PHOTOMOSAICS OF ASTEROID 243 IDA

Ida.jpg is a set of four photomosaics of asteroid 243 Ida, the second
asteroid to be visited by a spacecraft.  Higher resolution versions of
these mosaics, with latitude-longitude grids and feature names, will
be published separately.  Note that the central longitudes on the 
equatorial views are 100 and 280, not 90 and 270.  This reduces distortion
in areas at the ends where the surface curves sharply.

Ida was observed by the Galileo spacecraft on 
28 August 1993.  Images are described in:

Belton, M.J.S. et al., 1996.  'Galileo's Encounter with 243 Ida: An Overview
   of the Imaging Experiment' (Icarus, 120:1-19)

and:

Thomas, P.C. et al., 1996.  'The Shape of Ida'  (Icarus, 120:20-32)

The latter paper includes a map of radius contours.  I digitized the
contours and interpolated to give a low resolution shape model, then
refined it by fitting it to limbs and terminators in the images.  The shape
model differs from the published model in several small details.  The
shape model is a matrix of radii at regular increments of latitude and 
longitude.  Positions in the mosaics are controlled by the digital shape 
model.  For this work, the three dimensional convex hull of the shape 
model was projected into the Morphographic Conformal Projection (the 
conventional Stereographic Projection modified for non-spherical worlds).
Longitudes are measured from the crater Afon, just south of the
equator at the blunter end of Ida.

As with all conformal (true shape) projections, the scale in these mosaics
varies, increasing from the centres to the outer edges.  The map projection
is described in:

Stooke, P.J. and Keller, C.P., 1990.  "Map Projections for Non-Spherical
Worlds / the Variable-Radius Map Projections", CARTOGRAPHICA, V. 27, No.
2, pp. 82-100.

This version of the file, with labels intact, is in the public domain.

Philip Stooke,
Department of Geography,
University of Western Ontario,
London, Ontario, Canada N6A 5C2
stooke@sscl.uwo.ca