This PDF file contains the front matter associated with SPIE Proceedings Volume 10423, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The European Space Agency is developing a direct detection Doppler Wind Lidar for measuring wind profiles from space. The main objective of Aeolus is to provide tropospheric and lower stratospheric wind profiles globally for the improvement of weather forecast on short and medium term. Aeolus data are expected to greatly contribute to weather and air quality monitoring and to scientific advances in atmospheric dynamics. The UV Lidar instrument, ALADIN, will deliver horizontally-projected single line-of-sight wind profiles from the Doppler shift of molecular and particle backscatter. The development of the AEOLUS mission passed a major milestone with the integration of the full instrument and its functional and performance tests in 2016 and a 6-month life test of the spare UV laser transmitter. The satellite has been assembled and has successfully been subjected to a programme of functional and environmental (vibration, acoustic, shock, EMC) tests. The preparation of thermal vacuum testing, including instrument performance in vacuum, is close to completion.

The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop as part of ESA’s Living Planet Programme, the third Earth Explorer Core Mission, EarthCARE, with the ojective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere. EarthCARE payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments data are processed individually and in a synergetic manner to produce a large range of products, which include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling. MSI is a compact instrument with a 150 km swath providing 500 m pixel data in seven channels, whose retrieved data will give context to the active instrument measurements, as well as providing cloud and aerosol information. BBR measures reflected solar and emitted thermal radiation from the scene. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes from ground to an altitude of 40 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol and molecular scattering, which gives access to aerosol optical depth. Co-polarised and cross-polarised components of the Mie scattering contribution are measured on dedicated channels. This paper will provide a description of the optical payload implementation, the design and characterisation of the instruments.

The FLuorescence Imaging Spectrometer (FLORIS) is the payload of the FLuorescence Explorer Mission (FLEX) of the European Space Agency. The mission objective is to perform quantitative measurements of the solar induced vegetation fluorescence to monitor photosynthetic activity. FLORIS works in a push-broom configuration and it is designed to acquire data in the 500–780 nm spectral range, with a sampling of 0.1 nm in the oxygen bands (759–769 nm and 686- 697 nm) and 0.5–2.0 nm in the red edge, chlorophyll absorption and Photochemical Reflectance Index bands. FLEX will fly in formation with Sentinel-3 to benefit of the measurements made by the Sentinel-3 instruments OLCI and SLSTR, particularly for cloud screening, proper characterization of the atmospheric state and determination of the surface temperature. The instrument concept is based on a common telescope and two modified Offner spectrometers with reflective concave gratings both for the High Resolution (HR) and Low Resolution (LR) spectrometers. In the frame of the instrument pre-development Leonardo Company (I) has built and tested an elegant breadboard of the instrument consisting of the telescope and the HR spectrometer. The development of the LR spectrometer is in charge of OHB System AG (D) and is currently in the manufacturing phase. The main objectives of the activity are: anticipate the development of the instrument and provide early risk retirement of critical components, evaluate the system performances such as imaging quality parameters, straylight, ghost, polarization sensitivity and environmental influences, verify the adequacy of critical tests such as spectral characterization and straylight, define and optimize instrument alignment procedures. Following a brief overview of the FLEX mission, the paper will cover the design and the development of the optics breadboard with emphasis on the results obtained during the tests and the lessons learned for the flight unit.

Sentinel-2 is an Earth Observation mission developed by the European Space Agency (ESA) in the frame of the Copernicus program of the European Commission. The mission is based on a constellation of 2-satellites: Sentinel-2A launched in June 2015 and Sentinel-2B launched in March 2017. It offers an unprecedented combination of systematic global coverage of land and coastal areas, a high revisit of five days at the equator and 2 days at mid-latitudes under the same viewing conditions, high spatial resolution, and a wide field of view for multispectral observations from 13 bands in the visible, near infrared and short wave infrared range of the electromagnetic spectrum. The mission performances are routinely and closely monitored by the S2 Mission Performance Centre (MPC), including a consortium of Expert Support Laboratories (ESL). This publication focuses on the Sentinel-2 Level-1 product quality validation activities performed by the MPC. It presents an up-to-date status of the Level-1 mission performances at the beginning of the constellation routine phase. Level-1 performance validations routinely performed cover Level-1 Radiometric Validation (Equalisation Validation, Absolute Radiometry Vicarious Validation, Absolute Radiometry Cross-Mission Validation, Multi-temporal Relative Radiometry Vicarious Validation and SNR Validation), and Level-1 Geometric Validation (Geolocation Uncertainty Validation, Multi-spectral Registration Uncertainty Validation and Multi-temporal Registration Uncertainty Validation). Overall, the Sentinel-2 mission is proving very successful in terms of product quality thereby fulfilling the promises of the Copernicus program.

Sentinel-4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus Defence and Space under ESA contract in the frame of the joint EU/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate applications – hence the motto of Sentinel-4 “Knowing what we breathe”. Sentinel-4 will provide accurate measurements of key atmospheric constituents such as ozone, nitrogen dioxide, sulfur dioxide, methane, and aerosol properties over Europe and adjacent regions from a geostationary orbit (see Fig. 1). In the family of already flown UVN spectrometers (SCIAMACHY, OMI, GOME and GOME 2) and of those spectrometers currently under development (Sentinel-5p and Sentinel-5), Sentinel-4 is unique in being the first geostationary UVN mission. Furthermore, thanks to its 60-minutes repeat cycle measurements and high spatial resolution (8x8 km2), Sentinel-4 will increase the frequency of cloud-free observations, which is necessary to assess troposphere variability. Two identical Sentinel-4 instruments (PFM and FM-2) will be embarked, as Customer Furnished Item (CFI), fully verified, qualified and calibrated respectively onto two EUMETSAT satellites: Meteosat Third Generation-Sounder 1 and 2 (MTG-S1 and MTG-S2), whose Flight Acceptance Reviews are presently planned respectively in Q4 2021 and Q1 2030. This paper gives an overview of the Sentinel-4 system1 architecture, its design and development status, current performances and the key technological challenges.

The Sentinel-5 instrument is currently under development by a consortium led by Airbus Defence and Space in the frame of the European Union Copernicus program. It is a customer furnished item to the MetOp Second Generation satellite platform, which will provide operational meteorological data for the coming decades. Mission objective of the Sentinel-5 is to monitor the composition of the Earth atmosphere for Copernicus Atmosphere Services by taking measurements of trace gases and aerosols impacting air quality and climate with high resolution and daily global coverage. Therefore the Sentinel-5 provides five dispersive spectrometers covering the UV-VIS (270…500 nm), NIR (685 …773 nm) and SWIR (1590…1675 and 2305…2385 nm) spectral bands with resolutions ≤1nm. Spatially the Sentinel-5 provides a 108° field of view with a ground sampling of 7.5 x 7 km² at Nadir. The development program is post PDR and the build-up of the industrial team is finalised. We report on the instrument architecture and design derived from the driving requirements, the predicted instrument performance, and the general status of the program.

We present a new mission concept, referred to as StereoSAR, with as primary aim to measure ocean surface currents at sub-mesoscales. To improve our understanding of the role surface currents play in a large variety of geophysical processes the mission will gather global measurements with high spatial and temporal resolution. A multi-static configuration based on a receive-only C-band dual polarimetric Synthetic Aperture Radar system working in synergy with Sentinel-1 is proposed. The Doppler Centroid Anomaly technique is used in order to measure Total Surface Current Velocity vectors by combining the mono-static observation and the squinted bi-static one. Simultaneous retrieval of Ocean Surface Wind Vectors and Ocean Swell Spectra is also performed. This paper presents an overview of the proposed mission concept and scenario. Some issues specific to multi-static Synthetic Aperture Radar are described and solutions offered. Finally, a preliminary performance assessment of the mission concept is included.

