Executive Summary : | Gravitational lensing is a unique probe in cosmology that involves a massive galaxy deflecting light from a distant source, causing multiple signals of the same source to be seen separated over time. This project aims to develop methodology and pipelines for science observations with the Rubin observatory's Legacy Survey of Space and Time (LSST) program, enabling the detection of gravitationally lensed supernovae (SNe - Type Ia), electromagnetic counterparts to lensed gravitational wave (GW) sources (kilonovae (KNe), and double-source-plane lenses. The pipelines will be tested and demonstrated on realistic mock lens systems created specifically for LSST. The unprecedented depth, imaging quality, and cadence of Rubin-LSST will enable the detection of hundreds of lensed SNe-Ia, double-source-plane lenses, and several lensed KNe counterparts to the GW sources discovered by the LIGO-Virgo-Kagra (LVK) observatories via multi-messenger astronomy. The proposed three types of gravitational lenses will offer complementary constraints and improved systematics than would be possible through any one kind of lens. Lensed SNe-Ia will help improve lens modeling systematics, lensed KNe will provide the most precise time-delay measurements, and double-source-plane lenses will be most sensitive to the effects of Dark Energy. The output of this project will help fill a significant gap in measuring the Hubble-Lemaitre constant from probes in the early Universe versus the late Universe, and allow for further observational data collection, analysis, and constraint on cosmological parameters within three years. |