Japan launches satellite to track greenhouse gases
BY STEPHEN CLARK
Posted: January 23, 2009
The first satellite devoted to measuring greenhouse gases in Earth's atmosphere arrived in space Friday after launching from an island spaceport in southwestern Japan.
The Greenhouse Gases Observing Satellite, or GOSAT, was deployed from the upper stage of an H-2A rocket about 16 minutes after blastoff, according to the Japan Aerospace Exploration Agency.
Greenhouse gases are produced by natural and human sources, including geological activity, biological activity and the burning of fossil fuels.
Scientists believe greenhouse gases trapped in Earth's atmosphere are responsible for rising global temperatures. Carbon gases can trap heat that would normally radiate into space, driving up the planet's average temperature, according to climate researchers.
That was the primary impetus behind the development of the $206 million mission.
"GOSAT is designed to observe the global distribution of greenhouse gases, such as carbon dioxide and methane, from space. I am convinced and excited that GOSAT will play an important role in the understanding of global warming," said Takashi Hamazaki, GOSAT project manager at JAXA.
GOSAT launched aboard an H-2A rocket from the Yoshinobu complex on Tanegashima Island at the southwestern tip of Japan. A hydrogen-fueled main engine and twin solid motors boosted the 174-foot-tall rocket off the launch pad at 0354 GMT (12:54 p.m. Japanese time) Friday.
The flight was delayed two days because of forecasted bad weather. The launch team battled thick clouds, rainy weather and cold temperatures all week, but meteorologists cleared the rocket for liftoff Friday despite gusty winds and rain showers.
The first stage's LE-7A main engine propelled the orange and white rocket to an altitude of 185 miles in the first six-and-a-half minutes of the mission. The second stage fired for more than eight minutes, honing in on a circular orbit about 425 miles high.
The upper stage was programmed to release seven other smaller payloads at four-minute intervals following the separation of GOSAT.
The largest secondary payload was a small demonstration satellite named SDS 1. The 220-pound craft carries experimental communications equipment, a developmental data processing chip and new computer components.
Other small satellites aboard the rocket included a collection of Japanese educational, experimental and scientific missions. They will observe lightning, measure gamma rays emitted from Earth, test space tethers, demonstrate a new remote sensing telescope, conduct trials of a laser ignition thruster, and help connect students with space.
The satellites, including GOSAT, are circling the planet in a sun-synchronous orbit with an inclination of about 98 degrees.
The satellite was commissioned by JAXA, the National Institute for Environmental Studies and the Japanese Ministry of the Environment.
"Several organizations conduct atmospheric, oceanic and terrestrial monitoring of greenhouse gases. To enhance these opportunities, various ministries and institutions launched a Japanese alliance for climate change observation," said Yasuhiro Sasano, director of the Center for Global Environmental Research at Japan's National Institute for Environmental Studies.
GOSAT's primary objective is to identify sources of atmospheric carbon dioxide and methane, partly to monitor international compliance with the Kyoto Protocol.
The Kyoto Protocol is an agreement between 37 industrialized countries and Europe to reduce greenhouse gas emissions by an average of five percent, compared to 1990 levels, by 2012. The protocol was adopted in 1997 and became binding in 2005.
GOSAT's measurements will locate areas with high greenhouse gas emission and absorption rates. The satellite will also track clouds of carbon dioxide spread across the globe by wind patterns.
The satellite's primary instrument consists of two sensors: an infrared spectrometer and a cloud and aerosol imager.
The spectrometer will observe infrared rays of sunlight reflected from Earth back into space. The sensor will look for the chemical signatures of carbon dioxide and methane in the light to build a map of their worldwide concentrations.
GOSAT's imager will account for clouds and aerosols than can produce measurement errors.
The instrument package, called TANSO, will collect 56,000 data points of greenhouse gas densities every three days.
Scientists now rely on less than 300 observation posts on the ground, ships, or aircraft to gather information on greenhouse gases. Most of those locations are in Europe.
Japan plans to share data from GOSAT with other nations, and officials hope to begin distributing greenhouse gas maps by 2010.
The maps will be constructed in large sub-continental blocks depicting the regional emission and absorption rates by both human and natural sources.
Japanese scientists are eager to partner with U.S. researchers leading the Orbiting Carbon Observatory mission, which is scheduled to launch next month aboard a Taurus rocket from Vandenberg Air Force Base, Calif.
Scientists from both missions have been working together since 2004, said David Crisp, OCO's principal investigator.
The GOSAT and OCO teams worked to build a common ground validation network to help combine data from the missions. The satellites will also fly in similar orbits to observe the same locations at nearly the same time, officials said.
"This is particularly important for this measurement because these two satellites will be making a measurement that must be about three times more precise than other trace gas measurements made from space," Crisp said.
The cross-calibration between OCO and GOSAT will improve confidence that both satellites are making accurate measurements.
OCO's spectrometer will provide greater sensitivity on carbon dioxide measurements but is unable to detect methane. GOSAT's orbit is designed to bring the satellite over the same location more often, allowing the craft's lower resolution instrument to create a new global map every three days.
"Together, OCO and GOSAT provide independent measurements that will help scientists better understand this important greenhouse gas and its impacts on our present and future climate," Crisp said.