EUMETSAT is conducting the activities for the development of the second generation EUMETSAT Polar System Second Generation (EPS-SG), to replace the current EPS from 2021 onwards and contribute to the Joint Polar System to be set up with NOAA. EPS-SG covers nine observation missions in support of operational meteorology and climate monitoring. The observation missions will be supported by ten instruments that will be carried by a two-satellite system. The Metop Second Generation (Metop-SG) satellites will occupy the same orbit as their Metop predecessors in a Sun synchronous, low earth orbit at 820 km altitude and 09:30 descending equatorial crossing time. The observation missions will be implemented by multi-spectral optical and polarisation imaging, atmospheric sounding in the optical and microwave spectral domains, radio occultation sounding, scatterometry as well as microwave and sub-millimetre-wave imaging. Two polar ground stations will receive global data from both satellites. A network of direct-broadcast reception stations will allow to support a North-Atlantic/European regional mission with high timeliness. Additionally, raw mission data are continuously broadcasted to local users world-wide. Global and regional data will be processed at EUMETSAT into well-calibrated and geo-located sensor data, and further on into geophysical products. All data will be disseminated to users in near-real time and archived in the EUMETSAT Data Centre for later retrieval by users.

We have developed the HydroCube mission concept with a constellation of small satellites to remotely sense Snow Water Equivalent (SWE) and Root Zone Soil Moisture (RZSM). The HydroCube satellites would operate at sun-synchronous 3- day repeat polar orbits with a spatial resolution of about 1-3 Km. The mission goals would be to improve the estimation of terrestrial water storage and weather forecasts. Root-zone soil moisture and snow water storage in land are critical parameters of the water cycle. The HydroCube Signals of Opportunity (SoOp) concept utilizes passive receivers to detect the reflection of strong existing P-band radio signals from geostationary Mobile Use Objective System (MUOS) communication satellites. 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. To address the ionospheric delay at P-band frequencies, the signals from both MUOS bands (360-380 MHz and 250-270 MHz) would be used. We have conducted an analysis to trade off the spatial resolution for a space-based sensor and measurement accuracy. Through modeling analysis, we find that the dual-band MUOS signals would allow estimation of soil moisture and surface roughness together. From the two MUOS frequencies at 260 MHz and 370 MHz, we can retrieve the soil moisture from the reflectivity ratio scaled by wavenumbers using the two P-band frequencies for MUOS. A modeling analysis using layered stratified model has been completed to determine the sensitivity requirements of HydroCube measurements. For mission concept demonstration, a field campaign has been conducted at the Fraser Experimental Forest in Colorado since February 2016. The data acquired has provided support to the HydroCube concept.

Five programs, i.e. ASTER, GOSAT, GCOM-W1, GPM and ALOS-2 are going on in Japanese Earth Observation programs. ASTER has lost its short wave infrared channels. AMSR-E stopped its operation, but it started its operation from Sep. 2012 with slow rotation speed. It finally stopped on December 2015. GCOM-W1 was launched on 18, May, 2012 and is operating well as well as GOSAT. ALOS (Advanced Land Observing Satellite) was successfully launched on 24th Jan. 2006. ALOS carries three instruments, i.e., PRISM (Panchromatic Remote Sensing Instrument for Stereo Mapping), AVNIR-2 (Advanced Visible and Near Infrared Radiometer), and PALSAR (Phased Array L band Synthetic Aperture Radar). Unfortunately, ALOS has stopped its operation on 22nd, April, 2011 by power loss. GOSAT (Greenhouse Gas Observation Satellite) was successfully launched on 29, January, 2009. GOSAT carries 2 instruments, i.e. a green house gas sensor (TANSO-FTS) and a cloud/aerosol imager (TANSO-CAI). The main sensor is a Fourier transform spectrometer (FTS) and covers 0.76 to 15 μm region with 0.2 to 0.5 cm-1 resolution. SMILES (Superconducting Millimeter wave Emission Spectrometer) was launched on September 2009 to ISS and started the observation, but stopped its operation on April 2010. GPM (Global Precipitation Mission) core satellite was launched on Feb. 2014. GPM is a joint project with NASA and carries two instruments. JAXA has developed DPR (Dual frequency Precipitation Radar) which is a follow on of PR on TRMM. ALOS F/O satellites are divided into two satellites, i.e. SAR and optical satellites. The first one of ALOS F/O is called ALOS 2 and carries L-band SAR. It was launched on May 2014. JAXA is planning to launch follow on of optical sensors. It is now called Advanced Optical Satellite and the planned launch date is fiscal 2019. Other future satellites are GCOM-C1 (ADEOS-2 follow on), GOSAT-2 and EarthCare. GCOM-C1 will be launched on 2017 and GOSAT-2 will be launched on fiscal 2018. Another project is EarthCare. It is a joint project with ESA and JAXA is going to provide CPR (Cloud Profiling Radar). EarthCare will be launched on 2019.

The Dual-frequency Precipitation Radar (DPR) on the Global Precipitation Measurement (GPM) core satellite was developed by Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT). The objective of the GPM mission is to observe global precipitation more frequently and accurately. The GPM core satellite is a joint product of National Aeronautics and Space Administration (NASA), JAXA and NICT. NASA developed the satellite bus and the GPM Microwave Imager (GMI), and JAXA and NICT developed the DPR. The inclination of the GPM core satellite is 65 degrees, and the nominal flight altitude is 407 km. The non-sunsynchronous circular orbit is necessary for measuring the diurnal change of rainfall. The DPR consists of two radars, which are Ku-band precipitation radar (KuPR) and Ka-band precipitation radar (KaPR). GPM core observatory was successfully launched by H2A launch vehicle on Feb. 28, 2014. DPR orbital check out was completed in May 2014. DPR products were released to the public on Sep. 2, 2014 and Normal Observation Operation period was started. JAXA is continuing DPR trend monitoring, calibration and validation operations to confirm that DPR keeps its function and performance on orbit. The results of DPR trend monitoring, calibration and validation show that DPR kept its function and performance on orbit during the 3 years and 2 months prime mission period. The DPR Prime mission period was completed in May 2017. The version 5 GPM products were released to the public in 2017. JAXA confirmed that GPM/DPR total system performance and the GPM version 5 products achieved the success criteria and the performance indicators that were defined for the JAXA GPM/DPR mission.

The Global Change Observation Mission (GCOM) aims to establish and demonstrate a global, long-term satelliteobserving system to measure essential geophysical parameters to facilitate understanding the global water circulation and climate change, and eventually contribute to improving future climate projection through a collaborative framework with climate model institutions. GCOM consists of two polar orbiting satellite observing systems, 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. The follower satellite, GCOM-C with Second Generation Global Imager (SGLI), will be launched in Japanese fiscal year 2017. SGLI enables a new generation of operational moderate resolution-imaging capabilities following the legacy of the GLI on ADEOS-II (Advanced Earth Observing Satellite-II) satellite. The SGLI empowers surface and atmospheric measurements related to the carbon cycle and radiation budget, with two radiometers of Visible and Near Infrared Radiometer (VNR) and Infrared Scanning Radiometer (IRS) which perform a wide-band (380nm-12μm) optical observation not only with as wide as 1150-1400km FOV (field of view) but also with as high as 250-500m resolution. Also, polarization and along-track slant view observation are quite characteristic of SGLI, providing the sensor data records for more than 28 standard products and 23 research products including clouds, aerosols, ocean color, vegetation, snow and ice, and other applications. Sensor instrument proto-flight tests including optical characterization tests such as radiometric and geometric were completed, and satellite system proto-flight tests have finished including thermal vacuum, vibration and acoustic test. In this paper, the pre-launch phase instrument characterization of SGLI flight model and status of GCOM-C satellite system flight model along with the overview of them will be described. Especially we focus on the pre-launch geometric and radiometric performance test results, in-orbit calibration activities and methodologies: VNR's on-board calibrator, IRS's on-board calibrator and calibration maneuver, and in-orbit verification plan during a commissioning phase lasting approximately 3 months.

