Having marked its first anniversary on orbit, NASA’s Solar
Radiation and Climate Experiment (SORCE) satellite has hit its
stride. In concert with other satellites, SORCE’s observations
of the sun’s brightness are helping researchers better
understand climate change, climate prediction, atmospheric
ozone, the sunburn-causing ultraviolet-B radiation and space
weather.
In fall 2003, SORCE was fortunate to see and measure
exceptionally high levels of the sun’s activities. In late
October and November the sun sent solar flares and coronal mass
ejections hurtling Earthward, disrupting satellites and other
transmissions, triggering an intense geomagnetic storm, and
enabling sightings of the northern lights as far south as
Arkansas, Texas and Oklahoma.
The third most powerful solar flare ever observed in X-rays,
high-energy photons with very short wavelengths, erupted from
Sunspot 486 October 28, 2003, at approximately 6 a.m. Eastern
Standard Time. The same spot released a large X11 flare on the
afternoon of October 29. As the sunspot moved across the face
of the sun, total solar brightness decreased by 0.3 percent.
SORCE tracked the decreases in Total Solar Irradiance (TSI) and
the increases in X-rays, as well as changes in the other parts
of the solar spectrum. SORCE’s suite of instruments measures
solar brightness in soft X-ray bands and at wavelengths from
ultraviolet through the visible and near-infrared spectrum.
This is the most comprehensive dataset ever collected of the
complex brightness changes that occur in the solar spectrum
during a major eruptive event.
Having accurate knowledge of the sun’s brightness variations on
all time scales, from flares to centuries, at all wavelengths
heating the Earth’s atmosphere, land and oceans is essential to
understand, model and predict impacts of the sun on Earth.
Two of the SORCE instruments, the Total Irradiance Monitor
(TIM) and the Spectral Irradiance Monitor (SIM), will
ultimately be part of the operational measurements made by the
National Polar-orbiting Operational Environmental Satellite
System (NPOESS) satellites beginning in 2013. Solar irradiance
has been monitored since the 1970s to create a long-term record
for study by researchers.
“The spacecraft and instruments have all been performing
beautifully since launch, and the new solar data exceed all of
our expectations,” said Gary Rottman, SORCE Principal
Investigator at University of Colorado’s Laboratory for
Atmospheric and Space Physics (LASP) in Boulder, Colorado. “The
sun also cooperated by putting on an unusual display of intense
activity in late October that provided some of the largest
sunspots ever recorded and produced major flares surpassing all
previous observations. These unexpected phenomena will help us
better understand how the sun functions and how it influences
the terrestrial environment.”
“For the very first time we have observations capable of
characterizing simultaneously the variations in the total solar
irradiance and in the visible and near infrared part of the
solar electromagnetic spectrum that provides the primary energy
to the Earth’s surface,” said Dr. Judith Lean, Research
Physicist at the Naval Research Laboratories and a member of
the National Academy of Sciences. “Simple models exist of solar
spectrum variability, which general circulation models use to
simulate climate response to solar forcing. SORCE data already
indicate the models need to be revised at infrared wavelengths;
they promise unprecedented new understanding of the mechanisms
of solar spectral-irradiance variability and their possible
climatic impacts.”
SORCE is a joint partnership between NASA and LASP. As a
principal investigator-led mission, NASA provided management
oversight and engineering support. Scientists and engineers at
the University of Colorado designed, built, calibrated and
tested the four science instruments on the satellite. The
Mission Operations Center and the Science Operations Center are
both located at the University.
For information about the SORCE mission in the Internet, visit:
