Used in a variety of applications, satellites house an array of expensive and highly sensitive equipment. Missiles and other high-altitude vehicles are used to launch these satellites into the Earth’s orbit. In some instances, harsh flight conditions put damaging stress on vital satellite instrumentation. Using a portable PC-based data acquisition system, engineers are able to monitor the effects of ambient factors during missile-test launches into orbit.

Application Summary
To study the earth’s ozone layer, NASA launches sophisticated mini-satellites, like the Total Ozone Mapping Spectrometers (TOMS), into low-Earth orbit. Engineers send TOMS into orbit aboard Pegasus missile/winged vehicles, which are air-launched from a Lockheed L-1011 carrier aircraft. During TOMS development, engineers were concerned that flight conditions might destroy sensitive satellite equipment, such as optical sensors that degrade when subjected to environmental stress.

To evaluate how the TOMS satellite would be affected during launch, engineers needed to measure several variables in the carrier missile’s fairing environment during flight. Variables included acoustic vibration, temperature, contamination, air velocity, humidity, heat transfer rate, and calorimeter voltage.

Potential Solution
The test engineers quickly realized that traditional test-and-measurement instruments would be much too bulky and too difficult to transport for the project. Instead, they needed a compact, reliable, stand-alone test system that would easily fit in the Pegasus fairing and collect data from multiple channels. In addition to being portable, the system had to be rugged as it would be subjected to high-altitude flight dynamics and extreme temperature conditions of -40^oC to 50^oC.

IOtech’s Solution
Consulting with IOtech, the engineering team designed a light-weight, simulated payload that featured a self-contained data acquisition system. The payload system, easily mounted within the vehicle’s fairing, was equipped to measure 69 channels of flight-environmental data from various sources.

The system featured IOtech’s DaqBook, a portable PC-based data acquisition system. Housed in DBK10 expansion-card enclosures, the system featured three IOtech DBK expansion/signal conditioning cards. IOtech’s DBK15 universal current/voltage card collected air velocity and pressure measurements. A DBK16 strain-gage card gathered data from two calorimeters, and four DBK82 high-accuracy thermocouple cards collected data from numerous sensors. A DBK30A battery module supplied power to all of the system’s components. Mixed-analog signals were supplied by calorimeters, pressure transducers, humidity sensors, and air velocity sensors.

The system’s 256-channel capacity easily handled the test’s 69-channel requirement. The DaqBook’s 16-bit A/D resolution easily provided the required accuracy for the project.

Software was used to control and view data as it was being collected, and LabVIEW^® was used to analyze and present analog data after it was acquired. The software ran on an IOtech-recommended notebook PC that was seamlessly compatible with the system.

Key to the project’s success was the system’s mobility and durability. The DaqBook and expansion modules matched the notebook PC’s form factor (8.5” x 11.5” x 1.375”) and were mounted on top of each other with brackets, creating a compact system that easily fit inside the payload assembly box. The total system weighed a total of 27.9 lbs., easily meeting the project’s weight limitations. The DaqBook system easily withstood the harsh flight environments, thanks in part to its rugged metal enclosures that protected and isolated the system’s circuitry.

Conclusion
The DaqBook system’s multichannel data acquisition capability, light weight, and ease of use made it possible for engineers to assess the conditions aboard the satellite launch missile. With the results, the engineers were able to assure that sensitive equipment would not be damaged during flight. The DaqBook system’s extensive I/O and signal conditioning capabilities and low cost per channel make it a perfect solution for applications that require high performance and portability.

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