Showing papers by "Michael Levi published in 2014"

The Zwicky transient facility observing system

Abstract: The Zwicky Transient Facility (ZTF) is a synoptic optical survey for high-cadence time-domain astronomy. Building upon the experience and infrastructure of the highly successful Palomar Transient Factory (PTF) team, ZTF will survey more than an order of magnitude faster than PTF in sky area and volume in order to identify rare, rapidly varying optical sources. These sources will include a trove of supernovae, exotic explosive transients, unusual stellar variables, compact binaries, active galactic nuclei, and asteroids. The single-visit depth of 20.4 mag is well matched to spectroscopic follow-up observations, while the co-added images will provide wide sky coverage 1.5 – 2 mag deeper than SDSS. The ZTF survey will cover the entire Northern Sky and revisit fields on timescales of a few hours, providing hundreds of visits per field each year, an unprecedented cadence, as required to detect fast transients and variability. This high-cadence survey is enabled by an observing system based on a new camera having 47 deg^2 field of view – a factor of 6.5 greater than the existing PTF camera - equipped with fast readout electronics, a large, fast exposure shutter, faster telescope and dome drives, and various measures to optimize delivered image quality. Our project has already received an initial procurement of e2v wafer-scale CCDs and we are currently fabricating the camera cryostat. International partners and the NSF committed funds in June 2014 so construction can proceed as planned to commence engineering commissioning in 2016 and begin operations in 2017. Public release will allow broad utilization of these data by the US astronomical community. ZTF will also promote the development of transient and variable science methods in preparation for the seminal first light of LSST.

A high-accuracy, small field of view star guider with application to SNAP

Abstract: To accomplish its mission, the spaceborne observatory SNAP (SuperNova Accel- eration Probe) requires a pointing stability of < 0.03 arcseconds during exposures lasting up to 500 seconds. A Monte Carlo simulation of the photoelectron statistics from the guiding star investigates geometrical (such as the pixel size of the detector or the plate scale) and physical parameters (such as the magnitude of the star). It is shown that simple centroiding calculations can lead to the desired accuracy with guide stars as faint as magnitude 16. Availability of these stars is verified thanks to the HST Guide Star Catalog complemented with a statistical model of the distribution of stars. Thus a through-the-lens sensor that uses stars as faint as magnitude 16 to provide the necessary guiding signals is feasible. In one year of study, the SNAP (SuperNova Acceleration Probe) satellite can discover, follow the light curve, and obtain spectra at peak brightness for more than 2000 supernovae. SNAP instrumentation includes a wide field optical imager (field of view of one square degree) and a small IR imager, which, combined with filters, will allow photometry from 0.35 to 1.7 µm and a three arm spectrograph sensitive in the same range of wavelengths. SNAP instrumentation will be used with a simple, predetermined observing strategy designed to monitor a 20 square degree region of sky both near the north ecliptic pole (16 h 25 min + 57 deg) and near the south ecliptic pole (4 h 30 min 52 deg), discovering and following supernovae that explode in these regions. More information on the scientific background of this mission can be found at the URL http://snap.lbl.gov. The data from the wide field optical imager will serve both as search images and for follow-up photometry. The detection of supernovae is ac- complished by a repeated comparison of fixed fields to reference images. The optical photometer obtains wide-field frames overlapping the positions of