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The Multimission Archive at STScI Newsletter

April 15, 2005 Space Telescope Science Institute Volume 15

The Multimission Archive at STScI (MAST) Newsletter disseminates information to users of the HST, FUSE, GALEX, IUE, Copernicus, EUVE, HUT, UIT, WUPPE, IMAPS, BEFS, TUES and VLA-FIRST data archives supported by MAST. Inquiries should be sent to

Index of Contents
Archive Status
Pipeline MultiDrizzle Image Orientation
High Level Science Products at MAST
New Search Page for VLA FIRST Co-added Images
New Web-based Tutorial Available
MAST Tools
The Virtual Observatory at MAST and STScI
MAST Distributing the First Full Public Release of GALEX Data
MAST User Survey
Suggestion Box
MAST User's Group Meeting
Linking Archived Data with the Astronomical Literature

Archive Status

Over the past year, the total DADS holdings (HST and FUSE data) at MAST grew from 18 Tb (on March 1, 2004) to just over 23 Tb as of March 1, 2005. We have frequently seen monthly average retrieval rates in excess of 50 Gb per day, and sometimes as high as 100 Gb/day! Despite this, retrieval times have remained well under our target median of 24 hours --- in fact, for most of the past year, median retrieval times have been under one hour (see chart).

While the HST archive dominates the archive in terms of data archived and retrieved, other datasets are utilized. MAST began archiving and distributing GALEX data products in November 2004. MAST now holds around 8.25 GB of GALEX image data. Since distribution of GALEX data began in November, 2004, MAST has distributed over 400GB of GALEX data. As subsequent deliveries are made, we expect the GALEX archive to grow to around 7 TB. See the GALEX article in this newsletter for a description of the types of data products and how to search for GALEX data.

Total MAST Holdings are nearly 32 TB as of March 1, 2005.

The Digitized Sky Survey (DSS) remains one of the most popular datasets that MAST maintains. An average of nearly 150,000 searches are made of the DSS each month.

The plot to the right shows the number of datasets downloaded each month for each mission. Obviously the active missions are downloaded more often, but data from the older missions and short duration missions are still regularly used.
It is interesting to examine the retrieval of spectra by instrument. To the left is a plot of the average number of datasets retrieved each month per spectragraph over the past year. It becomes clear that on average, FUSE data are the most frequently retrieved spectral data, followed closely by STIS data. IUE also has a fair number of retrievals per month, even though the instrument has been inactive for nearly 9 years.

Pipeline MultiDrizzle Image Orientation

The default orientation for pipeline MultiDrizzle ACS images ("*_drz.fits") has been changed to the unrotated image frame, instead of having North toward the top. This leads to smaller images which are easier to transfer and display, and can still be readily oriented North-up within most image display programs such as "ds9". More importantly, images delivered in the unrotated frame allow for instrument-specific effects to be much more easily identified and accounted for, including bad columns, stellar diffraction spikes, CTE trails, and PSF effects, and are also more useful for polarimetric, coronagraphic and grism data. The ACS CTE correction formulae can also be more readily applied to unrotated images. If images with North up are still required, these can be generated by appropriately setting the "final_rot" parameter when running MultiDrizzle off-line on the calibrated FLT files delivered from the pipeline.

The default orientation change was implemented March 25, 2005 at 12:50 PM EST.

High Level Science Products at MAST

High-Level Science Products (HLSP) are "value added" data products contributed by our users. They include processed images and spectra, object catalogs, and spectral and image atlases. Our collection of HLSP has grown considerably over the past year. In order to make it easier to find a specific HLSP, or to search for HLSPs that might be useful for a particular scientific question, we have created a new HLSP search interface that allows users to search by wavelength, type of product, and object type. The search page is accessed from

MAST welcomes the contribution of scientifically useful HLSP based on our missions. Updated guidelines for contributing HLSP may be found at

New HLSP that we have added in the past year include:

  • Hubble Ultra-Deep Field (HUDF):

    The deepest existing optical image of the sky, taken with the Advanced Camera for Surveys and NICMOS. Reduced images and object catalogs are available.

    Version 2 of the NICMOS treasury data was archived in April 2005.

  • Evans & Koratkar AGN spectral atlas:
    an atlas of recalibrated HST/FOS spectra of AGN and Quasars.

    Adjacent is a thumbnail of the spectra for NGC 1068 Cloud B from this atlas. Click on the thumbnail for a larger preview.

  • FUSE composite quasar spectrum: a mean quasar spectrum from 630-1156 Angstrom, contructed by Scott et al. (ApJ v615, p135 from 128 FUSE observations of 85 low redshift (z<0.67) AGNs.

  • Archival Pure Parallel Program
    (version 0.5 released in spring 2004; version 1 spring 2005): this program is processing and combining about 2,000 WFPC2 images, primarily in the wide UBVI filters, obtained in parallel with other HST instruments (PI S. Casertano).

