Solar Dynamic Observatory in Semi-Annual Eclipse Season

Launched in 2010, Solar Dynamics Observatory (SDO) is a NASA mission that will observe Sun for over five years.  It is part of the Living With a star program. SDO has now moved into its semi-annual eclipse season. During this time of the year the Earth blocks the telescope's view of the sun for a period of time each day.

The sun is being observed through a glass window by the Helioseismic and Magnetic Imager (HMI) that is on SDO. Based on the temperature changes the window alters it shape quickly.

"You've got a piece of glass looking at the sun, and then suddenly it isn't," says Dean Pesnell, the project scientist for SDO at NASA's Goddard Space Flight Center in Greenbelt, Md. "The glass gets colder and flexes. It becomes like a lens. It's as if we put a set of eye glasses in front of the instrument, causing the observations to blur."

In order to neutralize this effect, HMI has been designed with heaters to warm the window during an eclipse.  By adjusting the timing and temperature of the heater, the HMI team has learned the best procedures for improving resolution quickly. When there is no adjustment made in the HMI front window heaters it takes about two hours to return to optimal observing.

 "We allocated an hour for these more blurry images," says Pesnell. "And we've learned to do a lot better than that. With 45 eclipses a year, the team gets a lot of practice."

SDO will enter its next eclipse season on March 3, 2013.