Getting Started with HUT

The Hopkins Ultraviolet Telescope (HUT) was the spectrographic component of a triad of coaligned telescopes that flew in Space Shuttle missions during December 1990 and March 1995. HUT was designed to overlap and extend to short wavelengths the coverage of previous ultraviolet missions and was contemporaneous with the IUE satellite. The HUT missions were instrumental in helping to define the key science requirements of the FUSE satellite.

Target fluxes were detected by photoamplification of bursts produced by a phosphor and scanned at a video rate. The phosphor bursts are time-tagged, accumulated, and located by a centroid-finding routine in two dimensions. The centroid positions are computed to bins of 1/4 of the physical pixel spacing of the detector, thus producing a partially-processed, 1 x 2048 spectrum in the first ('raw') data file that the user sees.

The search form may be used to select data from the HUT database by object name, coordinates, date of observation, or target class (general). The data files of interest can then be marked and retrieved. The returned dataset will consist of several type of files, which are described in the Data Products page. For bright objects an investigator's scientific objective can usually be met without doing a careful subtraction of geocoronal Lyman alpha. For fainter targets it is often necessary to start with the uncalibrated data and subtract an appropriate Lyman alpha and air glow background spectrum. User requests generate a tar file consisting of gzipped fits file of all possible files. For most purposes a user might want to work with just the following files:

object_[N,D,A]_METsum_imcscor.ph
object_[N,D,A]_METsum_imcscor.ct
object_[N,D,A]_METsum_imcslya.ct

and relevant calibration data files. The nomenclature referred to is defined in the data types page. (D, N, A is shorthand for observations made during the day side, night side, or 'combined' sides of the orbit.) This nomenclature is defined in the Data Products page. Because of its generally better quality, users will in general prefer ASTRO-2 data of a given object to ASTRO-1.