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 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 1995A&A...297..588V, 1997 Cat. J/A+A/324/366), the Harper
& Taylor (1994A&A...284..619H 1994A&A...284..619H) ephemerides and the Dourneau
(1993A&A...267..292D 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
(ftp://ftp.bdl.fr/pub/NSDC/saturn/raw_data/position/).
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 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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
vienne.dat 123 11408 Catalog of astrometric data
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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)
ftp://ftp.bdl.fr/pub/NSDC/saturn/raw_data/position :
BDL position of Satellites of Saturn
Byte-by-byte Description of file: vienne.dat
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Bytes Format Units Label Explanations
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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
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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).
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History:
Copied at ftp://ftp.bdl.fr/pub/NSDC/saturn/raw_data/position
(End) Patricia Bauer [CDS] 07-Dec-2001