What Are You Up To? Installed this year, Cielo is Los Alamos National Labs' newest nuclear weapons modeling and simulation platform. As such, specifics on what it's working on at any given time are closely held. Cielo works for three national laboratories: Los Alamos National Laboratory (LANL), Sandia National Laboratories (SNL), and Lawrence Livermore National Laboratory (LLNL). Like its sister system Roadrunner, it performs advanced physics and predictive simulations to assure the safety, security, and effectiveness of the U.S. nuclear deterrent.