File:                   AAREADME.TXT
Last update:            01-SEP-2011 (NJB)



Regarding Vesta data provided by Dr. Robert Gaskell:

   The Vesta DSK files having names of the form

      vesta_gaskell*110825*.bds
      vesta_gaskell*110825*.xfr.gz

   were created from a Vesta plate model file provided
   to NAIF by Dr. Robert Gaskell on August 25, 2011.

   Files having names of the form

      *_64_*
      *_128_*
      *_256_*

   were created by downsampling the original plate
   model file.

   Contact Dr. Gaskell for information concerning the
   construction of the original plate model file.

   Files created from older data have been moved to
   the subdirectory

      old_versions



SPICE DSK files
===========================================================

This directory contains SPICE DSK ("digital shape kernel")
files. These files provide topography data for ephemeris
objects.

Binary DSK files have names of the form

   *.bds

The binary files were created on a PC and have the "little-endian"
binary file architecture. These files are readable only on host
systems with this architecture.

Each DSK is also available in gzipped transfer format. These 
files have names of the form

   *.xfr.gz

The gzipped transfer files can be used on any host environment 
where the Alpha DSK Toolkit is supported. The files must be 
uncompressed and converted to binary format on the host system
before they can be read. See the section "Porting DSK files"
below for further information.

See the corresponding comment files, which have names of the form 

   *.cmt

for descriptions of the files' contents.


Images of the models are provided in files having names of 
the form

   *.png
   *.jpg

The image files are created using artificial lighting, coloring, and
viewing geometry, so they should not be construed as a reflection of
the relative geometry of target bodies and other solar system objects,
particularly the sun.


Accessing DSK data from an application program
===========================================================

There is currently an Alpha test version of the SPICE Toolkit that
reads and writes DSK files. See the web page at URL

   http://naif.jpl.nasa.gov/naif/DSK_alpha_test

for the release announcement describing this Alpha test software.

The Alpha DSK Toolkit was released July 1, 2010. Note that the
file format used by this DSK software version is *incompatible*
with formats used by earlier prototype versions.

The current DSK format will continue to be supported by future, 
official versions of the SPICE Toolkit.


Porting DSK files
===========================================================

DSK files use the SPICE DAS format. SPICE does not yet support run-time
translation of non-native DAS files, so these files must be converted
to the native format of the host system on which they're to be read.
 
DSKs in gzipped transfer format can be used on any host system once the
files have been unzipped and converted to binary format on that system.
 
Binary DSK files can be converted using the SPICE utility BINGO, which
is available from the NAIF web site at the URL

   http://naif.jpl.nasa.gov/naif/utilities.html

The files can also be converted using the SPICE utilities TOXFR and
TOBIN. See the Convert Required Reading convert.req in your installed
SPICE Toolkit or the Porting Kernels tutorial on the NAIF web site at
URL

   ftp://naif.jpl.nasa.gov/pub/naif/toolkit_docs/
   Tutorials/pdf/individual_docs/09_porting_kernels.pdf

for details.


Reading DSK comments
===========================================================

The comments in a binary DSK file can be read using the SPICE 
utility COMMNT. The DSK must be the the format used by
your host computer system in order to be readable (see
"Porting DSK files" above). For your convenience copies
of the comment areas of these kernels are included in
text format in this directory.


Summarizing DSK files
===========================================================

Coverage summaries of binary DSK files may be displayed using the
DSK utility program DSKBRIEF.


Old DSK format files
===========================================================

Old, prototype DSK formats are no longer supported by NAIF
and are not usable by the Alpha DSK Toolkit. See the notes
above under "Accessing DSK data from an application program."



Plate model format files
===========================================================

Shape models using the older plate model format---a precursor of the
DSK format---are still available on the NAIF server in the path

   ftp://naif.jpl.nasa.gov/pub/naif/deprecated_kernels

Do not confuse the old plate model format with plate models represented
in the DSK format. Both kinds of files can represent topography using
collections of triangular plates, but the file formats and associated
API software are different. Future versions of the SPICE Toolkit will
support only the DSK format.

The SPICE Toolkit does not contain APIs that perform geometry
computations using files in the old plate model format, nor will it be
modified to do so in the future. However, the old plate model format is
based on the E-kernel format, and the SPICE E-kernel readers can be
used to extract data from plate model files.

APIs that access the old plate model files are provided by the NAIF
plate model library, which is not part of the SPICE Toolkit. Contact
NAIF for details.