NOAA-21 is the NOAA primary operational polar satellite in the Joint Polar Satellite System (JPSS), plays a crucial role in global environmental monitoring by providing critical data for weather forecasting, climate studies, and environmental management. Ensuring the accuracy and reliability of this data requires rigorous calibration and validation (Cal/Val) processes. This presentation will provide an overview of the NOAA-21 Cal/Val process, status updates, key advancements and outcomes, and lessons learned from the Cal/Val activities for NOAA-21. The recommended Cal/Val process improvements for the future Low Earth Orbit (LEO) missions will also be introduced.

The NISAR Science Payload consists of an L-band SAR instrument (L-SAR) and an S-band SAR instrument (S-SAR) each with their own feed sharing a single 12m reflector. The instrument design, based on “SweepSAR” architecture for wide-swath coverage, is a multi-beam polarimetric system employing on-board time-to-angle digital beam forming to each of the receive channels. The instrument exhibits a few “features” that are not present in the conventional SAR system that utilizes a rectangular phased-array antenna and electronically steering the antenna beam in “ScanSAR” operation mode. The most prominent feature is the large reflector-feed antenna, whose geometry is more susceptible to the on-orbit thermal environment. When the geometry gets changed thermally, the mechanical boresight will be perturbed, and the antenna patterns will be distorted. For NISAR science objectives, the instrument can be used as a repeat-pass interferometer with polarimetric capability; Science imposed a set of “Performance” requirements and a set of “Pointing” requirements on L-SAR and these two sets are inter-related. The large reflector-feed antenna cannot be tested with the instrument in a deployed configuration and is the driver of several test-as-you-fly exceptions. To verify that the system is meeting project requirements before launch and to understand what’s expected once on-orbit, a set of inter-related system models were developed and used to evaluate L-SAR’s sensitivity when the radar antenna is subject to on-orbit thermal environment influences affecting pointing and performance. The results from these models run as a whole, portends what to expect during the mission and the results also are used to certify L2 requirements.

Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW) is a Japanese Earth observation satellite carrying two mission instruments, Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3) and Advanced Microwave Scanning Radiometer 3 (AMSR3). TANSO-3 is a grating type imaging spectrometer to observe CO2, CH4 and NO2 and has two observing modes; wide mode and focus mode. Compared with the Fourier Transform Spectrometer (FTS) method adopted in Greenhouse gases Observing SATellite (GOSAT) and GOSAT-2, TANSO-3 can observe a much larger number of locations in a wide area. This paper describes the design overview and pre-launch tests of TANSO-3.

The Advanced Land Observing Satellite-4 (ALOS-4) is a satellite to observe the Earth's surface using its onboard phased array type L-band synthetic aperture radar (PALSAR-3). The L-band radar technology has continuously been developed in Japan. With further improved observation performance compared to the predecessor PALSAR-2 aboard the ALOS-2, JAXA and its prime contractor, Mitsubishi Electric Corporation, developed ALOS-4 aiming at achieving both high resolution and a broader observation swath. ALOS-4 will increase the observation frequency to once every two weeks so that disaster prevention agencies can find abnormal changes such as unusual volcanic activity, land subsidence, or landslides at an early stage to warn people nearby. In addition, the observation swath will be drastically increased from 50km to 200km while keeping the high resolution. Therefore, we can observe a broader area at the same time when a large-scale disaster that damages wide areas occurs, such as a huge earthquake or multiple eruptions at the same time. ALOS-4 was launched by the 3rd H3 launch vehicle at JAXA’s Tanagashima Space Center, Japan. This paper describes the ALOS-4’s initial operation results and its performance.

