PDS_VERSION_ID     = PDS3

RECORD_TYPE        = STREAM
OBJECT             = TEXT
  NOTE             = "Known errors and/or anomalies in the volumes"
  PUBLICATION_DATE = 2010-03-31
END_OBJECT         = TEXT
END

ERRORS AND/OR ANOMALIES IN THE CURRENT VOLUME

Volume CORADR_0189, Version 02
------------------------------

1.  The Cassini Radar Transition file (EXTRAS/CRT_189_V02.TAB) contains
no information about ScanStart and ScanEnd transitions.

2.  The uncompressed LBDR product has an attached label.
Normally, a file that has been compressed with ZIP would have been
generated without an attached label.

3.  In the volume index table (INDEX/INDEX.TAB), double quotes enclose
all the date/time values.  Normally, PDS date/time values are not
quoted, but quoting makes parsing easier for some applications.

4.  The HTML documents in the DOCUMENT directory contain HTML character
codes that, while all-ASCII, are not easily interpretable by someone
who is reading the HTML documents as text documents.  For example,
"&#945;" represents the lower-case Greek character "alpha" and is
rendered as such in a web browser.  Equivalent and more legible character
codes (e.g., "&#alpha;") are available as of the HTML 4.0 specification
but cannot be used here, as PDS requires HTML documents to comply to the
HTML 3.2 specification.

5.  Antenna temperature, brightness temperature, and receiver temperature are
defined in Janssen, M. A., "An Introduction to the Passive Microwave Remote
Sensing of Atmospheres," Chapter 1 in Atmospheric Remote Sensing by
Microwave Radiometry, (M. Janssen, ed.), pp. 1-35, Wiley & Sons,
New York (1993).  The archived value in the SBDR and LBDR files gives
uncalibrated antenna temperature in units of Kelvin.
The best current algorithm for correcting the archived antenna temperatures is
Ta_corrected = Ta_archive * ( 0.920 - 0.0041*( t - 1.90 ) )
where t = time in years and fractional years since 2004.0
(0 UTC on 1 Jan 2004)
This algorithm is based on the radioastronomical flux scale at 2-cm wavelength
by direct comparison of distant (unresolved) Titan measurements by the Cassini
radiometer with VLA measurements of Titan reported by Butler and Gurwell,
2004.  This algorithm will improve with time as more distant Titan
measurements are obtained and as more radioastronomical comparison sources are
included.
Butler, B. J., Gurwell, M. A. 2004. Radio Wavelength Observations of Titan
with the  VLA. Bull. Am. Astron. Soc. 36, 6.04.
This algorithm applies also to all preceeding volumes.

6. Ideally the calibrated antenna temperature is referenced to cold sky at
2.7 K, although no guarantee is made that this zero-level accounting has been
correctly made.  Also, the antenna temperature is not necessarily the
brightness temperature seen in the main beam; e.g., there will be an offset
if the sidelobes happen to fall on other than cold sky.  The antenna pattern
has low but significant gain at large angles from the boresight which can
introduce thermal power from other targets besides the intended target in
the main lobe.  In particular, there is an offset to be expected and
accounted for when an extended source like Titan or Saturn is observed
from a close distance.  System gain is the quantity that multiplies the
raw sky counts to convert to the uncalibrated Kelvin scale.
Receiver_temp is the receiver noise temperature Tr (comparison made at
internal reference switch).   The receiver temperature plus the antenna
temperature is equal to the total signal (raw counts times system gain).

7. ant_temp_std is a measure of the rms uncertainty of Ta, and is only an
estimation.  It is obtained as the standard deviation of Ta for three points,
Ta(I-1), Ta(I), and Ta(I+1), and is a useful measure that identifies
questionable data.  For example, it gets large when the beam is sweeping
across a brightness discontinuity.

8. Checksums were not computed for floating point valued BIDRs. The 
CHECKSUM keyword was assigned a zero value.

  

ERRORS AND/OR ANOMALIES IN PREVIOUS VOLUMES

Not Applicable
