Basically names are of the form
TUESnnnn_m_o.fits
where the target ID ("nnnn") is a special 4-digit target identification number
and the observation number ("m") refers to the order in which the exposures
(for a given target) were obtained. A third number ("o") indicates several pointings were obtained
during a single observation (sometimes to improve the alignment of the
telescope). A "_PH" denotes an integration from single photon events recorded
onboard but integrated after the mission.
See also the TUES file naming conventions described in the
data products page.
A HST archive model of G191B2B
http://garnet.stsci.edu/STIS/models/tables/g191b2b_mod_002.tab"
was used as a reference for the absolute flux
calibration. The calibration was additionally checked with a model of
BD +28°4211 (R.Napiwotzki). We guess an accuracy of ±10% for the flux
calibration. This is valid, if the object was fully centered within the
diaphragm. There are, however, some observations for which the object was
not completely centered. The reasons are probably due to temperature drifts
of the telescope causing a shift of the alignment. In some cases
also slightly wrong coordinates of the target might have led to a
decentralization.