The Japanese Advanced Optical Satellite (called “ALOS-3”) is a successor of the optical mission of the Advanced Land Observing Satellite (ALOS) “DAICHI” (2006-2011). The main objectives of the ALOS-3 project are to take images of the global land area with high GSD (<1 m) and wide swath (>70 km), and build a large image database to prepare for disasters, etc. By extracting the difference before and after the disaster, the situation of the damage would be grasped quickly. ALOS-3 also contribute to maintenance and update of the geospatial information of all over the world. The satellite has capabilities to take stereo images, thus the Digital Surface Model (DSM) of the interested area would also be provided. The data which will be acquired by ALOS-3 is expected to be useful in various social needs. ALOS-3 is scheduled to be launch in FY2020.

Hyperspectral Imager Suite (HISUI) is a next-generation Japanese sensor that will be mounted on Japanese Experiment Module (JEM) of ISS (International Space Station) in 2019 as timeframe. HISUI hyperspectral sensor obtains spectral images of 185 bands with the ground sampling distance of 20x31 meter from the visible to shortwave-infrared wavelength region. The sensor is the follow-on mission of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) in the visible to shortwave infrared region. The critical design review of the instrument was accomplished in 2014. Integration and tests of a Flight Model (FM) of HISUI hyperspectral sensor have been completed in the beginning of 2017. Simultaneously, the development of JEMExternal Facility (EF) Payload system for the instrument is being carried out. The system includes the structure, the thermal control sub-system and the electrical sub-system. The tests results of flight model, such as optical performance, optical distortion and radiometric performance are reported.

Hyperspectral Imager Suite (HISUI) is a Japanese future space-borne hyperspectral instrument being developed by Ministry of Economy, Trade, and Industry (METI). HISUI will be launched in 2019 or later onboard International Space Station (ISS) as platform. HISUI has 185 spectral band from 0.4 to 2.5 μm with 20 by 30 m spatial resolution with swath of 20 km. Swath is limited as such, however observations in continental scale area are requested in HISUI mission lifetime of three years. Therefore we are developing a scheduling algorithm to generate effective observation plans. HISUI scheduling algorithm is to generate observation plans automatically based on platform orbit, observation area maps (we say DAR; “Data Acquisition Request” in HISUI project), their priorities, and available resources and limitation of HISUI system such as instrument operation time per orbit and data transfer capability. Then next we need to set adequate DAR before start of HISUI observation, because years of observations are needed to cover continental scale wide area that is difficult to change after the mission started. To address these issues, we have developed observation simulator. The simulator’s critical inputs are DAR and the ISS’s orbit, HISUI limitations in observation minutes per orbit, data storage and past cloud coverage data for term of HISUI observations (3 years). Then the outputs of simulator are coverage map of each day. Areas with cloud free image are accumulated for the term of observation up to three years. We have successfully tested the simulator and tentative DAR and found that it is possible to estimate coverage for each of requests for the mission lifetime.

Landsat-9, the next in the series of Landsat satellites, will have the same complement of two sensors as Landsat-8: The Operational Land Imager (OLI) that covers the reflective solar part of the spectrum in 9 spectral bands and the Thermal Infrared Sensor (TIRS) with two bands in the thermal infrared region. The main changes to the sensors for Landsat-9 will be to increase redundancy in the TIRS instrument, called TIRS-2, to bring it up to a five year design lifetime and fixes for anomalies observed on-orbit on Landsat-8 TIRS: Stray light and scene select mechanism encoder degradation. This work reports on the multi-pronged approach that will be used to ensure that stray light is reduced to required levels and properly characterized. Baffles to reduce stray light were designed and tested at several stages of sensor development. In parallel, optical modeling by NASA and independent teams was used to predict performance of the design changes to hold against test results as well as Landsat 8 TIRS on-orbit performance for model validation. A new subsystem-level test allows a large angular range to be tested to characterize out-of-field stray light that was not available during the first TIRS build. Combined, characterization results from modeling and ambient-, component-, subsystem-, and instrument-level testing will fully characterize TIRS-2 performance.

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) spacecraft has been on orbit for more than five years. It has been scheduled to view the moon approximately monthly since its nadir door open on November 21, 2011. The scheduled lunar observations have been used to monitor the VIIRS reflective solar bands (RSB) on-orbit gain changes. The VIIRS RSB are primarily calibrated by an onboard Solar Diffuser (SD) panel and an accompanying Solar Diffuser Stability Monitor (SDSM). Due to non-uniformity of the SD degradation, the SD/SDSM calibration may have non-negligible errors, especially for the short wavelength bands. Since lunar surface is very stable, the Moon can be used to provide more reliable on-orbit long-term gain changes of the RSB. The RSB calibration coefficients derived from the lunar calibration are generally consistent with those derived from the SD/SDSM calibration, but clear differences in trend are seen, especially for the short wavelength bands.

In the frame of the Copernicus program of the European Commission, Sentinel-2 is a constellation of 2 satellites on a polar sun-synchronous orbit with a revisit time of 5 days (with both satellites), a high field of view - 290km, 13 spectral bands in visible and shortwave infrared, and high spatial resolution - 10m, 20m and 60m. The Sentinel-2 mission offers a global coverage over terrestrial surfaces. The satellites acquire systematically terrestrial surfaces under the same viewing conditions in order to have temporal images stacks. The first satellite was launched in June 2015 and the second in March 2017. In cooperation with the European Space Agency (ESA), the French space agency (CNES) is in charge of the image quality of the project, and so ensured the CAL/VAL commissioning phase during the months following the launch. This cooperation is also extended to routine phase as CNES supports European Space Research Institute (ESRIN) and the Sentinel-2 Mission performance Centre (MPC) for validation in geometric and radiometric image quality aspects, and in Sentinel-2 Global Reference Image (GRI) geolocation performance assessment. This paper points on geometric image quality on Sentinel-2B commissioning phase. It relates to the methods and the performances obtained, as well as the comparison between S2A and S2B. This deals with geolocation and multispectral registration. A small focus is also done on the Sentinel-2 GRI which is a set of S2A images at 10m resolution covering the whole world with a good and consistent geolocation. This ground reference leads to ensure an accurate multi-temporal registration -on refined Sentinel-2 products over GRI- which is also presented in this paper.

