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Innovative SwRI facility offers unprecedented speeds for calibrating and developing spaceflight instruments

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San Antonio -- July 2, 2002 -- An innovative calibration and instrument development facility at Southwest Research Institute® (SwRI®) is helping scientists and engineers test and design space plasma instruments far faster and more reliably than previously possible.

"This facility is clearly one of the best in the world for this kind of calibration and development work," says Dr. David J. McComas, executive director of the SwRI Space Science and Engineering Division. "In addition to developing our own instruments, we're also looking to partner with other instrument development teams needing access to this kind of world-class facility."

A four-axis computer-controlled position system situated within a large ultra-high vacuum chamber and an energy and mass selected ion or neutral atom beam allow researchers to characterize their instruments' responses to the particles. Because a variety of particles come at the instrument from all directions in space, researchers move the instrument around in the chamber and expose it to a range of orientations, ion species, energies, and beam fluxes. The resulting data allow researchers to later determine the direction and distribution of the particles in the space environment.

Two 3,000-liter-per-second cryogenic pumps on the main chamber create a vacuum of 10-8 Torr within a few hours. The same vacuum conditions can take days to create in other calibration facilities, with some facilities never achieving such low pressures. This improvement allows researchers to develop instruments at unprecedented speeds.

"We can test in the morning, break vacuum and modify the instrument in the afternoon, and be testing in the 10-8 Torr range again the next morning," says McComas.

Spaceflight instruments that measure ions and neutrals, particularly those used on spacecraft built to examine the magnetosphere and heliosphere, can be tested or developed using this facility. SwRI researchers currently are using the facility to design an innovative extension of ion mass spectrometry for the proposed MMS (Magnetospheric Multi-Scale) mission. The facility already has been used to calibrate the first TWINS (Two Wide-angle Imaging Neutral-atom Spectrometers) instrument, scheduled to launch in 2003.

"We worked out a lot of instrument issues during the TWINS calibration and didn't have a single worry about the facility," says McComas. "In contrast, we had numerous problems the last time we did a calibration in the old facility. Now we get more data in days than we used to get in weeks."

The facility also is reliable and easy to operate. Safety interlocking systems protect the science instrument during testing and development so that control functions are allowed only when they're safe and appropriate. With science teams often working around the clock to calibrate and fine-tune their instruments, mistakes in the early hours of the morning are common. System interlocks prevent such errors.

"You can push a button to open a vent valve, but if that valve isn't supposed to be open while the pump is operating, the system won't let you do it," says McComas.

The SwRI chamber is entirely oil free. Calibration facilities that pump any oil leave very minute amounts of contamination in the chamber. Frequent residual gas analyses quantify the amount of contamination in the SwRI chamber to ensure the safety of the instrument. Complex hydrocarbons, in particular, can cause irreparable damage and greatly reduce the lifetimes of these types of spaceflight instruments.

In addition, the facility is arranged so that the door to the vacuum chamber opens into a clean room, while the vacuum system and components sit outside the clean room. This enables technicians to make system adjustments while preserving the integrity of the clean environment.

Team members from across the country also can access a web site that shows real-time temperatures, pressures, and status flags in the facility. Other computer monitors enable instrument data visualization and analysis while testing is in progress and observation of the particle beam. SwRI programmers engineered custom control and analysis software for the system.

SwRI funded development of the facility. In the future, the system will be modified to extend the upper energy from 30 to 50 kilovolts and may be adapted for electrons as well.

For more information, contact Maria Stothoff at (210) 522-3305, Communications Department, PO Drawer 28510, San Antonio, Texas 78228-0510. 

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