Since its successful launch in 2011, the VIIRS (Visible Infrared Imaging Radiometer Suite) on Suomi NPP (Suomi National Polar-orbiting Partnership) has been providing continuous global Earth observations with 22 spectral bands spanning 0.41 to 12.01 μm for over a decade. Originally designed for a 7-year lifespan, Suomi NPP VIIRS has consistently exceeded both its operational specifications and user expectations, successively served as the primary, secondary, and now tertiary satellite imaging radiometer for the NOAA’s Joint Polar Satellite System (JPSS) program. Meanwhile, VIIRS on NOAA-20 (launched 2017) and NOAA-21 (launched 2022) have become the secondary and primary imaging radiometers in succession. Building upon lessons learned from SNPP, NOAA-20 VIIRS has distinguished itself as having the most stable reflective solar bands with less than 0.15% responsivity degradation per year in the first 5 years before any correction, and has been endorsed by the World Meteorological Organization/Global Space-based Calibration System (WMO/GSICS) as the on-orbit stability reference. More recently, NOAA-21 VIIRS has become the primary instrument, demonstrating robust performance, especially after the second mid-mission outgassing. This paper evaluates the on-orbit performance of VIIRS instruments, incorporating comprehensive assessments with the calibration methodologies encompassing onboard, vicarious, intercalibration, and recalibration techniques. It focuses on the long-term stability, accuracy, and intersatellite bias assessments using various methods. The root cause for the radiometric biases for the reflective solar bands between Suomi NPP and NOAA-20/-21 is explored, and the recalibration methodology to improve stability and consistency is discussed. Collaborative initiatives with partner satellite programs such as MODIS, the recently launched PACE, EMIT, and the to-be-launched METImage on EPS-SG have also been initiated. These activities underscore the efforts towards achieving consistent, long-term global Earth observations, which are crucial for facilitating time series analyses that support studies on atmosphere, land, ocean dynamics, and artificial nightlight, thereby enhancing global climate change research and operational support for numerical weather predictions.

VIIRS is a key instrument on board the Suomi National Polar-orbiting Partnership and NOAA-20 satellites, launched in October 2011 and November 2017, respectively. The third VIIRS in the series carried on the NOAA-21 satellite was recently launched in November 2022. The quality of the VIIRS response versus scan angle (RVS) characterization is vitally important to ensure there is consistent calibration across the entire scan range. The RVS was characterized prelaunch in lab ambient conditions and is currently used to calibrate the on-orbit response for all scan angles. A spacecraft level pitch maneuver is typically scheduled during the initial intensive Cal/Val testing after launch and provides a rare opportunity for VIIRS to conduct observations of deep space over the entire scan range, which can be used to characterize the RVS for the thermal emissive bands (TEB). This study provides analysis of the NOAA-21 pitch maneuver data and methodology to determine the VIIRS TEB RVS. A comparison of the RVS results determined from the pitch maneuver observations and those from prelaunch lab measurements is provided for each band, detector, and mirror side of the half angle mirror. Comparison of biases in brightness temperature as a function of scan angle is also conducted by inter-comparing with co-located Cross-Track Infrared Sounder (CrIS) on the NOAA-21 satellite to examine the RVS stability in reference to CrIS.

This study inter-compares NOAA-21, NOAA-20, and S-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) operational RSB SDRs with the NASA Plankton, Aerosol Cloud and Ocean Ecosystem (PACE) Ocean Color Instrument (OCI) and JPL Earth Surface Mineral Dust Source Investigation (EMIT) observations over well-established pseudo invariant calibration sites (PICS) over desert areas, including Algeria3, Algeria3, Arabia-2, Libyan-1, and Libyan-4. Time series of VIIRS visible and near infrared bands (VisNIR, M1-M5, M7, and I1-I2) top of atmosphere (TOA) reflectance were compared with matching PACE OCI observations from April 11, 2024 to October 15, 2024. Preliminary results suggest that S-NPP VisNIRs agree better with PACE OCI than NOAA-20 and NOAA-21. M1-M4, M7, and I1-I2 bias lower than OCI for all three VIIRS. Moreover, shorter wavelength bands (M1-M4) show large biases, and biases decrease as wavelengths increase. Bands M5, M7, and I1-I2 agree with OCI within 5% for majority of cases. VIIRS shortwave infrared bands (SWIR, M8, M10-M11, and I3) and VisNIR I-bands (I1-I2) were compared with co-located JPL EMIT observations (June -November 2023) over the desert sites. Preliminary results indicated VIIRS agree with EMIT within 3% in majority of cases. Meanwhile, larger uncertainty may exist in the VIIRS-EMIT inter-comparison results due to the limited cases available and the residual BRDF and atmospheric effects. Additional PACE OCI and JPL EMIT data over PICSs will be analyzed as additional observations become available in the future.

In this study, Global Precipitation Measurement (GPM) mission Dual-Frequency Precipitation Radar’s (DPR’s) precipitation estimates are validated with long-term (2014-2022) measurements of seven Joss–Waldvogel disdrometers installed in north Taiwan. The results show that the GPM DPR shown greater performance when predicting the rain parameters in stratiform precipitation as opposed to convective precipitation. Furthermore, regardless of single and dual-frequency algorithm, the mass-weighted mean diameter had better agreement than the normalized intercept parameter.

The MODIS instrument has been operating on both the Terra and Aqua spacecraft for more than 20 years. After the last orbital maintenance maneuvers performed for Terra and Aqua in early 2020 and 2021, respectively, their orbits have been drifting. The orbit drift brings a challenge of maintaining a consistent radiometric calibration for the MODIS reflective solar bands (RSB). In the current Collection 6.1 and upcoming Collection 7 Level 1B (L1B) data products, the calibration of the RSB relies on measurements from an on-board solar diffuser (SD) combined with ancillary data from scheduled lunar observations and pseudo-invariant Earth targets. The lunar and Earth view data is collected at various scan angles to track changes in the response versus scan angle (RVS). The orbit drift causes changes in the solar illumination and satellite view angles to the Earth targets. The simultaneous nadir overpass (SNO) approach provides a direct comparison of spectrally matching bands between MODIS and any one of the VIIRS sensors on the SNPP, NOAA-20 and NOAA-21 satellites, in which impacts of scene variability, solar illumination and sensor view angles are largely reduced. This study shows how the orbit drift affects frequency, location and angular match between MODIS and VIIRS crossovers. We extended the SNO approach from MODIS near-nadir views to off-nadir scan angles to examine the stability of MODIS to VIIRS reflectance ratios at various scan angles. Trending results starting from 2018 based on SNO with NOAA-20 VIIRS are presented for Terra and Aqua MODIS bands 1-4, 8 and 9.

The Ocean Color Instrument (OCI) onboard NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission has performed three monthly lunar calibrations. The moon is an extended source over a large dark background, making it an ideal target for evaluating OCI’s straylight and crosstalk performance. The lunar data analysis showed the straylight and crosstalk to be lower than the prelaunch measurements, especially in the along-track direction, where very little straylight is detected. Based on lunar data, the prelaunch measured crosstalk coefficients were reduced, and a crosstalk correction was tested on both lunar and solar calibration data. Applying the revised crosstalk correction, the crosstalk contaminations are significantly reduced to under 0.1% at 2 to 3 pixels away from the lunar boundary for bands above 350nm. Below 350nm, the crosstalk correction residuals gradually increase due to a lack of high-quality prelaunch measurements. Lastly, applying the crosstalk correction changes the calibrated radiance for all science data. This is due to the different spectral shapes between the solar diffuser and the observed scenes. For the moon, the crosstalk correction has an impact of ~0.4% on the overall calibrated radiance for the 400 to 600nm bands and up to 20% impact on the UV bands.

For high-throughput remote sensing systems, wide field-of-view optical designs utilizing freeform or non-traditional optical surfaces are increasingly being introduced and developed. Manufacturing these enabling optical components and integrating them effectively requires optical metrology solutions to guide fabrication and assembly processes. Interferometry measures the optical path difference between test and reference beams by analyzing phase-shifted interferograms. This technique requires a null configuration setup, often employing null lenses or computer-generated holograms (CGHs), and is suitable for various surfaces, including flat, spherical, aspheric, and freeform mirrors. Deflectometry, on the other hand, measures surface slope distributions by analyzing light reflections off the optical surface using a series of camera images. This method captures the irradiance distribution to determine local surface slopes, which are then integrated to reconstruct the surface height map. It offers high precision and a broad dynamic range, making it suitable for a wide range of optical surface types. Together, these techniques provide advanced capabilities for the development and deployment of wide field-of-view remote sensing systems, paving the way for future space innovations.

