T. A. Nagy

Retrieval Techniques and Graphics Displays Using a Computerized Stellar Data Base

A computerized astronomical data retrieval system, based on the Goddard Cross Index of star catalogs and operable from a remote terminal, has been developed. It permits retrieval of stellar data as a function of the object’s identification numbers, descriptive parameters (magnitude and/or spectral type), or position in the sky. In addition, software has been developed to retrieve the full data entry from any of the eleven catalogs currently included in the Goddard Cross Index, such as the Yale Bright Star Catalog (YBS), the Boss General Catalog (GC), and others — all in one computer run.

Responsibilities and Practical Limitations in the Operation of an Astronomical Data Center

The operation of an astronomical data center requires that many decisions be made concerning the handling of the astronomical catalogs and data distributed. Should a data center be, as Wilkins (1977) described it, passive, in that catalogs and data are collected and distributed blackbox-wise upon request, or should a data center be active and have experts in various fields to scrutinize, correct, reformat, and document data where necessary? These questions will be addressed and illustrated by describing the current operations and future goals of the Astronomical Data Center at NASA/GSFC.

DEVELOPMENT OF THE EQUATORIAL INFRARED CATALOGUE FROM SATELLITE DATA

More than 40,000 infrared measurements of stellar sources have been obtained since November, 1976 during the ongoing process of compiling an Equatorial Infrared Catalogue. Because of the problem of eliminating spurious sources, which has affected earlier space surveys, we are making an extensive effort to verify the sources by means of (a) repetitive observations by satellite sensors, (b) crosscorrelation with a large data base developed from ground-based and space surveys at other wavelengths, and (c) investigation of a significant subset of the sources with a ground-based infrared telescope. As sources are verified, they are transferred from a working list to a screened preliminary version of the catalogue. The catalogue comprises the only survey of a significant area of the sky that has been accomplished (or is presently planned) with positional accuracies of a few arc seconds at a wavelength of ≥ 2 µm.

High-Precision Infrared Sky Survey At Wavelength 2.7 μm

Preliminary results of an infrared survey of the equatorial sky zone (declinations 10° S to 10° N) with U. S. Air Force satellite sensors show that positions of previously unknown infrared sources are measured with an rms accuracy of 4 arc seconds, which is six times better than the best previous infrared survey. The search area per source for further study is thus 36 times smaller, so that identification of the infrared sources with optical objects in catalogs and sky photographs is facilitated, as is reacquisition of the sources with ground-based infrared telescopes. The survey extends the content of near-infrared source catalogs to lower flux densities and adds information at a wavelength not observable from the ground. Objects found in the survey include cool giants and supergiants, long-period and semi-regular variable stars, and sources identified with faint red stars visible on the Palomar Observatory Sky Survey.

The Astronomical Data Base and Retrieval System at NASA

More than 250 machine-readable catalogs of stars and extended celestial objects are now available at the NASA/Goddard Space Flight Center (GSFC) as the result of over a decade of catalog acquisition, verification and documentation. Retrieval programs are described which permit the user to obtain from a remote terminal bibliographical listings for stars; to find all celestial objects from a given list that are within a defined angular separation from each object in another list; to plot celestial objects on overlays for sky survey plate areas; and to search selected catalogs for objects by criteria of position, identification number, magnitude or spectral type.

The Critical Evaluation of Stellar Data

Many catalogues of astronomical data appear in book form as well as in a machine-readable format. The latter form is popular because of the convenience of handling large bodies of data by machine and because it is an efficient way in which to transmit and make accessible data in books which are now out of print or very difficult to obtain. Some new catalogues are prepared entirely in a machine-readable form and the book form, if it exists at all, is of secondary importance for the preservation of the data.