Exploring the Gamma Ray Universe (Manne Siegbahn Memorial Lecture)

The Gamma ray Large Area Space Telescope (GLAST) project began in 1992, a year after the launch of EGRET onboard the CGRO spacecraft. Capitalizing on the advances in particle detector technology, the GLAST project developed an observatory, which would extend the discovery space of EGRET by over an order of magnitude. After its launch in 2008, GLAST was renamed Fermi-LAT and has performed an all-sky survey of the gamma ray sky ever since. This talk will present details of how the instrument was designed and how the design choices contributed to the success of this mission. Highlights from the first 6 years of the Fermi-LAT mission will be presented.