3D imaging by aerial photography is an important tool for environmental monitoring, infrastructure inspections, etc. The plenoptic imaging system, composed of a micro-lens array, acquires multiple images with various view angles simultaneously and thus is more accurate than traditional stereo vision systems, for precise baseline length in stereo matching and subpixel algorithm of multiple images with pixel shifts. Moreover, in dark environments, lighting from an unmanned aerial vehicle may cause specular reflection from the surface of targets and disturbs height detection. The plenoptic imaging system for 3D aerial photography is designed with working distance of about 3m, field of view of 1.5m x 1.1m, lateral resolution of 0.5mm, and height resolution of 0.3m. The design is modeled in Blender software and simulated with various lighting conditions. With a small light source close to the plenoptic imaging system, detected heights at the region with obvious specular reflection are distorted. On the other hand, with an area light source close to the surface of targets, detected heights are more accurate. The lighting environment can be achieved by focusing an area light source on the surface of targets by an external optical system. Generally an internal coaxial lighting infrastructure is applied to avoid mechanical interference, and the detailed optical system with an internal coaxial light source will be designed and simulated in the future.

Surface quality of optical lenses is an important parameter to achieve optimal imaging quality. Surface imperfections such as scratches, pits, or digs which may be caused during manufacturing or handling induce light scattering and degrade the overall performance of the imaging system. For a lightweight lens, the pockets behind the lens will affect the defect judgment due to excellent optical transmittance. This article discusses the measurement flow of automatic optical inspection for large lenses, defect detection algorithm, and the practicality of application of this technique for inspection of large lenses. Surface defect detection module comprises of high dynamic range camera combined with telecentric imaging lens creating an imaging system with resolution of 2.7μm. Inspection of the whole surface before and after coating is carried out through concentric scanning and different illustrating angles. The images are captured with a 20% overlap between two consecutive images to ensure complete coverage of the whole surface. Image processing algorithms are applied to detect and classify any surface defects on the surface. Detection results consists of exact size, type, and location of the defects are analyzed by the system and summarized into an inspection report. Compared to classical manual inspection this system provides reproducible and objective detection results and allows users to perform revalidation after measurement is finished.

The interferometry is often adopted to check the optical quality and support the alignment in assembly for high precision demand optical system. The interferometer could acquire the system wavefront error (WFE) and obtain the delicate variation of aberration terms. For those optical systems applied to the space mission, the transition from atmosphere to vacuum environment would lead to the dimensional changes of mechanical structure within the scale of micrometer and eventually diminish optical performance. Consequently, as stated above, it is essential to validate the whole optical system in vacuum circumstance. Before the system actually being launched into the space, they are usually placed in the thermal vacuum chamber during ground testing in order to validate if the design could withstand the harsh environments such as high vacuum level and large temperature difference. Nevertheless, it is a big challenge to build up an in-situ optical measurement architecture for large aperture optical system in the thermal vacuum chamber due to the finite internal space of chamber, limited aperture size of transmission view port of chamber door and thermal dissipation problem of measuring instruments. In this paper, we demonstrate an innovative way of interferometry for monitoring the optical performance variation of FORMOSAT-8 (FS-8) optical system assembly (OSA) in our current vacuum chamber that the test telescope and the diverger lens were located in the vacuum environment, while the interferometer stayed in the ambient circumstance. The interferogram was successfully obtained thanks to the rigorous optical alignment process and the speical designed reference tools.

