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GALPROP  
GBM(Gamma-ray Burst Monitor)
The GBM is the other instrument on Fermi. It is made of 12 NaI (sodium iodide) and 2 BGO (bismuth germanate) detectors.
The GBM detects emission from gamma-ray bursts, solar flares, terrestrial gamma-ray flashes ...		 
GCN(Gamma-ray Coordinates Network)  
GEANT  
ghostsGhosts are events where two particles enter the LAT in a small enough time frame that the LAT considers the interactions a single event.
A typical example would be a gamma ray and proton entering the LAT near simultaneously.
This caused a fraction of gamma-ray events to be vetoed.
This problem was first addressed in Pass7 and substantial improvements have been made in Pass8 to recover gamma-ray data from these ghost events.		 
GI(Guest Investigator) 
GLAST(Gamma-ray Large Area Space Telescope)
GLAST is the name that Fermi was referred to before it was launched.
It is tradition to give NASA missions a different name after launch, as a good-luck superstition.		 
GlastRelease  
GLEAM  
GRB (group)(Gamma-Ray Burst)GRB group page
gt_____The standard set of software used to analyze LAT data are called the Science Tools.
Each individual tool has a specific function.
The names all start with "gt", for "GLAST", which was the original pre-launch name of Fermi.		Science Tools references
   
   

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nadir  
nadir observations  
NaI

(sodium iodide)
The Gamma-ray Burst Monitor (GBM), the second instrument on Fermi, is made of 12 NaI detectors (and 2 BGO ones).
The NaIs detect photons between ~8 keV and 40 MeV.
They are positioned around the spacecraft to view the entire sky at all times.
The GBM team uses the amount of signal in each NaI detector to calculate localizations. 

 
   

O

P

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Pass #, version #  
phi  
pipeline  
pointed observations  
pole pointing  
PSF(point-spread function) 
PSR(pulsar)Pulsar group page
PWN(pulsar wind nebula) 
   

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SAA

(South Atlantic Anomaly)
The SAA is a region of the sky over the southern part of the Atlantic ocean that contains a lot of charged particle activity.
Both the LAT and the GBM detect charged particles as part of the background, so when the spacecraft enters the SAA,
the detectors are turned off (data is not stored).
The LAT and GBM have slightly different definitions of the borders of the SAA. 

 
Science Tools  
SeeVogh  
selection  
senior review  
SMC(Small Magellanic Cloud) 
SNR(supernova remnant)SNR group page
source (event class)  
survey mode  
star trackers  

T

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TDRSS(Tracking and Data Relay Satellite System) 
TGFs(terrestrial gamma-ray flashes) 
theta  
ToO(Target of Opportunity) 
transient  
transient (event class)  
TRK(Tracker)
The Tracker is a part of the LAT whose purpose is twofold: 1) To convert gamma rays into electron-positron pairs, and
2) To track these pairs of charged particles through the instrument in order to figure out where the original gamma ray came from.
The Tracker is made of alternating layers of tungsten foils (to convert the gamma rays) and silicon strip detectors (to track
the pairs), arranged in 64 columns (8 by 8). 		 
Trunc64  
TS(test statistic) 

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zenithThe point on the sky that is opposite to the Earth for the Fermi spacecraft.
(diagram from Wikipedia)
(imagine the person is Fermi) 
zenith angle cutThe zenith angle cut defines the maximum zenith angle for all the photons that will be used in an analysis.
The zenith angle cut is used to cut down on the emission from the Earth limb (the part of the Earth that is in the LAT field of view).