PDS_VERSION_ID        = PDS3
RECORD_TYPE           = STREAM

OBJECT                = TEXT
   PUBLICATION_DATE    = 2008-06-17
   NOTE                = "Description of contents of BROWSE directory"
END_OBJECT            = TEXT
END

SHARAD RDR browse products are organized into subdirectories in a structure 
that parallels that of the DATA directory. The DATA directory is divided into
a number of subdirectories, each containing data collected through the use
of a single Operation Sequence Table (See the SHARAD EDR and RDR Archive
Volume Software Interface Specification for a complete description).
Each browse product corresponds to an RDR product.

In each BROWSE subdirectory, there are two types of files. One
is an JPEG browse image of the corresponding RDR.  It has the same
name as the corresponding RDR except that it ends with a '_b.jpg' instead
of '.dat'.  The second file is a detached label describing the
JPEG image including information on how it was generated.  It ends with
a '_b.lbl'.

Each JPEG format browse image is based on a SHARAD RDR data product.  The 
following parameters are parsed from the RDR frame.

 RDR Field                          Variable(s)
 -----------------                  ------------------
 RANGE_SHIFT                        sft 
 ECHO_SAMPLES_REAL                  re 
 ECHO_SAMPLES_IMAGINARY             im
 SUB_SC_EAST_LONGITUDE              slon (orbit start)
                                     elon (orbit end)
 SUB_SC_PLANETOCENTRIC_LATITUDE     slat(orbit start)
                                     elat (orbit end)
 
 The real and imaginary parts of the signal are then joined
 via a traditional log-scale transform:
 
 sig = 10 * log10 (re^2 + im^2)
 
 The sig is sorted numerically and the mean value for the lowest
 100 sig values is added to a running average noise value.
 
 The mean noise is subtracted from each pixel value, transforming 
 the 'sig' variable into 'san', or 'signal above noise.'
 
 san = 10*log10(10.^(0.1*sig)-10^(0.1*noise));
 
 The san values are scaled so the pixel brightness values
 correspond linearly to an absolute range of 0 to 40 decibels.
 Finally, the radargram is shifted to adjust for the RANGE_SHIFT
 value.