Getting Started

Introduction

The Hubble Space Telescope (HST) Data Archive (HDA) contains science data from all completed HST observations and calibration files. As of October 1, 2004, the archive contains over 20 Terabytes of data. In addition to all the science data sent to observers and all the calibration reference files, the archive contains engineering files that may be useful for diagnosing some questions about observations. As data are archived, information about observations and the targets is extracted from the headers of the data files and stored in an on-line catalog.

HST data become available to the astronomical community (or to any individual with the interest and hardware capabilities required to analyze the data) upon the expiration of a proprietary period. Most general observer (GO) and guaranteed time observer (GTO) observations have proprietary periods of a year, but some observations have shorter or longer proprietary periods. Nearly all calibration observations are made public immediately upon receipt. The archive catalog contains information about all observations that have been made with HST. Access to the HDA is open to everybody. Registration is necessary to retrieve proprietary data. Proprietary datasets may be retrieved by GOs and GTOs with the appropriate authorization (contact the archive hotseat at archive@stsci.edu). Public data may be anonymously or via a users registration name and password.

There are two different ways to access data in the HDA: StarView and a World Wide Web (WWW) interface. StarView is an astronomical database browser and research analysis tool. Developed in Java, StarView provides an easy to use, highly capable user interface that runs on any Java enabled platform as a stand-alone application. More details and instructions on how to install StarView are available at the StarView Home Page. The HDA can also be accessed via an interface available from the archive Web Search page. Most users will find the Web interface more convenient to use, as it does not require any client-server software installation and can be accessed by any Web browser. Note, however, that the Web interface does not provide all the functions of StarView as regards HST data. A basic description of the process of retrieving HST data using StarView and the Web interface can be found in the first chapter of the HST Data Handbook.

STScI automatically processes and calibrates all data received from HST via a so-called "pipeline." Pipeline processing assembles data into datasets, calibrates the data according to standard procedures, and stores both uncalibrated and calibrated (for some instruments) datasets in the HDA. Almost all the files in the HDA are stored in FITS format. Most observations have multiple image planes; for example, WFPC2 images usually have four planes, one for each CCD chip. HST data can be analyzed or recalibrated using the Space Telescope Science Analysis System or STSDAS. Detailed information can be found at the STSDAS WWW page.