Effects Of Space Environment On Mir To Be Measured With New Device

The Space Portable Spectroreflectometer, a device for measuring the effects of the space environment on spacecraft materials, is scheduled to fly aboard the Space Shuttle Endeavour on the STS-86 mission. Launch is targeted for no earlier than September 25.

The device is designed to test spacecraft materials such as those being used to construct the International Space Station. NASA and its international partners are scheduled to begin on-orbit assembly of the Space Station in June 1998.

"The Spectroreflectometer is the first hand-held, battery-powered device of its kind," said principal investigator Ralph Carruth of NASA's Marshall Space Flight Center in Huntsville, AL. "It will allow astronauts to monitor and assess the condition of actual spacecraft surfaces, rather than relying on information gathered from samples of previous experiments."

During a spacewalk planned for later this year, Russian cosmonauts and a U.S. astronaut will use the device to measure how much energy can be absorbed by the thermal control coatings, or radiator surfaces, of the Mir space station. "Radiators, where excess heat is dumped from the space station, are a vital part of the spacecraft's cooling system," said Jim Zwiener, co-investigator for the device at Marshall. "If the radiators degrade, the cooling system degrades, so these are critical surfaces."

Measurements will be used to determine the deterioration of radiator surfaces caused by the space environment. "Also, in the vacuum of space, gases generated by -- and released from -- the spacecraft collect on the spacecraft's surfaces, resulting in contamination," said Zwiener. The gas deposits are visible as a discoloration of the spacecraft's white paint surfaces.

Measurements will be taken from four sites on Mir -- three on the core module and one on a smaller adjacent module. To take measurements, the device will be held against the space stationÕs surface for approximately two minutes. "During tests, light consisting of wavelengths from near ultraviolet to infrared will be emitted by sources within the device," explained Carruth. "The device measures then how much of this light is reflected, which also indicates how much is absorbed and the extent of deterioration."

The device will display the measurements on a small screen, and the astronauts will read the information to researchers on the ground. "Following the spacewalk, more detailed information will be downlinked to the ground from the device via a computer aboard Mir," said Carruth.

The radiator surfaces of Mir are very similar to those being manufactured for the Russian components of the International Space Station. Based on ground testing, researchers have constructed models of expected surface deterioration for the future space station. "Comparisons of findings from this study with computer models will allow researchers to better predict and plan for the health of the International Space Station," said Carruth.

The experiment also will test the design of the measuring device. "Plans are to not only use the device to monitor the effects of the space environment on the surfaces of the International Space Station," said Carruth, "but it may also be used to monitor other spacecraft, such as the Hubble Space Telescope."

NASA's Space Environments and Effects Program at Marshall will also use information gathered from the experiment to enhance the development of advanced technologies in the area of space environments for future NASA missions.

The Space Portable Spectroreflectometer was built for NASA by AZ Technology, Inc., in Huntsville, AL.