The vibration and shock tests went well. The flight battery and the
instrument thermal simulator are installed, and today we are moving the
spacecraft into the thermal vacuum chamber. This photo shows Kim Brown and
Bruce finalizing the blankets on the spacecraft. The gold-colored blankets
are kapton-covered aluminum. The instrument blanket is silver-teflon. The
cut-outs in the blanket are thermal radiators for the components mounted on
the other side. The white-painted composite is visible through the blanket
cut-outs. The safety vent plumbing is visible on the outside of the
instrument simulator between the star tracker and the support strut. This
plumbing is used by the real instrument should the hydrogen warm and vaporize
during ground operations just prior to launch. Normally, the hydrogen will
stay frozen, but this vent provides a safe path for the combustible gas just
in case it doesn't.
We expect to close the thermal vacuum chamber door Wednesday afternoon to start the pump-down. We will power up Thursday morning to begin the first of six balance points. During thermal balance we fix the external thermal environment and measure the temperatures of the spacecraft components after they stabilize. We then compare those temperatures to what was predicted by the thermal model, and we adjust the thermal model to make the predictions agree. Then we use the thermal model with the on-orbit environmental conditions to predict the temperatures of components on the spacecraft during the mission. If those predictions exceed the operational limits of the components, we must resize the thermal radiators.
Previous updates:
August 18, 1997
October 20, 1997
October 31, 1997
November 7, 1997
November 14, 1997
November 21, 1997
December 5, 1997
December 23, 1997
January 9, 1998
January 16, 1998
January 23, 1998
January 30, 1998
February 6, 1998
February 20, 1998
March 12, 1998
March 23, 1998
April 3, 1998