Our Sun is a violent star and is capable of producing explosive
flares and hurling clouds of matter toward Earth – activities that in the
past have interfered with satellite communications and electric power
transmission grids on Earth.

To learn more about the forces that create these disruptions on the
Sun, scientists from Japan, the United States and the United Kingdom are
working together to build instruments to fly in 2005 on the Solar-B mission,
a satellite being developed by Japan’s Institute of Space and Astronautical
Science (ISAS).

“NASA is working with scientists across the country to design and
build the major elements of the three instruments for Solar-B,” said
Lawrence Hill, project manager for Solar-B at NASA’s Marshall Space Flight
Center in Huntsville, Ala. “NASA has just completed the design phase, and
we’ll soon begin building the instruments that will help us understand the
star closest to home.”

The Solar-B spacecraft will be placed into a Sun-synchronous orbit
around the Earth. This is a polar rather than an equatorial orbit and allows
the instruments to remain in continuous sunlight for nine months of each
year. The Solar-B instruments will observe how magnetic fields on the Sun’s
surface, called the photosphere, interact with the Sun’s outer atmosphere,
the corona, that extends millions of miles out into space.

“This high-temperature outer solar atmosphere is the only place in
the universe where scientists can make very detailed observations of how
magnetic fields interact with the hot ionized gases, or plasmas, that make
up all stars,” said Dr. John Davis, Solar-B project scientist at the
Marshall Center. “The instruments will work together to show how changes in
magnetic fields deep inside the Sun erupt through the different layers of
the Sun’s atmosphere, creating the violent disturbances that sometimes
affect us on Earth.”

The origin of the Sun’s violent behavior lies with its magnetic
field, which is generated deep in the star’s interior. The magnetic field
is buoyant and rises to the surface where it is often visible as sunspots,
which are large concentrations of magnetic flux. Energy is stored in the
magnetic field.

As the field rises into and through the solar atmosphere, energy can
be released either gradually to heat the outer atmosphere to temperatures in
excess of a million degrees or explosively in solar flares or coronal mass
ejections (CMEs). Solar-B’s scientific mission is to observe the
distribution of the magnetic field at the photosphere where it first becomes
visible and to study how it releases its energy to the surrounding

“By studying, in detail, how the character of the field changes with
time over a solar cycle, we hope to learn how the field is generated and if
and how the field affects solar luminosity,” said Davis.

Recent measurements of the energy flowing from the Sun, the solar
“constant”, shows the Sun to be less luminous at the minimum of the sunspot
cycle when Solar-B will be launched. The records of sunspot observations
from 400 years ago indicate an extended period when sunspots were extremely
rare, and the sunspot cycle even disappeared. This period coincided with a
series of very harsh winters in Europe known as the “Little Ice Age.”

Solar scientists have found suggestions that extremely small
magnetic features in the solar photosphere are responsible for the changes
in the luminosity. Solar-B will enable the first comprehensive set of
observations to determine the role of these features in long-term solar
luminosity changes and provide better answers to this provocative question
of how the Sun impacts Earth’s climate.

Solar-B is an international mission sponsored by ISAS based in
Sagamihara, a suburb of Tokyo, Japan, with its partners-NASA and the
Particle Physics and Astronomy Research Council based in Swindon, United
Kingdom. The heart of the Solar-B mission is a large solar optical
telescope that is being developed by the Japanese Institute. To measure the
magnetic fields, structures and flow patterns in the photosphere, NASA will
provide a set of instruments for the telescope’s focal plane. X-Ray and
Extreme Ultraviolet Telescopes, each of which contain major components
supplied by the three international partners, will record how the energy
stored in and released by the magnetic field propagates through the Sun’s
outer atmosphere.

The Marshall Center is managing the development of the NASA-provided
components for the Solar-B Focal Plane Package, the X-ray Telescope and the
Extreme Ultraviolet Imaging Spectrometer. For more details on how these
components operate together, visit


When Solar-B instrument fabrication and testing is completed by the
investigators and accepted by NASA, the instruments will be shipped to Japan
for further testing and integration with the rest of the Solar-B satellite.

Solar-B is scheduled for launch from Kagoshima, Japan, in August or
early September 2005. Once the satellite is in orbit, NASA and the science
teams will support instrument operations and data collection from the
operations center located at ISAS in Sagamihara.

Solar-B is part of the Sun Earth Connection science theme, managed
by NASA’s Office of Space Science, Washington, DC, and the Solar Terrestrial
Probes Program at NASA’s Goddard Space Flight Center in Greenbelt, Md.