GLAST will carry two instruments: the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The LAT is GLAST's primary instrument and consists of four components: the Tracker, the Calorimeter, the Anticoincidence Detector (ACD), and the Data Acquisition System (DAQ). These instrument components working together will detect gamma rays by using Einstein's famous equation (E=mc(squared) in a technique known as pair production. The GLAST Burst Monitor is a complementary instrument and consists of low-energy detectors, high-energy detectors, and data processing unit. The GBM can see all directions at once, except for the area where Earth blocks its view. When the GBM detects a bright gamma-ray burst, it immediately sends a signal to the LAT to observe that area of the sky.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 220.127.116.11.0