Browsing by Author "Huang, Cheng-Yung"

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A Near-Real-Time Automatic Orbit Determination System for COSMIC and Its Follow-On Satellite Mission: Analysis of Orbit and Clock Errors on Radio Occultation
(2014-06-01)
Li, Yi-Shan
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Hwang, Cheinway
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Tseng, Tzu-Pang
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Huang, Cheng-Yung
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Bock, Heike
The COSMIC-2 mission is a follow-on mission of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) with an upgraded payload for improved radio occultation (RO) applications. The objective of this paper is to develop a near-real-time (NRT) orbit determination system, called NRT National Chiao Tung University (NCTU) system, to support COSMIC-2 in atmospheric applications and verify the orbit product of COSMIC. The system is capable of automatic determinations of the NRT GPS clocks and LEO orbit and clock. To assess the NRT (NCTU) system, we use eight days of COSMIC data (March 24-31, 2011), which contain a total of 331 GPS observation sessions and 12 393 RO observable files. The parallel scheduling for independent GPS and LEO estimations and automatic time matching improves the computational efficiency by 64% compared to the sequential scheduling. Orbit difference analyses suggest a 10-cm accuracy for the COSMIC orbits from the NRT (NCTU) system, and it is consistent as the NRT University Corporation for Atmospheric Research (UCAR) system. The mean velocity accuracy from the NRT orbits of COSMIC is 0.168 mm/s, corresponding to an error of about 0.051 mu rad in the bending angle. The rms differences in the NRT COSMIC clock and in GPS clocks between the NRT (NCTU) and the postprocessing products are 3.742 and 1.427 ns. The GPS clocks determined from a partial ground GPS network [from NRT (NCTU)] and a full one [from NRT (UCAR)] result in mean rms frequency stabilities of 6.1E-12 and 2.7E-12, respectively, corresponding to range fluctuations of 5.5 and 2.4 cm and bending angle errors of 3.75 and 1.66 mu rad.
Constellation challenges and contributions of Taiwan weather monitoring satellites
(2008)
Fong, Chen-Joe
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Yen, Nick
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Chu, Vicky
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Yang, Eddy
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Huang, Cheng-Yung
National Space Organization (NSPO) of Taiwan in the past ten years has successfully launched three different types of satellites. The latest one is FORMOSAT-3/COSMIC, a joint Taiwan-US project, which was successfully launched on April 15, 2006. The FORMOSAT-3 is a constellation of 6 satellites and each satellite is equipped with GPS Occultation Receiver (GOX), Tri-Band Beacon (TBB), and Tiny Ionospheric Photometer (TIP). The constellation is on the way to its final orbit configuration. All satellites remain healthy except spacecraft Right model no. 2 (FM2) with a problem of power shortage and FM3 currently staying at an orbit of 711 km due to a mechanism issue to be solved. The current sounding profiles retrieved from the GPS occultation measurements are over an average of 1800 daily. The sounding profiles have been used to study atmospheric and ionospheric structures and total electron content, and assimilated into numerical atmospheric and space weather predictions models to improve the accuracy of prediction. Taiwan has taken an active role and grown remarkably well in remote sensing researches during the last decade. Taiwan will continue to share her resources with the international community for scientific research and applications. In this paper, we will present an overview of significant contributions of the FORMOSAT-3/COSMIC satellite mission to the global community. We will also describe the constellation challenges and novel operations solutions and the future follow-on mission planning. (1 2).
FORMOSAT-3/COSMIC Constellation Spacecraft System Performance: After One Year in Orbit
(2008-11-01)
Fong, Chen-Joe
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Yang, Shan-Kuo
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Chu, Chung-Huei
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Huang, Cheng-Yung
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Yeh, Jia-Jing
The FORMOSAT-3 mission, also known as Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), is the third major project of the Formosa Satellite (FORMOSAT) series implemented by the National Space Organization of Taiwan. FORMOSAT-3/COSMIC is a joint Taiwan/U.S. mission consisting of six identical low Earth orbit satellites. All six cluster satellites were successfully launched by a single Minotaur launch vehicle on April 15, 2006. The retrieved global positioning system (GPS) radio occultation (RO) data have been freely available online to the science community since shortly after the completion of satellite bus in-orbit checkout. Having completed the verification and validation, the worldwide science communities are highly satisfied with the RO data. Scientists have hailed the RO sensors as offering the most accurate, precise, and stable thermometers in space. After one year in orbit, all six FORMOSAT-3/COSMIC satellites were in good condition (except FM2, which had power shortage issues) and were on their way toward the final constellation of six separate orbit planes with 30 degrees separation. Four out of six satellites had already reached their final mission orbit of 800 kin by mid-May 2007. Together, the six satellites have generated a total of more than 2500 RO data per day. However, only 50%-70% of the RO data as received one year after launch could be retrieved into useful atmosphere profiles. The retrieved RO data, about 1800 per day on average, have been assimilated into numerical weather prediction models by many major weather forecast centers and research institutes. This paper provides an overview of the constellation mission, the spacecraft system performance after one year in orbit, the technical challenges we have encountered, and the performance enhancements we have accomplished.
