Southwest Research Institute is a research laboratory with scientists and engineers involved
in a number of specialties. They have been a subcontractor to NASA and DOD (more specifically,
the Air Force) for most of the time these government agencies existed. One of the projects
carried out in 1997 and 1998 was the CAPER sounding rocket, a platform for analyzing the
'magnetosphere', a region where the earth's magnetic field interacts with ions and atoms
making up the 'solar wind'.
This particular sounding rocket is launched from a facility in Svalbard, an island
north of the arctic circle that is part of Norway. The sounding rocket is launched during the
northern hemisphere's solar minimum, in other words on the coldest and darkest day available.
The sounding rocket lofts a number of instruments, which in this case are developed by a
collection of research groups at various universities. The SWRI component of this is an
instrument called TICHS/TECHS. TICHS is an ion detector (atomic nucleus) and TECHS
is the electron detector. The specific nuclei they were looking for are hydrogen
Each instrument is designed to measure the number of 'events' at various energies, meaning
the impact of particles with certain energies (sort of an analogy for speed, but inexact).
These particles radiate from the sun, and are eventually caught up in Earth's magnetic field,
where they migrate toward the poles following magnetic lines of force.
The instruments apply a series of voltages to a plate, which causes ions or electrons that
do not fall in that energy range to be diverted. As the instrument is flying through space,
the instruments repeatedly cycle through various voltages and count the number of voltage
spikes indicating an interaction with a particle. This information is downloaded to a
tracking facility located under the arc of the flight path.
Before the instruments can be launched, they are calibrated in a vacuum chamber. An ion
or electron source is aimed at the instrument, and reading from the instrument are recorded,
stored, and compared to the energy of the reference source. If the instrument records ten
events at a particular emission energy, then it is assumed that in the flight ten events
represents this same amount of energy.
My involvement in this project was to develop the software for collecting data while it
was in the vacuum chamber. We chose to use National Instruments LabView 5.0 and
National Instruments data acquisition boards, including a DIO (Digital IO) and an MIO
(Multiple IO) which was used to measure both analog and digital values.
We needed to acquire data at 80,000 samples per second, and we found out right away that
LabView for Windows did not run sampling at anywhere near this rate. The boards were
rated for 400,000 samples per second, however the computer itself could not absorb and
process this much information while it was also running real time displays on Windows.
Our solution to this was to write code in C, running in an exclusive mode, where short
bursts of data were gathered in a hurry, then the burst was absorbed by the windows side,
where it was displayed and logged. This proved to be an effective solution.
The machine we were using at the time was a brand-new 200Mhz Pentium 2 with 64Mb of
RAM. It's likely that 2 Ghz Pentiums would perform better, but probably will still
not operate at 80,000 SPS.
What we learned from this is to use buffered data acquisition boards, in which data can
be read without being dependent on the operating system software to keep up. Needless
to say these are more expensive, but we found out that the expense is easily justified.
Note: this work was done by Meredith Poor but not through Resource Logic, Inc. This
particular project was proposed and executed by another company.