FORMOSAT-5 is the fifth space program initiated by National Space Organization (NSPO) of National Applied Research Laboratories (NARL)， the Republic of China (ROC). FORMOSAT-5 will be operated in a sun-synchronous orbit at altitude of 720 km. Operating in this orbit， FORMOSAT-5 can have two-day revisit property， and can reach the goal of two-day global coverage with FOR of 45 degrees. However， the lunisolar attraction causes a slight variation in the satellite inclination， the accumulated deviation in Right Ascension of Ascending Node (RAAN) can be significant after 2 to 3 years， and the Local Time of Descending Node (LTDN) will drift out of the range of mission-required value. Three different scenarios for different initial orbits are proposed. For each scenario， the initial orbit and the long-term evolution of FOMOSAT-5 are simulated through STK simulation. Finally， initial orbit adjustment analysis and strategy are proposed， and adding some proper inclination in the ideal orbit at the appropriate LTDN will reduce fuel use and will extend the life cycle of a satellite mission.

FORMOSAT-2 (FS-2) is the first operational remote sensing satellite of the National Space Organization (NSPO) for science in Taiwan. The Remote Sensing Instrument (RSI), with high spatial resolution (8m) and 8-bits radiometric resolution, is the primary payload of FS-2. FORMOSAT-5 (FS-5) RSI has the similar spectral bands and bandwidths to FS-2 RSI but better radiometric resolution (12-bits) and spatial resolution in multispectral bands (4m). To fit the large fluctuation of surface reflectivity, an option of selecting gain factor is designed for the proper dynamic range of radiometric signal. When observing a high reflectivity region, the lower gain number should be selected to avoid the possible saturation of output signal, while a larger gain number would be favorable for a low reflectance region to enhance the signal to noise ratio (S/N Ratio). Therefore, the objective of present research is to generate global gain number of each spectral band for RSI FS-2/FS-5. For this topic, the Moderate-Resolution Imaging Spectroradiometer (MODIS) global surface reflectance product (MOD09) associated with solar geometry and Second Simulation of a Satellite Signal in the Solar Spectrum, (6S, a radiative transfer code) are employed to derive the reflected radiance in each spectral band at the top of atmosphere. With the radiometric coefficients of RSI, the maps of global gain number can be constructed accordingly. The generated gain number maps of FS-2 RSI agree with the operational maps of National Space Organization (NSPO) in most land areas and some marine areas. The results of FS-5 RSI also conform well to the criteria of gain setting in the areas of land, ocean and polar region in terms of surface reflectivity. The overall result suggests that the global gain maps generated in this study can competently offer the setting of FS-5 RSI gain number for the global observation after launched.

Attitude and Orbit Control Subsystem (AOCS) is the very vital one and usually one of the most complicated subsystems. It is in charge of maintaining the satellite on its orbit and controlling the pointing in the required range to achieve the expected performances. It is also designed to be a highly sophisticated system that not only contains various pieces of actuator and sensor hardware but also equips many exquisite software algorithms for control, guidance, and navigation purposes etc. in order to support different mission requirements. The Polarity validation plays an extremely important role in the verification of AOCS because any failure due to the polarity problem of AOCS hardware may make the satellite cannot fulfill its mission or lead to the worst-complete loss of the satellite. Therefore, in this paper, we introduce test strategies and demonstrate the test results for the FORMOSAT-5 (FS-5) AOCS Polarity Tests.

The Remote Sensing Instrument (RSI) is the main payload on board the FORMOSAT-5 satellite, which is the first space program that National Space Organization (NSPO) takes the full responsibility for. It is a Cassegrain type telescope built on a honeycomb panel with Carbon Fiber-Reinforced Plastic (CFRP) face sheets and aluminum alloy core. NSPO develops the bus and the RSI by integrating the domestic resources. The RSI assembly is mounted horizontally on the spacecraft bus. This configuration design concept mainly comes from the heritage of its predecessor, the FORMOSAT-2 Satellite. After delivery of the RSI structure, it is then dis-assembled for the next step assembly flow, namely the integration of the optical elements, primary mirror (M1), secondary mirror (M2), etc. The optical elements, especially the M1, are quite sensitive to any stress induced during the assembly flow. It is necessary to have a thorough plan to minimize the stresses introduced in the processes. This makes the task of re-assembly of the structure elements quite challenge. This paper presents the re-assembly flow used for FORMOSAT-5 RSI structure. Section 2 describes the elements for the RSI Structure, while detail assembly flow is depicted in Section 3. Section 4 documents the data generated from strain gauges during the re-assembly flow.

Formosat-5 remote sensing instrument has successfully passed the thermal cycle and thermal balance test. According to the temperature data of the hot and cold balance test, the thermal property in the simulation model is correlated with the test results. The thermal properties include the interface thermal conductivity and the effective emissivity of the multi-layer insulation. The sensitive analysis of these parameters in simulation compared with the thermal balance test results are used to find the trend to update the parameters in the model. The thermal capacity of the parts in the model is verified by the comparison with the cold transient test. After the model correlation, the temperature difference between the model and the thermal test results are within 5℃. The thermal model after correlation can improve the temperature prediction of the remote sensing instrument in the space.

The purpose of the self-compatibility is to verify that the satellite, configured in operational modes, do not occur any malfunction or degradation of performances when operated in nominal TM/TC and X-band downlink system by radio frequency interface.

FORMOSAT-5 Remote Sensing Instrument (RSI) is the first remote-sensing payload 100% developed by National Space Organization (NSPO) in Taiwan, which contains large lens, electronic unit (EU), and telescope with high resolution CMOS sensor. RSI engineering team not only designed/manufactured the self-reliant RSI system but also assembled all components into a functioning instrument. This paper describes how the RSI important RSI performance parameters (such as SNR, MTF…… etc.) being verified and the integration & test methodology used during the instrument development. The radiometric calibration indicates that measured SNR of multispectral band are consistent with their corresponding requirements. Based on measured relative radiometric parameters, such as relative response and offset, relative radiometric calibration can properly adjust the uneven response behavior of sensor elements observed from raw imagery. The measured output signal is linearly proportional to given input radiance during radiance conversion process. For geometric calibration, polynomial coefficients of light-of-sight vector of RSI sensor with three-order degree and three Euler angles (such as roll, pitch, yaw angles) between coordinates of RSI alignment and satellite master cube are derived. For image sharpness, the measured along-track CTF of all bands are still within the potential users' acceptability. The measured across-track CTF of all bands are above their corresponding specifications. In addition, RSI calibration plan to guarantee its integrity with preliminary prediction results that is also presented. FORMOSAT-5 imagery would be believed to provide lots of essential and critical information for many applications related to monitor the Earth's resources and environment, such as base map generation, land cover classification, land use change detection, disaster mitigation, and image fusion…etc., to FORMOSAT-5 user community.