This study investigates motion simulation and compensation techniques for airborne Synthetic Aperture Radar (SAR) to enhance imaging accuracy and quality. SAR utilizes platform motion to create a synthesized long aperture, improving azimuth resolution independently of frequency and distance. However, unexpected platform motion, such as from wind or turbulence, can introduce non-linear trajectory changes, causing Doppler frequency shifts that blur images. To address this, we simulate airborne motion trajectories under various conditions, including wind speed, direction, and sensor influence, and apply motion compensation algorithms like the Map Drift Algorithm (MDA)[1], Beam Center Motion Compensation (BC MoCo) [2], and Subaperture Topography and Aperture Dependent (SATA)[2]. This research simulates complex airborne environments, generating realistic low- and high-frequency disturbances to test compensation effectiveness across time and frequency domains.

The spotlight acquisition mode of Synthetic Aperture Radar (SAR) offers high spatial resolution in the azimuth direction. Generally, the Omega-K algorithm is used for the focusing process of the spotlight acquisition mode with defined processing steps. However, a suitable region selection after the Stolt interpolation remains unclear. In this paper, we generate spotlight echo data with several point targets and process the focused image using the Omega-K algorithm. We propose an analysis of region selection based on the 2-D spectral supports for final imaging. Particularly, the quality of the final image depends significantly on the chosen region within the 2-D spectral supports. We present analysis results on suitable region selection and full aperture utilization. In conclusion, we propose a method for selecting a suitable region. It is crucial for the final image quality.

The system will integrate image information from multiple FORMOSAT-8 satellites, allowing general users to query historical image data in real-time and store their query information. FORMOSAT-8 images will be provided as products and services through distributors. The system will offer a comprehensive image ordering platform, enabling distributors to order historical images or task satellite imagery products. Distributors can also integrate the image query system with their own platforms via API. The system will also provide high-resolution image tile subscription services. High-resolution satellite images of Taiwan will be regularly uploaded, allowing subscribers to view high-resolution satellite images from different time periods in real-time through WMTS. Subscribers can also integrate these services into their own platforms via API.

Low-Earth orbit (LEO) and better ground sampling distance (GSD) have been a trend for earth observation satellites. A compact optical remote sensing imager (RSI) is required accordingly from a systematic point of view. Therefore, a pathfinding project has been raised to develop an optomechanical structure for this RSI. The project is primarily led by the National Cheng Kung University in collaboration with the Taiwan Instrument Research Institute. This article mainly reports the structural analysis of optomechanical structure, including modal analysis, sine vibration, and random vibration. Furthermore, this report establishes a heritage design and analysis procedure for future projects.

Satellite observations with 300-GHz band radiometers are expected to bring advantages to atmospheric remote sensing, such as sounding of water vapor profiles and estimating thin cloud properties. However, it had been difficult to satisfy the accuracy and precision requirements of the observation, owing to high noise levels of 300-GHz band receivers. The system noise temperature of receivers is proportional to a radiometer's brightness temperature resolution. It is a reason why the lower noise level receiver is desired to a radiometer. We have experimentally confirmed that the receiver using a 300-GHz LNA achieved about one fifth of system noise level compared to that of without LNA.　 It implies that we can develop a 300-GHz band spaceborn radiometer with 1 GHz bandwidth, 100msec integration time and about 1K of brightness temperature resolution. Our final goal is to contribute to improving the accuracy of the vertical profile water vapor and the amount of ice clouds by satellite observations with our 300 GHz-band radiometer.

Due to its limited energy resources, Taiwan heavily relies on imported natural gas and coal for electricity generation. With the European Union planning to implement a carbon tax on heavy industries by 2026 and the United Nations targeting net-zero carbon emissions by 2050, the urgency for green electricity has intensified. This research identifies optimal locations for wind turbines and photovoltaic panels to maximize renewable energy production in Taiwan. Our analysis utilized satellite remote sensing data (AMSR-2, SSMI, GMI, SMAP, ASCAT) validated by the ESA's ERA5 model. Findings indicate that the Taiwan Strait, especially near Changhua, is highly suitable for wind turbines, with wind speeds ranging from 5 m/s to 20 m/s, peaking in winter. For photovoltaic panels, effectiveness is influenced by solar radiation values (G) and efficiency losses above 25°C. Short Wave Radiation (SWR) data from Himawari-8/9 shows that southern Taiwan has high average SWR values, ranging from 170 W/m² to 270 W/m². Additionally, combining the 2-meter land temperature data from the ERA5 reanalysis, we computed the predictable power generation across Taiwan. The results also show that southwestern Taiwan is favorable, with monthly averages from 20 W/m² to 40 W/m². Located within 23.5°N, this area benefits from direct sunlight during the summer solstice and is predominantly flat with low altitudes, ensuring prolonged exposure to sunlight. This study provides crucial insights for strategic renewable energy development in Taiwan, supporting global efforts towards achieving net-zero carbon emissions.

