Fermi Gamma-ray Space Telescope
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.
| Instruments | Energy Range | Field of View | Localization |
|---|---|---|---|
| Large Area Telescope (LAT) | 20 MeV–>300 GeV | 2.5 ster | ≤1° radius (statistical, 90%) |
| Gamma-ray Burst Monitor (GBM) | 8 keV–30 MeV | 8.8 ster | ≳1–10° radius (statistical + systematic) |
GCN Notice Types in GCN Classic and GCN Classic Over Kafka:
Detailed Descriptions and Examples
| Type | Contents | Latency |
|---|---|---|
FERMI_GBM_ALERT | Trigger info | ~5 seconds |
FERMI_GBM_FLT_POS | Flight localization, classification | ~10 seconds |
FERMI_GBM_GND_POS | Updated ground localization using finer lookup tables | 20–300 seconds |
FERMI_GBM_FIN_POS | Final trigger localization | 15 minutes |
FERMI_GBM_SUBTHRESH | Ground pipeline detected signals | 0.5–6 hours |
FERMI_LAT_POS_INI | Onboard LAT detection, initial position | 2–4 seconds |
FERMI_LAT_POS_UPD | Updated onboard localization with more data | 2–32 seconds |
FERMI_LAT_GND | Ground localization of onboard trigger | 8–12 hours |
FERMI_LAT_OFFLINE | Ground-detected GRB localization | 8–12 hours |
FERMI_LAT_TRANS | Unknown source transient | 1 days |
FERMI_LAT_MONITOR | Known source flare | 1 days |
Common GCN Circular Types:
| Type | Latency | Example |
|---|---|---|
| GBM identification of a GRB | 15 minutes | GRB 220530A |
| GBM analysis of a GRB | 4 hours | GRB 220528A |
| LAT observation of a GRB | 8 hours | GRB 220228A |
| GBM subthreshold detection | 8 hours | GRB 220325A |
| GBM observations of SGR flares | 1 day | SGR 1935+2154 |
| GBM follow-up of GW trigger | 8 hours | LIGO/Virgo S200128d |
| LAT follow-up of GW trigger | 8 hours | LIGO/Virgo S200128d |
| GBM follow-up of a neutrino | 8 hours | IceCube-211216A |
| LAT follow-up of a neutrino | 8 hours | IceCube-211216A |
Yearly Trigger Rates:
| Instrument | Type | Rates |
|---|---|---|
| GBM | Short gamma-ray burst | 35–40 |
| Long gamma-ray burst | 200 | |
| Soft gamma-ray repeater flares | 35–40 | |
| Terrestrial gamma-ray flashes | 80–90 | |
| Solar flares | 90–95 | |
| LAT | Gamma-ray burst | 15–20 |
Trigger Rates determined from catalogued information including the Fermi-GBM Trigger Catalog, the Fermi-GBM GRB Catalog, and the Fermi-LAT GRB Catalog.