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Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

Mission (Not) Impossible

Five-year Solar Dynamics Observatory satellite will investigate causes of the sunís variability and how it produces space weather that affects us on earth
NASA
NASAís Solar Dynamics Observatory (SDO), which was launched in February, is sending back high-resolution images of the sun. SDO will help scientists learn how solar activity is created and how space weather results from that activity. NASA says it will measure the sunís interior, magnetic field, the hot plasma of the solar corona, and the irradiance. (Images courtesy NASA unless otherwise noted)
The Earth is superimposed on a solar eruptive prominence as seen in extreme UV light (March 30, 2010) to give a sense of how large these solar eruptions are.
As the arcing loops above an active region began to rotate into a profile view, SDO captured the dynamic, magnetic struggles taking place. Particles spiraling along magnetic field lines trace their paths. Magnetic forces in the active region are connecting, breaking apart, and reconnecting. These images were taken in extreme ultraviolet light.
NASA/ESA/Williams College Eclipse Expedition
On July 11, the new moon passed directly in front of the sun, causing a total solar eclipse in the South Pacific. In this image, the solar eclipse is shown in gray and white from a photo provided by the Williams College Expedition to Easter Island and was embedded with an image of the sun's outer corona taken by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft and shown in red false color. LASCO uses a disk to blot out the bright sun and the inner corona so that the faint outer corona can be monitored and studied. The dark silhouette of the moon was covered with an image of the sun taken in extreme ultraviolet light at about the same time by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory.
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By Barry Hochfelder

There are three instruments aboard the SDO: The Atmospheric Imaging Assembly (AIA), the Helioseismic and Magnetic Imager (HMI) and the Extreme Ultraviolet Variability Experiment (EVE). HMI and AIA were both built by Lockheed Martin Solar and Astrophysics Laboratory (LMSAL) and feature six CCD sensors from e2v (Chelmsford, UK). EVE will measure fluctuations in the sunís ultraviolet output; HMI will map solar magnetic fields and look beneath the sunís opaque surface using a technique called helioseismology; and AIA will photograph the sunís surface and atmosphere at IMAX quality every 10 seconds. Previous observatories have taken pictures, at best, every few minutes with much inferior resolution.

HMI looks beneath the surface at whatís called the solar dynamo, a network of deep plasma currents that generates the sunís explosive magnetic field. The dynamo is beneath 140,000 miles of overlying hot gas. SDO penetrates that with a form of seismology. Solar physicists use acoustic waves generated by the sunís own turbulence. The HMI detects the waves, which researchers on earth transform in pictures.

EVE will observe the sun at wavelengths where it is most variableóthe extreme ultraviolet (EUV). EUV photos are high-energy cousins of regular UV rays that cause sunburn (our atmosphere blocks solar EUV). In space, however, solar EUV emission is easy to detect and a sensitive indicator of solar activity. EVE will reveal how fast the sun can change.

Four specially processed back illuminated e2v CCD203-82 (4k x 4k) sensors sensitive to extreme UV wavelengths are incorporated into the four AIA telescopes which will observe the Sun in wavelength range of 9.4nm to 170nm. In total, the AIA filters will produce a high-definition image of the sun in eight selected wavelengths out of the 10 available every 10 seconds to reveal key aspects of solar activity. The bands include nine ultraviolet and extreme UV bands and one visible light band. These telescopes will provide the bulk of SDOís data stream. The AIA instrument is under the direction of Dr. Alan Title at LMSAL, and will use solar images taken in multiple wavelengths to study the energetics of the solar atmosphere and itís interaction with the surface magnetic fields.

Two front-illuminated e2v CCD203-82 (4k x 4k) sensors are used in the HMI instrument to image the Sun in visible light at 617nm. The HMI instrument (built by LMSAL) is under the direction of Prof. Philip Scherrer at Stanford University (Palo Alto, Calif.), and will measure both solar surface magnetic fields and the Sunís surface motion as a probe of the solar interior.



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