministry of the Environment (MOE). One of GOSAT-GW's mission instrument is Total Anthropogenic and Natural Emissions Mapping Spectrometer-3 (TANSO-3). TANSO-3 is a 3-band grating imaging spectrometer with two different selectable spatial observation modes, Wide Mode and Focus Mode. MOE and National Institute for Environmental Studies (NIES) are responsible for global observation of greenhouse gases (GHGs) and air pollutants, carbon dioxide (CO₂), methane (CH₄), and nitrogen dioxide (NO₂), by TANSO-3. TANSO-3 instrument is being developed by Japan Aerospace Exploration Agency (JAXA) with the funding from MOE. The missions of TANSO-3 include (1) monitoring of whole-atmosphere mean concentrations of CO₂ and CH₄, (2) validation of nationwide anthropogenic emissions of GHGs, and (3) detection of GHGs emissions from large sources, such as megacities and power plants. The validation of nationwide anthropogenic emissions of GHGs is one of emerging challenges related to the Paris Agreement and contributions of TANSO-3's global data strongly expected. NO2 data from TANSO-3 will be also utilized in the identification and characterization of point sources which use fossil fuels and their plumes.

Hyperspectral Imager Suite (HISUI) is a remote sensing instrument mounted on the International Space Station (ISS). HISUI provides spectral images at 185 bands from visible to short wavelength infrared (SWIR) region (400 – 2500 nm) with the ground sampling distance (GSD) of 20 meters for the cross track and 31 meters for the along track. HISUI is the follow-on mission of the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) that also covers spectral range from visible to SWIR region. The observation data of the hyperspectral sensor is expected to play an important role in the future spatial-spectral data for the resource exploration, environmental observation, agriculture, forestry, fisheries and so on. The initial checkout for a flight model of HISUI have been successfully carried out in 2019. This paper describes the In-orbit performances such as special, spectral and radiometric. All performance of HISUI in VNIR and SWIR regions fully satisfies the specification, and non-specification items, such as wavelength range, sampling interval, offset, dark noise radiometric sensitivity, are confirmed that the performances of all components are maintained as expected.

The paper presents the results of the 2021 CarbonCGI project, specified by ESA Future Earth Observation department, dedicated to high-resolution observations of GHG (Greenhouse Gas) with CGI (Compact Gas Imager). CarbonCGI aims at detecting and characterizing faint anthropogenic emissions of Carbon dioxide and Methane gas, from low orbit satellite to complement and extend CO2M mission [1]. CGI are developed in an integrated team of scientists and engineers involved in the framework of CarbonCGI project, the IRT (Research and Technological Institute) NS3 (New Space Small Sensor) project and the scientific activities of the industrial chair TRACE [2]. Compact Gas Imagers developments cover the atmospheric transport inverse modelling (level 4), the radiative transfer modelling (level 2), the simulation of acquisition chain, data correction, registration and calibration, as well as detailed design of sensor and critical components (level 0-1).

Remote sensing and characterization of high temperature targets on the Earth’s surface is required for many cross-disciplinary science investigations and applications including fire and volcano impacts on ecology, the carbon cycle, and atmospheric composition. For decades this research has been hindered by insufficient spatial resolution and/or detector saturation of satellite sensors operating at short and mid-infrared wavelengths (1-5μm) where the spectral radiance from high temperature (<800 K) surfaces is most significant. To address this critical need, the Jet Propulsion Laboratory and partnering institutions are developing a compact modular high dynamic range (HDR) multispectral imager concept, with the flexibility to operate in the short, mid- or long-wavelength infrared spectral bands.

The VIIRS instruments onboard the SNPP and NOAA-20 satellites have identical spatial resolutions and the same spectral bands. Similar prelaunch tests and identical on-orbit calibration algorithms established the foundation for their consistent Earth measurements. Calibration assessment and consistency comparisons are useful to maintain their performance and measurement accuracy. Simultaneous nadir overpasses (SNO) between two satellites are commonly used for a direct calibration comparison between sensors. However, there are no SNO between SNPP and NOAA20. Hence, a reference sensor or Earth measurements are normally used to bridge the comparison. As a reference, we focus on the Advanced Baseline Imager (ABI) onboard the GOES-R series spacecraft and its application to the SNPP and NOAA-20 VIIRS comparison. GOES16 and GOES17 are the first two satellites of the GOES-R series and were launched on November 19, 2016 and March 12, 2018, respectively. Their operational positions are on the equator with longitudes of 75.2° West over land and 137.2° West over ocean, respectively. The ABI is the primary imaging instrument of these spacecrafts for the Earth’s weather, oceans, and environment, with observations (every 10 minutes) that provide vast data for GEO- Low Earth orbit (LEO) and LEO-LEO comparisons utilizing it as an intermediate reference sensor. VIIRS and ABI have spectrally matched bands and can have simultaneous measurements over any selected site every day. The simultaneous measurements over the same site also have various scan angles. These features provide advantages for a VIIRS-to-ABI comparison. The spectral response function difference between instruments, sites selected, and view angles will have effects on the instrument measurements. Their impacts on the calibration comparison, including the use of double differences, will be discussed. By collecting VIIRS measurements over a large range of view angles, the view angle effect will also be investigated. The collection of an ample amount of data provides an advantage for statistical analyses and potential big data applications to sensor calibration assessments. This method can also be applied to other sensor calibration comparison and performance assessments, such as GOES16 and GOES17 ABI, and Terra and Aqua MODIS.

