Background
The National Science Foundation (NSF),
through its Office of Polar Programs,
supports long-duration balloon (LDB) flights
in Antarctica to conduct astrophysical
experiments. Circling the continent on
unique stratospheric winds at altitudes
of roughly 37 kilometers (22.9 miles)
for periods of up to 31 days, experiments
operate in an area that is almost free
of atmospheric interference. For some
experiments, this provides scientists
with conditions equivalent to flight aboard
a satellite or the space shuttle, at much
lower cost.
Unique conditions
Two unique geophysical conditions above
Antarctica make long-duration balloon
flights that circumnavigate the continent
possible during the austral summer:
- First, a nearly circular pattern of
gentle east-to-west winds establishes
itself in the Antarctic stratosphere
lasting for a few weeks. The circulation
is generated by a long-lived high-pressure
area caused by the constant solar
heating of the stratosphere. This
allows the launching and recovery
of a balloon from roughly the same
geographic location and permits a
flight path that is almost entirely
over land.
- Second, because the sun never sets
during the austral summer, the balloon
is illuminated continuously, both
directly and by reflection from the
underlying clouds or snow. As a result,
the balloon maintains a constant temperature
and is able to maintain a stable altitude.
In other areas of the world, the daily
heating and cooling cycles change
the volume of gas in the balloon,
causing it to rise and fall and expend
ballast, severely limiting flight
times.
As an international zone under the Antarctic
Treaty, balloons can be launched, flown
and recovered anywhere on the continent
without diplomatic complications experienced
in other areas of the globe.
History
Since 1988, NSF and NASA have developed
techniques for flying and recovering large
balloon payloads -- in the range of two
tons -- at altitudes of roughly 37 kilometers
(22.9 miles) for extended periods.
Over the past decade there have been LDB
flights in most Antarctic research seasons
-- roughly mid-December through mid-January
-- frequently with two balloons being
flown during the season.
During the 2001-2002 Antarctic research
season, the balloon-borne Trans-Iron Galactic
Element Recorder (TIGER) experiment, designed
to search for the origin of cosmic rays,
achieved a flight-duration record over
Antarctica. Launched at 6:30 a.m. EST
on Dec. 20, 2001, the balloon traveled
approximately 1,400 kilometers (869 miles)
before landing, 31 days, 20 hours later,
at 3:03 a.m. EST, Jan. 21, 458 kilometers
(284 miles) from McMurdo Station, NSF's
logistical hub in Antarctica.
For more information about TIGER, see:
http://cosray2.wustl.edu/tiger/
For more information about the TIGER flight
path from NASA, see: http://192.149.107.13/ldb/balloona.jpg
In 1998, the Balloon Observations of Millimetric
Extragalactic Radiation and Geophysics
(BOOMERANG) experiment obtained the first
detailed images of the universe in its
infancy. The images revealed the structure
that existed in the universe when it was
a tiny fraction of its current age and
1,000 times smaller and hotter than it
is today.
For more information about BOOMERANG, see:
http://www.nsf.gov/od/lpa/news/press/00/pr0025.htm
Logistics of Antarctic ballooning
NASA operates the National Scientific Balloon
Facility in Palestine, Texas, which supports
balloon flights worldwide. Antarctic experiment
packages are prepared at the NSBF, but
must be sent to McMurdo Station via NSF's
cargo facilities in Port Hueneme, Calif.
through Christchurch, New Zealand.
Flight operations are conducted from Williams
Field, near McMurdo Station, which provides
complete logistical support, including
transportation, housing, supplies and
heavy equipment to balloon teams.
The Antarctic research season runs from
October through February. However, regional
weather does not normally stabilize until
early December. Because recovery aircraft
are more in demand near the end of the
season, the Antarctic balloon launch window
lasts only about six weeks. By early February,
icebreakers have created a channel through
the sea ice that that rings the continent
to allow a supply ship to bring in heavy
equipment for the next season. This cargo
often includes truckloads of helium for
the following year's balloon flights.
In this picture, images of the early universe
as seen by the BOOMERANG experiment have
been overlaid onto the sky to indicate
what size fluctuations in the Cosmic Microwave
Background would appear if a standard
35mm camera were sensitive to microwave
light. The color map of the CMB images
has been changed here to aesthetically
match the rest of the picture.
Credit: Boomerang team |
 |
The building near McMurdo Station, NSF's
logistics hub in Antarctica, where long-duration
balloon payloads are assembled.
Credit: Peter West / National
Science Foundation
A balloon payload being prepared for launch.
Credit: Peter West / National
Science Foundation
A balloon-borne experiment is hoisted
by a crane in preparation for transporting
to the launch area near Williams Field,
Antarctica.
Credit: Peter West / National
Science Foundation
A balloon payload is ferried out to the
launch area.
Credit: Peter West / National
Science Foundation
With Mt. Erebus, the world's southernmost
active volcano, as a backdrop, the balloon
that carried the BOOMERANG telescope on
its 10-day trip around the Antarctic continent
is inflated. The launch was preceded by
two months of assembly at McMurdo Station,
NSF's logistics hub in Antarctica.
Credit: Boomerang team |