Satellite multi-detector cross-track scanners, such as MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible-Infrared Imaging Radiometer Suite), require synchronization of optical and orbital characteristics to avoid gaps in Earth coverage between scans. Prelaunch tests have revealed that such scan-to-scan gaps will occur near nadir in VIIRS observations from the future JPSS-1 (Joint Polar Satellite System) and JPSS-2 satellites. Our analysis of VIIRS geolocation products shows that the gaps do not occur for the instrument currently on orbit onboard the S-NPP (Suomi National Polar-orbiting Partnership) spacecraft. When the same analysis is applied to the MODIS data products, it reveals that small, near-nadir gaps exist in MODIS observations from both Aqua and Terra satellites. Although magnitude of the MODIS scan overlap gaps (up to 100 m for Terra and 25/175 m for Aqua) is quite small in comparison to the 1-km pixels, it is rather significant for the bands with the 250-m and 500-m pixels. Despite the size of the gaps, it appears that their effects on scientific analyses (e.g., NDVI) have not been reported since launch of the MODIS instruments. Because the gaps currently predicted for the JPSS-1 and -2 VIIRS are similar in size to the ones occurring for MODIS, one can expect that their effects on science data will be similarly negligible. A model that uses S-NPP orbit data as well as the S-NPP VIIRS telescope’s focal length and scan rate predicts the overlap that agrees very well with the analysis of the geolocation data. For JPSS-1/-2 VIIRS focal length and scan rate, the model predicts scan overlap gaps of more than 100 m. With a shorter focal length and a faster scan rate than for the JPSS-1/-2 VIIRS, the scan overlap gaps are expected to be avoided altogether for VIIRS on the future JPSS-3 and -4 satellites.

The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the key sensors among a suite of remote sensing instruments on board the Terra and Aqua spacecrafts. Since the beginning of each mission, regularly scheduled lunar observations have been used in order to track the on-orbit gain changes of the reflective solar bands. However, for the short-wave infrared bands, 5-7 and 26, the measured signal is contaminated by both electronic crosstalk and an out-of-band response due to transmission through the MODIS filters at undesired wavelengths. These contaminating signals cause significant oscillations in the derived gain from lunar observations for these bands, which limits their use in determining the scan mirror response versus scan angle at these wavelengths. In this paper, we show a strategy for correcting the electronic crosstalk contamination using lunar observations, where the magnitude and the source of the contaminating signal is clear. For Aqua MODIS, we find that the magnitude of the electronic crosstalk contamination is small, and the lunar calibration remains relatively unaffected. For Terra MODIS, the contamination is more significant, and the electronic crosstalk correction shows a significant reduction in the oscillations of the lunar calibration results.

Signatures of electronic crosstalk contamination are clearly seen in Aqua MODIS Moon images from bands 20 to 30 (1.375 and 3.75 - 9.73 μm). Electronic crosstalk can potentially impact L1B products, causing image artifacts such as striping and radiometric bias, the severity of which will depend on the amount of signal leaked, how it compares to the flux levels in the receiving image, and on the ability of the calibration in absorbing the contamination. In this paper, we address two distinct manifestations of electronic crosstalk contamination seen in Aqua MODIS lunar images that we call the simple and complex ghosts. The simple ghosts appear in lunar images from bands 20 to 30, affect detector 1 only, and each ghost is caused by signal leak from one sending detector only. The complex ghosts form negative regions in Aqua MODIS lunar images from bands 27 to 30 and are caused by multiple sending detectors and bands. We map the crosstalk signatures back to their respective sending bands/detectors, by determining the displacement between the main lunar image and the crosstalk ghosts. We assume the contaminating signal is proportional to the signal of the sending band/detector and derive linear crosstalk coefficients for the simple ghosts in bands 20 to 26 and 28 to 30 and for the complex ghosts in band 29 for the entire mission. The linear crosstalk coefficients can then be applied in the correction of L1A Earth and calibration data that will generate corrected L1B images from which we can assess the impact the contamination has on the L1B product.

It has been found that there is severe electronic noise in the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) bands 27-30 which corresponds to wavelengths ranging between 6.7 μm to 9.73 μm. The cause for the issue has been identified to be crosstalk, which is significantly amplified since 2010 due to severe degradation in the electronic circuitry. The crosstalk effect causes unexpected discontinuity/change in the calibration coefficients and induces strong striping artifacts in the earth view (EV) images. Also it is noticed, that there are large long-term drifts in the EV brightness temperature (BT) in these bands. An algorithm using a linear approximation derived from on-orbit lunar observations has been developed to correct the crosstalk effect for them. It was demonstrated that the crosstalk correction can remarkably minimize the discontinuity/change in the calibration coefficients, substantially reduce the striping in the EV images, and significantly remove the long-term drift in the EV BT in all these bands. In this paper, we present the recent progresses in the crosstalk effect analysis and its mitigation. In addition, we will show that besides these four bands, the TEBs in Aqua MODIS and Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite also have significant crosstalk contaminations. Further, it will be demonstrated that the crosstalk correction algorithm we developed can be successfully applied to all the contaminated TEBs to significantly reduce the crosstalk effects and substantially improve both the image quality and the radiometric accuracy of Level-1B (L1B) products for the bands.

The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite is a passive scanning radiometer and an imager. The VIIRS regularly performs on-orbit radiometric calibration of its reflective solar bands (RSBs) through observing an onboard sunlit solar diffuser (SD). The reflectance of the SD changes over time and the change is denoted as the SD bidirectional reflectance distribution function degradation factor. The degradation factor, measured by an onboard solar diffuser stability monitor, has been shown to be both incident sunlight and outgoing direction dependent. In this Proceeding, we investigate the factor’s dependence on SD position. We develop a model to relate the SD degradation factor with the amount of solar exposure. We use Earth measurements to evaluate the effectiveness of the model.

Terra and Aqua MODIS instruments have continued to operate normally since their launch in December 1999 and May 2002. MODIS reflective solar bands (RSB) with wavelengths ranging from 0.41 to 2.3 μm are calibrated on-orbit by an on-board solar diffuser (SD) and a solar diffuser stability monitor (SDSM). In addition, a spectroradiometric calibration assembly (SRCA) is used regularly to characterize and track on-orbit changes in RSB spectral, spatial, and radiometric performance. On a near-monthly basis, lunar observations are scheduled and performed to support sensor on-orbit calibration and characterization, such as radiometric calibration stability monitoring for the RSB. This paper provides a brief review of MODIS design requirements related to its RSB calibration performance and an assessment of MODIS RSB on-orbit calibration stability on both the short- and long-term timescales. Examples from different approaches are presented to demonstrate on-orbit performance of MODIS RSB calibration stability.

The new 3rd generation geostationary (GEO) imagers will have many of the same NPP-VIIRS imager spectral bands, thereby offering the opportunity to apply the VIIRS cloud, aerosol, and land use retrieval algorithms on the new GEO imager measurements. Climate quality retrievals require multi-channel calibrated radiances that are stable over time. The deep convective cloud calibration technique (DCCT) is a large ensemble statistical technique that assumes that the DCC reflectance is stable over time. Because DCC are found in sufficient numbers across all GEO domains, they provide a uniform calibration stability evaluation across the GEO constellation. The baseline DCCT has been successful in calibrating visible and near-infrared channels. However, for shortwave infrared (SWIR) channels the DCCT is not as effective to monitor radiometric stability. The DCCT was optimized as a function wavelength in this paper. For SWIR bands, the greatest reduction of the DCC response trend standard error was achieved through deseasonalization. This is effective because the DCC reflectance exhibits small regional seasonal cycles that can be characterized on a monthly basis. On the other hand, the inter-annually variability in DCC response was found to be extremely small. The Met-9 0.65-μm channel DCC response was found to have a 3% seasonal cycle. Deseasonalization reduced the trend standard error from 1% to 0.4%. For the NPP-VIIRS SWIR bands, deseasonalization reduced the trend standard error by more than half. All VIIRS SWIR band trend standard errors were less than 1%. The DCCT should be able to monitor the stability of all GEO imager solar reflective bands across the tropical domain with the same uniform accuracy.