    This is a thumbnail of the preview for a part of the LMC at RA=84.5275 Dec=-69.0214. The product name is pu5hny501. Click on the thumbnail to see a larger preview.

  • CoolCAT:
    HST STIS echelle spectral catalog of late-type stars (PI Thomas Ayres)

    To the right is a thumbnail of the preview of the data for Beta Aqr. Click on the thumbnail to see the full-size preview.

    The products from the Grism-ACS Program for Extragalactic Science project are slitless (grism) spectra obtained with the ACS in the Hubble Ultra-Deep Field (HUDF; PI Sangeeta Malhotra).

    To the left is a thumbnail of the calibrated spectrum for object number 3822 in the UDF catalog. Click on the thumbnail to see a full size preview image.

New search page for VLA-FIRST Co-added Images

Several hundred new coadded VLA FIRST images were added or replaced in the past year and there are now over 29,000 files included in this on-line archive. The data have all been placed in the anonymous ftp area on To make retrieval of these data easier, MAST has added a new search page for the VLA FIRST co-added data at See the updated Getting Started page for more information about how to retrieve these data (

New Web-based Tutorial Available

Many of our users just visit MAST to download their data. However, MAST provides many sophisticated tools to search for, browse, and cross-correlate data. If you have a specific task that you don't know how to accomplish, or would just like to learn more about the capabilities of the MAST interface, visit our new web-based tutorial at You will find a general overview of how to navigate the newly reorganized MAST website, a guide to the various interfaces, a summary of MAST Tools, hints for searching for and retrieving data, and a guide to further documentation.

MAST Tools

We are constantly improving our existing tools and adding new ones. Here are some highlights from the past year:

  • The Spectral Data Coplot Utility

    ( now has the option of displaying the average of "like" spectra. Two buttons have been added to plot just the average of like spectra or to coplot this average along with the constituent spectra. In both cases the mean spectrum is labeled "Average spectrum" and plotted in black.

    The averaging option works only for "like" spectra. The averaging option keys on the total number of points represented in the first (primary) spectrum (irrespective of the wavelength limits entered). The averaging option of the Coplotter is a "dumb" feature, meaning that it can be used only to compute averages from spectral files having the same number of total points, i.e. spectra observed in a common instrumental configuration. For example, an LWP or LWR IUE spectrum will not be properly coaveraged with an IUE SWP spectrum (or a HST/GHRS spectrum with another GHRS spectrum observed with a different grating). If a secondary spectrum is added which fails this equality-of-points test, the secondary will be overplotted but not coaveraged. Garbage in, garbage out!

    The averaged spectrum is a straight mean of the input flux vectors. One exception is that for IUE data, pixels with flags less than -512 are assigned zero weights and those data are not included in the average (even if corresponding pixels from other spectra in the coaddition have good flags).

    In the example to the right, three SWP low dispersion spectra of Capella and their average are shown.

  • Scrapbook enhancements

    FUSE spectra are now included in the spectral part of the MAST Scrapbook (

    The plot to the right is the FUSE plot of the star HD 120991 (observation Q1140101000) that is the current "representative" FUSE observation for this target.

    Links to 2MASS images are now included in the MAST scrapbook (using data type = images). The 2MASS data (available as both jpg images and FITS files) are 20'x20' and are centered on the listed MAST observations.

  • VizieR Search Form Enhancement

    The VizieR search form now offers the ability to search on ADC-defined astronomical terms as well as keyword searches on author's name, catalog title, and catalog description. This allows searching on many object classes.

  • New version of VOPlot is now accessbile

    A new version of VOPlot is now accessible from the MAST search results pages. VOPlot is a tool for visualizing astronomical data, designed to work with data in the Virtual Observatory compatible VOTable format. For more information see

  • SpecView

    SpecView, a sophisticated Java application for 1-D spectral visualization and analysis of astronomical spectrograms, is now available. SpecView is capable of reading all the HST spectral data formats, as well as data from a few other instruments (such as IUE, FUSE, ISO, FORS and SDSS), MAST spectral previews, and data from generic FITS and ASCII tables. It can also read and write spectrogram data in Virtual Observatory SED format.

    SpecView was developed by Ivo Busko of the Science Software Branch at STScI with input from MAST archive scientists. To download the application and for more information see the web page:

  • StarView

    StarView was upgraded to version 7.3 in July of 2004. Version 7.3 features protocol to aid users behind strict firewalls, improved database connectivity, and many improvements that enhance performance, reliability, and usability. Please visit to download or learn more about StarView.

The Virtual Observatory at MAST and STScI

Visit our web page at to read about how MAST is participating in the National/International Virtual Observatory. This page also provides useful VO-related links. Check this site for updates about our ongoing activities. A more general site devoted to VO activities at STScI is

Some examples of recent VO-related developments at MAST are: