Gemini Observatory is a ground-based international observatory with 8.1 m telescopes in each hemisphere to provide all-sky coverage. We offer optical and IR imaging and spectroscopy. Laser adaptive optics systems provide near diffraction-limited image quality, taking advantage of our two excellent observing sites (Maunakea and Cerro Pachón). Each telescope keeps three of our larger suite of instruments mounted on the telescope at all times and switches between them routinely during the night. The nighttime operations are all conducted remotely from our base facilities located approximately one hour from the summits. Science Operations is responsible for the routine operation of the established instruments and is heavily involved in the commissioning phases of new instruments. We offer multiple avenues to request observing time (standard semester calls, annual calls for long and large programs, monthly calls for fast turnaround, and an always-available director’s discretionary time) and multiple ways to observe (classical, queue, eavesdropping). Here, we will describe our operation model — how we manage and meet the challenges of the nightly/daily science operations.
Cerro Las Campanas located at Las Campanas Observatory (LCO) in Chile has been selected as the site for the Giant
Magellan Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of
potential GMT sites at LCO. Atmospheric precipitable water vapor (PWV) adversely impacts mid-IR astronomy
through reduced transparency and increased background. Prior to the GMT site testing effort, little was known regarding
the PWV characteristics at LCO and therefore, a multi-pronged approach was used to ensure the determination of the
fraction of the time suitable for mid-IR observations. High time resolution monitoring was achieved with an Infrared
Radiometer for Millimeter Astronomy (IRMA) from the University of Lethbridge deployed at LCO since September of
2007. Absolute calibrations via the robust Brault method (described in Thomas-Osip et al.1) are provided by the
Magellan Inamori Kyocera Echelle (MIKE), mounted on the Clay 6.5-m telescope on a timescale of several per month.
We find that conditions suitable for mid-IR astronomy (PWV < 1.5 mm) are concentrated in the southern winter and
spring months. Nearly 40% of clear time during these seasons have PWV < 1.5mm. Approximately 10% of these nights
meet our PWV requirement for the entire night.
Cerro Las Campanas located at Las Campanas Observatory in Chile has been selected as the site for the Giant Magellan
Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of potential
GMT sites at LCO. Seeing data have been obtained at three potential sites, and are compared with identical data taken at
the site of the twin Magellan 6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere
have been collected. Co. Las Camapanas and the Magellan site are nearly identical in their seeing statistics, and
apparently their average ground-layer characteristics.
The European Southern Observatory (ESO), the Institute for Space Imaging Science (ISIS) and the AstroMeteorology
group at the Universidad de Valparaiso collaborated on a project to understand the precipitable water
vapour (PWV) over the La Silla Paranal Observatory. Both La Silla and Paranal were studied with the goal of
using them as reference sites to evaluate potential E-ELT sites. As ground-based infrared astronomy matures,
our understanding of the atmospheric conditions over the observatories becomes paramount, specifically water
vapour since it is the principle source of atmospheric opacity at infrared wavelengths. Several years of archival
optical spectra (FEROS) have been analysed to reconstruct the PWV history above La Silla using an atmospheric
radiative transfer model (BTRAM) developed by ISIS. In order to better understand the systematics involved, a
dedicated atmospheric water vapour measurement campaign was conducted in May 2009 in close collaboration
with Las Campanas observatory and the GMT site testing team. Several methods of determining the water column
were employed, including radiosonde launches, continuous measurements by infrared radiometers (IRMA),
a compact echelle spectrograph (BACHES) and several high-resolution optical echelle spectrographs (FEROS,
HARPS and MIKE). All available observations were compared to concurrent satellite estimates of water vapour
in an attempt to ground-truth the satellite data. We present a comparison of the methods used, and results
from the archival study and measurement campaign. A mean PWV of 3.4 ± 2.4 mm is found for La Silla using
FEROS data covering the period 2005-2009. Important lessons on the strengths and limitations of satellite data
are presented. The value of a stand-alone high time resolution PWV monitor has been demonstrated in the
context of parallel observations from Las Campanas and La Silla.
Cerro Las Campanas located at Las Campanas Observatory (LCO) in Chile has been selected as the site for the Giant
Magellan Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of
potential GMT sites at LCO. Meteorological (cloud cover, temperature, pressure, wind, and humidity) and DIMM
seeing data have been obtained at three potential sites, and are compared with identical data taken at the site of the twin
Magellan 6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere above LCO have
been collected with a MASS/DIMM. Furthermore, we consider photometric quality, light pollution, and precipitable
water vapor (PWV). LCO, and Co. Las Campanas in particular, have dark skies, little or no risk of future light pollution,
excellent seeing, moderate winds, PWV adequate for mid-IR astronomy during a reasonable fraction of the nights, and a
high fraction of clear nights overall. Finally, Co. Las Campanas meets or exceeds all the defined science requirements.
In preparation to characterize the Giant Magellan Telescope site and guide the development of its adaptive
optics system, two campaigns to systematically compare the turbulence profiles obtained independently with
three different instruments were conducted at Las Campanas Observatory in September, 2007 and January 2008.
Slope detection and ranging (SLODAR) was used on the 2.5-m duPont telescope. SLODAR measures the C2n
profile as a function of altitude through observations of double stars. The separation of the observed double
star sets the maximum altitude and height resolution. Ground layer (altitudes < 1 km) and free atmosphere
turbulence profiles are compared with those obtained with a lunar scintillometer (LuSci) and a multi-aperture
scintillation sensor (MASS), respectively. In addition, the total atmospheric seeing was measured by both
SLODAR and a differential image motion monitor (DIMM).
We present simultaneous precipitable water vapour (PWV) measurements made at the Las Campanas Observatory
in late 2007 using an Infrared Radiometer for Millimetre Astronomy (IRMA) and the Magellan Inamori
Kyocera Echelle (MIKE) optical spectrograph. Opacity due to water vapour is the primary concern for ground
based infrared astronomy. IRMA has been developed to measure the emission of rotational transitions of water
vapour across a narrow spectral region centred around 20 μm, using a 0.1 m off-axis parabolic mirror and a
sophisticated atmospheric model to retrieve PWV. In contrast, the MIKE instrument is used in conjunction
with the 6.5 m Magellan Clay telescope, and determines the PWV through absorption measurements of water
vapour lines in the spectra of telluric standard stars. With its high spectral resolution, MIKE is able to measure
absorption from optically thin water vapour lines and can derive PWV values using a simple, single layer
atmospheric model. In an attempt to improve the MIKE derived PWV measurements, we explore the potential
of fitting a series of MIKE water vapour line measurements, having different opacities.
Las Campanas Observatory has been designated as the location for the Giant Magellan Telescope (GMT).
We report results obtained since the commencement, in 2005, of a systematic site testing campaign at LCO.
Meteorological (cloud cover, temperature, pressure, wind, and humidity) and DIMM seeing data have been
obtained at three potential sites, and are compared with identical data taken at the site of the twin Magellan
6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere above LCO have
been collected with a MASS/DIMM. We examine the contribution to the seeing arising from turbulence in the
ground layer (defined here as below an altitude of 500 m) through the difference between the turbulence integrals
in the full atmosphere (as measured by DIMM) and in the free atmosphere (as measured by MASS). Additionally,
we consider photometric quality, light pollution, and precipitable water vapor at LCO.
We present results from our two year study of ground-layer turbulence as seen through the 6.5-meter Magellan
Telescopes at Las Campanas Observatory. The experiment consists of multiple, moderate resolution, Shack-
Hartmann wavefront sensors deployed over a large 16 arcminute field. Over the two years of the experiment,
the ground-layer turbulence has been sampled on eleven nights in a variety of seeing and wind conditions. On
most nights the ground-layer turbulence contributes 10% to the total visible-band seeing, although a few nights
exhibit ground-layer contributions up to 30%. We present the ground-layer turbulence on the sampled nights as
well as a demonstration of its strength as a function of field size. This information is combined with data from a
MASS-DIMM seeing monitor adjacent to the Magellan Telescopes to infer the annual ground-layer contribution
to seeing at Las Campanas.
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