Taiwan's Earth Observation Systems
The ROCSAT-2 program, approved by the Executive Yuan of ROC, on Oct 1997, is in the planning stage. ROCSAT-2 is designed to perform near realtime remote sensing of the ocean and landmass in the vicinity of Taiwan. The data from the ROCSAT-2 mission can be applied towards land use, agriculture and forestry, natural disaster evaluation, environmental monitoring, education, and foster international cooperation in various scientific researches. In addition to the remote sensing mission, the scientific mission of investigating the upper atmospheric lighting phenomena is included in ROCSAT-2. In order to achieve these mission objectives, a small class, low earth-orbit remote sensing satellite will be developed. The existing ROCSAT ground system will be upgraded to support this mission.
Taiwan is an island prone to natural disasters brought on by typhoons during the summer months. Timely availability of remote sensing data is critical for Taiwan in the aftermath of these disasters. The ROCSAT-2, as the satellite for ROC, will focus mainly on satisfying local user needs. Therefore, frequent revisit of Taiwan and timely availability of the data for Taiwan are unique characteristics that distinguish ROCSAT-2 from other commercial satellites. The applications of such remote sensing include governing the use of land, agriculture, natural disaster assessment, environmental monitoring, scientific research, and educational activities. In addition to its remote sensing mission, ROCSAT-2 also has the scientific mission of investigating various lighting phenomena in the upper atmosphere.
The major characteristics of the satellite are: the mission orbit of 891 km altitude, sun synchronous (revisiting Taiwan for imaging every day); with panchromatic and multi-spectral bands in Visible/NIR/SWIR; panchromatic ground sampling distance (GSD) better than 5 meters [it is widely reported that the resolution is actually 2 meters] and multi-spectral GSD better than 20 m; swath larger than 50 km; field of regard of 45 degree (almost global coverage); real-time imaging and downlink while ground antenna elevation angle above 20 degree. The electron-optical imager can simultaneously capture four panchromatic, multi-spectrum images and then transmit this data to government agencies, private sector companies, and research organizations.
In February 1999 Dornier Satelliten Systeme GmbH, a subsidiary of DaimlerChrysler Aerospace, won a US$83 million contract to build parts for the ROCSAT-2. However the German government refused to issue the required export license to DASA Dornier, in response to Chinese diplomatic pressure. China claimed that Taiwan would use the satellite's high resolution imaging system for military surveillance, rather than its stated civilian purposes. In December 1999 Taiwan awarded French company Matra-Marconi Space the ROCSAT-2 contract, with plans to equip the satellite with 14 main instruments reduced to six. Beijing dropped its objections once the French promised that the satellite would not be converted for military applications. The launch date of ROCSAT-2 is scheduled for May 2002 on an American Athena launch vehicle, with a mission lifetime more than 5 years.
The ROCSAT Ground System (RGS) contract was awarded to the AlliedSignal Technical Services Cooperation (ATSC) of USA. Through a contractual requirement, four Taiwanese subcontractors, i.e., Tatung, SysCom, TTNS and CTCI, have been selected by ATSC as subcontractors to participate in the development of the system. The two Telemetry, Tracking and Command (TT&C) stations provide the links between the RGS and satellites. There are two stations in the mission located at north and south of Taiwan, respectively. In normal operation, TT&C is controlled by Mission Operations Center (MOC) located in Hsinchu. In an emergency, the operation personnel can reside in the stations and TT&C will perform the same functions as the MOC.
The Republic of China's second satellite -- ROCSAT-2 -- left Taiwan 01 December 2003 for the United States. Preparations to transport the 750kg satellite from Hsinchu in northern Taiwan to Vandenberg Air Force Base in California for a planned liftoff 17 January 2004 were completed. The satellite has been placed in a 2,100kg container into which nitrogen has been injected to ensure stable conditions for the long journey to the United States. The container, owned by the NSPO's contractor Astrium Co. of France, will be airlifted to Los Angeles and then delivered by truck to Vandenberg Air Force Base located on the Pacific coast in central California.
The satellite was scheduled to be launched in late February 2004. Electrical circuit problems were discovered in ROCSAT-2's launcher in early December, prompting U.S. Orbital Sciences Corp (OSC), the operator of the satellite's launch vehicle, to suggest that the launch be postponed from January 17 to February 26. After its fourth circle around the globe, a station in Chungli, Taiwan, will start receiving information from it. By early March the the launch could be scheduled between late March and early April 2004.
The launch of the ROCSAT-2 satellite, which carries a price tag of NT$4.7 billion, will lead Taiwan into a new era of space research. The ROCSAT-2 satellite is different from its predecessor in that it will have practical applications involving remote-sensing technologies to help upgrade Taiwan's capabilities in disaster prevention, land mapping and environmental monitoring.
The ROCSAT-2 satellite can take pictures of objects on the ground as small as two meters across. The satellite is designed to orbit the Earth 14 times a day, including two passes over Taiwan, at 891 km above the Earth. In addition to its remote sensing mission, the ROCSAT-2 has the scientific mission of investigating various lighting phenomena in the upper atmosphere.
The ROC government launched a 15-year space technology development plan in 1991. In its initial stage, the NSPO is concentrating on a satellite project known as ROCSAT, which consists of three different satellite ventures. The first venture involved the ROC's first satellite -- ROCSAT-1 -- which was built by the U.S. firm TRW and successfully launched in 1999 from Cape Canaveral, Florida, while the third satellite, ROCSAT-3, is an ROC-U.S. joint venture, which will be launched in 2005. Some components of these satellites will be manufactured in Taiwan under the auspices of technology transfer from foreign contractors.
Satellite Orbital Characteristics:
- sun-synchronous orbit with satellite altitude = 891 km
- inclination 98.99
- orbit adjustment: after drifting 400 km from assigned orbit (about every 6 months)
- revisit Taiwan twice daily (one at daytime and the other at night-time)
- life span 5 years (over 70% reliability)
- figure of satellite tracks
- Pan Chromatic pushbroom CCD:ˇ@ 60 km swath with 2m - 5m resolution
- MSS at 15 m resolution
- stereo capability
- swathˇ@ 60 km,ˇ@ maximal nadir angle = 30-degrees
- downlink with X-band 50 Mbps ~ 100 Mbps, spot beam antenna
- on-board recorderˇ@ 10 Gb, plus spare
