PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Known errors and/or anomalies in the volumes" PUBLICATION_DATE = 2008-12-16 END_OBJECT = TEXT END ERRORS AND/OR ANOMALIES IN THE CURRENT VOLUME Volume CORADR_0162, Version 02 ------------------------------ 1. The Cassini Radar Transition file (EXTRAS/CRT_162_V02.TAB) contains no information about ScanStart and ScanEnd transitions. 2. The uncompressed LBDR and BIDR products have attached labels. 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, "α" 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. The active mode science data segment fields in the SBDR and LBDR products are invalid and flagged accordingly. Distant satellite observations do not generate burst by burst active mode results. Instead, the science results for distant satellite observations are summarized in the AAREADME.TXT file in the top level directory of this volume. 6. The science data quality flag only specifies the validity of the active and passive boresight geometry when the corresponding active or passive data valid bit is zero (valid). For example, if bit 1 is set (invalid) then all the active boresight geometry is invalid even though bits 7 and 8 may be zeroed. 7. The user should be aware that the antenna main beam usually covers all or a significant fraction of the target body during distant satellite observations. The boresight geometry fields are of limited value since they apply only to the center of the antenna beam. In some cases spacecraft pointing control puts the boresight off of the target and these fields are then invalid. 8. The instrument is operating in a special mode for this data take. Multiple bursts in flight are used to accomodate the very high range to the target. This slightly alters the meaning of the active mode geometry fields in the science data segment of the SBDR and LBDR files. 9. 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. 10. 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). 11. 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. ERRORS AND/OR ANOMALIES IN PREVIOUS VOLUMES Not Applicable