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Asteroid sidereal photometric astrometry from observed epochs
Implementation of sidereal photometric astrometry approach described by Slivan (2014):
The Sidereal Photometric Astrometry (SPA) method of spin vector determination (Drummond et al., 1988) is a computationally efficient approach to identify plausible pole solution regions, and is quite robust because the only assumption is unchanging asterocentric longitudes of the epochs. It permits pole searches of sufficient resolution to be able to see the behavior of the search space near RMS error minima, and thus reveal whether the data are in fact sufficient for spin vector solutions, identify true possible pole regions, and exclude spurious solutions and other fluctuations in the metric. Using SPA speeds determination of creditable poles by reducing the number of trial poles that have to be tested through convex inversion, and provides the needed initial values for the pole location.
Release Notes
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(Updated 2023 Mar 13) Phase angle bisectors: For objects numbered through (5139) the application will calculate the PAB coordinates for epochs from the years 1983 and later, if the user input form fields for longitude and latitude are left blank. PAB information for objects or epochs outside the server catalog will need to be entered directly by the user.
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An appropriate estimate of the uncertainty for the sidereal period is important for testing fitted sidereal period values. Review of the information in Slivan (2012) and Slivan (2013) is recommended.
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Output is a downloadable .fits format file whose image data pixel values are the RMS errors from the SPA pole fits.
On the rectangular graph, the pole ecliptic coordinates (longitude; latitude) in degrees corresponding to pixel at (x,y) are (x−1°; y−91°). -
Application recommended for .fits image display: “SAOImage DS9” (http://ds9.si.edu/)
DS9 settings used to make the graphs in Slivan (2014) : scale “zscale”; color map “I8” inverted; brightness and contrast adjustments by holding down right mouse button and dragging cursor in window, up/down for contrast and left/right for brightness.
Users of this Web tool are kindly asked to include an acknowledgment in publication, and encouraged to reference the paper (Slivan, 2014) which describes the calculations.