OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...
OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...
OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...
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Optical Link Study Group (<strong>OLSG</strong>) <strong>Final</strong> <strong>Report</strong><br />
IOAG.T.<strong>OLSG</strong>.20<strong>12</strong>.V1<br />
the Mojave Desert at an altitude of 1100 m above sea level. Monitoring of the atmospheric<br />
channel at GDSCC is performed in similar fashion to that at TMF, deploying the following<br />
instrumentation.<br />
• Sun-Photometer—similar to TMF<br />
• Sun-Scintillometer—similar to TMF<br />
• Cloud Camera—Similar to TMF, but includes a second generation of thermal<br />
infrared imager with a field of view of 110 degrees<br />
• Weather Station—similar to TMF<br />
• Nighttime Seeing Monitor—Nighttime atmospheric turbulence is monitored by a<br />
nighttime seeing monitor. The instrument consists of a simple imaging system<br />
that is continuously monitoring the star Polaris. The astronomical seeing is<br />
derived from measurements of the centroid motion of the single image of Polaris<br />
in the focal plane detected by a CCD. This process provides similar measurements<br />
to those of the DIMM, but the measurements are not as accurate.<br />
• Boundary Layer Scintillometer (BLS)—The atmospheric turbulence at the ground<br />
layer is measured using a BLS. The instrument consists of a Light-Emitting Diode<br />
(LED) transmitter and a receiver spaced by few hundred meters. The structure<br />
coefficient of the refractive index (Cn2) is monitored by this instrument during<br />
the entire day at an interval of five minutes (see Figure 10). The periodical<br />
minima in Figure 10 correspond to times before sunset and after dawn.<br />
Figure 10: Measurements of the ground layer structure coefficient of the<br />
refractive index at Goldstone (time is in UTC).<br />
• Particle monitor—A particle counter monitors the aerosol concentration in the<br />
atmosphere. Aerosol concentration at Goldstone is composed essentially of dust.<br />
Dust concentration is responsible for variation of atmospheric transmittance and<br />
radiance, while dust contamination can affect the performances of a telescope<br />
due to the scattering of the direct sunlight. The particle counter provides<br />
measurements of the concentration of dust in the atmosphere for different<br />
particle sizes (from 0.3 to 10 mm). Measurements are provided every five<br />
minutes.<br />
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