We report on the development, installation and operation of the first three
of seven stations deployed at the ARIANNA site's pilot Hexagonal Radio Array in
Antarctica. The primary goal of the ARIANNA project is to observe ultra-high
energy (>100 PeV) cosmogenic neutrino signatures using a large array of
autonomous stations each dispersed 1 km apart on the surface of the Ross Ice
Shelf. Sensing radio emissions of 100 MHz to 1 GHz, each station in the array
contains RF antennas, amplifiers, 1.92 G-sample/s, 850 MHz bandwidth signal
acquisition circuitry, pattern-matching trigger capabilities, an embedded CPU,
32 GB of solid-state data storage, and long-distance wireless and satellite
communications. Power is provided by the sun and LiFePO4 storage batteries, and
the stations consume an average of 7W of power. Operation on solar power has
resulted in >=58% per calendar-year live-time. The station's pattern-trigger
capabilities reduce the trigger rates to a few milli-Hertz with 4-sigma
thresholds while retaining good stability and high efficiency for neutrino
signals. The timing resolution of the station has been found to be 0.049 ps,
RMS, and the angular precision of event reconstructions of signals bounced off
of the sea-ice interface of the Ross Ice Shelf ranged from 0.14 to 0.17
degrees. A new fully-synchronous 2+ G-sample/s, 1.5 GHz bandwidth 4-channel
signal acquisition chip with deeper memory and flexible >600 MHz, <1 mV RMS
sensitivity triggering has been designed and incorporated into a single-board
data acquisition and control system that uses an average of only 1.7W of power.
Along with updated amplifiers, these new systems are expected to be deployed
during the 2014-2015 Austral summer to complete the Hexagonal Radio Array.Comment: 17 Page, 27 Figures, 1 Tabl
