ınbul 2004 
ping with 
eraphische 
Vol. 36, p. 
eukum, G., 
ion Stereo 
irtography, 
29-38. 
Real” 3D 
CA Intern. 
7. 
les of ICA 
versity of 
'echniques, 
'esentations 
phic Conf, 
CARTOGRAPHY OF THE ICY SATURNIAN SATELLITES 
T. Roatschl , I. Oberstl, B. Giesel, M. Wáhlischl, V. Winklerl, K.-D. Matzl, R. Jaumannl, G. Neukum?2 
1) Institute of Planetary Research, German Aerospace Center; Rutherfordstr. 2; D-12489 Berlin; Germany (please direct 
all correspondence to: T. Roatsch, thomas.roatsch@dlr.de) 
2) Freie Universitit, Institute for Geosciences, Berlin, Germany 
ABSTRACT 
We have re-measured control points and re-computed a control point network for Saturn’s satellite Dione. Our network 
is based on16 images (obtained by the narrow-angle cameras of Voyager I and II), 135 control points, and 741 point 
measurements. We obtained mean point accuracies of 1.8 km, 2.9 km, and 1.2 km for X, Y, and Z, respectively. The 
radius of Dione was re-determined to be 562.5 km +/- 0.2 km with a RMS deviation of 3 km, consistent with 560 km 
(RMS: 5 km) found by Davies et al. 1983. Subsequently, we generated a sequence of controlled digital base mosaics 
for the five (among the largest) satellites Mimas, Enceladus, Tethys, Dione, and Rhea. The images are reprojected in 
viercator and Polar Stereographic projections using satellite chape parameters, as recommended by IAU. On the basis 
of these mosaics, maps in printable format have been produced. Our data products update previous control point 
networks and maps of these satellites, released by the RAND Corporation and the USGS (United States Geological 
Survey), respectively, between 1982 and 1992. Our maps constitute an important basis for the planning of the Cassini 
mission, which will begin its orbital tour through the Saturnian system in June 2004 (http://saturn.jpl.nasa.gov). 
(http://www.jpl.nasa.gov/voyager). The satellites are 
locked in synchronous rotation and exposed to strong tidal 
and rotational forces; therefore, they have assumed a strong 
ellipsoidal shape. In addition, owing to the restricted 
viewing geometry during the two fast flybys, the effective 
image resolution varies strongly over the surface of each 
satellite. Thus, any cartography work on these satellites is 
far from routine and requires non-standard methods of image 
processing. 
1. INTRODUCTION 
The Cassini spacecraft is preparing to enter orbit about 
Saturn on July, 1st, later this year, and will then carry out a 
comprehensive exploration and mapping program of its icy 
satellites. Motivated by these future prospects, we are 
presently carrying out a comprehensive photogrammetric 
and cartographic study of these satellites, using images 
obtained by the Voyager-1 and -2 spacecraft during their 
Saturn flybys in 1980 and 1981 
  
  
Mean radius Equatorial radius Polar radius 
(subplanetary) (along-orbit) 
km km km km 
Mimas 198.6 +/- 0.6 209.1 +/- 0.5 196.2 +/- 0.5 191.4 +/- 0.5 
Enceladus 249.4 +/- 0.3 2356.3 t/- 0.3 247.3 +/- 0.3 244.6 +/- 0.5 
Tethys 529.8 +/- 1.5 535.6 +/- 1.2 8282. 1/- 12 325.8 37-12 
Dione 560 +/- 5 *) --**) 
Rhea 764 +/- 4 . --**) 
  
  
*) revised in this study: r = 562.5 +/- 0.2 km 
**) no tri-axial shape parameters available 
Table 1: IAU shape parameters (Seidelmann et al., 2003) 
for details) to compensate for the intrinsic geometric 
From the large number of available Voyager images, we distortion of the Vidicon sensor. 
selected a small number with appropriate coverage and 
Image quality (see Appendix, Table Al). Though Voyager 
had obtained many narrow band filter images, only clear 
filter images were used in our processing. All Voyager 
Images are available online from the Planetary Data System 
(PDS) Imaging Node (http://pds-imaging.jpl.nasa.gov). The 
Images were initially converted from PDS to VICAR (Video 
Image Communication And Retrieval, 
http://rushmore.jpl.nasa.gov/vicar. html) format and 
radiometrically calibrated to account for dark current and 
flat field . The images were then geometrically calibrated 
using resecau mark measurements and standard resampling 
methods (Benesh and Jepsen, 1978; see 
http://www-mipljpl.nasa.gov/external/vicar.html 
2. DIONE 
Control point networks and maps of the satellites of Saturn 
have been released earlier by the RAND Corporation Davies 
and Katayama (1983a,b,c; 1984) and the USGS (United 
States Geological Survey). We first focused on the satellite 
Dione, for which (except perhaps Rhea) the best image data 
are available. 
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