The Radiometric Calibration Network (RadCalNet, www.radcalnet.org) routinely provides top-of-atmosphere (TOA) reflectance data from instrumented ground sites. The data represents the nadir view of the ground for different sites that cover areas ranging from 50 m × 50 m to 1 km x 1 km. The smaller sites can only be used with high resolution sensors (≤ 30 m), but the larger sites, such as Railroad Valley (RRV) in Nevada can also be used for the validation or vicarious calibration of medium resolution sensors (> 250 m spatial resolution). Prior to utilising RadCalNet data in this manner, this paper describes the application of a high and a medium resolution sensor to assess potential biases between the RadCalNet data and satellite data at two different spatial resolutions. Results are shown for initial comparisons over RRV for the high resolution Sentinel-2 MultiSpectral Instrument (S2-MSI) and the medium resolution Sentinel-3 Ocean and Land Colour Instrument (S3-OLCI), and indicate the potential for RadCalNet to validate and vicariously calibrate sensors with differing spatial resolutions. The comparison analysis includes taking into account the temporal differences between the Sentinel-2 and Sentinel-3 overpasses and the time of RadCalNet data collection, as well as the spectral response functions (SRF) of the bands for both instruments. The comparison against the RRV site has shown there are significant biases between the RadCalNet data and S2-MSI and S3-OLCI for non-nadir viewing geometries that may be due to directional viewing and illumination effects and the non-Lambertian character of the RadCalNet RRV site.

The Radiometric Calibration Network (RadCalNet, www.radcalnet.org) routinely brings together data from several instrumented ground sites to provide users with top-of-atmosphere (TOA) reflectance data. These data are provided on cloud free days between 09:00 and 15:00 for the spectral range 400 to 1000 nm (and up to 2500 nm depending on available instrumentation) at a 10 nm spectral resolution. The data represents the nadir view of the ground. A key aspect to RadCalNet is a strict adherence to SI-traceability leading to well-understood and defensible uncertainty analysis to ensure that the different sites operating within RadCalNet are consistent with one another. This process includes the requirement to validate uncertainty analyses. One way in which this can be achieved is through field-based comparisons between independently measured reflectance of the ground and the RadCalNet data product for that date / time. To test the potential of such comparisons for uncertainty validation, a comparison campaign has been un- dertaken by the UK’s National Physical Laboratory (NPL) with the University of Arizona (UA) in March 2017 at the Railroad Valley radiometric test site in Nevada, USA using instruments developed for the purpose by UA and the Czech Metrology Institute (CMI). The measurements taken at the site with a new instrument, the Multispectral Transfer Radiometer (MuSTR) have been compared against the RadCalNet bottom-of-atmosphere (BOA) dataset to determine the equivalence of the reflectance. Radiances from MuSTR have also been compared against radiance measurements from the in-situ instrumentation at the site using a 48 % reflectance tarpaulin as a target. The comparisons presented here have demonstrated the utility of field-based comparisons for RadCalNet. In addition, a potential methodology for these comparisons has been developed and potential areas for improvement, including the systematic development of field-based uncertainty analyses, have been identified.

The Moderate-Resolution Imaging Spectroradiometer (MODIS), launched in 1999 on Terra and 2002 on Aqua spacecraft respectively, is a scanning radiometer that covers a wavelength range from 0.4 μm to 14.4 μm and scans the Earth over an angular range from -55° to +55°. After a few years in the Terra mission, it became extremely challenging to characterize the changes in the sensor gain and response versus scan angle (RVS) at short wavelengths due to significant degradation and increased polarization sensitivity. To better characterize the system-level degradation, the MODIS Characterization Support Team (MCST) developed an enhanced approach in Collection-6 (C6) L1B algorithm by supplementing the on-board calibration data with the Earth-scene response trends at various scan angles obtained from the pseudo-invariant desert sites. However, the trends at short wavelengths experienced significant impact due to the increased polarization sensitivity, especially at the end of scan. In this study, a polarization correction algorithm developed by MCST is applied to the Terra MODIS RSB response trends obtained from the desert sites. The trends after polarization correction are used to derive the gain and RVS based on the existing MODIS C6 calibration algorithm. Impact of the polarization correction is examined for gain, RVS and their fitting uncertainties over the entire mission. The results of this study provide useful information on how to further improve accuracy and stability of the calibrated L1B product.

Safran is presenting two concepts of optical payloads for microsatellites combining high performances and extremely compact volume. The first one offer 10-m Ground Sampling Distance (GSD) over 60x40 km² area from 600 km orbit optimized for twilight conditions. The second one is offering a much higher resolution of 1.8-m over 11x7,5 km² area from the same 600 km orbit. The two concepts are based on advanced innovative diffraction limited optical system packaged in a unique very compact volume lower than 8U = 200x200x200 mm making them the ideal solution for 15- 100 kg microsatellites. The maximum number of pixels is served to the end-user space imagery community thanks to 35 mm Full Frame sensors offering, as of today, 6000x4000 pixels. Up to 10 spectral bands from 475 to 900 nm can be offered thanks to 2D structured filters.

Sentinel-5/UVNS 1 is an Earth observation spectrometer system that is operating in nadir looking push broom mode from a low Earth orbit. While having a wide across-track field of view (≈ 2700 km) it covers approximately 7 km at nadir in flight direction during one dwell. However a high contrast in the scene in along track may lead to disturbance of the Instrument Spectral Response Function (ISRF) and with this a variation of measured spectrum. In order to reduce the effect of scene contrast along track, instead of a spectrometer slit two mirrors are introduced, in between which the light path is extended such as a one dimensional wave guide. The entrance length across track however is wide enough to let light pass unchanged. This new concept is called Slit Homogenizer (SH) within theSentinel-5 project. The entrance of the SH is placed on the image plane of the preceding op- tics. The exit of the SH represents the object plane of the subsequent spectrometer in the along track (spectral) direction. This article proposes a simulation model of a SH together with a preced- ing generic optics based on scalar diffraction theory. The model is used to evaluate quantitatively the homogenizing ability of the device. Some parameters in the discussed examples are taken from Sentinel-5/UVNS instrument but the model and its application is not limited to that mission.

The Visible/Infrared Imaging Radiometer Suite (VIIRS) is the NOAA operational follow-on to the Moderate Resolution Imaging Spectrometer on NASA’s Earth Observing System. VIIRS operates on the Joint Polar-orbiting Satellite System which is the now current NOAA low-earth orbit operational Meteorological Satellite system. The VIIRS has Moderate (750 m nadir resolution) and Imaging (375 m nadir resolution) bands, as well as a band with large dynamic range that operates as a 750 m resolution, full swath imaging band in both day and night viewing conditions. This presentation will look at one specific M-band centered at 680 nm and one I-band centered at 640 nm which are nested spectrally, but for which the I-band has an 80 nm bandwidth and the M-band has a 20 nm bandwidth. We will show that an additional band of 60 nm (centered at 630 nm) may be synthesized from these two bands because the trailing edges of the spectral response of these two bands are nearly identical. The synthetic band will have lower radiometric accuracy and is considered most useful for diagnostic rather than specific quantitative objectives. Potential guidelines for the use of this synthetic band are provided also. A coarse uncertainty budget is shown that provides the uncertainty sources unique to the synthetic band, which are in addition to the uncertainties of the input bands. The concept of constructing a synthetic spectral band in this manner is considered an appropriate remote sensing concept only in the context of spectro-radiometric calibration approaches when tunable laser-source, absolute detector based calibrations are provided due to the enhanced calibrations with this class of standard devices. Traditional radiometric calibrations using integrating spheres are not considered sufficiently precise or sufficiently accurate to support computations of this nature. This may be thought of as a solution looking for a problem. Then we will show the results of an investigation into applying this solution to the detection of Harmful Algal Blooms (HAB). Laboratory results from the literature are introduced showing that species common to HAB in the Florida USA Gulf Coast have an absorption feature centered near 630 nm. This species is Karenia brevis which is the most common algae in West Florida shelf HABs. HAB outbreaks observed within the 6-year VIIRS dataset will be investigated using this synthesized band to assess the usefulness of this band as another tool for the study of coastal processes.

Principal Component (PC) compression is the method of choice to achieve band-width reduction for dissemination of hyper spectral (HS) satellite measurements and will become increasingly important with the advent of future HS missions (such as IASI-NG and MTG-IRS) with ever higher data-rates. It is a linear transformation defined by a truncated set of the leading eigenvectors of the covariance of the measurements as well as the mean of the measurements. We discuss the strategy for generation of the eigenvectors, based on the operational experience made with IASI. To compute the covariance and mean, a so-called training set of measurements is needed, which ideally should include all relevant spectral features. For the dissemination of IASI PC scores a global static training set consisting of a large sample of measured spectra covering all seasons and all regions is used. This training set was updated once after the start of the dissemination of IASI PC scores in April 2010 by adding spectra from the 2010 Russian wildfires, in which spectral features not captured by the previous training set were identified. An alternative approach, which has sometimes been proposed, is to compute the eigenvectors on the fly from a local training set, for example consisting of all measurements in the current processing granule. It might naively be thought that this local approach would improve the compression rate by reducing the number of PC scores needed to represent the measurements within each granule. This false belief is apparently confirmed, if the reconstruction scores (root mean square of the reconstruction residuals) is used as the sole criteria for choosing the number of PC scores to retain, which would overlook the fact that the decrease in reconstruction score (for the same number of PCs) is achieved only by the retention of an increased amount of random noise. We demonstrate that the local eigenvectors retain a higher amount of noise and a lower amount of atmospheric signal than global eigenvectors. Local eigenvectors do not increase the compression rate, but increase the amount of atmospheric loss and should be avoided. Only extremely rare situations, resulting in spectra with features which have not been observed previously, can lead to problems for the global approach. To cope with such situations we investigate a hybrid approach, which first apply the global eigenvectors and then apply local compression to the residuals in order to identify and disseminate in addition any directions in the local signal, which are orthogonal to the subspace spanned by the global eigenvectors.

In this paper we describe the characteristics and performances of a monolithic sensor designed for low frequency motion measurement of spacecrafts and satellites, whose mechanics is based on the UNISA Folded Pendulum. 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 introduce and discuss the general methodology used to extend the application of ground-based folded pendulums to space, also in total absence of gravity, still keeping all their peculiar features and characteristics.

The METimage instrument is part of the EPS-SG (EUMETSAT Polar System Second Generation) program. It will be situated on the MetOp-SG platform which in operation has an objective of collecting data for meteorology and climate monitoring as well as their forecasting. Teledyne e2v has developed and characterised the CMOS VISNIR detector flight module part of the METimage instrument. This paper will focus on the silicon results obtained from the CMOS VISNIR detector flight model. The detector is a large multi-linear device composed of 7 spectral bands covering a wavelength range from 428 nm to 923 nm (some bands are placed twice and added together to enhance the signal-to-noise performance). This detector uses a 4T pixel, with a size of 250μm square, presenting challenges to achieve good charge transfer efficiency with high conversion factor and good linearity for signal levels up to 2M electrons and with high line rates. Low noise has been achieved using correlated double sampling to suppress the read-out noise and give a maximum dynamic range that is significantly larger than in standard commercial devices. The photodiode occupies a significant fraction of the large pixel area. This makes it possible to meet the detection efficiency when front illuminated. A thicker than standard epitaxial silicon is used to improve NIR response. However, the dielectric stack on top of the sensor produces Fabry-Perot étalon effects, which are problematic for narrow band illumination as this causes the detection efficiency to vary significantly over a small wavelength range. In order to reduce this effect and to meet the specification, the silicon manufacturing process has been modified. The flight model will have black coating deposited between each spectral channel, onto the active silicon regions.

In recent years the European Space Agency (ESA) has been pursuing studies dedicated to Earth imaging from space in the Long Wave Infrared region for applications ranging from monitoring of evapotranspiration, and water resources management to the development of urban heat island and monitoring of high temperature events. Among the various solutions being studied is also that of a low cost instrument with moderate needs in terms of resources. . One potential enabler for such type of mission could be the technology of microbolometer detectors. The latest generation of microbolometer arrays now available offer large formats (XGA) and small pixel sizes which are favourable for keeping the instrument size within reasonable limit while addressing larger swath compared to VGA format. A major concern however, in using commercial microbolometers in space is their ability to sustain the radiation environment of space but also the harsh mechanical environments. COTS microbolometers are potentially susceptible to SEE (single even effects) because of the use of commercial CMOS technology/libraries and no implementation of specific design rules (i.e. space tailored rad hardened). In the past, and in the context of their national program, CNES has performed a space evaluation of COTS microbolometer arrays of 640x480 with 25 μm pitch[3]. Despite successful gamma irradiations and vibration tests; degradation of the ROIC has been evidenced during the heavy ions tests, which makes the full qualification of COTS microbolometers for future space programmes mandatory. Similar tests have been performed on an even earlier device (384x288 with a pitch of 35 μm) under the ESA EarthCARE programme[2]. ESA and Thales Alenia Space have recently run an activity with the objective to validate a third-generation COTS microbolometer offered by ULIS (France) against the relevant environment for a candidate Thermal InfraRed (TIR) space mission. The micro-bolometer selected is the PICO 1024E[1], which offers 1024x768 pixels of size 17 μm square. The validation sequence included the main types of irradiation tests required by a space application as well as vibration and shock tests. Ageing tests are included and synergetic effects are also investigated. The detector performances were tested before, after and during any test sequence. In this paper, the results of this activity achieved in the beginning of 2017 are reported.

CdTe and CZT materials are technologies for gamma and x-ray imaging for applications in industry, homeland security, defense, space, medical, and astrophysics. There remain challenges in uniformity over large detector areas (50~75 mm) due to a combination of material purity, handling, growth process, grown in defects, doping/compensation, and metal contacts/surface states. The influence of these various factors has yet to be explored at the large substrate level required for devices with higher resolution both spatially and spectroscopically. In this study, we looked at how the crystal growth processes affect the size and density distributions of microscopic Te inclusion defects. We were able to grow single crystals as large as 75 mm in diameter and spatially characterize three-dimensional defects and map the uniformity using IR microscopy. We report on the pattern of observed defects within wafers and its relation to instabilities at the crystal growth interface.

It is more difficult and challenging to implement Nano-satellite (NanoSat) based optical Earth observation missions than conventional satellites because of the limitation of volume, weight and power consumption. In general, an image compression unit is a necessary onboard module to save data transmission bandwidth and disk space. The image compression unit can get rid of redundant information of those captured images. In this paper, a new image acquisition framework is proposed for NanoSat based optical Earth observation applications. The entire process of image acquisition and compression unit can be integrated in the photo detector array chip, that is, the output data of the chip is already compressed. That is to say, extra image compression unit is no longer needed; therefore, the power, volume, and weight of the common onboard image compression units consumed can be largely saved. The advantages of the proposed framework are: the image acquisition and image compression are combined into a single step; it can be easily built in CMOS architecture; quick view can be provided without reconstruction in the framework; Given a certain compression ratio, the reconstructed image quality is much better than those CS based methods. The framework holds promise to be widely used in the future.

