This documents describes DSC benchmarking experiments using cycle 2A data. We investigated classification algorithms based on boosting, neural networks, mixture clustering and radial basis function networks. Two different magnitudes were used (17 and 20). Moreover classification was done with astrometry as well as without. Gaia DPAC: CU8-DU-MPIA DSC Benchmarking GAIA-C8-TN-MPIA-CE-001-01

The quest for the distance of the Vela and Geminga pulsars yielded, so far, a set of four WFPC2 images for each object. The availability of couples of images taken at the same period of the year, thus affected by the same parallactic displacement, prompted us to use Vela and Geminga as test cases to assess the reliability of HST astrometry.

We present the results of our analysis of Hubble Space Telescope (HST ) and deep ground-based images to isolate the massive progenitor stars of the two recent core-collapse supernovae 2008bk and 2008cn. The identification of the progenitors is facilitated in one of these two cases by high-precision astrometry based on our HST imaging of SNe at late times.

We determined the separations of the radio sources in the triangle formed by the BL Lac objects 1803+784 and 2007+777, and the QSO 1928+738 from in-tercontinental interferometric observations carried out in November 1991 at the frequencies of 2.3 and 8.4 GHz. Difference phase-delay astrometry yielded the following separations: ∆α (1803+784)−(1928+738) =–1 h 27 m 2.

We present the results of our analysis of Hubble Space Telescope (HST) and deep groundbased images to isolate the massive progenitor stars of the two recent core-collapse supernovae 2008bk and 2008cn. The identification of the progenitors is facilitated in one of these two cases by high-precision astrometry based on our HST imaging of SNe at late times.

Aims. Chromatic effects are usually associated with refractive optics, so reflective telescopes are assumed to be free from them. We show that all-reflective optics still bears significant levels of such perturbations, which is especially critical to modern micro-arcsecond astrometric experiments. Methods. We analyze the image formation and measurement process to derive a precise definition of ...

We performed the astrometry of H2O masers in the Galactic star-forming region G48.61 + 0.02 with the VLBI Exploration of Radio Astrometry (VERA). We derived a trigonometric parallax of 199 ± 7 μas, which corresponds to a distance of 5.03 ± 0.19 kpc. The distance to G48.61 + 0.02 is about a half of its far kinematic distance, which was often assumed previously. This distance places G48.61 + 0.02...

The Space Interferometry Mission (SIM) will be 10-m Michelson interferometer in Earth-trailing solar orbit. AS a part of NASA's Origins program, it will be the first space-based optical interferometer designed for precision astrometry. As well as enabling forefront astronomical science, SIM will serve as a technology pathfinder for future Origins missions, such as the Terrestrial Planet Finder ...