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Towards a Legacy Archive for Hubble Instruments


The Space Telescope Science Institute (STScI), the Canadian Astronomy Data Centre (CADC) and the ST-ECF are working together to optimize the future scientific return from the Hubble archives by producing enhanced data products and efficient data discovery and access services - to be collectively known as the Hubble Legacy Archive (HLA) - with the goal of capturing expertise in Hubble and assuring the maximum utility of Hubble data for long term use by the community. A more detailed description is available in an article in the ST-ECF Newsletter.

Earlier, similarly motivated, high-level science products have already been produced by collaborative projects between the three sites, both indiviually and collectively. These may be regarded as precursors of the HLA and can be divided into three classes. Firstly there are high level products from specific science projects. Examples are the GOODS ESO VLT/FORS spectra, which are not Hubble data, but are closely related to major Hubble projects. Secondly there are high-level data products created from more extensive uniform data sets taken from the archives. An example is the WFPC2 associations project. Lastly there are "final" calibrated products from specific instruments that are no longer in operation.

WFPC2 associations

CADC, the ST-ECF and the Multimission Archive at STScI (MAST) provide combined images from the Wide Field Planetary Camera 2 (WFPC2) on Hubble. The combined images are the products of the basic registration and averaging of related sets of WFPC2 images, referred to as associations, that is usually performed by archival researchers after the retrieval of individual images. The associations may have improved astrometry and registration provided by Hubble pointing jitter data (associations of Type A) or by cross-correlation (Type B). Full details and query of the archive of WFPC2 associations is available here.

FOS Final Archive

The Faint Object Spectrograph (FOS) was one of the original axial instruments on Hubble. The FOS, which was removed from Hubble during the Second Servicing Mission in February 1997, was used to make spectroscopic observations of astrophysical sources from the near ultraviolet to the near infrared (1150-8000 Angstroms). The ST-ECF have improved the FOS data archive by resolving issues with the STSDAS FOS calibration pipeline using physical models. In August 2001 the POA project team released v1.2 of the STPOA IRAF external package, which contains the final version of the replacement FOS calibration pipeline called 'poa_calfos'. FOS datasets processed with this pipeline formed the FOS final archive. Full details of the recalibration and access to the final archive are available here.

ACS slitless spectroscopy in the Hubble Ultra Deep Field

During the Hubble Ultra Deep Field (HUDF) observations, HRC auto-parallels were obtained with the F220W, F555W and F892N filters and the G800L grism. The G800L grism provides slitless spectra at 24A/pixel with resolution depending on the size of the dispersing object. The grism coverage is 5500-10500A with peak sensitivity about 7500A. Since the HUDF was taken at two distinct position angles there are as a result two separated fields covered by the HRC parallel observations. Drizzled images in the three imaging filters, drizzled grism images and individual extracted spectra are provided for both fields. The data can be downloaded and spectra are available for on-line viewing here.

ESO Great Observatories Origins Deep Survey (GOODS) spectroscopy In the CDF-S

As part of the Great Observatories Origins Deep Survey (GOODS), multi-object, optical to NIR spectroscopy in the Chandra Deep Field South (CDF-S) has been carried out, using the ESO FORS2 instrument mounted at the Kueyen Unit Telescope of the VLT at the Cerro Paranal Observatory, Chile. 1204 spectra of 930 unique targets were obtained in service mode with the FORS2 spectrograph providing in total 943 redshift measurements with quality flag A, B or C (A=solid redshift, B=likely redshift, C=potential redshift). 725 of the unique targets have an assigned redshift with quality flag A, B or C. The average of the redshift distribution is z=1.5 (median z=1.1). The typical redshift uncertainty is estimated to be +/-0.005. The calibrated spectra can be downloaded and there are interactive search facilities for access here.

Maintained by Richard Hook <>