In January 2010, we replaced version 1 of the CIRS data set
(COCIRS_0nnn) with version 2.
In April 2010, we regenerated the entire reformatted CIRS dataset
(COCIRS_5nnn) using the version 2 data.
The deliveries of version 1 were made quarterly over the span of
several years. During that time the CIRS team made incremental
adjustments in the calibration algorithm and calibration files
used to prepare the volumes for delivery. The team redelivered
the entire calibrated data set in December 2009 as version 2. All
of the data in version 2 was calibrated with the same algorithm
and set of calibration files.
In every regard, the new data files appear to be more reliable
and better calibrated than the old.
With the improved calibration software, the team are better able
to reject invalid spectra (which often occur while a shutter is
opening or closing) and are better able to select the best
calibration spectra to apply to any given observation.
Consequently calibrated spectra pointed at deep space are now
much closer to zero, and many anomalies and artifacts have
disappeared. Another consequence is that there is not an exact
one-to-one correspondence between files in version 1 and version 2.
In January 2011, the entire reformatted data set was regenerated again in order to clean up
minor errors mostly relating to documentation. No significant changes were made to
the data files which had been generated in or subsequent to the the major revision in
April 2010. The January 2011 version is considered stable pending a follow-up
review by the original peer review panel.
In July 2011, the CIRS team again redelivered their entire data set,
this time as version 3.1.
On line, we replaced version 2 of the CIRS data set with version 3.1.
The version 3.1 release incorporates a further refinement in the
calibration algorithm.For interferograms collected using CIRS Flight Software Version 6
(executed in July of 2010), non-co-added data will have the 1/2 Hz
noise spikes suppressed while no noise spike suppression will be
done on co-added data.
In addition several changes to the contents of the data files were made.
These changes necessitate modifications to our reformatting pipeline software
which we are in the process of making.
In the meantime, the reformatted volumes remain based on version 2 of the data, and
new volumes, beginning with COCIRS_1007, currently are available only in the original format.
For a complete list of changes in versions 2 & 3, see the end of the
DATASET.CAT file. Identical copies of
this file are in the CATALOG directory of each volume.
The CIRS archive consists of three, multi-volume data sets. One
data set covers the Jupiter encounter, and the other two span the
entire Saturn portion of the mission. The two Saturn data sets contain
exactly the same data in two different formats.
The archive volumes contain CIRS data products: raw data
(interferograms) and calibrated data (spectra), with associated
pointing, navigation and spacecraft orientation information,
instrument documentation, calibration files, calibration
algorithms, representative software for handling the CIRS data
files, and documentation necessary to produce higher level
calibrated products.
3. Data Formats
The CIRS data volumes delivered by the team involve variable
length files in a rather complicated file structure. We are producing
parallel volumes for the Saturn encounter containing re-formatted data
and metadata designed to simplify access to the data. Consequently there
are two data sets for the Saturn encounter easily distinguished by the
first numerical digit in the volume IDs:
COCIRS_0nnn or COCIRS_1nnn indicate volumes in the original format.
COCIRS_5nnn or COCIRS_6nnn indicate the corresponding re-formatted volumes.
In the re-formatted version, the files have been converted from
variable-length to fixed-length formats. ASCII versions of most binary
files are also provided. In addition, file boundaries have been
adjusted so that the data and metadata (timing and geometry
information) associated with individual Cassini activities and with
individual CIRS focal planes are found within a single set of files;
no file contains information from more than one activity or one focal
plane.
The following two links provide more detailed information on the current versions of the
original and re-formatted data respectively.
Original Format - details and
additional format specific documentation for the original structure.
Re-formatted - details and
additional format specific documentation for the re-formatted structure.
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