PDS_VERSION_ID         = PDS3
RECORD_TYPE            = STREAM
OBJECT                 = TEXT
  PUBLICATION_DATE     = 2019-10-11
  INTERCHANGE_FORMAT   = ASCII
  NOTE                 = "N/A"
END_OBJECT             = TEXT
END

Cassini RADAR delay/Doppler Radargram Data Archive




1.	Introduction

This archive contains Ku-band (13.78 GHz) radar altimetry data acquired by the Cassini's 
RADAR instrument, which used 4.25 MHz chirped signal to probe the surface of Titan.
Significant changes in the dielectric permittivity cause reflections to occur over a Doppler
footprint that extends at least a few kilometers. Each radargram is composed of real-values 
of the radar backscatter power, arranged with time delay on the vertical axis and along-track 
distance on the horizontal axis. The peak power of the echo contained in each column 
correponds to the normalized radar cross section recorded in the relative Doppler bin 
with the values expressed in dB. A consistent set of synthetic aperture radar processing 
parameters described in [Poggiali et., 2019] and in the labels associated with the products 
has been adopted. The level of thermal noise depends both from the instrument and from the 
peculiar target surface observed, and fluctuates over time.

In every directory a TAB-format file provides information on acillary and scientific data
relative to each Doppler bin in along track and a TAB-format file containing the actual waveforms. 
While the Doppler footprints dimension and spacing is not constant in along-track, because of the
peculiar hyperbolic flyby geometry of the Cassini observations, the round-trip time is constantly
sampled at 0.1 microseconds steps. For user convenience we included also a png-format image 
of each delay/Doppler radargram exhibiting power in logarithmic scale, with surface height on the 
vertical axis and along-track  distance on the horizontal axis.

This archive includes data processed by Valerio Poggiali and Alexander Hayes with the valuable 
collaboration of Marco Mastrogiuseppe.

2.  File Formats

This section describes file formats for the kinds of files contained on the archive volume.

2.1. Document File Format
Document files with the .TXT suffix are ASCII files which may have embedded PDS labels.
Each line in a .TXT file ends with a carriage return character (ASCII 13) and a line feed 
character (ASCII 10). This allows the files to be readable under various operating systems.

Documents may contain formatting and figures that cannot be rendered as ASCII text. In these 
cases, the documents are given in PDF (Portable Document Format) format, an industry standard 
that is frequently used for distributing documents. Free software for viewing PDF files is 
available from many sources, including http://get.adobe.com/reader/.


2.2. Tabular File Format
Tabular files (*.CSV) are ASCII files formatted for direct reading into many database 
management systems or spreadsheet programs on various computers. All fields are separated 
by commas. The records are of fixed length, and the last two bytes of each record
contain the ASCII carriage return and line feed characters.

All tabular files are described by PDS labels, detached from the product file. 
The PDS label file has the same name as the data file it describes.

2.3. PDS Label Format
All data files in the archive have detached PDS labels. PDS labels 
are ASCII text files intended to be read by humans and by software. A PDS 
label consists of a series of statements in the form "keyword = value", 
where keywords are defined in either the main PDS Data Dictionary.

Each line of text in a detached label ends with a carriage return character
(ASCII 13) and a line feed character (ASCII 10). This allows the files to be
readable under various operating systems.

2.5. Science Data File Formats
For each Cassini track there is a data product: an ASCII file formatted for direct reading 
into many database management systems or spreadsheet programs on various computers. 
All values are separated by the ASCII carriage return and can be rearranged in rows and columns
by using the information contained in the relative label. The records are of fixed length.

3.  Archive Contents
Files in this archive are organized into subdirectories below the
top-level directory. The following table shows the structure and content of 
these directories. In the table, directory names are enclosed in square 
brackets ([]). Each Delay/Doppler product is associated to a different
observation, thus, i.e., T39_ib is the inbound track acquired during the 
flyby T39 of Titan (i.e.: T39_ob would be the outbound). 
If multiple outbound tracks have been acquired during the same
flyby, a progressive number is added at the end (i.e.: T57_ob1 and T57_ob2).
If a dataset has been segmented in more parts and the altimetry observation
is contained in one of the secondary segments a '_s2' suffix is added at the 
end (i.e.:  T92_ib and T92_ob_s2). Furthermore, if during an observation
multiple antenna beams have been used a '_bX' suffix is added to indicate
which beam was used (i.e.: T104_ib and T104_ob_s2_b3).

[TOP-LEVEL-DIRECTORY]                                                       
  |                                                                           
  |-- AAREADME_DDA.TXT     This file                                          
  |                                                                           
  |-- POGGIALI2019.PDF     Detailed description of the processing adopted (IEEE TGRM publication)
  |                                                                           
  |--[TXX_Xb]              Directories containing the data products and labels           
  |  |
  |  |-- tXXX_Xb_reprocX-dda.PNG	Quick look figure of the Dela/Doppler radargram
  |  |-- tXXX-Xb-reprocX.PNG	Quick look figure of the standard radargram
  |  |  
  |  |--[PRODUCTS]       		Description of files in this subdirectory          
  |  |-- DDABDR_DATA_XX_XXXX_V01	Dda waveforms product
  |  |-- DDABDR_SUMMARY_XX_XXXX_V01	Ancillary and scientific data product          
  |  |-- DDABDR_DATA_XX_XXXX_V01	Label for the dda waveforms product
  |  |-- DDABDR_SUMMARY_XX_XXXX_V01	Label for the ancillary and scientific data product             
  |  |

4.  Whom to Contact for Information

For questions concerning this volume set, contact:

    Alexander Gerard Hayes

    Web Site:  https://hayesresearchgroup.com/alexander-hayes/
    E-mail:    hayes@astro.cornell.edu

For general information related to the PDS, contact:

    XXX XXX

    WWW Site:  XXX
    E-mail:    XXX


5.  Cognizant Persons

This archive volume designed and produced at Cornell University by Valerio Poggiali.
