On-board reduction of dispersed fringes for DIVA


Sonja Hirte, Ralf-Dieter Scholz, Potsdam, Siegfried Röser, Ulrich Bastian, Heidelberg, Elena Schilbach, Potsdam


Complete text (abstract only):

DIVA (Deutsches Interferometer für Vielkanalphotometrie und Astrometrie), a small interferometric satellite for astrometry and photometry, is currently under development as a successor of Hipparcos and a precurser of the ESA cornerstone mission GAIA. DIVA will scan the sky in a fashion similar to Hipparcos. The observing technique and therefore the raw data reduction will be rather different. Dispersed interferometric fringes as a new type of signal will be directly recorded by CCD mosaics operated in drift-scan mode on board the continuously rotating satellite. They allow combined astrometric (perpendicular to the fringes, i.e. in the direction of the drift scan) and spectro-photometric measurements (in the direction of the dispersion of the fringes).

We have investigated different simple algorithms for the on-board processing of the dispersed fringes for real-time attitude determination. For this purpose we used simulated polychromatic dispersed fringe patterns of stars with known spectra. In the simulations we used the specific instrument parameters envisaged for the DIVA instrument, including fringe smearing due to TDI mode in the scan direction, on-chip binning in the direction of the dispersion and realistic assumptions on various noise contributions.

On the basis of simulations of images of stars of different magnitudes and spectral types, we presented estimates of the achievable on-board accuracy of the astrometric measurements.

Bibliographical details:

Sonja Hirte, Ralf-Dieter Scholz, Siegfried Röser, Ulrich Bastian, Elena Schilbach: On-board reduction of dispersed fringes for DIVA. In: Peter Brosche, Wolfgang R. Dick, Oliver Schwarz, Roland Wielen (Eds.): The Message of the Angles - Astrometry from 1798 to 1998. Proceedings of the International Spring Meeting of the Astronomische Gesellschaft, Gotha, May 11-15, 1998. (Acta Historica Astronomiae; 3). Thun ; Frankfurt am Main : Deutsch, 1998, p. 213.