The Impact of Observing Strategy on Cosmological Constraints with LSST

TL;DR

This paper assesses how different LSST observing strategies affect cosmological measurements, providing metrics and recommendations to optimize survey design for better scientific constraints.

Contribution

It introduces metrics to evaluate the impact of observing strategies on cosmological probes and analyzes over 100 simulated survey designs to guide LSST planning.

Findings

Adjusting survey footprint significantly affects constraints.

Ensuring diverse filter visits improves data quality.

Regular cadence enhances cosmological parameter estimation.

Abstract

The generation-defining Vera C. Rubin Observatory will make state-of-the-art measurements of both the static and transient universe through its Legacy Survey for Space and Time (LSST). With such capabilities, it is immensely challenging to optimize the LSST observing strategy across the survey's wide range of science drivers. Many aspects of the LSST observing strategy relevant to the LSST Dark Energy Science Collaboration, such as survey footprint definition, single visit exposure time and the cadence of repeat visits in different filters, are yet to be finalized. Here, we present metrics used to assess the impact of observing strategy on the cosmological probes considered most sensitive to survey design; these are large-scale structure, weak lensing, type Ia supernovae, kilonovae and strong lens systems (as well as photometric redshifts, which enable many of these probes). We evaluate these metrics for over 100 different simulated potential survey designs. Our results show that multiple observing strategy decisions can profoundly impact cosmological constraints with LSST; these include adjusting the survey footprint, ensuring repeat nightly visits are taken in different filters and enforcing regular cadence. We provide public code for our metrics, which makes them readily available for evaluating further modifications to the survey design. We conclude with a set of recommendations and highlight observing strategy factors that require further research.