FORMOSAT-3/COSMIC Spacecraft Constellation System, Mission Results, and Prospect for Follow-On Mission
(2009-02-01)
Fong, Chen-Joe
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Yen, Nick L.
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Chu, Chung-Huei
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Yang, Shan-Kuo
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Shiau, Wen-Tzong
The FORMOSAT-3/COSMIC spacecraft constellation consisting of six LEO satellites is the world's first operational GPS Radio Occultation (RO) mission. The mission is jointly developed by Taiwan's National Space Organization (NSPO) and the United States' UCAR in collaboration with NSF, USAF, NOAA, NASA, NASA's Jet Propulsion Laboratory, and the US Naval Research Laboratory. The FORMOSAT-3/COSMIC satellites were successfully launched from Vandenberg US AFB in California at 0 140 UTC 15 April 2006 into the same orbit plane of the designated 516 km altitude. The mission goal is to deploy the six satellites into six orbit planes at 800 kin altitude with a 30-degree separation for evenly distributed global coverage. All six FORMOSAT-3/COSMIC satellites are currently maintaining a satisfactory good state-of-health. Five out of six satellites have reached their final mission orbit of 800 kin as of November 2007. The data as received by FORMOSAT-3/COSMIC satellites constellation have been processed in near real time into 2500 good ionospheric profiles and 1800 good atmospheric profiles per day. These have outnumbered the worldwide radiosondes (similar to 900 mostly over land) launched from the ground per day. The processed atmospheric RO data have been assimilated into the Numerical Weather Prediction (NWP) models for real-time weather prediction and typhoon/hurricane forecasting by many major weather centers in the world. This paper describes the FORMOSAT-3/COSMIC satellite constellation system performance and the mission results that span the period from April 2006 to October 2007; and reviews the prospect of a future follow-on mission.
Mission Results from FORMOSAT-3/COSMIC Constellation System
(2008-11-01)
Fong, Chen-Joe
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Huang, Cheng-Yung
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Chu, Vicky
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Yen, Nick
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Kuo, Ying-Hwa
The FORMOSAT-3/COSMIC spacecraft constellation consisting of six low-Earth-orbit satellites is the world's first operational Global Positioning System radio occultation mission. Its mission is jointly developed by Taiwan's National Space Organization and the United States's University Corporation for Atmospheric Research in collaboration with NASA's Jet Propulsion Laboratory and the Naval Research Laboratory for the three onboard payloads, which include the Global Positioning System occultation receiver, the triband beacon, and the tiny ionospheric photometer. The FORMOSAT-3/COSMIC mission was launched successfully from Vandenberg Air Force Base on 15 April 2006 into the same orbit plane of the designated 516 km circular parking orbit altitude. All six FORMOSAT-3/COSMIC satellites are maintained in a good state of health except spacecraft flight model 2, which has a power shortage, and flight model 3, currently staying at an orbit of 711 km due to a mechanism problem to be solved, and are on their way toward the final constellation of six separate orbit planes with 30 deg separations as planned. Five out of six satellites have reached their final mission orbit of 800 km as of November 2007. The FORMOSAT-3/COSMIC has processed over 1800 good atmospheric sounding profiles per day on average, which is larger than the number of worldwide radiosondes launched per day (similar to 900, mostly above the land). The atmospheric radio occultation sounding data are assimilated into the numerical weather prediction models for real-time weather prediction and typhoon/hurricane forecast. The global and some major nations' weather prediction centers have shown a significant positive impact and the forecast result will be also adapted to Taiwan's disaster warning and relief system once constellation deployment is completed by the end of 2007. With the invention of the open-loop technique by University Corporation for Atmospheric Research, the quality, accuracy, and lowest penetration altitude of the radio occultation sounding profiles are better than CHAMP data. This paper also describes the mission highlight, the constellation spacecraft system performance summary, the constellation mission operation result, and the mission science results.