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.
EDITORS: High-resolution images of the calibration and instrument
development facility are available at www.swri.org/press/callab.htm.
