Solar Dynamics Observatory ―an eye on the Su n

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Solar Dynamics Observatory―an eye on the Sun
By Bryan Dyne
13 March 2010

One month after its successful launch, NASA’s Solar Dynamics
Observatory has begun capturing high-resolution images of solar
phenomena at 10-second intervals. The imaging technique makes use of
advanced new mirrors originally developed to build faster computer
chips, but adapted for one of the three main instruments on board the
SDO, the Atmospheric Imaging Assembly.

The AIA instrument consists of an array of four telescopes that will
provide a view of the Sun of unprecedented breadth and depth, taking
full-disk images at 10 different wavelengths every 10 seconds. Each
image will be 4096 pixels by 4096 pixels, described as “almost IMAX
quality” by Lawrence Livermore National Laboratory, where the
technology was developed using a technique called extreme ultraviolet
lithography.

NASA launched SDA on February 11 from Launch Complex 41 at the Kennedy
Space Center aboard an Atlas V launch vehicle. Eighty-seven minutes
later, the solar panels of SDO successfully deployed.

The launch of the SDO is epochal in the study of heliophysics. Its
predecessor, the Solar and Heliospheric Observatory (SOHO) has been
the flagship for solar physics for almost two decades. SDO will take
over that role, using newer and more powerful instruments to probe the
inner workings of the Sun. In addition to the AIA, these include the
Extreme Ultraviolet Variability Experiment (EVE) and the Helioseismic
and Magnetic Imager (HMI).

EVE is designed to monitor variations in the energy radiated by the
Sun. Telescopes on the Earth have studied the Sun's light production
for centuries, but the Earth's atmosphere obscures most of the Sun's
rays. Solar radiation occurs across the electromagnetic spectrum, and
only telescopes in space can study the high-energy X-ray and
ultraviolet radiation that are the signatures of high-temperature
physics at the Sun's surface.

Using a technique called helioseismology, a process that traces the
path of sound waves within the Sun, HMI sees the inside of the Sun.
Specifically, HMI will look at how processes that occur inside the Sun
cause the magnetic fields that are seen on the surface. It will also
produce data to study the magnetic fields found in the Sun's corona,
or outer atmosphere. The goal is to enhance our understanding of the
magnetic activity which is a precursor to high solar activity that can
harm electronics and humans in orbit.

The AIA's primary function is to observe the Sun's corona. With four
cameras working in tandem, it will give the most precise view of the
solar corona available. In conjunction with ground observations and
SDO's other instruments, AIA will produce data to study the very hot
gas it holds. Ultimately, its goal is to help development of
forecasting tools needed to predict solar activity that will affect Earth.

SDO is the first satellite of NASA's Living With a Star (LWS) program.
Every second of every day, the Sun emits what is called solar wind,
which constantly bombards the Earth with charged particles, or ions.
Normally, the Earth's magnetic field is adequate protection from this
onslaught, but a solar flare or coronal mass ejection―concentrations
of high energy light or large clouds of ions, respectively―aimed at
the Earth can cause anything from minor glitches in satellites to
knocking out whole power grids on the Earth’s surface, as happened to
Canada’s HydroQuebec power grid in 1989. The LWS program focuses on
studying the causes of these events so they can be predicted and
safeguarded against.

The SDO spacecraft itself is a powerful instrument. Unlike SOHO, which
is 5 light seconds (~932,000 miles or ~1,500,000 kilometers) away from
the Earth, SDO is in a geosynchronous orbit around Earth, 22,000 miles
up. The first advantage of being close is that less fuel is required
to reach orbit. The second is that the data rate from SDO is far
higher than SOHO's. SOHO would need an antenna as large as a football
field to return the same amount of data to Earth from its position,
compared to the SDO.

SDO will sending Earth 1.6 terabytes of data a day, 50 times the rate
of any previous NASA mission. The annual data transmission, about one
petabyte, is a hundred times as much data as all the written works in
the Library of Congress.

Solar activity plays a key role in everyday life. Providing warmth to
the planet is just one way it affects Earth's population. The energy
emitted is capable of making a mockery of unprotected electronics as
well as literally frying astronauts caught in a solar storm. Using
satellites like the SDO to gain an understanding the processes that
create solar storms will help avoid future devastating events.

http://wsws.org/articles/2010/mar2010/sola-m13.shtml

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