Engineers at Goddard Space Flight Center in Greenbelt, Md., recently tested NASA's Solar Dynamics Observatory (SDO) to determine its mass properties. SDO, the first mission of NASA's Living With a Star program, will study the sun's atmosphere in unprecedented detail to reveal how variations on the sun influence Earth and nearby space.

For three days beginning on March 31, SDO sat on a slowly spinning "Miller Table" in the Spacecraft Checkout and Integration Area, a "clean room" at Goddard. Test engineers like Sheldon Kalnitsky measured the spacecraft's mass, center of gravity, and moments and products of inertia to provide SDO's launch mass properties as accurately as possible. The moment of inertia describes how the spacecraft resists changes to its rate of rotation in each direction—important information to know prior to SDO's planned November launch.

"This is the final verification test of the observatory before shipping," said Son N. Ngo, the SDO mechanical lead engineer. "The final data will be used to verify requirements for the launch vehicle."

For more information about SDO, visit:

http://sdo.gsfc.nasa.gov