The Large Synoptic Survey Telescope (LSST) will explore the entire southern sky over 10 years starting in 2022 with unprecedented depth and time sampling in six filters, ugrizy. Artificial power on the scale of the 3.5 deg LSST field-of-view will contaminate measurements of baryonic acoustic oscillations (BAO), which fall at the same angular scale at redshift z ~ 1. Using the HEALPix framework, we demonstrate the impact of an “un- dithered” survey, in which 17% of each LSST field-of-view is overlapped by neighboring observations, generating a honeycomb pattern of strongly varying survey depth and significant artificial power on BAO angular scales. We find that adopting large dithers (i.e., telescope pointing o sets) of amplitude close to the LSST field-of-view radius reduces artificial structure in the galaxy distribution by a factor of ~10. We propose an observing strategy utilizing large dithers within the main survey and minimal dithers for the LSST Deep Drilling Fields. We show that applying various magnitude cutos can further increase survey uniformity. We find that a magnitude cut of r < 27:3 removes significant spurious power from the angular power spectrum with a minimal reduction in the total number of observed galaxies over the ten-year LSST run. We also determine the effectiveness of the observing strategy for Type Ia SNe and predict that the main survey will contribute ~100,000 Type Ia SNe. We propose a concentrated survey where LSST observes one-third of its main survey area each year, increasing the number of main survey Type Ia SNe by a factor of ~1.5, while still enabling the successful pursuit of other science drivers.
We present an innovative method for photometric calibration of massive survey data that will be applied to the
Large Synoptic Survey Telescope (LSST). LSST will be a wide-field ground-based system designed to obtain
imaging data in six broad photometric bands (ugrizy, 320-1050 nm). Each sky position will be observed multiple
times, with about a hundred or more observations per band collected over the main survey area (20,000 sq.deg.)
during the anticipated 10 years of operations. Photometric zeropoints are required to be stable in time to 0.5%
(rms), and uniform across the survey area to better than 1% (rms). The large number of measurements of
each object taken during the survey allows identification of isolated non-variable sources, and forms the basis
for LSST's global self-calibration method. Inspired by SDSS's uber-calibration procedure, the self-calibration
determines zeropoints by requiring that repeated measurements of non-variable stars must be self-consistent when
corrected for variations in atmospheric and instrumental bandpass shapes. This requirement constrains both the
instrument throughput and atmospheric extinction. The atmospheric and instrumental bandpass shapes will
be explicitly measured using auxiliary instrumentation. We describe the algorithm used, with special emphasis
both on the challenges of controlling systematic errors, and how such an approach interacts with the design of
the survey, and discuss ongoing simulations of its performance.