Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

Fermi Gamma-ray Space Telescope

Fermi Gamma-ray Space Telescope logo

Launch Date: June 11, 2008

Extended Mission Lifetime: 2025+ (Pending NASA Senior Review)

End of Operations: No specific requirement (no consumables, no significant degradation)

Data Archive: Fermi Science Support Center (FSSC)

Fermi is a probe class mission operated by NASA in partnership with DOE, and agencies in Italy, France, Sweden, Japan, and Germany. It surveys the sky over a wide gamma-ray band with two instruments, the LAT and GBM. Both instruments provide alerts to GCN autonomously upon the detection of transients.

InstrumentsEnergy RangeField of ViewLocalization
Large Area Telescope (LAT)20 MeV–>300 GeV2.5 ster≤1° radius (statistical, 90%)
Gamma-ray Burst Monitor (GBM)8 keV–30 MeV8.8 ster≳1–10° radius (statistical + systematic)

GCN Notice Types in GCN Classic and GCN Classic Over Kafka:

Detailed Descriptions and Examples

FERMI_GBM_ALERTTrigger info~5 seconds
FERMI_GBM_FLT_POSFlight localization, classification~10 seconds
FERMI_GBM_GND_POSUpdated ground localization using finer lookup tables20–300 seconds
FERMI_GBM_FIN_POSFinal trigger localization15 minutes
FERMI_GBM_SUBTHRESHGround pipeline detected signals0.5–6 hours
FERMI_LAT_POS_INIOnboard LAT detection, initial position2–4 seconds
FERMI_LAT_POS_UPDUpdated onboard localization with more data2–32 seconds
FERMI_LAT_GNDGround localization of onboard trigger8–12 hours
FERMI_LAT_OFFLINEGround-detected GRB localization8–12 hours
FERMI_LAT_TRANSUnknown source transient1 days
FERMI_LAT_MONITORKnown source flare1 days

Common GCN Circular Types:

GBM identification of a GRB15 minutesGRB 220530A
GBM analysis of a GRB4 hoursGRB 220528A
LAT observation of a GRB8 hoursGRB 220228A
GBM subthreshold detection8 hoursGRB 220325A
GBM observations of SGR flares1 daySGR 1935+2154
GBM follow-up of GW trigger8 hoursLIGO/Virgo S200128d
LAT follow-up of GW trigger8 hoursLIGO/Virgo S200128d
GBM follow-up of a neutrino8 hoursIceCube-211216A
LAT follow-up of a neutrino8 hoursIceCube-211216A

Yearly Trigger Rates:

GBMShort gamma-ray burst35–40
Long gamma-ray burst200
Soft gamma-ray repeater flares35–40
Terrestrial gamma-ray flashes80–90
Solar flares90–95
LATGamma-ray burst15–20

Trigger Rates determined from catalogued information including the Fermi-GBM Trigger Catalog, the Fermi-GBM GRB Catalog, and the Fermi-LAT GRB Catalog.

Looking for U.S. government information and services? Visit