Fermi Science Support Center

Gamma Ray Burst Observations

During survey observations, the GBM instrument monitors the entire available sky (that remains unocculted by the Earth) to watch for transients. (During pointed observations, some of the GBM detectors are pointed at the Earth, leaving a portion of the sky unmonitored.) Upon detection of an event, the GBM software analyzes the event characteristics and assigns the event a likely classification. If it is a GRB, the GBM forwards information to the LAT for further analysis.

At that time, the LAT begins monitoring the region of the GRB for an increase in gamma-ray candidate events. If it detects a significant increase in these events near the burst location, a autonomous repoint recommendation (ARR) is sent to the spacecraft. The spacecraft can then either accept or reject the request based on the current operational mode. Nominally, the spacecraft will accept the recommendation, and slew to the target loation where it remains pointed for five hours. During periods when the GRB location is occulted, the observatory will track around the earth at 50 degrees from the limb and will meet the GRB location as it emerges. At the end of the five hour dwell time, the spacecraft resumes the nominal observing timeline.

GBM/LAT Burst Locations with SWIFT correlations
GBM/LAT Burst Locations with SWIFT Correlations
Credit: Fermi-LAT and GBM Collaborations

Additional GRB Information

A number of resources are available to learn about the Fermi burst observations: