The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). DES started its first observing season on August 31, 2013 and observed for 105 nights through mid-February 2014. This paper describes DES “Year 1” (Y1), the strategy and goals for the first year's data, provides an outline of the operations procedures, lists the efficiency of survey operations and the causes of lost observing time, provides details about the quality of the first year's data, and hints at the “Year 2” plan and outlook.
We have built an Atmospheric Transmission Monitoring Camera (aTmCam), which consists of four telescopes and
detectors each with a narrow-band filter that monitors the brightness of suitable standard stars. Each narrowband filter is
selected to monitor a different wavelength region of the atmospheric transmission, including regions dominated by the
precipitable water vapor and aerosol optical depth. The colors of the stars are measured by this multi narrow-band
imager system simultaneously. The measured colors, a model of the observed star, and the measured throughput of the
system can be used to derive the atmospheric transmission of a site on sub-minute time scales. We deployed such a
system to the Cerro Tololo Inter-American Observatory (CTIO) and executed two one-month-long observing campaigns
in Oct-Nov 2012 and Sept-Oct 2013. We have determined the time and angular scales of variations in the atmospheric
transmission above CTIO during these observing runs. We also compared our results with those from a GPS Water
Vapor Monitoring System and find general agreement. The information for the atmospheric transmission can be used to
improve photometric precision of large imaging surveys such as the Dark Energy Survey and the Large Synoptic Survey
We review a conceptual design for a moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT).
The spectrograph is designed to make use of the large field-of-view of the GMT and be suitable for observations of very
faint objects across a wide range of wavelengths. We also review the status of the instrument and on-going trade studies
designed to update the instrument science objectives and technical requirements.
The Visual Integral-Field Replicable Unit Spectrograph (VIRUS) instrument is a baseline array 150 identical fiber fed
optical spectrographs designed to support observations for the Hobby-Eberly Telescope Dark Energy Experiment
(HETDEX). The collimator subassemblies of the instrument have been assembled in a production line and are now
complete. Here we review the design choices and assembly practices used to produce a suite of identical low-cost
spectrographs in a timely fashion using primarily unskilled labor.
Traditional color and airmass corrections can typically achieve ~0.02 mag precision in photometric observing conditions.
A major limiting factor is the variability in atmospheric throughput, which changes on timescales of less than a night.
We present preliminary results for a system to monitor the throughput of the atmosphere, which should enable
photometric precision when coupled to more traditional techniques of less than 1% in photometric conditions. The
system, aTmCam, consists of a set of imagers each with a narrow-band filter that monitors the brightness of suitable
standard stars. Each narrowband filter is selected to monitor a different wavelength region of the atmospheric
transmission, including regions dominated by the precipitable water, aerosol optical depth, etc. We have built a
prototype system to test the notion that an atmospheric model derived from a few color indices measurements can be an
accurate representation of the true atmospheric transmission. We have measured the atmospheric transmission with both
narrowband photometric measurements and spectroscopic measurements; we show that the narrowband imaging
approach can predict the changes in the throughput of the atmosphere to better than ~10% across a broad wavelength
range, so as to achieve photometric precision less than 0.01 mag.