NCAR is involved in numerous international collaborations.
Staff Notes Monthly will be highlighting several in the next few issues.
NCAR scientists and engineers, working with colleagues in Germany and
Spain, are moving ahead with plans to build a powerful solar telescope
that will be carried high up in the atmosphere by a balloon.
Bruce Lites and Kim Streander
At the heart of what's known as the Sunrise project is a lightweight,
one-meter telescope that will circle Antarctica for about two weeks at
an altitude of approximately 130,000 feet (39,600 meters). Its advanced
instrumentation will provide high-resolution images of the Sun's
outer surface, or photosphere, enabling scientists to get unprecedented
views of small-scale magnetic fields that drive solar variability and
profoundly affect Earth's atmosphere.
The international team expects to launch the telescope in late 2007.
If the instrument can be recovered intact and funding is available, it
will be launched again the following year to obtain additional images.
A computer-generated image of the Sunrise telescope
and gondola, with its large solar panels. The gondola will be carried
by a 30-million-cubic-foot balloon.
"This project will allow us to view features of the Sun that we've
never seen before," says Bruce Lites (HAO), a principal investigator
on the Sunrise project. "We hope to see magnetic fields continually
interacting with convective motions and affecting the outer solar atmosphere."
The telescope is being developed at a time when an array of sophisticated
new solar instruments are coming on line. They include the one-meter
Swedish Solar Telescope that is capturing unprecedented images from a
site on the Canary Islands; the Solar B project, which will place a suite
of instruments in a Sun-synchronous orbit around Earth next year, and
a coronal multichannel polarimeter being developed by HAO to examine
magnetic fields in the corona.
Images from the ground-based Swedish telescope have been dazzling the
scientific community for more than a
year. They show, for the first time, the three-dimensional structure
of the Sun's photosphere, as well as small sunspots that traverse
what appear to be raised ridges.
As detailed as these images are, Sunrise will provide far more information,
in part because it will reach an
altitude at which it will not have to contend with distortions
caused by Earth's atmosphere. The balloon-mounted telescope
is expected to capture images as small as 40 kilometers across, compared
to 90 kilometers for the Swedish telescope. In addition, Sunrise will
train its instruments on the same small area of the Sun for two
weeks, thereby allowing researchers to witness dynamic changes in magnetic
fields. Ground-based telescopes, in contrast, cannot continually capture
images from the Sun because of Earth's rotation.
"Throughout this decade, we'll be seeing much more detailed
images of the Sun from a number of experiments," Bruce says "Sunrise
should be a big part of this research picture."
New insights into magnetic fields
Learning more about the Sun has long been a high scientific priority.
The Sun is the main source of light and energy for life on Earth and
the principal driver of atmospheric motion. Solar disruptions, such as
coronal mass ejections, have profound impacts on our upper atmosphere,
touching off geomagnetic storms that affect sensitive communications
and other systems on Earth. But scientists need specialized instruments
to examine the Sun in detail, and they remain uncertain about the causes
of solar variability and disruptions.
The primary goal of the Sunrise project is to investigate the structure
and dynamics of the Sun's magnetic field. The magnetic field fuels
solar activity and causes variations in radiation, which may be a significant
factor in long-term changes in our climate.
The project also may help scientists glean insights into magnetic fields
in general. The universe contains numerous objects, such as stars, that
are dominated by magneto-hydrodynamical and plasma processes, but only
the Sun is close enough to examine in any detail.
"Sunrise will broaden our understanding of the really fundamental physical
processes of the outer atmosphere of stars and the forces that drive stellar
winds," Bruce explains.
NCAR staffers, using NSF funding and a grant from NASA, will design the
gondola and telescope pointing system. They are also working on the data
system and cameras for one of the key instruments, a polarimetric spectrograph
for high-precision spectral line measurements.
German researchers at several institutes, including the Max Planck Institute
for Aeronomy, are building the telescope, creating a tracking and alignment
system for the telescope, providing optics and mechanisms for the polarimetric
spectrograph, and designing a filtergraph for high-resolution images
in the visible and UV spectral ranges. Spanish researchers at the Astrophysics
Institute of the Canary Islands are designing the Imaging Magnetograph
Experiment, which will provide two-dimensional magnetic field maps.
Working with international collaborators is vital on such a major
project, Bruce explains. "The solar community is not large, so
solar physicists around the world need to work with each other," he
says. "In times of limited funding, it's especially important
to pool our resources and move forward on really big projects."
At HAO, Kim Streander is the instrument project manager. A number of
other HAO staffers are involved in the project, including HAO director
Michael Knölker, David Elmore, Terry Leach, Alice Lecinski, and
Ron Lull. In ATD, Clarke Chambellan and Jack Fox are working on the gondola
and telescope pointing system. The balloon, supplied by the National
Science Balloon Facility, will be designed to hold 30 million cubic feet
of air so that it can carry the 4,000-pound payload.
The design challenges include creating a set of instruments to keep the
telescope aimed at a specific area of the Sun. The telescope's
angle must remain within 15 arc seconds, or 1/240th of a degree—no
small feat on a soaring balloon that will be twisting in flight.
The instruments, including an anti-spin device that will act as a big
flywheel to keep the gondola pointed at the Sun,
will be tested next year on a trial flight in Texas.
"This is an exciting project, and it definitely confronts us with
some interesting challenges," says Jack Fox, director of ATD's
Design and Fabrication Services.
Also in this
Windham soars to Washington
Profile: Mark Tschudi
auditorium draws large crowds
organize women's self-protection class
win AMS awards
insights into solar output