This study analyzed coastal water quality at selected regional validation sites such as the Gulf of Mexico and Florida Bay using VIIRS, PACE/OCI, and JPL EMIT observations. The goal was to evaluate the capability of these sensors in monitoring water quality along the coast and lakes, as well as the ability to detect cyanobacteria using satellite and ground data. First, several key variables from the PACE/OCI level 2 ocean color products, such as Inherent Optical Properties (IOP) and Apparent Optical Properties (AOP) over the region of interest were analyzed to see correlations for water clarity, turbidity, color dissolved organic matter (CDOM), phycocyanin, and phycoerythrin; Second, cyanobacteria index maps were generated using hyperspectral observations from EMIT and PACE/OCI; Third, laboratory tests with spectroscopic analysis of water samples were performed, including measurements of clear, and turbid water to identify spectral characteristics.

As the LEO satellite industry rapidly expands, the demand for remote sensing and telecommunications in marine and suburban areas is increasing. Developing higher bandwidth communication interfaces has b ecome a crucial focus in the space industry. Free space optical (FSO) communication offers bandwidths hundreds of times greater than traditional microwave links, enabling the efficient transmission of large volumes of data. However, current commercial sate llite tracking systems lack the high precision needed for space-ground laser communication. For high-speed data transmission, the laser beams between the ground station and the satellite must be precisely aligned. In this Taiwan Space Agency’s (TASA) project, we were originally designed optical ground station to communicate with HICALI (High -speed Advanced Optical Communication Equipment) onboard the Engineering Test Satellite No. 9. This project is changed to specifically communicate with future High-Precision LEO Remote Sensing and Laser Communications Satellites including 6U CubeSat(s) built by National Yang Ming Chiao Tung University (NYCU). The system consists of a medium-sized telescope, a mount, and a newly developed high-precision controller, which meets the accuracy requirements for FSO communication. By analyzing optical images of targets, we achieve the necessary tracking accuracy for satellite -ground FSO communication. This system not only enhances the transmission efficiency in space -ground laser communications but also improves the remote sensing and data transmission capabilities of LEO satellites. This paper provides an overview of the current optical ground station, the system performance and lessons learned.

Past experience from postlaunch calibrations of Suomi-NPP (SNPP), NOAA-20, and NOAA-21 Visible Infrared Imaging Radiometer Suite (VIIRS) indicates the critical need for quick and accurate predictions of sensor optical throughput response changes. For example, the solar diffuser is a critical component of the VIIRS instrument and serves as a reference standard for the on-orbit calibration of VIIRS reflective solar bands (RSBs). However, the solar diffuser can experience degradation over time resulting from various factors, including exposure to solar ultraviolet (UV) radiation, energetic particles, and contaminants in the space environment. The changes in the optical properties of the solar diffuser material can impact the accuracy and stability of VIIRS radiometric calibration. SNPP VIIRS RSB suffered rapid postlaunch optical throughput degradation in the near-infrared (NIR) band gains (inverse of solar-F factor calibration coefficient) due to mirror contamination along the optical path. Given the short-term and long-term VIIRS radiometric calibration update needs and the delays between planning and execution of post-launch calibration updates, it is critical to accurately predict VIIRS sensor response changes in days or weeks ahead. The advancement of recurrent neural network (RNN) machine learning algorithm for time series prediction provides potential means for fast and accurate calibration time series prediction. In this study, long short-term memory (LSTM) RNN model is used to train and predict VIIRS calibration time series such as VIIRS solar diffuser spectral reflectance change time series. LSTM neural networks are a type of RNN architecture designed to model sequential data and capture short- and long-term dependencies and are well-suited for calibration time series forecasting due to their ability to remember information over extended time periods and to handle sequences of varying lengths. The calibration time series of solar diffuser reflectance change from SNPP VIIRS are used as example input sequences and target values to train the LSTM model. The prediction performance is assessed in terms of prediction error as a function of prediction horizons from one to seven days for spectral bands of VIIRS. The relative Root Mean Square Error (RMSE) of seven-day LSTM predictions of spectral degradations of SNPP solar diffuser reflectance is within 0.2%. The suitability of applying LSTM machine learning model for VIIRS calibration time series predictions is discussed.

