J/MNRAS/505/5253ivo://CDS.VizieR/J/MNRAS/505/5253doi:10.26093/cds/vizier.75055253CDSZhang Q.F.Zhou X.M.Tan Y.Lainey V.Cooper N.J.Vienne A.Qin W.H.,Li Z.Peng Q.Y.2024-08-21T20:17:59Z2021-07-02T07:56:53ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsolar-systemsolar-system-planetsastrometryIn the caviar software package, a standard tool for astrometry of images from the Cassini imaging science subsystem (ISS), Gaussian fitting is used to measure the centre of point-like objects, achieving a typical precision of about 0.2 pixels. In this work, we consider how alternative methods may improve on this. We compare three traditional centroiding methods: two-dimensional Gaussian fitting, median, and modified moment. Results using 56 selected images show that the centroiding precision of the modified moment method is significantly better than the other two methods, with standard deviations for all residuals in sample and line of 0.065 and 0.063 pixels, respectively, representing a factor of over 2 improvement compared to Gaussian fitting. Secondly, a comparison of observations using Cassini ISS images of Anthe is performed. Anthe results show a similar improvement. The modified moment method is then used to reduce all ISS images of Anthe during the period 2008-2017. The observed-minus-calculated residuals relative to the JPL SAT393 ephemeris are calculated. In terms of {alpha}xcos({delta}) and {delta} in the Cassini-centred international celestial reference frame, mean values of all residuals are close to 0km, and their standard deviations are less than 1km for narrow angle camera images, and about 4km for wide angle camera images.2021MNRAS.505.5253Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/505/5253CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/505/5253https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/505/5253http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/505/5253https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/505/5253https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/505/5253http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/505/5253GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/505/5253/table4 (Astrometric observation of Cassini's Imaging Science Subsystem Narrow Angle Camera (NAC) and Wide Angle Camera (WAC) images of Anthe)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/505/5253/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/505/5253/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/505/5253/table4?GETtext/xml+votable180.050000true146.58365806-8.021206940.0055555555555555566/4146 4159 4498 4696 4830 6516 6518 6521-6524 6608 8259 8321 8328 8558 8563 8568 9222 9233 9284 9330 9404 9480 9542 9627 9717 9733 15026 15030-15031 15081 15084 15086 24621 24634 24900 24912 25252 25678 25691 25812 26677 26679 26722 26728 26730 26768 26816 26818-26819 26825 26827 27139 27354 27434 30432 30474 30611 30616-30617 31206-31207 31471 31478 31515-31516 31536 31652 31807 31848 32446-32447 32491 32494 38104 38218 38305 38356 38517 38723 38736-38737 40349 42640 43386 43423 43461 43994 43996-43997 44005 44011-44012 44027 44232 44705 44712 44901 44917 47636https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/505/5253?format=asciidefaultJ/MNRAS/505/5253/table4Astrometric observation of Cassini's Imaging Science Subsystem Narrow Angle Camera (NAC) and Wide Angle Camera (WAC) images of AntheImageImage identification numbermeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsDate of the observationstime.epochnullableRAcdegCamera's right ascensiondegpos.eq.raDEcdegCamera's declinationdegpos.eq.decTwistCamera's Twist angledeginstr.offsetdoubleSampleBody's sample position after phase correction (1)pixpos.cartesian.x;instr.detfloatLineBody's line position after phase correction (1)pixpos.cartesian.y;instr.detfloatRAICRSBody's right ascension (ICRF) after phase correctiondegpos.eq.ra;meta.mainDEICRSBody's declination (ICRF) after phase correctiondegpos.eq.dec;meta.mainBiasXPhase error in samplepixstat.errorfloatBiasYPhase error in linepixstat.error;time.phase;spect.linefloat