Optical contamination evidence from Skylab and Gemini flights.

Area of Science:

• Spacecraft materials science
• Optical engineering
• Environmental effects on spacecraft

Background:

• Understanding spacecraft contamination is crucial for mission success and optical instrument performance.
• Previous space missions have experienced varying degrees of external surface contamination.
• The Skylab and Gemini programs provided opportunities to study these effects.

Purpose of the Study:

• To present final results from the T027 experiment on the Skylab mission regarding optical surface contamination.
• To analyze contamination on optical windows and mirrors from the Gemini 12 mission.
• To characterize the type, thickness, and optical impact of contaminants.

Main Methods:

• Exposure of a sample array system with 248 optical surfaces on the Skylab orbital workshop.
• Analysis of returned samples for contaminants and their optical properties.
• Postflight examination of Gemini 12 optical windows and mirrors, including scattered luminance measurements.

Main Results:

• The Skylab sample array showed no significant contamination on most surfaces, with some localized contamination near the extravehicular hatch quadrant.
• Gemini 12 optical surfaces exhibited degradation up to 35% in UV wavelengths and increased solar absorptance.
• The identified contaminant was a silicone-based material, ranging from 22 nm to 88 nm in thickness.

Conclusions:

• External optical surfaces on Skylab experienced minimal contamination, below ground instrument sensitivity for most areas.
• Silicone-based contaminants can significantly degrade optical performance, particularly in UV regions, as demonstrated by Gemini 12 results.
• Threshold stellar visibility curves were derived from contaminated Gemini 12 window data, correlating with scattered light.