The Taiwan Space Agency (TASA) has actively contributed to international disaster relief and monitoring activities through its imaging missions with FORMOSAT-2 and the current FORMOSAT-5, in collaboration with Sentinel Asia. Our past experiences include fulfilling domestic needs such as national land planning, crop monitoring, coastline detection, water resource analysis, and regular ecological tracking. Through continuous collaboration with both domestic and international organizations, we have progressively developed a comprehensive understanding of satellite imaging system requirements. The development of the FORMOSAT-8 scheduling system builds on these past experiences, utilizing the established tasking database model and integrating it with the frontend interface. The process starts with an external user requirements survey, followed by the planning of user needs and the integration of internal operation team workflows. We have defined the data communication between the Data Management Subsystem (DMS) and the Planning and Scheduling Subsystem (PSS). This report will explain the current scheduling system's processing workflow.

MODIS Collection 6.1 (C6.1) is the current official version of its NASA Level-1B (L1B) product, while the Collection (C7) production is presently underway. Amongst the various improvements from its preceding Collections, the most impactful development in C6.1 was the application of a correction to reduce the crosstalk contamination between the MODIS photovoltaic longwave infrared (PV LWIR) bands. In the case of Terra MODIS, such correction was applied via reprocessing to the long-term record, whereas for Aqua MODIS, it was implemented starting March 2022 after the spacecraft and MODIS entered into a safe mode state that significantly increased the crosstalk contamination between the instrument’s PV LWIR bands. In MODIS C7, such correction is applied from mission beginning. Over recent years, both MODIS sensors have seen a gradual crosstalk increase, this in turn has caused drifts across different Earth view scenes despite the correction application, since it can’t completely remove the crosstalk contamination. These drifts are most critical for Aqua band 29 (vastly used by the science community) and Terra band 30. In the case of Aqua MODIS band 29, this is true for both C6.1 and C7, whereas for Terra MODIS band 30, the downward trend is most significant in C6.1 and overcorrected in C7. This led the MODIS Characterization Support Team (MCST) to assess and develop a strategy to reduce these drifts in C7. The methodology involves updating the algorithm used to generate the on-orbit derived calibration coefficients and scaling the crosstalk correction coefficients. However, after several discussions with science teams whose higher-level products ingest the MODIS Level-1B products, the latter was dispensed. The original and revised strategies are discussed. Overall, the agreed upon approach successfully reduces the long-term drifts for all the MODIS PV LWIR bands whose algorithm was updated. Close to pushing the quarter century mark, the Terra and Aqua MODIS legacy instruments will be essential to perpetuate long-term environmental data records after these are superseded by more novel sensors such as VIIRS. Hence the need for the algorithm updates presented in this work to maintain stable data archives.

This paper presents the design and performance of the imager lens for the star sensor in the FORMOSAT-8B remote sensing satellites program, which is also asked to be the candidate lens, implemented for the Faraday Dragon rideshare mission. The lens, designed with a dual-Cooke refractive system, is optimized for a wide field of view and minimal aberrations, essential for capturing distant stars. The design process follows six key steps, from defining project goals to collaborating with integration teams. The lens exhibits high performance, achieving a success rate of over 95% in attitude determination at a slew rate of 0.8°/sec under specific conditions.