Satellite telemetry is the vital indicators to estimate the performance of the satellite. The telemetry data, the threshold range and the variation tendency collected during the whole operational life of the satellite, can guide and evaluate the subsequent design of the satellite in the future. The rotational parts on the satellite (e.g. solar arrays, antennas and oscillating mirrors) affect collecting the solar energy and the other functions of the satellite. Visualization telemetries (pictures, video) are captured to interpret the status of the satellite qualitatively in real time as an important supplement for troubleshooting. The mature technology of commercial off-the-shelf (COTS) products have obvious advantages in terms of the design of construction, electronics, interfaces and image processing. Also considering the weight, power consumption, and cost, it can be directly used in our application or can be adopted for secondary development. In this paper, characteristic simulations of solar arrays radiation in orbit are presented, and a suitable camera module of certain commercial smartphone is adopted after the precise calculation and the product selection process. Considering the advantages of the COTS devices, which can solve both the fundamental and complicated satellite problems, this technique proposed is innovative to the project implementation in the future.

The possibilities of the Raman method of radiocarbon measurements in the field of gas analysis are investigated. With the help of veneer gas mixtures of carbon monoxide, carbon dioxide-12, carbon dioxide-13, methane, formaldehyde, the micrometric characteristics of Raman lidars were found, which in most cases coincided with the claimed ones. When gas mixtures are supplied, the diluent gas in which differs from air, the broadening of the spectral lines associated with the interactions between the particles, the results, to significant errors in the measured concentration. These effects, which negate the advantages of the measurement method, are investigated in the framework of this paper. The results of determining the coefficients for correcting the readings of gas analyzers with the achievement of inaccuracies from various diluent gases, as well as the data of the prototype Raman lidar.

The super-resolution imager based on the coded aperture is a novelty technology. It breaks the constraints of conventional optical imager in techniques and principles. The spatial resolution of the optical system is increased 1-fold than the conventional system. In this paper, we have studied and analyzed the principle of super-resolution imager based on coded aperture. We can add a high robust coded aperture in the stereotyped low-resolution camera to achieve improvement of the original camera image resolution. In order to fully prove the advantages, we have designed a complete and easy-to-experiment optical system based on the principle of the system.The Optical system focal length is 90mm. It is coaxial optical path and its total length is 538.5mm. The MTF value is near the diffraction limit at 56lp / mm. We can obtain good quality images by the system.Laboratory experiments verify that the spatial resolution of the optical system is 1 times higher than that of the conventional ones.

Electro-Optical design of a push-broom space camera for a Low Earth Orbit (LEO) remote sensing satellite is performed based on the noise analysis of TDI sensors for very high GSDs and low light level missions. It is well demonstrated that the CCD TDI mode of operation provides increased photosensitivity relative to a linear CCD array, without the sacrifice of spatial resolution. However, for satellite imaging, in order to utilize the advantages which the TDI mode of operation offers, attention should be given to the parameters which affect the image quality of TDI sensors such as jitters, vibrations, noises and etc. A predefined TDI stages may not properly satisfy image quality requirement of the satellite camera. Furthermore, in order to use the whole dynamic range of the sensor, imager must be capable to set the TDI stages in every shots based on the affecting parameters. This paper deals with the optimal estimation and setting the stages based on tradeoffs among MTF, noises and SNR. On-board SNR estimation is simulated using the atmosphere analysis based on the MODTRAN algorithm in PcModWin software. According to the noises models, we have proposed a formulation to estimate TDI stages in such a way to satisfy the system SNR requirement. On the other hand, MTF requirement must be satisfy in the same manner. A proper combination of both parameters will guaranty the full dynamic range usage along with the high SNR and image quality.

Accuracy assessment of the satellite remote sensing depends on the angular attitude estimation precision. The 1 arc second error in attitude estimation causes 2.5-meter error in the accuracy derived from remote sensing data for the 500 km orbit. Different kind of momentum wheels, propulsions and sensors help correct spacecraft torque moment to stabilize it in the orbit. Star tracker is the most precise optical sensor for spacecraft angular attitude estimation. An onboard guide star catalog containing data for star pattern identification is essential for star tracker operating. The total number of stars, the faintest stellar magnitude, completeness and uniformity are the key specifications of a star catalog influencing many characteristic of a star tracker. The steps of creating guide star catalog are: instrumental stellar magnitude estimation with respect to the star tracker spectral response, clusterization of nearby stars, removing of unreliable stars and final star selection. An iterative algorithm for thinning down the catalog allows reducing appreciably the number of stars in the catalog and improving its uniformity. The key point of the algorithm is the lower bound evaluation of star number in the FOV (field of view) for every boresight position within a triangle area. The algorithm uses recursive quaternary division of the icosahedron for the celestial sphere tessellation. The correction methods of stellar aberration and star proper motion are discussed as well.

The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key scientific instrument that was launched into Earth orbit by NASA in 1999 on board the Terra (EOS AM) satellite and in 2002 on board the Aqua (EOS PM) satellite. Terra and Aqua MODIS collect the entire Earth’s images every 1 to 2 days in 36 spectral bands. MODIS band 1 (0.620- 0.670 μm) and band 2 (0.841-0.876 μm) have nadir spatial resolution of 250 m and their measurements are crucial to derive key land surface products. This study evaluates the performance of the Collection 6 (C6, and C6.1) L1B of both Terra and Aqua MODIS bands 1 and 2 using Simultaneous Nadir Overpass (SNO) data to compare with AVHRR/3 sensors. We examine the relative stability between Terra and Aqua MODIS in reference to NOAA N15 and N19 the Advanced Very High Resolution Radiometer (AVHRR/3). The comparisons for MODIS to AVHRR/3 are over a fifteenyear period from 2002 to 2017. Results from this study provide a quantitative assessment of Terra and Aqua MODIS band 1 and band 2 calibration stability and the relative differences through the NOAA N15 and N19 AVHRR/3 sensors.

We propose a concept of an imaging near-IR spectrometer for sensing of planetary surfaces. This instrument is intended to analyze mineralogical and, in some cases, petrographic composition of the upper surface layer in the planetary regolith; to identify and monitor OH/H2O bearing minerals and water adsorption in this layer. The scheme of the spectrometer was designed on a basis of an acousto-optic tunable filter (AOTF) that allows imaging of samples in two orthogonal polarization planes simultaneously. Images are registered as a light (e.g. solar one) reflected and scattered from an observed target in the near infrared spectral range. The AOTF’s electrical tuning provides fast and flexible spectral scanning of an image through whole the range analyzed – potentially, ten microseconds per a spectral point. Thus, it is possible to explore reflectance spectra of specified areas on a sample and to detect its minerals composition and microstructure variations. In parallel, one can estimate polarization contrast at different wavelengths thanks to the AOTF’s birefringence properties. In this paper we report design and performance of a laboratory prototype for the near-IR spectro-polarimeteric imaging AOTF system operating in the spectral range from 0.8 to 1.75 μm. Reflectance spectra of some minerals were measured with the spectral resolution of 100 cm^-1 (passband 10 nm at 1 μm). When imaging samples the spatial resolution as high as 0.5 mm was reached at the target distance of one meter. It corresponds to 100 by 100 resolving elements on the CCD matrix for each of two polarizations of the reflected light. Such a concept is also being designed for the spectral range from 1.7 to 3.5 μm.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra spacecraft is one of the key instruments in NASA's Earth Observing System. Since 2000, MODIS has collected continuous data in 36 spectral bands ranging in wavelength between 0.4 μm and 14.2 μm. Since before launch, signal contamination in the form of electronic crosstalk has been observed in many of the MODIS thermal emissive bands, particularly for bands 27-30, a correction for which has been applied to the current Collection 6 algorithm. The mid-wave infrared bands in Terra MODIS, 20-25, also show signs of electronic crosstalk contamination, which can be seen clearly during observations of the Moon. In this paper, we'll present an impact assessment of electronic crosstalk on the mid-wave infrared bands in Terra MODIS. We will also derive correction coefficients from the lunar observations, which can be applied to correct the calibrated radiance in the MODIS Level-1B product. We will provide an analysis of these results and potential improvements to the MODIS Level-1B product.

