For Immediate Release
Subject: FORMOSAT-3/COSMIC Science Mission
Six identical micro-satellites comprising the FORMOSAT-3/COSMIC (Formosa Satellite #3 and Constellation Observing System for Meteorology, Ionosphere and Climate) mission were successfully launched into a low-earth circular orbit at 516 km from Vandenberg Air Force Base, California at 18:40 Local Time on April 14, 2006. The FORMOSAT-3/COSMIC mission provides the first satellite constellation for monitoring global weather using the Global Positioning System (GPS) radio occultation (RO) technique. The mission is a Taiwan-US collaborative project jointly carried out by the National Space Organization (NSPO) in Taiwan and the University Corporation for Atmospheric Research (UCAR) in the United States. The instruments on board the satellites are all working normally. During a deployment period of ~13 months, each satellite will rise to its final orbit at an altitude of ~800 km, an orbit plane inclination angle of 72°, and a separation angle between the neighboring orbit planes of 24° in longitude. Information about the FORMOSAT-3/COSMIC mission information may be found at Taiwan's National Space Organization Web site and UCAR's COSMIC Web site. The satellites are expected to last for 5 years. The mission’s science goal is to obtain in near-real time of temperature, pressure and water vapor in the neutral atmosphere and electron density in the ionosphere. The observations will be used to support operational global weather prediction, climate monitoring and research, space weather forecasting, and ionosphere and gravity research. The World Meteorological Organization will distribute the FORMOSAT-3/COSMIC data to the weather centers of its member countries.
The FORMOSAT-3 satellites will be the first to provide global atmospheric data for both research and operations in near real time using the radio occultation technology by measuring the bending of radio signals from the U.S. Global Positioning System (GPS) as the signals pass through Earth's atmosphere and ionosphere. The radio occultation is a technique for determining the property of an inhomogeneous medium by measuring the refractive bending of radio signals passing through the medium. Just as the water molecules in a glass change the path of visible lights from the air into water (or vice versa) so that a pencil appears bent, molecules in the air bend GPS radio signals as they pass through the atmosphere. By measuring the amount of this bending, scientists can determine underlying atmospheric conditions, such as air density, temperature and moisture, and electron density in the ionosphere.
The GPS radio occultation technique has been deployed in satellites such as GPS-MET, CHAMP and SAC-C and the atmospheric data obtained have been shown to be highly accurate. However, these are single satellite operation without mutual coordination. The FORMOSAT-3 mission’s six satellites use the GPS radio occultation technique on a large scale in near real time to provide continuous monitoring of worldwide atmospheric conditions. The satellites will take at least 2,500 measurements of vertical profiles of atmospheric air density, temperature and water vapor every 24 hours around the globe, filling in current data gaps over the oceans and the polar region. This is about twice the daily ground-based observation of about 1500 measurements, which are concentrated mostly over low and middle latitude land regions. The data's high vertical resolution will complement the high horizontal resolution of conventional weather satellite measurements. Temperature, air density and water vapor profiles derived from the FORMOSAT-3 GPS data will help meteorologists observe and forecast typhoons, hurricanes, and other storm patterns over the oceans and improve many areas of weather prediction. The stability, consistency, and accuracy of the measurements should also help scientists quantifying long-term climate change trend.
Two data centers will receive and process the raw data from GOX, TIP and TBB’s ground receivers: (1) the Taiwan Analysis Center for COSMIC (TACC) at the Central Weather Bureau in Taiwan and (2) the COSMIC Data Analysis and Archive Center (CDAAC) located at UCAR. The FORMOSAT-3/COSMIC processed data will be ready for distribution within 3 hours from the time of raw data collection. The FORMOSAT-3/COSMIC data and products will be made available to the international science and operational communities from TACC or CDAAC. These data products include vertical profiles of bending angles, refractivity, electron density, temperature, pressure, and water vapor, and 135.6 nm radiances observed by the Tiny Ionospheric Photometer. Users of FORMOSAT-3/COSMIC data products are required to register at the TACC Web site by submitting a Data Use Agreement electronically to NSPO for review and approval. The registration will then be automatically forwarded to UCAR. A copy of the Data Use Agreement is available on the TACC and the CDAAC web sites.
During the next few months the FORMOSAT-3 satellites will stay relatively close to each other in longitude and the GPS radio occultation soundings would be very dense. It is an excellent and rare opportunity for performing cross validation of the radio occultation data with other observations (ground based radiosonde, weather satellite, and balloons, etc.). NSPO will conduct an Intense Observation Period (IOP) campaign to carry out the data validation and to assess the impact of FORMOSAT-3/COSMIC data on typhoon intensity and track prediction and forecasts of heavy rainfall events over East Asia. The IOP campaign will be held during May-October, 2006. Two field campaigns will be conducted in the vicinity of Taiwan, one to study the Mei-Yu front and associated disturbances during May and June and the other to study typhoons during July-October. Researchers around the world are invited to participate in the IOP campaign.
The National Center for Atmospheric Research and UCAR Office of Programs are operated by UCAR under the sponsorship of the National Science Foundation and other agencies. Opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any of UCAR's sponsors.