An Orbital Sciences-built Minotaur rocket successfully launched six small satellites from Vandenberg Air Force Base, Calif., April 14 on a mission to study the Earth’s atmosphere and track climate change.
The April 14 launch marked the fifth launch of an Orbital-built Minotaur rocket since its debut in 2000.
The $100 million satellite network is known as the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) in the United States and Formosat-3 in Taiwan. The six satellites are designed to provide real-time atmospheric data daily for both research and operational weather forecasting.
The satellites will accomplish this task by measuring the bending of radio signals from the U.S. Global Positioning System (GPS) as those signals travel through Earth’s atmosphere. The technique can be used to track hurricanes and climate change, and monitor the effects of space weather in the atmosphere.
The project is the product of an agreement between the American Institute in Taiwan and the Taipei Economic and Cultural Representative Office in the United States.
The six spacecraft are based on a system design provided by the Boulder-based University Corporation for Atmospheric Research (UCAR), a consortium of 69 universities focused on atmospheric and related sciences.
Taiwan’s National Science Council and its National Space Organization provided more than $80 million for the system. The U.S. National Science Foundation, lead agency for COSMIC science activities, and its partners, including NASA, the National Oceanic and Atmospheric Administration (NOAA), the U.S. Air Force Space Test Program and the Office of Naval Research, also contributed to the project.
The six microsatellites, which each weigh roughly 62 kilograms including fuel, were adapted for the mission from Orbital Sciences Corp.’s MicroStar spacecraft design .
Each of the satellites is just several centimeters deep but fully loaded with four GPS antennas; a Tiny Ionospheric Photometer to calculate the total electric density of the area where the satellite faces the Earth; and a Tri-Band Beacon to transmit radio signals at three different frequencies.
The satellites will be deployed in circular orbits at an altitude of some 700-800 kilometers . They are expected to reach their final mission orbits in 13 months.
The COSMIC microsatellites will track signals from the GPS satellites as they cut through Earth’s atmosphere. GPS signals undergo changes in frequency and amplitude when they encounter water vapor or other physical components of the atmosphere. Those changes can be measured using a process called radio occultation. That is, molecules in the air bend GPS radio signals as they pass through (are occulted by) the atmosphere.
By measuring the amount of the bending, research scientists can determine underlying atmospheric conditions, such as air density, temperature and moisture, and electron density.
The COSMIC satellites will take approximately 2,500 measurements every 24 hours in a nearly uniform distribution around the globe. Because the satellites’ radio signals pierce thick cloud cover and precipitation, weather conditions will not interfere with data gathering.
The altered signals are to be turned into valuable views of humidity and temperature throughout the lower atmosphere. Information about the electrical structure of the upper atmosphere, Earth’s gravitational field, and other data also will be extracted. Researchers and forecasters around the world will have access to the data via the Internet.
Temperature and water vapor profiles derived from the GPS data should prove helpful to meteorologists who observe, research and forecast hurricanes, typhoons and other storm patterns over the oceans, as well as improve many areas of weather prediction. The stability, consistency and accuracy of the measurements should be a boon to scientists quantifying long-term climate-change trends, according to COSMIC experts at UCAR.
Additionally, COSMIC measurements of electron density in the ionosphere are expected to enhance analysis and forecasting of space weather, including geomagnetic storms that can disrupt sensitive satellite and communications systems and even impact power grids on the ground.
The COSMIC system is a gap-filler of sorts. It will yield data over vast stretches of the oceans where there are no weather balloon observations. And the data’s high vertical resolution will complement the high horizontal resolution measurements of several existing weather satellites.
William Kuo, director of the UCAR COSMIC office, said COSMIC will make use of the newly developed “open-loop tracking technique” which would allow deep penetration into the Earth’s troposphere — a region of the atmosphere that starts at the Earth’s surface and extends 8 to 14.5 kilometers in altitude.
“We can get high-quality sounding to within 1,640 feet (500 meters) of the surface … even over the tropics. This will provide valuable information on atmospheric water vapor, which is important for hurricane and severe weather prediction,” Kuo said.
Comments: ldavid@space.com