Calibration is a critical step to ensure data quality and to meet the requirement of quantitative remote sensing in a broad range of scientific applications. One of the least expensive and increasingly popular methods of on-orbit calibration is the use of pseudo invariant calibration sites (PICS). A spatial homogenous and temporally stable area of 34 km2 in size around the center of Kunlun Mountain (KLM) over Tibetan Plateau (TP) was identified by our previous study. The spatial and temporal coefficient of variation (CV) this region was better than 4% for the reflective solar bands. In this study, the BRDF impacts of KLM glacier on MODIS observed TOA reflectance in band 1 (659 nm) are examined. The BRDF impact of KLM glacier with respect to the view zenith angle is studied through using the observations at a fixed solar zenith angle, and the effect with respect to the sun zenith angle is studied based on the observations collected at the same view angle. Then, the two widely used BRDF models are applied to our test data to simulate the variations of TOA reflectance due to the changes in viewing geometry. The first one is Ross-Li model, which has been used to produce the MODIS global BRDF albedo data product. The second one is snow surface BRDF model, which has been used to characterize the bidirectional reflectance of Antarctic snow. Finally, the accuracy and effectiveness of these two different BRDF models are tested through comparing the model of simulated TOA reflectance with the observed one. The results show that variations of the reflectances at a fixed solar zenith angle are close to the lambertian pattern, while those at a fixed sensor zenith angle are strongly anisotropic. A decrease in solar zenith angle from 50º to 20º causes an increase in reflectance by the level of approximated 50%. The snow surface BRDF model performs much better than the Ross-Li BRDF model to re-produce the Bi-Directional Reflectance of KLM glacier. The RMSE of snow surface BRDF model is 3.60%, which is only half of the RMSE when using Ross-Li model.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP (National Polar-orbiting Partnership) satellite has been in operation for over five years. VIIRS has 22 bands with a spectral range from 0.4 μm to 2.2 μm for the reflective solar bands (RSB). The Earth view swath covers a distance of ~3000 km over scan angles of ± 56.0° off nadir. The on-board calibration of the RSB relies on a solar diffuser (SD) located at a fixed scan angle and a solar diffuser stability monitor (SDSM). The response versus scan angle (RVS) was characterized prelaunch in ambient conditions and is currently used to determine the on-orbit response for all scan angles relative to the SD scan angle. Since the RVS is vitally important to the quality of calibrated level 1B products, it is important to monitor its on-orbit stability, particularly at the short wavelengths (blue) where the most degradation occurs. In this study, the RVS stability is examined based on reflectance trends collected at various scan angles over the selected pseudo-invariant desert sites in Northern Africa and the Dome C snow site in Antarctica. These trends are corrected by the site dependent BRDF (bi-directional reflectance function) model to reduce seasonally related fluctuations. The BRDF corrected trends are examined so any systematic drifts in the scan angle direction would indicate a potential change in RVS. The results of this study provide useful information on VIIRS RVS on-orbit stability performance.

The increasingly widespread applications of the Earth observation system information and the rapid development of modern technologies over the past decades have led to the imposition of remote sensing tools and, in particular, of the imaging spectrometers. These trends place high demands on the development and improvement of both the systems themselves and the characterization methods. This paper highlights features that are expected to be considered critical for imaging spectrometer performance: The basic steps for characterization of imaging spectrometer critical characteristics are indicated in the flow diagrams. The characterization methods and correspondence correction procedures are determined and the obtained results are presented.

IASI has 4 different detectors, CrIS has 9, IASI-NG will have 16 and MTG-IRS 25600. There is a clear interest to harmonise the sensor data originating from different detectors, if it can be done be removing the parts of the instrument artefacts, which are not common to all detectors. When IASI spectra are analysed in principal component (PC) score space, differences between the four detectors are clearly observed. These differences are caused by different characteristics and different strengths of the ghost effect among the detectors and although they are small when analysed in radiance space, they can have a distinct negative impact on the use of the data. Considering that a large part of the operationally disseminated IASI PC scores are dominated by instrument artefacts, the partial removal of instrument artefacts is also of interest for data compression purposes. The instrument artefacts can be partly removed by projection onto a subspace common to all detectors. We show how the techniques of canonical angles can be used to compute a set of orthogonal vectors capturing only directions which are close to directions found in the signal spaces of all detectors. This principle can also be applied to detectors on-board different satellites, as we demonstrate with the example of IASI-A and IASI-B. The danger of the method is that a single deficient detector, ’blind’ to one or more directions of the atmo- spheric signal, could potentially ’contaminate’ the data from the other detectors. We discuss how to detect and avoid this problem and check it in practice with CrIS data.

This paper presents a computationally efficient algorithm for attitude estimation of remote a sensing satellite. In this study, gyro, magnetometer, sun sensor and star tracker are used in Extended Kalman Filter (EKF) structure for the purpose of Attitude Determination (AD). However, utilizing all of the measurement data simultaneously in EKF structure increases computational burden. Specifically, assuming n observation vectors, an inverse of a 3n×3n matrix is required for gain calculation. In order to solve this problem, an efficient version of EKF, namely Murrell’s version, is employed. This method utilizes measurements separately at each sampling time for gain computation. Therefore, an inverse of a 3n×3n matrix is replaced by an inverse of a 3×3 matrix for each measurement vector. Moreover, gyro drifts during the time can reduce the pointing accuracy. Therefore, a calibration algorithm is utilized for estimation of the main gyro parameters.

Power Supply is one of the most important subjects in Remote Sensing satellite. Having an appropriate and adequate power resources, A Remote Sensing satellite may utilize more complex Payloads and also make them more operable in orbit and mission timeline. This paper is deals with a design of electrical power supply subsystem (EPS) of a hypothetical satellite with remote sensing mission in Low Earth Orbits, without any restriction on the type and number of Payloads and only assuming a constraint on the total power consumption of them. EPS design is in a way that can supply the platform consumption to support Mission and Payload(s) requirements beside the power consumption of the payload(s). The design is also modular, as it can be used not only for the hypothetical system, but also for the other systems with similar architecture and even more needs on power and differences in some specifications. Therefore, a modularity scope is assumed in design of this subsystem, in order to support the satellite in the circular orbits with altitude of 500 to 700 km and inclination of 98 degrees, a sun-synchronous orbit, where one can say the design is applicable to a large range of remote sensing satellites. Design process will be started by high level and system requirements analysis, continued by choosing the best approach for design and implementation based on system specification and mission. After EPS sizing, the specifications of elements are defined to get the performance needed during operation phases; the blocks and sub-blocks are introduced and details of their design and performance analysis are presented; and the modularity is verified using calculations for the confined area based on design parameters and evaluated by STK software analysis results. All of the process is coded in MATLAB software and comprehensive graphs are generated to demonstrate the capabilities and performance. The code and graphs are developed in such a way to completely review the design procedure and system efficiency in worst case of power consumption scenario at the beginning and end of satellite life