Solar observatory launched to space by Japanese rocket
BY STEPHEN CLARK
Posted: September 22, 2006
Japan launched an international solar physics satellite into orbit Friday with a trio of powerful instruments that scientists hope can answer key questions about the Sun's magnetic field.
Making its last flight, the solid-fueled booster deployed the almost 2,000-pound satellite into orbit about eight-and-a-half minutes after blastoff. The rocket was shooting for a Sun-synchronous orbit about 373 miles high.
Tagged at about $70 million per launch, the M-5 launcher is being replaced by a less expensive design. Officials with the Japanese Aerospace Exploration Agency believe the new rocket will cost about $22 million each flight, according to a JAXA spokesperson.
JAXA said the M-5's replacement will feature a first stage based on the larger H-2A rocket's 50-foot long solid rocket booster, which is called the SRB-A. The new two-stage launcher - scheduled for a first flight in 2010 - will use the M-5's third stage as a second stage to deliver approximately 1,100 pounds to low Earth orbit.
At least one satellite - the Planet-C craft that is planned to orbit Venus - was moved from the M-5 to launch on the H-2A rocket in 2010.
Solar-B is setting off on a three-year mission, during which its package of instruments will take the best look yet at the Sun's enigmatic magnetic field. The mission could be extended if the spacecraft remains in good health.
The craft's science payload was built by a variety of international partners in Japan, Europe, and the United States. The instruments were designed specifically to complement each other during the mission, said John Davis, Solar-B project scientist at NASA's Marshall Space Flight Center.
Davis said the cost of the mission to NASA was $172 million.
All three primary instruments will be searching for clues about the
physics driving magnetic field processes in the solar corona that control
much of the Sun's behavior. The suite of instruments is scheduled to begin
testing operations in about one month.
"I think they are going to reveal to us a lot about how the energy of the magnetic field is transferred into the atmosphere and produces all of these beautiful pictures of coronal mass ejections and solar flares, which also can affect the Earth in various ways."
The Solar Optical Telescope aboard the satellite will be able to detect small variations in the Sun's magnetic field as it builds and releases energy in violent events such as coronal mass ejections and solar flares in active regions scattered across the Sun.
"We will follow active regions as they rotate across the face of the Sun, making these very precise measurements of the magnetic field," said Ted Tarbell of Lockheed Martin, the principal investigator for the telescope's focal plane package.
"Since we can observe continuously, we should see that energy build up, be released, and build up again. We hope to learn eventually how to use these kinds of instruments to predict when these space weather events will happen," Tarbell said.
"You'll actually be able to track the affects of the magnetic field all the way through the atmosphere. We feel that all the things that go on in the upper atmosphere in the Sun are due to the releases of the energy that is stored in the magnetic field," Davis said.
Billed as the largest solar telescope ever, the instrument should be able to resolve objects as small as 100 miles across on the Sun's surface in the visible wavelength.
Ground observations have occasionally achieved even higher resolution, according to Tarbell.
"But the really exciting thing about the space instrument is that it will have this excellent quality 24 hours a day, seven days a week, all the time."
Although primarily designed and manufactured by Japanese scientists, the telescope's focal plane package instrument was provided by NASA and developed by Lockheed Martin and the High Altitude Observatory in Colorado.
Tarbell said his team at Lockheed Martin has been working to develop such an instrument for about 25 years.
The X-ray telescope can capture images of the Sun very rapidly, allowing scientists to track rapidly changing events in the corona. The images will be strung together on the ground in a movie-like sequence to observe the corona in animation, said Ed DeLuca, the X-ray telescope's principal investigator at the Smithsonian Astrophysical Observatory.
All three instruments are designed to work very closely together by observing the same region of the Sun simultaneously, DeLuca explained.
"The mission is designed to work as a whole. It really comes out of recognition that in modern solar physics, there isn't a single telescope that is going to allow you to address the complicated problems that we're facing," he said. "You need data from multiple telescopes that are simultaneously looking at these areas and seeing how are these changes occurring.
"Solar physics is really a multi-wavelength, multi-instrument business these days, and Solar-B is trying to combine key bits of that into a single satellite."
The third instrument aboard Solar-B is an extreme ultraviolet imaging spectrometer that will work in concert with the rest of the spacecraft's science payload. The primary objective for the spectrometer is to measure the speed of solar particles and the temperature and density of a plasma layer that surrounds the Sun.
"We can use all this information to build a very detailed picture of the physical conditions in the corona, the quiet solar atmosphere, in solar active regions, and in dynamic events such as flares," said John Mariska, the instrument's co-investigator at the United States Naval Research Laboratory.
The spectrometer was provided by an international consortium with teams in the United States, the United Kingdom, Norway, and Japan.