An-Ming Wu

Some aspects of ROCSAT-2 system engineering

Abstract The ROCSAT-2 is designated to the second satellite of the Republic of China. It is expected to be launched in 2003, and is designed primarily to image the region of Taiwan Island. The satellite will be operated in a circular sun-synchronous orbit with exactly 14 revolutions per day. By virtue of the nearly global coverage of the orbit, the images taken by ROCSAT-2 can also be acquired through international cooperation if the foreign ground stations are capable of receiving the downlink data. The satellite will provide high tasking agility for along-track or cross-track imaging with 45° field of regard. The remote sensing instrument (RSI) has four Landsat-like multi-spectral visible bands. It will provide images for 2 m ground sampling distance (GSD) in panchromatic band and 8 m GSD in multi-spectral bands over 24 km swath in the nadir direction. The secondary payload of ROCSAT-2 is a scientific instrument called the imager of sprite, the upper atmospheric lightning (ISUAL). It will be the first payload to observe the upper atmospheric lightning from space. The objective of this experiment is to study the nature of the electrodynamic coupling between thundercloud and upper atmosphere. The system engineering analysis for ROCSAT-2 is presented in this paper.

FORMOSAT-2 Mission: Current Status and Contributions to Earth Observations

This paper presents an overview of the current status and data applications of FORMOSAT-2, Taiwaneses first earth observation satellite mission. Highlights of its contributions to monitoring of global natural disasters and earth environmental changes will be illustrated. The FORMOSAT-2 satellite successfully complements existing high spatial resolution imaging satellites such as SPOT-5, IKONOS, and QuickBird, among others, with its unique capability of daily revisits worldwide. The FORMOSAT-2 follow-up program to ensure data continuity to the user community is briefly introduced.

An Introduction to FORMOSAT-2’s Global Effectiveness

FORMOSAT-2 (was called ROCSAT-2 formerly) of Taiwan’s National Space Organization (NSPO) is a small satellite of 746 kg mass for two remote sensing missions. Its mission orbit is sun-synchronous of 891 km altitude for exactly 14 revolutions per day. For earth observation, the payload is an advanced high resolution remote sensing instrument (RSI) with ground sampling distance (GSD) 2 m in panchromatic (PAN) band and 8 m in four multi-spectral (MS) bands. For upward lightning observation, the payload is an imager of sprites and upper atmospheric lightning (ISUAL). Launch date of FORMOSAT-2 was on 20 May 2004. After nearly 3 years of mission operations in orbit, i.e., more than one half of the mission life of 5 years, it is a proper time to assess and evaluate its worldwide effectiveness in Earth observation. To evaluate the effectiveness of developing a satellite, especially to a country with very limited resources such as Taiwan, we need to include all aspects. This paper gives the global effectiveness of FORMOSAT-2 a rather detailed assessment from the following areas: public education in Taiwan, Earth science and ecological niche research, preservation of the world heritages, contribution to the International Charter: space and major disasters, observation of suspected north Korea and Iranian nuclear facilities, and scientific observation of the atmospheric transient luminous events (TLEs). It can be concluded that FORMOSAT-2’s global effectiveness is pronounced and definitely promised. The development of FORMOSAT-2 is very valuable, not only to Taiwan but also to the whole world.

Performance Enhancement of FORMOSAT-3 Follow-on Using Formation Flying

After about 20 years of dedicated effort, the National Space Organization (NSPO) of Taiwan has successfully completed the development of Formosa satellites (FORMOSATs or FSs) 1 (FS1), 2 (FS2), and 3 (FS3). The international space community has given very positive comments on NSPOs contribution. Currently, NSPO is planning the future programs and designates FORMOSAT-7 (FS7) to be the follow-on of FS3. This paper presents the preliminary study results on the advantage of using formation flying for FS7 compared with the constellation flying of FS3. Due to the fact that the attitude control is not a major factor to affect the number of occultation data collected, it could be concluded that the formation flying is helpful but not mandatory in FS7. This conclusion is obtained by trading-off the complexity, cost, and development time of the program. We need to do is to design the orbits of the planned 12 micro-satellites to ensure the maximum number of data collection. However, during the deployment phase of FS3, it has been found that the formation flying immediately after the separation of the 6 satellites from the launch vehicle is a very important time period for instrument calibration onboard each individual satellite. Fortunately the 6 satellites of FS3 formed a formation immediately after separation from the launch vehicle without much extra effort. Therefore, no design change of the micro-satellite is required to accommodate the requirement. This experience can be duplicated in FS7 program.