A data acquisition and control system (DACS) has been designed and constructed
for use during propagation experiments with the OLYMPUS satellite. OLYMPUS is
a European Space Agency experimental satellite that broadcasts coherent at
12, 20 and 30 GHz and is viewed from Blacksburg, Virginia at an elevation angle of
13.9°. This low elevation angle yields a relatively long atmospheric path which serves
to accentuate propagation effects.
The DACS is a custom design which collects propagation, environmental and
status information and periodically calibrates external equipment. Beacon signal
strength is measured via a hybrid analog/digital receiver. The analog portion the
receiver utilizes the coherency of the satellite beacons to track 20 and 30 GHz signals to the noise floor. The digital portion of the receiver is contained within the DACS and consists of a stand-alone microprocessor which filters the beacon signal to determine the power in a 3 Hz bandwidth. Additional DACS circuitry collects
analog and digital input channels and controls external through digital output channels. Digital outputs are used to reference the collected to known by
performing periodic calibrations on external equipment. Analog input channels are
used to measure quantities including external temperature, wind speed wind direction, while digital inputs monitor alarm conditions.
The VIEW program utility permits an operator to graphically view data in real
time. In addition, collected data is stored to tape without an interruption in data
collection. DACS operation has been virtually continuous since data collection was
started on August 3, 1990.
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