In Taiwan’s satellite program, the Formosat-8 (F-8) team recently showcased images of the moon taken from the National Space Organization (TASA) before their space mission. Even from a distance of 380,000 kilometers away, the lunar surface, with various-sized craters visible, was captured clearly. The project leader of F-8, Liu Xiaojing, carefully examined the image and commented, “This should score a 75, but it can be even better.”
According to reports by Central News Agency, compared to the Formosat-5 which assisted in disaster relief efforts during the 403 Hualien earthquake, the “successor” F-8 can be considered a comprehensive evolution. Chairman of the National Science Council of the ROC, Wu Zhengzhong, mentioned that the first satellite of F-8 is scheduled to launch in October 2025 aboard a SpaceX rocket. Once successfully in orbit, it will capture higher quality and more real-time images of the Earth’s surface.
Formosat-5 was Taiwan’s first self-developed high-resolution optical remote sensing satellite, with its main payload being a telescope for observing the Earth from space. Seven years ago, during the initial operation of F-5, the biggest setback was the inaccurate focusing, resulting in blurry and unclear images. The team, determined to salvage the situation, worked on post-processing corrections under the leadership of Liu Xiaojing, a former high school math teacher who utilized her experience in image processing and mathematics to rectify the focus issues. This allowed the images captured by F-5 to become commercially viable and even supported disaster relief missions in multiple countries.
Liu Xiaojing stated, “Currently, 90% of the effort put in by the F-8 remote sensing payload team is to avoid repeating past mistakes.”
Huang Boxuan, an important member of the Formosat-8 project team and head of the TASA Optical Payload Group, was also part of the Formosat-5 project. He pointed out that the optical payload of F-8 has improved in precision control of lens assembly and lens performance, surpassing F-5 by 1 to 2 times. The instruments, equipment, facilities, and manpower used have also undergone synchronous improvements.
Huang Boxuan mentioned that the key reason F-5 failed to capture clear images in the past was due to deviations in the collimator used for focus. To address this issue, TASA procured a new collimator, which is not only the same type as that used by international satellite companies but has also been tested in space with a focusing telescope.
Furthermore, to ensure that the precision components carried by F-8 can withstand the extreme conditions of outer space, the team conducted Optical Thermo-Vacuum Testing on the optical remote sensing payload. Throughout the testing process, TASA personnel had to monitor temperature and humidity changes 24 hours a day, observing how these factors affected the optical system’s focal plane position and any conditions that could lead to defocusing, along with compensatory measures.
“Back then, F-5 did not undergo such rigorous testing,” recalled Liu Xiaojing. Huang Boxuan added that passing the test now is akin to providing an additional insurance policy for F-8.
Remote sensing satellites are often referred to as the “modern eyes in the sky,” with resolution being crucial for the clarity of images. Director of TASA, Wu Zongxin, mentioned that in the future, F-8 will be in service in a 561-kilometer sun-synchronous orbit, where the ground resolution of its main payload can reach 1 meter, and after post-processing can achieve 0.7 meters—superior to F-5’s resolution of 2 meters. In other words, when F-5 and F-8 capture images of the same area from outer space, F-8’s higher resolution leads to clearer and sharper imaging.
Moreover, aside from F-8’s faster image transmission speed compared to F-5 – three to four times quicker – its “revisit capability” (the ability of a satellite to take repeated images of the same location) is also superior.
Liu Xiaojing explained that while the F-5 project only had one satellite passing over Taiwan once every two days, F-8 comprises a constellation of six satellites. Once all six are operational, the revisit capability is expected to increase significantly to capturing images three times a day, enhancing real-time image acquisition by accounting for factors such as cloud cover that may change between morning and afternoon visits.
In addition to the primary six satellites of F-8, there are two advanced versions planned with original ground resolutions below 1 meter, and the aim for post-processing resolution is below 0.5 meters.
Fulfilling a role commonly seen in military espionage films, analysts believe that beyond Formosat-8, the Synthetic Aperture Radar (SAR) satellites, such as the all-weather, day-and-night capable Formosat-9 series, which can penetrate cloud cover for imaging, could form a comprehensive Earth observation satellite system. Such a system holds the potential to bolster all-time monitoring of the situation around the Taiwan Strait.
Formosat-8 has now completed the research and development of 17 key components in four major categories: optical remote sensing payload, flight control, electrical, and mechanical. Many of these components are more lightweight and cost-effective than those used in Formosat-5. The satellite is currently undergoing integration testing and environmental testing. Once the satellite is successfully launched and operational, obtaining flight records through verification testing will be pivotal in establishing the foundational framework for Taiwan’s space industry supply chain.
Liu Xiaojing noted that a subsystem used for downloading image data is the X-band transmitter, which demands high transmission rate performance. Purchasing such components abroad is often restricted by output power, frequency channels, and some countries may even refuse to sell them. Hence, TASA chose to develop these components in-house.
She further mentioned that concerning the propulsion modules crucial for satellite maneuverability, the propulsion module this time is self-made rather than outsourced. Unlike the toxic fuel hydrazine used in the past, environmentally friendly high-concentration H2O2 (hydrogen peroxide) is now utilized as the propellant.
Liu Xiaojing pointed out that even the design of the grooves and complex piping in the propulsion module, including the selection of materials, had to be meticulously considered to avoid chemical reactions with H2O2, thereby ensuring the longevity of the propulsion system—a series of challenges to overcome.
With an aim of exceeding an 80% self-made rate overall, Formosat-8 is moving forward on this target. Wu Zhengzhong stated that once Formosat-8 successfully goes into orbit, it will showcase Taiwan’s capabilities in designing, analyzing, manufacturing, and testing 400-kilogram class-meter resolution remote sensing satellites.
Liu Xiaojing emphasized that the six satellites of Formosat-8 will be launched in six separate missions, allowing the TASA team to continuously evolve on the same satellite design foundation. She stated, “I hope the first one scores an 80, and we must do better with each subsequent launch.”