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| term | definition | link |
|---|---|---|
| Earth limb / Earth's limb | The Earth is a bright emitter of gamma rays, due to cosmic rays interacting with the atmosphere. | |
| EBL | (Extragalactic Background Light) When used in gamma-ray astrophysics, EBL usually means the infrared-optical-ultraviolet light that fills intergalactic space, coming from all the stars that ever existed. Gamma rays can be absorbed by the EBL through the process of photon-photon pair production, in which a high-energy gamma ray collides with a low-energy IR-optical-UV photon to produce an electron-positron particle pair. | |
| EDISP | (energy dispersion) The energy dispersion is a measure of how accurately we can reconstruct the energy of a photon from the energy it deposits in the LAT calorimeter. The energy dispersion is a part of the LAT Instrument Response Functions (IRFs); however information on the energy dispersion is not automatically taken into account in the Science Tools for standard LAT analysis. | Cicerone |
| effective area | The number of photons detected divided by the source flux. The LAT effective area is a function of photon energy and inclination angle. | |
| EGB | (Extragalactic Background) After accounting for known sources of gamma rays from individual sources and diffuse radiation within our Milky Way Galaxy, there is a residual component called the EGB. Some or most of the EGB is thought to originate from unresolved sources at large distances. | |
| EPO (group) | (Education and Public Outreach) | EPO group link |
| event | An "event" is a catch-all name for "things that the LAT detects" (although sometimes it is used specifically to mean photons). In practice, these are either photons or cosmic rays. | |
| event class | Events that are detected by the LAT are sorted into different classes based on how confident we are that the event is a photon. | Cicerone |
| Evo | Video conferencing software that has now been superseded by SeeVogh. | |
| exposure |
F
| term | definition | link |
|---|---|---|
| F2F | Face-to-face | |
| FA | (flare advocate) Flare Advocates are volunteers who watch the LAT gamma-ray sky on one-week shifts, looking for flares of known or unknown gamma-ray sources. | Flare Advocates Confluence Main Page |
| FITS / fits / .fits / fit (file type) | (Flexible Image Transport System) FITS files are often used in astronomy, and are made of one or more HDUs (Header and Data Unit). Each HDU has a header with general information about the file, the instrument, etc., as well as a table or image. Public LAT data is always (?) distributed as FITS files. | FITS Support Office |
| FltOps | (Flight Operations) | |
| FOT | (Flight Operations Team) The FOT is the staff at the Mission Operations Center (at NASA Goddard), which controls the spacecraft. The FOT is responsible for, among other things, inputting special maneuvers such as TOOs. | |
| FOV / FoV | (field of view) The FOV is the useful solid angle on the sky seen by a Fermi instrument at one time. The LAT FOV is about 2.4 steradians; the GBM FOV is about 8.5 steradians (everything in the sky not blocked by the Earth). | |
| front | The front half of the LAT is the 12 layers of thinner tungsten (which converts the photons into electron-positron pairs) that are at the top of the LAT. Photons that convert in this region tend to better reconstructed than photons that convert in the back (or bottom). It is possible to only use the front or back events on their own in an analyses, but generally, the fact that events are either front- or back-converting is automatically accounted for in the analysis software and instrument response functions. | |
| front-converting | Front-converting events are photons that are converted into electron-positron pairs in the top portion of the LAT (see front). | |
| FSRQ | (Flat Spectrum Radio Quasar) FSRQs, along with BL Lac objects, make up the sub-class of Active Galactic Nuclei called blazars, the most common type of extragalactic source seen by the LAT. | |
| FSSC | (Fermi Science Support Center) | Fermi Science Support Center |
| FSW | (Flight Software) | |
| FT1 (file) | FT1 files are the LAT public data files with information on each individual photon. | |
| FT2 (file) | FT2 files are the LAT public data files with information on the spacecraft (where it is, where it's pointing, etc.). | |
| FTOOLS | A package of tools to manipulate FITS files. | FTOOLS main page |
| FUG | (Fermi Users Group) An advisory panel of scientists from gamma-ray and related disciplines. The FUG represents all scientists who use Fermi data. | Fermi Users Group |
| fv | (Fits Viewer) fv is a program to view FITS files. | fv main page |
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