84
Zac
harias
et
al.
5. Outlook
Signi cant updates in the software are in progress to further reduce systematic
errors in the derived positions, handle galaxies and nebulae, crowded elds and
to resolve most wide double stars. A particular problem is the unique match of
images from various catalogs. A given epoch di erence and confusion limit can
only detect a certain range of proper motions. The UCAC observing program is
designed to achieve a high level of completeness for stellar sources fainter than
8th magnitude. Improved proper motions on the 4 mas/yr level for all stars will
be obtained by a new reduction of all applicable Northern and Southern Proper
Motion survey (NPM & SPM Lick, Yale / San Juan) plates. Scanning of all
those plates on PMM (USNO, Flagsta ) will be complete later this year.
Acknowledgments.
We are grateful to the entire UCAC team and the
CTIO sta , in particular the observers D. Castillo and M. Martinez. CTIO is
operated by NOAO/AURA and supported by the National Science Foundation
(NSF).
References
H g, E., Fabricius, C., Makarov, V.V., Bastian, U., Schwekendiek, P., Wicenec
A., Urban, S., Corbin T., & Wyco , G., 2000, Astron. Astrophys., in
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Johnston, K.J.(PI) 1999, Full-sky Astrometric Mapping Explorer, FAME Con-
cept Study Report, US Naval Observatory, Washington DC.
Monet, D.G. et al., 1999, USNO A2.0 catalog on CD-ROM.
Platais et al. 1998, Astron. J.,
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see also, http://www.astro.yale.edu/spm/spm2cat/spm2.html.
Zacharias, N., Urban, S.E., Zacharias, M.I., Hall, D.M., Ra erty, T.J., Germain,
M.E., Holdenried, E.R., Pohlman, J.W., Gauss, F.S., Monet, D.G. &
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Zacharias, N., Zacharias, M.I., Urban, S.E. & H g, E., 2000b, Astron. J. in
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