About DTWG Data

1. Organization

• The DTWG archive consists of a single volume data set.


• The archive volume contains the descent trajectory data for the Huygens Probe as it descended through Titan's atmosphere. The DTWG data is comprised of two sets of products: those derived for the entry phase (from an altitude of 1270 km above Titan's surface to T0, the time at which the parachute deployment sequence was initiated) and those derived for the descent phase (from T0 until the time that the Probe impacted the surface of Titan). The derived entry parameters include Probe altitude, latitude, longitude, angle of attack, reconstructed aerodynamic parameters, modeled Probe mass, and Probe position and velocity vectors. The descent phase data products include the atmospheric pressure at the Probe, the Probe's altitude, latitude, longitude, and descent velocity.

2. Directory Structure

The DTWG archive data volume contains the following directories:

• BROWSE - The browse directory contains browse images (in the form of JPEG files) of plots showing altitude vs. time (for both entry and descent phase) and velocity vs. time (descent phase only).


• CATALOG - The catalog directory contains general information about the data set, including information about the instrument, personnel involved, and references.


• DATA - The data directory contains the seven data products of the DTWG (described in more detail in the EAICD - see below).


• DOCUMENT - The documentation directory contains important DTWG documents. See below for more details.


• EXTRAS - The extras directory contains three folders containing the input files for the descent trajectory computation, software used for the DTWG computation, and ephemerides of Saturn and its satellites.


• GEOMETRY - The geometry directory contains the SPICE kernels that were relevant to the DTWG reconstruction effort.


• INDEX - The index directory contains the archive index for the entire data volume.

3. Documentation

• Users are strongly encouraged to review the DTWG AAREADME.TXT file. This file appears in the root directory of the DTWG volume.


• Further details of the DTWG archive volume can be found in the "Experimenter to Archive Interface Control Document" (EACID) Document, which is found in the DOCUMENT directory on the data volume.


• Other important information about the DTWG recontruction effort is also found in the DOCUMENT directory on the data volume.