  The SPEAR (or 'FIMS') instrumentation has been used to conduct the first
large-scale spectral mapping of diffuse cosmic far ultraviolet (FUV, 900-1750
AA) emission, including important diagnostics of interstellar hot (10^4 K -
10^6 K) and photoionized plasmas, H_2, and dust scattered starlight. The
instrumentation's performance has allowed for the unprecedented detection of
astrophysical diffuse far UV emission lines. A spectral resolution of 550 and
an imaging resolution of 5' is achieved on-orbit in the Short (900 - 1175 AA)
and Long (1335 - 1750 AA) bandpass channels within their respective 7.4 deg x
4.3' and 4.0 deg x 4.6' fields of view. We describe the SPEAR imaging
spectrographs, their performance, and the nature and handling of their data.
