Process Information: Scrapbook

The MAST Scrapbook is composed of three components: database tables of representative observations from MAST missions, query/search and display software, and thumbnails of spectral plots and images for display. The core element is the two database tables known as the "Table of Representative Spectra" (TORS) and the Table of Representative Images (TORI). The TORS/TORI catalogs contain entries of representative observations for most targets and instrument/mission combinations available in the MAST archives. The construction of these tables and the other components of the MAST scrapbook are described below.

Construction of the TORS/TORI Tables

The detailed selection of the representative observations to be included in the TORS/TORI catalogs varied with each instrument. Prior to the observation selection process, a set of "rules" or specifications were developed for the selection of "the" representative dataset of a multiply observed target in an automated and unbiased way. The specifications included parameters such as exposure lengths and dates of observations. For most missions, the observation choosen for a given grating/wavelength configuration was based on the maximum exposure time, and, to provide the broadest wavelength coverage, the lowest dispersion. For images, observations were selected for a given position on the sky based solely on exposure time.

The specifications for selecting the representative spectral observations are available for each of the following scrapbook missions:

• HST/FOS,
• HST/GHRS,
• HST/STIS,
• Astro/HUT,
• Astro/WUPPE,
• IUE,
• EUVE, and
• ORFEUS/TUES.
• ORFEUS/BEFS.
• FUSE.

The specfications for the imaging missions included in the scrapbook are:

• HST/ACS
• HST/WFPC2
• HST/STIS
• HST/FOC
• Astro/UIT

Software to select representative spectra from the archives was written for each mission. A preliminary list of unique targets was first created and used as input to the selection software. The software queried the associated instrument database to obtain a list of all candidate observations, then used the specification rules to determine the "representative" observation. The selected observations were then ingested into the TORS/TORI catalogs.

In practice, the determination of entries for the TORS required subjective judgment whenever there was a possibility of target confusion, such as for close binaries, dense clusters, or uncertain optical identifications of UV_bright sources. Another potential source of confusion were extended objects such as resolved galaxies or nebulae, for which observations of a central region have been identified in SIMBAD or NED. Thus, for a supernova remnant filament, a representative observation was likely to be represented by the brightest knot within the extended structure. (The reader should recall that entrance apertures of various spectrographs will subtend different areas on the sky. Thus, spectra of multiple or extended targets from different instruments sometimes do not refer to the same source.) In cases of target confusion, a MAST astronomer compared the spectrum with the description of the object listed in the original proposal, published literature, and/or the spectral type, magnitude, and position given by SIMBAD/NED.

Another consideration preventing the complete automation of the TORS/TORI catalog construction was the assignment of "preferred" SIMBAD/NED object names. In some cases, the targets had not yet been added to the SIMBAD/NED catalogs, so the SIMBAD/NED names were left blank. Sometimes, the correct SIMBAD/NED name could not be assigned with complete confidence and were therefore left blank. The TORI table also included "random" exposures (e.g. parallels) for which no attempt was made to determine the observed objects.

The TORI table entries were based upon "pointings". (The definition of a pointing may differ for each mission and are dscribed in the individual mission specification pages.) After determining which observations were considered part of a pointing, the selection of representative observations was further refined using filters, exposure lengths, and observation dates. Each pointing was assigned a pointing number which was used during the selection process (and also by the display program) to group the representative images.

An example of the TORS table entries follows:

An example of the TORI table entries:

Search Procedure

The scrapbook allows searches by target name or coordinates and was designed with three search options: search on coordinates, search on SIMBAD or NED "preferred" target names, and search on target names specified by the mission or observer. The use of these options is explained further in the help page. In the first ("Coordinates") option, coordinates are determined for input target names using SIMBAD or NED, and the search proceeds by selecting observations within the specified search radius (the name resolve step is skipped if the user enters coordinates directly). For the second option ("Resolved Target Name"), a string search is performed comparing the user-specified target name with the SIMBAD/NED target names stored in the TORS/TORI tables. This option is useful for searches in a crowded field, when coordinate resolution could lead to confusion. The third option ("Input Target Name") allows a user to compare the input target name to the mission/observer target name and also permits utilization of a wildcard symbol %. (The last two modes only work if the user enters a target name rather than coordinates.)

Creation of Thumbnails and Display

The final step in creating the spectral scrapbook was the design of the search results page. The page begins with a short description of the users input parameters, followed by a table describing the MAST data sets matching the users input parameters, with entries in the mission/instruments field linked to the appropriate MAST mission home page. The displayed fields correspond to the data in the TORS/TORI tables with the addition of the angular separation field (for coordinate searches) which describes the separation between the found entries and the users specified (or the name-resolver derived) coordinates.

Following the table are thumbnail plots or images, grouped by mission and/or instrument. The mission/instrument name heading each section is a link to a MAST search form which allows more detailed searches for objects within a specific MAST mission. The displayed thumbnails represent the first "n" entries found for each mission, where "n" is the optional "max thumbnails per mission" parameter from the scrapbook form, and is set to 10 by default. The thumbnails serve as "icons" for further investigation. Links under each thumbnail can be used to display "preview" plots, exposure information, downloadable data files, and literature links. For most missions the thumbnails are miniaturized versions of the preview plots. For HST missions (temporarily at least), the preview contains only a full-sized plot which is created on the fly from the HST preview database. Neither the thumbnails nor the preview plots are meant to convey quantitative information; for some spectral missions (e.g. TUES) they are equivalent to the downloadable data, but for most they are not.

Following the thumbnails is a link to the MAST cross correlation search tool. Clicking this link will display a table of the first "n" entries found in each MAST mission table for the user-specified target, where, again, "n" is the "max thumbnails per mission" parameter specified on the scrapbook search form.