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J/A+A/380/727       1995 Saturnian satellite observations    (Vienne+, 2001)

Saturnian satellite observations made in Brazil during the 1995 opposition with an astrometric analysis. Vienne A., Thuillot W., Veiga C.H., Arlot J.-E., Vieira Martins R. <Astron. Astrophys. 380, 727 (2001)> =2001A&A...380..727V (SIMBAD/NED BibCode)
ADC_Keywords: Planets ; Positional data Keywords: Saturn - satellites of Saturn - astrometry Abstract: This paper provides an analysis of astrometric measurements of the main Saturnian satellites made thanks to CCD observations performed in 1995 at the Laboratorio Nacional de Astrofisica at Itajuba in Brazil. The astrometric reduction is discussed, especially the small corrections done here, but most of time neglected elsewhere. A catalog of 6006 differential positions has been obtained. They have been compared to different ephemerides, the Vienne & Duriez ephemerides (TASS 1.7, 1995A&A...297..588V, 1997 Cat. J/A+A/324/366), the Harper & Taylor (1994A&A...284..619H) ephemerides and the Dourneau (1993A&A...267..292D) ephemerides. These observations provide a large set of modern observations, and appear to be of good precision. This accuracy is needed for future use of these data to improve the dynamical models. These positions are included in the data base NSDC dedicated to the natural satellites ( Description: 6006 differential positions of the main Saturnian satellites issued from astrometric measurements of CCD observations performed in 1995 at the Laboratorio Nacional de Astrofisica at Itajuba in Brazil. Most of these frames have no reference stars, then we applied an inter-satellites reduction. We have used the positions of Tethys, Dione, Rhea and Titan given by TASS1.7 to determine the scale factor and the orientation of the receptor (1995A&A...297..588V, 1997 Cat. J/A+A/324/366). The comparison of the observed positions and the computed positions shows that the dispersion of the observations is 0.07". Furthermore, the quality and the number of the positions of the satellites not used in the calibration is good: 0.08" for the 216 positions of Mimas, 0.14" for Hyperion (324), 0.11" for Iapetus (524). The format and the conventions of the present catalog are very near to the one of Strugnell & Taylor (1990A&AS...83..289S). The coordinates are given apart from a scale factor and from a rotation, but all astrometric corrections are done. So, these positions are really astrometric ones in that meaning that, no astrometric consideration is necessary to use them, even if one wants to touch up the calibration. Nevertheless, the raw pixels are also given in order to allow anyone to reduce again the frames. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file vienne.dat 123 11408 Catalog of astrometric data
See also: J/A+AS/139/305 : Position of Saturn's satellites (1982-1988) (Veiga+, 1999) J/A+AS/121/65 : 1990-1994 Saturn's satellites astrometry (Harper+ 1997) J/A+AS/136/257 : Saturn's satellites in 1995/97 (Harper+ 1999) J/other/KFNT/15.483 : Positions of Thebe and Amalthea (Ledovskaya+ 1999) J/A+AS/107/559 : Position of Uranian satellites (Veiga+, 1994) J/A+AS/113/557 : Uranian satellites (Veiga+, 1995) J/A+AS/120/107 : 1989-1994 CCD observations of Triton (Veiga+ 1996) J/A+AS/131/291 : 1995-1997 CCD positions of Triton (Veiga+ 1998) J/A+AS/136/445 : CCD observations of Nereid (Veiga+, 1999) J/A+AS/138/247 : Uranian satellites 1995-1998 (Veiga+, 1999) J/A+AS/143/405 : Astrometric observations of Helene (Veiga+, 2000) : BDL position of Satellites of Saturn Byte-by-byte Description of file: vienne.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Opp [118] Opposition number, 1=1874 to 118=1995 5- 8 I4 yr OBS.Y UTC date of the observation (year) 10- 11 I2 --- OBS.M UTC date of the observation (month) 13- 22 F10.7 d OBS.D UTC date of the observation (decimal day) 24- 29 F6.3 s TT-UTC TT-UTC (difference Terrestital Time/UTC) 31- 33 I3 --- Obs UAI observatory code from the Minor Planet Center 35- 37 I3 --- Ref [301] Reference code of the catalog (301 for the present observations) 39 I1 --- ObsType [0/3] Observation type. 0=RA, DE; 1=ΔRA*cosDE, ΔDE; 2=ΔRA, ΔDE; 3=PA, separation 42- 43 A2 --- Objs Subject satellite, reference satellite (1) 45 I1 --- f_Obs1 [0/1] Flag of presence of the first coordinate 46 I1 --- f_Obs2 [0/1] Flag of presence of the second coordinate 49- 60 F12.7 --- Obs1 First coordinate 64- 74 F11.7 --- Obs2 Second coordinate 76 I1 --- RefSys [0/2] Reference system (2) 78 I1 --- RefFra [1/2] Reference frame (3) 80- 86 F7.3 arcsec O-C1 ?=999.999 Residuals of observations (4) 88- 94 F7.3 arcsec O-C2 ?=999.999 Residuals of observations (4) 97 I1 --- NSat The number of the satellite used as reference in the computation of o-c 100 I1 --- --- [0] no meaning in this series, index reserved 103 I1 --- NSeries The number of the series (5) 105-113 F9.3 pix Xpos ?=99999.999 Original coordinates in pixels 115-123 F9.3 pix Ypos ?=99999.999 Original coordinates in pixels
Note (1): Subject satellite, reference satellite: 0 for Saturn, 1 to 8 for S1 to S8 (* when there is no reference satellite that is for observation type 0, C for the center of the plate which is not a physical object) Note (2): Reference system: 0 = mean equator and equinox B1950 1 = true equator and equinox of date of observation 2 = mean equator and equinox of J2000 Note (3): Reference frame: 0 = topocentric 1 = geocentric 2 = heliocentric Note (4): Residuals of observations computed with TASS1.7 and with the format f7.3, it is 999.999 when the residuals are not computed and it is 888.888 when the residuals are greater than 100. in absolute value). Note (5): The scale and orientation are the same for all the observations of one series. For each series, they were an astrometric reduction in refraction and stellar aberration, the light-time correction was EarthSatell, the source of the theoretical positions used to reduce the plates is 3456tass1.7, and the coordinates are free of refraction and stellar aberration NSeries Scale Orientation (arcsec/pix) (rad) 1 0.294384053 0.004800195 2 0.547902822 0.531254729 3 0.547682483 2.625230525 4 0.547603319 0.529115226 6 0.547880584 0.530138505 Note that the orientation refers to the true equator of the date. But it is possible to touch up these parameters directly by comparing the "observed map" and the "computed map" (then given in the J2000 system, see Vienne, Thuillot & Arlot, 2001, Astrometric reduction of CCD observations of planetary satellites without reference star, in Note Sci. et Tech. de l'I.M.C.C.E., S077).
History: Copied at
(End) Patricia Bauer [CDS] 07-Dec-2001
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