The method for aligning the focal plane assembly (FPA) with the optical structure assembly (OSA) involves finding a position with optimal focus. The experimental setup includes a collimator with an effective focal length of 10,500 mm and a free aperture of 700 mm. An electronic ground support equipment (EGSE) is responsible for capturing the sensor signals. Processing these data allows the derivation of the contrast transfer function (CTF) value using a line-pair pattern. At the beginning of the FPA alignment process, the attitude and position of the FPA are controlled with the assistance of a hexapod positioning system (a six-axis robot). After determining the attitude and the best focus position of the FPA, shimming is performed to adjust the gap between the FPA and the OSA. Based on the shim thickness required at three orientations, shim rings with the relevant thickness are installed. Due to the uncertainties from shimming, shim ring thickness manufacturing tolerance, and the residual of the tip/tilt angle between the FPA and the OSA during alignment, it is crucial to confirm and fine-tune the shim ring thickness. Once the FPA is fixed on the OSA, moving the FPA for the through-focus measurement is not feasible. However, the distance between the primary mirror and the secondary mirror of the collimator is tunable. By adjusting this distance, the collimation beam can be modified to a converging or diverging beam, thereby changing the focal plane position. Consequently, through-focus measurements can still be conducted by moving the secondary mirror of the collimator.

Absolute radiometric calibration is crucial in remote sensing, ensuring that raw satellite data, like that from Sentinel-1A, are accurately converted into physical units representing Earth’s surface. Sentinel-1A, part of the ESA’s Copernicus program, is equipped with a Synthetic Aperture Radar (SAR) Sensor that captures high-resolution images in all weather conditions. SAR’s ability to penetrate clouds makes it invaluable for long-term monitoring and time-series analysis. Accurate time-series analysis requires consistent radiometric values across images to detect real changes, such as deforestation or urban expansion. Calibration converts radar backscatter values to normalized radar cross-sections, adjusting for sensor and atmospheric biases. This study applies time-series backscatters from Sentinel-1A to assess the stability of the calibration process over Rosamond, California, using data from 2 corner reflectors and 17 images. The findings will support radiometric calibration for Taiwan’s future SAR mission.

This paper presents the implementation of the design for manufacturability (DfM) methodologies and considerations in the development of a spaceborne telescope designed for remote sensing instruments (RSI) as part of the FORMOSA-8 satellite program. The study focuses on optimizing the telescope design to balance optical performance with limitations of manufacturability and challenges of specification constraints. A critical aspect of this process involves conducting a detailed tolerance sensitivity analysis across various system aperture sizes and ensuring traceability in measuring the performance of assembling and aligning lens elements. This approach evaluates the impact on key performance metrics, including wave front error (WFE), modulation transfer function (MTF), and the alignment performance of optical components. The methodologies developed were applied to the FORMOSA-8X satellite constellation, resulting in significant improvements during the assembly, integration, and testing (AIT) phases. The successful design balances manufacturability and performance, achieving the desired outcomes in the first iteration as result in doing design right the first time. Additionally, this paper explores the trade-offs encountered during the design process and offers recommendations for optimizing DfM in spaceborne telescopes. The paper also details the development of a spaceborne Ritchey-Chrétien telescope with corrector lens design, emphasizing the challenges related to specification requirements, the manufacturing process, and innovative solutions employed. The key factors, such as tolerance sensitivity, alignment accuracy, and environmental considerations, are addressed. The implications of these trade-offs design methodologies for future spaceborne catadioptric optical systems are discussed, including a review of the telescope's integration and testing for the FORMOSA-8X satellite program.

In this paper, we propose a black treatment method for optical-mechanical surfaces in observational remote sensing telescopes. This treatment effectively suppresses stray light, enhancing the dynamic range of the telescope's sensors. The black treatment process involves using a laser to create periodic holes followed by coating with a Blackening Matrix (BM). Measurement results show that the total integrated scatter (TIS) is less than 2.4% at incident angles from 8° to 70° and less than 4.2% at angles from 70° to 80°. These results demonstrate that the proposed method is more effective than traditional blackening techniques, making it a promising solution for future space applications where minimizing stray light is critical.