1. Cassini
  2. Instruments and Data
  3. CIRS

Organization

This page contains a brief overview of the directory and file structure of the re-formatted volumes. For a more complete discussion, see the TUTORIAL.TXT file. There is a copy of this file in the DOCUMENT directory on each re-formatted volume. The following discuss is extracted from the TUTORIAL.TXT.

1. Directory Names

The DATA directory on each volume contains five subdirectories, each of which contains a particular type of file:

APODSPEC - apodized, i.e. calibrated and resampled, spectra.

GEODATA - position and viewing geometry of the planet and moons.

POIDATA - pointing geometry on the planet or moon.

RINDATA - pointing geometry on the ring system.

TARDATA - listing of target bodies captured.

2. File Names

Data files are generally named as follows:

aaayymmddhhmm_FPn.*

aaa - a prefix indicating the file type:

ISPM = interpolated spectrum (APODSPEC subdirectory);

GEO = system geometry (GEODATA subdirectory);

POI = planet and satellite pointing (POIDATA subdirectory);

RIN = ring pointing (RINDATA subdirectory);

TAR = target body listing (TARDATA subdirectory).

yymmdd - two-digit year, month and day when the observation began.

hhmm - two-digit hour and approximate minute (UTC) when the observation began.

n - CIRS focal plane number: 1, 3 or 4.

Note that the prefixes ISPM, GEO, POI, RIN and TAR have direct analogs to the files in the original CIRS volumes. The ISPM files are found in the DATA/APODSPEC subdirectories and the others are found in the DATA/NAV_DATA subdirectories.

GEO files contain an additional suffix.:

GEOyymmddhhmm_FPn_bbb.*

bbb - the NAIF body ID indicating which moon’s position and viewing geometry is described by the file. The NAIF ID for Saturn is 699. The NAIF IDs for the Saturnian satellites are assigned as follows:

NAIF ID Body NAIF ID Body NAIF ID Body
601 Mimas 607 Hyperion 613 Telesto
602 Enceladus 608 Iapetus 614 Calypso
603 Tethys 609 Phoebe 615 Atlas
604 Dione 610 Janus 616 Prometheus
605 Rhea 611 Epimetheus 617 Pandora
606 Titan 612 Helene 618 Pan

Some binary ISPM files (in the APODSPEC subdirectory) contain an additional suffix:

ISPMyymmddhhmm_FPnx.*

x A, B, C, ….

The suffix changes each time the spectral resolution changes in the middle of a single CIMS request. In most cases, the resolution stays fixed for an entire request, in which case no suffix appears. This suffix is necessary to avoid using variable-length data files.

3. File Types

We refer to the ISPM files as data files and the GEO, POI, RIN and TAR files as metadata files.

Most files come in matched pairs, consisting of one ASCII table (.TAB) and one binary table (.DAT). These are described by the same combined-detached PDS label *.LBL. In general, the ASCII and binary files contain exactly the same information. The ASCII file may be simpler for the user to read but the binary file contains potentially more precise numeric information.

Here is an example:

RIN0407020156_FP3.DAT: binary table;

RIN0407020156_FP3.TAB: ASCII table;

RIN0407020156_FP3.LBL: combined-detached PDS label.

In addition, you will need the following format information to interpret the files:

RIN_ASCII.FMT: PDS ‘include’ file describing the columns and format of the ASCII file.

RIN_BINARY.FMT: PDS ‘include’ file describing the columns and format of the binary file.

They are found in the same subdirectory as the data files. As discussed below, the PDS labels contain a complete, detailed description of the format of each file.

The ISPM files are somewhat exceptional. The spectra are only found in the binary files; the ASCII files APODSPEC/ISPM*.TAB contain the header information about each CIRS spectrum but do not contain the spectra themselves. Also, although the binary ISPM files are occasionally broken up into pieces with suffixes A, B, C, etc., the ASCII file concatenates the information for the entire activity. (A column in the ASCII file indicates which binary file contains the corresponding spectrum).

Here is an example:

ISPM0407020930_FP1.TAB: ASCII table describing the whole observation.

ISPM0407020930_FP1.LBL: PDS label for the above.

ISPM0407020930_FP1A.DAT: binary table containing the first part of the data.

ISPM0407020930_FP1A.LBL: PDS label for the above.

ISPM0407020930_FP1B.DAT: binary table containing the second part of the data.

ISPM0407020930_FP1B.LBL: PDS label for the above.

4. Where to go next

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