Units

For consistency the following standard abbreviations and syntax rules, mostly adapted from SGP38, should be used. The principal units used in ASTERIX have been starred. Note that case can be important; in general lower case should be used and plurals avoided (e.g. `count', not `Counts').

          Unit              Abbreviation
   -----------------------------------------------
        *count                  count
        *photon                 photon
        *second                 s
         minute                 min
         day                    day
         year                   yr
        *centimetre             cm
         metre                  m
         kilometre              km
        *arcsecond              arcsec
        *arcminute              arcmin
        *degree                 deg
         radian                 rad
         steradian              sr
         gram                   g
         kilogram               kg
         electron volt          eV
        *kiloelectron volt      keV
        *erg                    erg
         joule                  J
         watt                   W
         herz                   Hz
         angstrom               A
         magnitude              mag
         kelvin                 K

Note that `channel', `bin' and `pixel' are understood (e.g. count/s implies counts per second per channel, for a spectrum) and need not be entered as explicit units.

In compound units, brackets should be used where necessary to avoid ambiguity. E.g. count/(arcmin**2*s), photon/(cm**2*s*keV).