Fermi Gamma-ray Space Telescope

The Fermi Gamma-ray Space Telescope (FGST or Fermi) is a space-based observatory used to perform gamma-ray astronomy observations from low-Earth orbit. Originally called the Gamma-Ray Large Area Space Telescope, or GLAST, the mission was renamed for the physicist Enrico Fermi after its launch in 2008. The mission is a joint venture of NASA, the United States Department of Energy and agencies and institutes in France, Germany, Italy, Japan, and Sweden.  In early 2021, Fermi completed its 70,000th orbit of the Earth.

Fermi instrumentation

Fermi's main instrument is the Large Area Telescope (LAT), which performs a continuous all-sky survey to study astrophysical sources of high-energy emissions such as active galactic nuclei, pulsars, and other cosmic particle accelerators, and to search for signatures of dark matter annihilation or decay. The LAT is an imaging high-energy gamma-ray telescope that can detect gamma rays from 20 MeV to more than 300 GeV.  The LAT's field of view covers about 20% of the sky and the instrument scans the whole sky every three hours. The LAT was constructed at the SLAC National Accelerator Laboratory, with contributions from the partner institutions of the LAT collaboration. The LAT collaboration includes more than 400 scientists and students at more than 90 universities and laboratories in 12 countries.

Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM), is being used to study transient gamma-ray phenomena such as gamma-ray bursts.

Collaboration and survey

KIPAC Professor Peter Michelson of Stanford University is the Principal Investigator and spokesperson for the collaboration. The collaboration has published papers on pulsars, active galactic nuclei, the Galactic center, indirect searches for dark matter, the extragalactic background light, globular clusters, cosmic-ray electrons, positrons, and protons, gamma-ray bursts, binary stars, supernova remnants, galactic novae, interstellar diffuse gamma-ray emission, solar flares, the Moon, and other subjects.  Because of their all-sky monitoring capability, the LAT and GBM are on the front lines in searches for electromagnetic counterparts of LIGO/VIRGO gravitational wave events triggered by merging black hole and neutron star systems. In 2020, the LAT detected high-energy gamma rays from a magnetar giant flare in the Sculptor galaxy.

LAT operations

The SLAC National Accelerator Laboratory also hosts the LAT Instrument Science Operations Center, or ISOC, which is managed by SLAC staff scientist and KIPAC member Dr. Robert Cameron. ISOC operates the LAT for the Fermi mission in cooperation with the Fermi Mission Operations Center and the Fermi Science Support Center, both at NASA's Goddard Space Flight Center.

The principal functions of the ISOC are to:

  • monitor the functionality and safety of the LAT by monitoring and trending its engineering telemetry
  • maintain the embedded software in the LAT and update it as needed
  • verify and optimize its science performance
  • receive, archive, and process raw event data transmitted from Fermi to the ground several times per day
  • perform event reconstruction processing on the raw LAT science data
  • deliver processed photon data to NASA for immediate public release
  • archive and host processed LAT event data (photon and non-photon) for the LAT collaboration
  • perform automated science processing of the photon data to refine prompt results on known or detected gamma-ray bursts
  • monitor and report light curves for selected celestial gamma-ray sources
  • search for and report light curves for flaring celestial gamma-ray sources
  • maintain the data processing, storage, and access infrastructure for the LAT collaboration

The ISOC makes use of the large-scale computing capabilities at SLAC, routinely using up to 2000 computer cores for data processing, with over one petabyte of data archived and available.