A new hyperspectral imager (HSI) is designed for the next-generation HY-1E ocean color monitoring satellite. This instrument requires a reduced ground sampling distance (GSD) of 100 m and increased number of spectral bands (from 8 to 10). A GSD of 100 m corresponds with a frame rate of approximately 70 Hz. The sensor has an elongated format of 2176 * 320 pixels of 30 μm to increase the sensitivity. Multiple sensors will be used in a staggered configuration to guarantee a full earth coverage in 2-3 days The overall length of the sensor is 73 mm and is subdivided in 4 segments of 16.32 mm each. Each segment is read out via two SAR ADC blocks. Each conversion takes 48 clock cycles resulting in ADC clock speed of 120 MHz. The ADC can also be read with 12 bit accuracy with increased conversion speed; and by oversampling the LSB’s it is possible to reach 16 bit accuracy. The pixel is equipped with a 4-fold High Dynamic range readout mechanism. Under low-illumination conditions all acquired signal charges are remaining in the pixel. When the illumination is increased, the additional charges will be accumulated in an additional capacitor. For even larger photon fluxes a third and a fourth capacitor are activated. In this way all intensity level are treated by the same sensitive area and in exactly the same integration time, eliminating all motion artefacts. The 4 gain stages can contain respectively 24, 120, 600 and 2500 ke- . For each gain stage the dynamic range is 5000:1 resulting in an overall dynamic range of 114dB. The Image sensor is designed in a Rad-Hard by Design (RHbD) way to cope with the LEO space environment. The dark current increase under the influence of 75 krad(Si) is a factor 3500, but the effect is largely annealed with a high temperature anneal. The SEE is higher than 37 MeV/mg/cm2 due to the use of DICE based digital blocks. The Image sensor is packaged in a custom designed ceramic package, closed with a dedicated filter window. All environmental and life time tests were executed on the assemblies.

The 2-μm near-infrared (NIR) camera, IR2, onboard Japan’s Venus orbiter Akatsuki acquired Venus images after the successful orbit insertion in December 2015. IR2 utilizes a platinum silicide (PtSi) Schottky-barrier array sensor (1040×1040 pixels) in which photon is detected by the photo-electric effect. This is by nature not a very high efficiency mechanism therefore unused light is subjected to multiple reflection within the silicon substrate (400-μm thick in IR2). Because very intense day crescent (some ~3 orders of magnitudes brighter) of Venus exists in the same field of view when the night-side disk is imaged, light spread from the former significantly affects the photometry of the latter. To restore the night-side features to a level that can be measured photometrically, we have developed a simulation to model the point-spread function (PSF) of IR2 in which effect of multiple light reflection is accounted for. Different elements in the array sensor (the NIR-sensitive PtSi pixels, the vertical scanning lines, and the charge-sweep device area) are considered and the light reflection is traced until the beam becomes weaker than a threshold. While the multiple rings (the innermost one corresponds to the critical angle of total internal reflection) are successfully reproduced, the cross pattern did not show up from this simulation and we had to artificially add it. The concept of simulation may be useful for other sensors of which substrate is relatively transparent for the wavelengths of interest while the target objects contain large dynamic range.

