The FORMOSA Satellite Series No. 3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) spacecraft constellation consisting of six low-earth-orbiting satellites is the world's first operational Global Positioning System (GPS) radio occultation mission. The mission has been jointly developed by the National Space Organization of Taiwan and the University Corporation for Atmospheric Research of the U.S. in collaboration with the Jet Propulsion Laboratory, NASA, and the Naval Research Laboratory for three onboard payloads, including a GPS Occultation Receiver, a triband beacon, and a tiny ionospheric photometer. The FORMOSAT-3/COSMIC mission was successfully launched from Vandenberg into the same orbit plane of the designated 516-km circular parking orbit altitude on April 15, 2006. After the six satellites completed the in-orbit checkout activities, the mission was started immediately at the parking orbit for in-orbit checkout, calibration, and experiment of three onboard payloads. Individual spacecraft thrust burns for orbit raising were performed to begin the constellation deployment of the satellites into six separate orbit planes. All six FORMOSAT-3/COSMIC satellites are maintained in a good state of health except spacecraft flight model no. 2, which has had power shortages. Five out of the six satellites had reached their final mission orbits of 800 km as of November 2007. This paper provides an overview of the constellation spacecraft design, constellation mission operations, constellation deployment timeline evolution, associated spacecraft mass property and moment of inertia results, orbit-raising challenges, and lessons learned during the orbit-raising operations.

AB STRACTThe FORMOSAT-3/COS MIC space craft con stel la tion con sist ing of six LEO sat el lites is the world's first op er a tional GPS Ra dio Occultation (RO) mis sion. The mis sion is jointly de vel oped by Tai wan's Na tional Space Or ga ni za tion (NSPO) and the United States' UCAR in col lab o ra tion with NSF, USAF, NOAA, NASA, NASA's Jet Pro pul sion Lab o ra tory, and the US Na val Re search Lab o ra tory. The FORMOSAT-3/COS MIC sat el lites were suc cess fully launched from Vandenberg US AFB in Cal i for nia at 0140 UTC 15 April 2006 into the same or bit plane of the des ig nated 516 km al ti tude. The mis sion goal is to de ploy the six sat el lites into six or bit planes at 800 km al ti tude with a 30-de gree sep a ra tion for evenly dis trib uted global cov er age. All six FORMOSAT-3/COS MIC sat el lites are cur rently main tain ing a sat is fac tory good state-of-health. Five out of six sat el lites have reached their fi nal mis sion or bit of 800 km as of No vem ber 2007. The data as re ceived by FORMOSAT-3/COS MIC sat el lites con stel la tion have been pro cessed in near real time into 2500 good ion o spheric pro files and 1800 good at mo spheric pro files per day. These have out num bered the world wide ra dio sondes (~900 mostly over land) launched from the ground per day. The pro cessed at mo spheric RO data have been as sim i lated into the Nu mer i cal Weather Pre dic tion (NWP) mod els for real-time weather pre dic tion and ty phoon/hur ri cane fore cast ing by many ma jor weather cen ters in the world. This pa per de scribes the FORMOSAT-3/COS MIC sat el lite con stel la tion sys tem per for mance and the mission results that span the period from April 2006 to October 2007; and reviews the prospect of a future follow-on mission.Key words: FORMOSAT-3, COS MIC, GPS ra dio occultation, Re mote sens ing, Con stel la tion de ploy ment, Or bit rais ing, Sat el lite, Op er a tion challenges Ci ta tion: Fong, C. J., N. L. Yen, C. H. Chu, S. K. Yang, W. T. Shiau, C. Y. Huang, S. Chi, S. S. Chen, Y. A. Liou, and Y. H. Kuo, 2009: FORMOSAT-3/COS MIC space craft con stel la tion sys tem, mis sion re sults, and pros pect for fol low-on mis sion. Terr. Atmos. Ocean. Sci., 20, 1-19, doi: 10.3319/ TAO.2008.01.03.01(F3C) IN TRO DUC TIONRa dio Occultation (RO) tech niques have been used in outer space to probe plan e tary ion o spheres and at mo spheres for over four de cades. In the early 1960s, sci ence teams at JPL/NASA and Stan ford Uni ver sity de vel oped one-way and two-way ra dio occultation tech niques, re spec tively, to probe Mars. The com bined tech niques have since been used to probe the at mo sphere of al most ev ery planet and their moons in the so lar sys tem Kliore et al. 1965;Mel bourne et al. 1994;Yunck et al. 2000).The GPS/MET ex per i ment (1995 -1997) car ried aboard the NASA-spon sored MICROLAB I sat el lite showed that the at mo spheric limb-sound ing tech nique us ing ra dio signals trans mit ted from GPS sat el lites of fers cer tain ad vantages over the tra di tional pas s...

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 • separation. Four out of six satellites had already reached their final mission orbit of 800 km 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. Test between ground segment and space segment and in charge of the communication infrastructure setup and interphase test between SOCC and the remote ground stations during FORMOSAT-3 I&T phase. He is currently the Deputy Operation Director of FORMOSAT-3 Mission Operation Team. His current research interests include GPS radio occultation for the FORMOSAT-3 follow-on mission, satellite simulator, mission planning and scheduling, and long-term trending development. Chung-Huei (Vicky) Chu received the B.S. degree in atmospheric sciences from the National Taiwan University, Taipei, Taiwan and the M.S. degree in meteorology from Penn State University, University Park. She is currently the FORMOSAT-3/COSMIC Mission Operations Manager of National Space Organization, Hsinchu, Taiwan. She has worked on FORMOSAT series satellite programs since 1994. She spent one year in the development of science data processing, five years in the flight operations and ground operations, and six years in mission analysis and system engineering. Cheng-Yung Huang received the B.

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