For each potential observation planned in the SCIPLAN file, we create a HUT Sequence Database file. (Multiple observations of a target will have multiple files.) The files are ASCII text in a keyword/entry format that is easy to edit. These files are used for several purposes. They are the receptacles for general information about each target (magnitudes, fluxes, coordinates, references from the literature, etc.), and as such can start to be built (on a target by target basis) even before the SCIPLAN planning takes place. Also, at various stages of the planning process, ``official" planning information from the MSFC outputs (e.g. roll angles, start and stop times for the planned observations, unique observation ID numbers, etc.) are fed back into the sequence database files to keep them current. Finally, as observation planning progresses, these files hold parameters that reflect the decisions made to set up each observation (selected aperture, guide stars to use, TV magnitude settings, expected count rates, whether special procedures are required, etc.). Most of the information placed in these files is in a fairly ``user-friendly" format (i.e. magnitudes, guide star positions in arcsec relative to the object position, etc.). When these files are completed and verified, software converts this information into the format needed for operating the telescope on orbit. (For example, the roll angle and guide star offsets [in arcsec] are converted into HUT TV pixel coordinates; this information is used by the HUT DEP to generate fiducial marks on the HUT TV at the expected positions of guide stars.) The transformed files are called ``sequence files" (as opposed to sequence database files).
Science team members are assigned responsibility for a certain class or number of targets. This responsibility involves checking and verification of information, selection of guide stars, setting of observation and instrument parameters, and calculation of expected count rates. ``Write" protections are set so that only the person responsible for that observation can edit the file. An exception is that information from MSFC planning files is inserted ``wholesale" by a superuser who has access to all the files.