The MODIS instruments onboard the Terra and Aqua satellites have been in operation for over 22 and 20 years, respectively. The instruments’ calibration accuracy has been maintained, even with instrument degradation. Electronic crosstalk in the thermal emissive bands (TEB) is a known issue with an increasing impact on the calibration and product. The Terra MODIS photovoltaic (PV) longwave infrared (LWIR) bands crosstalk corrections have been applied in Collection 6.1 (C6.1). However, the electronic crosstalk contamination for some detectors in the mid-wave infrared (MWIR) bands and the Aqua PV LWIR bands affect the Level-1B (L1B) product’s measurement accuracy and image quality. In Collection 7 (C7), crosstalk corrections for select detectors in the Terra and Aqua MWIR and Aqua PV LWIR bands are applied. The entire mission crosstalk coefficients for the select detectors and bands are derived from scheduled lunar observations and populated in the form of look-up tables (LUTs). Similar to the Terra PV LWIR bands crosstalk downward trends, the Aqua PV LWIR bands also show these trends, especially in recent years. The crosstalk coefficients and their trends provide a guideline for the correction application. Earth measurement analyses before and after the correction provide contamination and correction assessments. It has been shown that the product quality is enhanced with the crosstalk correction applied in C7. For C7, the crosstalk coefficient uncertainty is derived from the fit residuals between the measured values and a linear fit over a three-year sliding window. The uncertainty propagation is modeled and applied in the total uncertainty calculation in the L1B product. The TEB electronic crosstalk LUTs have been processed over the entire Terra and Aqua MODIS missions. This paper presents the C7 crosstalk correction, as well as its assessment and uncertainty propagation algorithm to the TEB uncertainty.

Proper utilization of the remote sensing payload output data in a real situation of a high-resolution satellite, deeply depends on the detailed orientation and relative attitude of the sensitive elements such as star sensors, optical payloads and etc. Very small unknown installation errors between star sensor and optical payload axes, will results in several hundred meters pointing error for imaging payload footprint on the ground targets. In practice, the final error and transform matrixes of elements coordinate systems to each other as well as to the satellites body must be accurately determined. Different methods are widely using in satellite industries where the CMM method is the most well-known of them. In this manuscript we introduced a practical methodology to extract the accurate mutual coordinate transformation matrix of sensitive satellite elements and to the satellite body. Our general approach was to improve the operational pointing accuracy of imaging payloads missions and improving the reliability of the final payload data. This method is using four theodolites in a predefined architecture along with some very accurate alignment cubes. After final assembly and integration of the whole satellite, final alignment accuracy depends on the individual instrument’s accuracies. Using proper instruments, the attitude of sensitive elements coordinate system with respect to the satellite body coordinate system is measured at the order of several arcseconds. The proposed method, in addition to improving the final accuracy, has other advantages such as simplicity in setup and speeding up the implementation.

The VIIRS sensor has 7 Thermal Emissive Bands (TEB) – spectra cover from 3.7 through 12.0 μm – that are calibrated on-orbit using observations from its on-board blackbody. As part of the prelaunch calibration activities, the on-orbit retrieved radiance total calibration uncertainty of the TEB was estimated for both VIIRS (onboard the S-NPP and NOAA-20 spacecraft) instruments currently in orbit. However, no uncertainty algorithm was developed nor implemented in the Level 1B (L1B) product for the NASA Science Investigator-led Processing Systems (SIPS). This study presents the methodology, analysis, and uncertainty look-up tables used to develop a calibration uncertainty algorithm for the VIIRS TEB that is currently being implemented in the NASA SIPS L1B product. The on-orbit retrieved total uncertainties for each TEB were compared to specified uncertainty limits at a series of scene temperatures. Results indicate that the estimated uncertainties were compliant with their respective specifications, except for bands M12 and M13 at lower scene temperatures. For the midwave infrared bands, the on-orbit detector response and response-versus-scan-angle are the most dominant uncertainty contributors over cold scenes, while the blackbody radiance terms drive the uncertainty on the warmer temperature end. The longwave infrared bands uncertainties are mostly determined by on-orbit detector response and response-versus-scan-angle over all scene temperatures. It was also found that the longwave infrared TEB uncertainties showed some scan angle dependence at the lower scene temperatures. The methods presented here can be used to develop similar L1B uncertainty algorithms for the TEB in the VIIRS sensors that will be onboard future Joint Polar Satellite System missions.

We present a tool under development at OHB, the purpose of which is evaluating the performance of in-orbit refocusing of Earth-Observing imaging systems. This software suite is designed to provide a robust and flexible mean to determine the constraints applicable to a variety of mission concepts and detector technologies. We illustrate its functionality by analyzing the performance of two calibration strategies befitting a LEO mission with a TDI-based imager.

The nature of optical diffraction limits the spatial resolution of a space-borne optical sensor to the diffraction limit. Using the Rayleigh criterion, we match the Airy Diameter of the optical sensor to the pitch size of a selected imaging detector, or vice versa. Since there is little choice when selecting space-proven imaging detectors, conventional approaches have few options for payload optimization in terms of compactness or volume. In this paper, we first propose an innovative concept of volume sharing multi-aperture payloads to achieve ground spatial resolutions several times higher than conventional approaches. With this approach, we can achieve 1 m ground sampling distance (GSD) at 500 km altitude with a small satellite of less than 100U volume.