scope:

Description of Driving Event:

Chandra silverized teflon MLI layers are degrading faster than pre-launch predictions, allowing the spacecraft to reach hotter temps earlier in the mission than predicted.

In its first 3 years on orbit, the Chandra X-Ray Observatory (CXO) has witnessed higher than expected temperatures across the sun facing side of the vehicle. It is now believed that these elevated temperatures are due to the better insulating properties of its Multi Layer Insulation (MLI) and a higher than expected degradation of its Silverized Teflon thermal surfaces. It is believed that the Radiative Heat Transfer Efficiency (e*) has decreased by 0% to 20% of its predicted value and that the solar absorptance coefficient (a) has increased by 40% of predicted and could potentially reach a value of 0.6 (worst case) at 15 years. The original assumption was that the solar absorptance would not exceed 0.25. The most likely cause of the higher than expected degradation is due to the more severe CXO radiation environment.

An extensive thermal analysis was performed to examine the thermal observations made by the Flight Operations Team. References 1, and 2, contain the results of the detailed study.