If you’re going to build a space station, how do you know which materials to
use? What will and won’t last for decades in the unforgiving environment of space? And just what is that environment, anyway? The Optical Properties Monitor (OPM) was a space flight experiment built to answer these questions.
From April to December 1997, the OPM, in its position on the outside of the
Mir’s Space Shuttle docking module, monitored the space environment around Mir and took measurements on material samples. It examined the samples for changes caused by exposure to the space environment. The OPM was transported to and from Mir in a SPACEHAB laboratory module flying in the payload bay of the Space Shuttle.
Many materials-exposure experiments had flown before, on the Space
Shuttle, Mir, Skylab, and even going all the way back to the days of the Saturn 5 and the Apollo missions and have continued since OPM’s flight on the Materials International Space Station Experiment (MISSE). However, most of these were passive experiments which relied on Earth-based analysis of the samples after the flight. Exposure to the Earth’s environment after the flight alters the samples and makes some types of measurements difficult or impossible.
The OPM was an active experiment which took its measurements while the exposed samples were still in the space vacuum. It was the first materials exposure experiment capable of taking in situ measurements and down linking the data to Earth while the experiment progressed.