Speaker
Dr
Nicholas Cooper
(Queen Mary University of London)
Description
Caviar is an IDL-based software package for the astrometric reduction of spacecraft images. The software was originally developed at Queen Mary University of London (QMUL) in 2003-4 for the reduction of images from the Imaging Science Subsystem (ISS) of the Cassini spacecraft. It has been used to reduce many thousands of Cassini images since the start of the main mission to Saturn in 2004, and will continue to be used until the end of the mission in 2017 and beyond. Published astrometry using the software includes the discovery of two new satellites of Saturn, Polydeuces and Anthe (Murray et al 2005, Cooper et al 2008) and an analysis of the tidal evolution of the Saturn system (Lainey et al 2015, submitted). The latest version of the software, developed at Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE), includes an extensive restructuring of the code and a new graphical user interface. This version is shortly to be made available publicly through the NASA PDS website.
The software is currently capable of performing two primary functions: the correction of errors in the camera pointing direction, and the measurement of the astrometric positions of natural satellites. The camera pointing correction is performed by iteratively matching reference stars to their imaged positions. Currently the Tycho2 and UCAC4 star catalogues are used for reference, with star positions obtained via the Vizier web interface. In common with the estimated star positions, the astrometric positions of unresolved satellites are derived using a centroiding technique based on DAOPHOT ‘Find’ (Stetson 1987), while the positions of resolved satellites are estimated by iteratively fitting a shape model to the measured position of the satellite limb in the image. Approximate satellite positions are obtained from the latest JPL ephemerides using IDL routines from the SPICE software library (Acton 1996).
Future plans include the addition of options to process data generated by imaging cameras from other spacecraft missions, including Mariner 9, Viking, Voyager, Galileo and New Horizons. A capability for the automatic batch processing of multiple images is also in development. In addition, an interface to the GAIA star catalogue will be added as soon as GAIA data is available.
References:
Acton, C. H. 1996. Ancillary data services of NASA's navigation and ancillary information facility, Planet. Sp. Science, 44, 65-70.
Cooper, N.J., Murray, C.D., Evans, M.W., Beurle, K., Jacobson, R.A., Porco, C.C., 2008. Astrometry and dynamics of Anthe (S/2007 S4), a new satellite of Saturn. Icarus 195, 765–777.
Murray, C.D., Cooper, N.J., Evans, M.W., Beurle, K., 2005. S/2004 S 5: A new co-orbital companion for Dione. Icarus, 179, 222-234.
Stetson, P.B., 1987, DAOPHOT--A composite program for crowded-field stellar photometry, Pub. Astron. Soc. of the Pacific, 191-222.
V. Lainey, R. A. Jacobson, R. Tajeddine, N. J. Cooper, C.D. Murray, V. Robert, G. Tobie, T. Guillot, S. Mathis, F. Remus, J. Desmars, J-E Arlot, J-P De Cuypers, V. Dehant, D. Pascu, W. Thuillot, C. Le Poncin-Lafitte, J-P Zahn, 2015, A new constraint on Saturn’s tidal parameters from astrometry with Cassini data. Icarus, submitted.
| Applicant type | First author |
|---|
Primary author
Dr
Nicholas Cooper
(Queen Mary University of London)
Co-authors
Prof.
Alain Vienne
(IMCCE)
Prof.
Carl Murray
(Queen Mary University of London)
Dr
Kevin Baillie
(IMCCE)
Mr
Louis-Etienne Meunier
(IMCCE)
Dr
Michael Evans
(Cornell University)
Dr
Qingfeng Zhang
(Jinan University)
Dr
Valery Lainey
(IMCCE)
Dr
William Thuillot
(IMCCE)
