High performance astronomical data communications in the LSST data management system

The Large Synoptic Survey Telescope (LSST) is an 8.4m (6.5m effective), wide-field (9.6 degree2), ground-based telescope with a 3.2 GPixel camera. It will survey over 20,000 degree2 with 1,000 re-visits over 10 years in six visible bands, and is scheduled to begin full scientific operations in 2016. The Data Management System will acquire and process the images, issue transient alerts, and catalog the world's largest database of optical astronomical data. Every 24 hours, 15 terabytes of raw data will be transferred via redundant 10 Gbps fiber optics down from the mountain summit at Cerro Pachon, Chile to the Base Facility in La Serena for transient alert processing. Simultaneously, the data will be transferred at 2.5Gbps over fiber optics to the Archive Center in Champaign, Illinois for archiving and further scientific processing and creation of scientific data catalogs. Finally, the Archive Center will distribute the processed data and catalogs at 10Gbps to a number Data Access Centers for scientific ,educational, and public access. Redundant storage and network bandwidth is built into the design of the system. The current networking acquistiion strategy involves leveraging existing dark fiber to handle within Chile, Chile - U.S. and within U.S. links. There are a significant number of carriers and networks involved and coordinating the acquisition, deployment, and operations of this capability. Advanced protocols are being investigated during our Research and Development phase to address anticipated challenges in effective utilization. We describe the data communications requirements, architecture, and acquisition strategy in this paper.