Called COSMIC - for Constellation Observing System for Meteorology, Ionosphere and Climate - in the United States and FORMOSAT-3 in Taiwan, the $100 million array of low-orbiting satellites will be the first to provide atmospheric data daily in real time over thousands of points on Earth for both research and operational weather forecasting. The satellites will measure the bending of radio waves from Global Positioning System satellites as their signals pass through Earth's atmosphere.
"The satellites will convert GPS measurements into a precise worldwide set of weather, climate, and space weather data," said Jay Fein, program director at the National Science Foundation's Division of Atmospheric Sciences, which funded COSMIC.
COSMIC relies on a technology known as radio occultation. Just as the water molecules in a glass change the path of visible light waves, molecules in the air bend GPS radio signals as they pass through the atmosphere. By measuring the amount of the bending, scientists can determine underlying atmospheric conditions, such as air density, temperature and moisture, and electron density.
"This is the first time the technique of radio occultation has been used on a large scale in real time to provide nearly continuous measurements of worldwide atmospheric conditions at all altitudes," said William Kuo, director of the UCAR COSMIC office, which provided the design for the array.
Orbiting at an altitude of 500 miles (800 kilometers), the COSMIC satellites will take approximately 2,500 measurements every 24 hours in a nearly uniform distribution around the globe. The system will provide independent data over vast stretches of the oceans where there are no weather balloon observations. The data's high vertical resolution will complement the high horizontal resolution of other weather satellite measurements.
Because the satellites' radio signals pierce thick cloud cover and precipitation, weather conditions will not interfere with data gathering, as is often the case for remote sensing platforms. The satellites will not need to be recalibrated and the instruments' accuracy and sensitivity will not change during the five-year mission--common problems with Earth-observing satellites over their lifetime. The data will be available to researchers and forecasters within a few hours of the observations.
COSMIC will derive temperature and water vapor profiles from GPS data, which should help meteorologists observe, research and forecast hurricanes, typhoons and other storm patterns over the oceans and improve many areas of weather prediction, atmospheric scientist said.
COSMIC's measurements also will improve analysis and forecasting of space weather - geomagnetic storms that can interrupt sensitive satellite and communications systems and affect power grids on the ground.
Several single-satellite systems have used GPS signals experimentally over the past decade, but COSMIC's six-satellite array is the first to provide the high-density global coverage required for both research and operational forecasting.
An Orbital Sciences Corp. Minotaur I rocket will lift the array at 5:10 p.m. Pacific Time from Vandenberg. The Minotaur I to be used in the FORMOSAT-3/COSMIC launch includes previously decommissioned U.S. Air Force Minuteman rocket motors for the vehicle's first and second stages. The company obtained the Minuteman motors under a U.S. Air Force Orbital/Sub-orbital Program-2, or OSP-2, contract. The third and fourth stages, structures and payload fairing are common with Orbital's Pegasus rocket.
Taiwan's National Science Council and National Space Organization provided more than $80 million of the funding, with the National Science Foundation - lead agency for COSMIC's science activities - and its partners providing the remaining $20 million.
Other major partners include NASA, NOAA, the U.S. Air Force Space Test Program and the Office of Naval Research. The Space and Missile Systems Center's Rocket Systems Launch Program of the U.S. Air Force provided logistical support.