POWER February 2011 - 27

ASSET MANAGEMENT
Space Weather Watchers
The National Oceanic and Atmospheric Administration
(NOAA) manages the Space
Weather Prediction Center as part of the
National Weather Service and has a separate
website (www.swpc.noaa.gov/elecpower/)
that provides electric utilities with alerts
and space weather forecasts. Although the
center uses data from multiple satellites-
including ACE and STEREO, described below-NOAA
is unable to provide predictions
fast enough that they would be useful to
the power industry, according to industry
officials.
NASA also attempts to provide space
weather forecasts. Several space satellites
that are managed by NASA watch Earth's
sun, attempting to learn about the littleunderstood
phenomena of solar eruptions
and solar storms. One goal is to provide
warning of potentially catastrophic storms
with enough lead time that humans can
take preventive action.
Four primary satellites continuously
watch the sun and report myriad data daily.
In general, each satellite is purpose-built
to collect particular data. The data collected
by each satellite, including photographs
and videos, are reported daily on web pages
accessible by the public.
SOHO
The oldest sun-gazing satellite, launched
in 1995, is SOHO, the Solar and Heliospheric
Observatory. It was developed
jointly by the European Space Agency and
NASA and is flown by NASA out of the
Goddard Space Flight Center in Maryland,
near Washington, D.C. This satellite moves
around the sun in a dance step with Earth
at the L1 Legrangian Point. According to
a NASA fact sheet, the combined gravity
of Earth and the sun keeps the satellite
locked in a direct line between the sun
and our planet, about 1.5 million kilometers
(km) away, providing an uninterrupted
view of the ultimate source of all
Earth's energy (Figure 2).
SOHO tries to answer three fundamental
questions about the sun: What are the structure
and dynamics of the sun's interior? Why
is there a solar corona, or halo, and how is
it heated to temperatures of about 1 million
degrees C? Where does the solar wind come
from, and how does it accelerate?
February 2011 | POWER
ACE
Launched in 1997, NASA's ACE (Advanced
Composition Explorer) satellite provides
real-time data used in NOAA's Space Weather
Prediction Center for forecasts and warnings
of solar storms. It, too, operates some
1.5 million km from Earth near the L1 point
and is equipped to stay in orbit until 2024.
Goddard also flies the ACE craft.
ACE features an array of equipment that includes
a cosmic ray isotope spectrometer to
determine the chemical isotopes that make up
galactic cosmic rays; two spectrometers, each
tuned for a different set of measurements, to
analyze the chemical composition of the solar
wind and intersteller matter; an ultra-low-energy
isotope spectrometer to measure ion flux;
electron, proton, and alpha particle monitors;
and a magnetometer.
STEREO
Launched in 2006, NASA's STEREO (Solar
Terrestrial Relations Observatory) provides
a three-dimensional look at solar phenomena.
Two nearly identical observatories-one
ahead of Earth in its orbit and the other trailing
behind-trace the flow of energy and
matter from the sun to Earth. They reveal the
3-D structure of coronal mass ejections, the
violent eruptions of matter from the sun that
can disrupt satellites and power grids.
Johns Hopkins University's Applied Physics
Laboratory outside Washington, D.C.,
built and operates STEREO. According to
a Johns Hopkins fact sheet, each of the
observatories is about the size of a large
wooden desk and has solar photovoltaic
power arrays about the length of a large
school bus (Figure 3). Data from the twin
observatories " will allow scientists to track
the buildup and liftoff of magnetic energy
from the Sun and the trajectory of Earthbound
coronal mass ejections in 3D, " says
the Baltimore-based university.
NASA has an iPhone app, 3D Sun, that uses
STEREO data to allow users to rotate our home
star, zoom in on active regions, and monitor
solar activity. It is available from the Apple
app store or from http://3dsun.org.
AMPERE
Last August, the Johns Hopkins physics lab,
Boeing Co. and Iridium Communications
announced a new system that uses comwww.powermag.com
2.
Eye in the sky. The SOHO satellite
was launched, according to NASA, to
" study the sun from its deep core to the
outer corona and the solar wind. " The satellite,
launched in 1995, weighs about 2 tons
and is about 25 feet across. Source: NASA
3. Visualizing solar storms. STEREO
captures a mosaic of ultraviolet images in different
wavelengths and can then combine
them into a single 3-D figure, as shown. Each
wavelength allows scientists to study different
feature of the sun. If you have a pair of
3-D glasses, you may want to watch a 3-D
video of the sun prepared using STEREO
images. Go to www.nasa.gov and search on
" STEREO " . Source: NASA
mercial satellites to monitor solar activity.
In a world of snazzy acronyms, this system
is known as AMPERE, for Active Magnetosphere
and Planetary Electrodynamics Response
Experiment. The system is said to
provide real-time magnetic field measurements
to forecast space weather with data
gathered from the new instruments mounted
on Iridium's fleet of commercial communications
satellites. The project is funded by
a $4 million National Science Foundation
grant. A press release claims, " This is the
first step in developing a system that enables
24-hour tracking of Earth's response
to supersonic blasts of plasma ejected from
the Sun at collection rates fast enough to
one day enable forecasters to predict space
weather effects. "
27
http://www.swpc.noaa.gov/elecpower/ http://www.nasa.gov http://www.3dsun.org http://www.powermag.com
POWER February 2011

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