Single observing configuration except in rare cases (see Comments).
Ranked Observing Configurations
In rare instances, an object may be observed in two different instrument apertures
at different times. In such cases precedence is given to the observation observed
in the largest aperture (generally, LWRS).
Problems:
The appearance of "worms," or vignetting of portions of spectrum may occasionally
be seen in the continuum. FUSE continua are flatfielded but not corrected for such
problems in pipeline processing.
Target selection is limited by detector and computer storage constraints. Observations
at low declinations are infrequently made due to guiding constraints imposed using the
magnetic torque bars for attitude control of the spacecraft, and also due to effects
of ram-pressure from the Earth's atmosphere.
Specifications for selected representative dataset:
Generally, select dataset with highest exposure time (accumulated counts)
and the largest arperture. Occasionally, one exposure was "hand picked"
out of several for an extended emission region, and a few of these might
violate the exposure time criterion.
Comments:
In rare cases (for a few bright stars) only the LIF channels of the instrument
were utilized in the observations. This contingency does not affect our selection
of a particular observation since the loss of the SiC channels should extend to
all observations of such targets.