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Experiment Title: Thermal Control Surfaces Experiment

Original Principal Investigator(s): King, Harry M. - Invest. Role: Original, Wilkes, Dr. Donald R. - Invest. Role: Original, Wilkes, Dr. Donald R. - Invest. Role: Present, Zwiener, Mr. James M. - Invest. Role: Present,

The natural and induced long term effects of the space environment on spacecraft surfaces are critically important to many of NASA's future spacecraft, including the 30 year lifetime Space Station, AXAF and the Hubble Space Telescope. The increasing duration of space missions requires significant extrapolation of flight and ground simulation data to provide predictions of end-of-life properties for thermal control surfaces. The damaging constituents of this environment include thermal vacuum, solar ultraviolet radiation, atomic oxygen, particulate radiation, micronoid and debris bombardment, and the spacecraft induced environment. The behavior of materials and coatings in the space environment continues to be a limiting technology for spacecraft and experiments. The inability to exactly simulate this complex combination of constituents results in a major difference in the stability of materials between laboratory testing and flight testing. The Thermal Control Surfaces Experiment (TCSE) flew on the Long Duration Exposure Facility (LDEF) to study these environmental effects on surfaces, particularly on thermal control surfaces. The TCSE is the most comprehensive thermal control surfaces experiment ever to be flown and it is a microcosm of complex electro-optical payloads being developed and flown by NASA and the DoD.

The optical properties of thermal control surfaces in the solar region of the spectrum are of primary interest to spacecraft thermal designers since these properties govern the solar-heat input to exposed surfaces (such as the thermal radiators) and therefore influence the temperature of the spacecraft. These properties, however, have been shown to be altered considerably under the space environment.

Prior to LDEF, no optical measurements of thermal control surfaces had been made in space. Temperature measurements of thermally isolated samples had been used to back-calculate solar absorptance and thermal emittance. This type of measurement is not as definitive as required and does not describe the spectral character of the sample surface. Spectral reflectance measurements of the samples are required to differentiate between different damage mechanism of environmental effects and to separate contamination effects. Additionally, because of the inability to simulate exactly the conditions of the coating surface temperature and the solar spectrum, there is a major difference between laboratory test data and in-flight experiment data. The TCSE was a comprehensive experiment that combined in-space measurements with extensive pre- and post-flight analyses of thermal control surfaces to determine the effects of exposure to the low Earth orbit space environment. The TCSE was the first space experiment to directly measure the total hemi-spherical reflectance of thermal control surfaces in the same way they are routinely measured in the laboratory.

Photograph Classification: Prelaunch

Associated Photograph(s):
LaRC - L84-07073
KSC - KSC-384C-209.03
JSC - None
LaRC - L90-13409
KSC - KSC-390C-1030.11
JSC - None
LaRC - L90-10375
KSC - None
JSC - S32-76-005

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