The Dark Energy Camera is a new imager with a 2°. 2 diameter field of view mounted at the prime focus of the Victor M. Blanco 4m telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaborationand meets or exceeds the stringent requirements designed for the widefield and supernova surveys for which the collaboration uses it. The camera consists of a five-element optical corrector, seven filters, a shutter with a 60 cm aperture, and a charge-coupled device (CCD) focal plane of 250 μm thick fully depleted CCDs cooled inside a vacuum Dewar. The 570 megapixel focal plane comprises 62 2k × 4k CCDs for imaging and 12 2k × 2k CCDs for guiding and focus. The CCDs have 15 μm × 15 μm pixels with a plate scale of 0 263 pixel −1. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 s with 6-9 electronreadout noise. This paper provides a technical description of the cameraʼs engineering, construction, installation, and current status.

ABSTRACT. The CHIRON optical high-resolution echelle spectrometer was commissioned at the 1.5 m telescope at CTIO in 2011. The instrument was designed for high throughput and stability, with the goal of monitoring radial velocities of bright stars with high precision and high cadence for the discovery of low-mass exoplanets. Spectral resolution of R ¼ 79 000 is attained when using a slicer with a total (including telescope and detector) efficiency of 6% or higher, while a resolution of R ¼ 136 000 is available for bright stars. A fixed spectral range of 415-880 nm is covered. The echelle grating is housed in a vacuum enclosure and the instrument temperature is stabilized to AE0:2°. Stable illumination is provided by an octagonal multimode fiber with excellent light-scrambling properties. An iodine cell is used for wavelength calibration. We describe the main optics, fiber feed, detector, exposure-meter, and other aspects of the instrument, as well as the observing procedure and data reduction.

We have converted the Palomar 60-inch telescope (P60) from a classical night assistant-operated telescope to a fully robotic facility. The automated system, which has been operational since September 2004, is designed for moderately fast (t 3 minutes) and sustained (R 23 mag) observations of gamma-ray burst afterglows and other transient events. Routine queue-scheduled observations can be interrupted in response to electronic notification of transient events. An automated pipeline reduces data in real-time, which is then stored on a searchable web-based archive for ease of distribution. We describe here the design requirements, hardware and software upgrades, and lessons learned from roboticization. We present an overview of the current system performance as well as plans for future upgrades.

Image persistence, an elevated dark current caused by prior illumination, has been a chronic problem in near infrared focal plane arrays. It has the potential to interfere with astronomical surveys requiring precision photometry, astrometry and/or shape measurement. We posit a mechanism whereby charge is captured by traps exposed to carriers as the depletion width shrinks when photo-generated charge accumulates on the electrically isolated photodiode. After the depletion width is reestablished by resetting the diode, trapped charge is slowly released, appearing to be a signal during the subsequent exposure(s). We present data illustrating the complex behavior of persistence for several 1.7 µm cutoff HgCdTe arrays on Teledyne H2RG multiplexers, and show that our simple model predicts this behavior at least qualitatively. We identify one inconsistency that has yet to be resolved and discuss mitigation options.

The Dark Energy Survey Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 520 Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be used to perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the remainder of the time, and after the survey, DECam will be available as a community instrument. Construction of DECam is well underway. Integration and testing of the major system components has already begun at Fermilab and the collaborating institutions.