M. G. Lattanzi

The Second-Generation Guide Star Catalog: Description and Properties

The Guide Star Catalog II (GSC-II) is an all-sky database of objects derived from the uncompressed Digitized Sky Surveys that the Space Telescope Science Institute has created from the Palomar and UK Schmidt survey plates and made available to the community. Like its predecessor (GSC-I), the GSC-II was primarily created to provide guide star information and observation planning support for Hubble Space Telescope. This version, however, is already employed at some of the ground-based new-technology telescopes such as GEMINI, VLT, and TNG, and will also be used to provide support for the James Webb Space Telescope (JWST) and GAIA space missions as well as the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, one of the major ongoing scientific projects in China. Two catalogs have already been extracted from the GSC-II database and released to the astronomical community. A magnitude-limited (RF = 18.0) version, GSC2.2, was distributed soon after its production in 2001, while the GSC2.3 release has been available for general access since 2007. The GSC2.3 catalog described in this paper contains astrometry, photometry, and classification for 945,592,683 objects down to the magnitude limit of the plates. Positions are tied to the International Celestial Reference System; for stellar sources, the all-sky average absolute error per coordinate ranges from 02 to 028 depending on magnitude. When dealing with extended objects, astrometric errors are 20% worse in the case of galaxies and approximately a factor of 2 worse for blended images. Stellar photometry is determined to 0.13-0.22 mag as a function of magnitude and photographic passbands (RF , BJ , IN ). Outside of the galactic plane, stellar classification is reliable to at least 90% confidence for magnitudes brighter than RF = 19.5, and the catalog is complete to RF = 20.

Detection and measurement of planetary systems with GAIA

We use detailed numerical simulations and the Andromed planetary system as a template to evaluate the capability of the ESA Cornerstone Mission GAIA in detecting and measuring multiple planets around solar- type stars in the neighborhood of the Solar System. For the outer two planets of the Andromed system, GAIA high-precision global astrometric measurements would provide estimates of the full set of orbital elements and masses accurate to better than 1{10%, and would be capable of addressing the coplanarity issue by determining the true geometry of the system with uncertainties of order of a few degrees. Finally, we discuss the generalization to a variety of congurations of potential planetary systems in the solar neighborhood for which GAIA could provide accurate measurements of unique value for the science of extra-solar planets.

Asteroids observations with the Hubble Space Telescope ? FGS I. Observing strategy, and data analysis and modeling process

Five main belt asteroids and one Trojan - selected mainly on the basis of their possible binary nature as deduced from light curve morphology - have been observed with the Fine Guidance Sensors (FGS#3 and FGSR#1) of the Hubble Space Telescope (HST). In this first paper we present the selection and observation strategy, data reduction and analysis. A careful analysis of the precision for derived parameters is also given. The HST/FGS proves to be valuable in determining asteroid sizes, shapes and spin axis orientations, and also to identify nearly-contact binary systems.

The AGK3U : an updated version of the AGK3

Details of construction of an updated version of the AGK3 are presented. Unlike the builders of the Positions and Proper Motions (PPM) catalog, we have gone forward in time to gain new positions to use to improve the AGK3 proper motions. The source of these new observations is the Palomar «Quick V» survey made for the construction of the Hubble Space Telescope Guide Star Catalog. We have been able to recover individual equatorial coordinates from a Schmidt plate with a typical standard deviation about the mean of 0.33″. Moreover, our means (i.e., the systematic errors) are at the 0.01″ level. These realistic, external errors compare favorably with the reduction of the AGK3 astrograph material (0.21″ per equatorial coordinate)

Astrometry from space: GAIA and planet detection

The proposed baseline GAIA mission will be able to detect the astrometric signature of Jupiter-size planets around of the order of a million stars, using either global or narrow-angle astrometry. If the mission can realize the higher astrometric accuracy that photon statistics allows for bright stars, lower-mass planets (from Earth size to ten times larger) can be found around ten to a few hundred stars.

GSC 1.2 — A Subplate Reduction of the GSC

The original version of the HST Guide Star Catalog (GSC 1.0, Lasker et al. 1990, and following papers) contains systematic errors which typically begin 1:5 from the plate center and increase with radius (Taff et al. 1990a). In a residual plot against CAMC stars this shows as high correlations between neighboring residuals. This is due to the inability of a global polynomial to map the metric of a Schmidt plate. A new reduction of the GSC measures (GSC 1.2) based on the subplate method (Taff 1989) is partially complete. We report on it for the northern data from the Palomar Quick V plates, with 20 minute exposures, nearly all taken in the 1982-1984 interval.

Catalog-to-catalog reductions - Results for the FK, N30, and GC catalogs

It is shown that previous computations of catalog-to-catalog differences, whether by the bin-and-average method or by least-squares adjustment combined with an expansion in an incomplete set of basis functions, have all been performed at inappropriate epoch(s) of place. As a consequence, such results are frequently much more informative regarding the systematic differences between the proper motion systems than they are with respect to the systematic differences between the positional systems. Moreover, and for the same reason, some sets of proper motion differences really do not portray the true state of the evolution of the proper motion systems. Finally, this has practical effects in other astrometrical work, for instance, in the analysis of earth rotation time series. This error is corrected by arguing for a more meaningful epoch of place for catalog-to-catalog comparisons. This method of infinitely overlapping circles is applied at these other epochs to the FK sequence of catalogs, the N30, and the GC, and as a corollary the effectiveness of this new technique is shown.

The Guide Star Catalog and the Digitized Sky Survey as Resources for other Surveys

In contemplating the planning and implementation. of all-sky survey missions — either from the ground, such as DENIS and 2MASS. or from space. such as GAIA — it is useful to recall that an important part of observational astronomy has historically been the creation of catalogs containing the reference and program objects required to support such observing programs. As the technological complexity and cost of large-scale astronomical projects has increased dramatically over the last decades, so has the demand to provide the best scientific return for these investments by optimizing observing efficiency, which in turn depends on the use of proper pointing and input catalogs.

Torino Programme on Radiosources Astrometry: Progress Report

Measurements of precise positions of optical counterparts of extragalactic radio-sources, with the aim to compare them with VLBI positions, is in progress at Torino Observatory. The Carlsberg Automatic Meridian Circle Catalogue (CAMC) is used for plate reductions. Presently, about 40% of the plate material required to complete the project has been taken and some significant improvements have been made both in the material and the reduction methods. Improvements are also due to the publication of a new volume of the CAMC catalogue that significantly increases the number of stars in the fields.

The Construction of 4 Dense Astrometric Standard Areas with the Carlsberg Automatic Meridian Circle

High precision work in photographic astrometry requires accurate monitoring of the telescope+filter+emulsion system being used.