1. Directory and File Naming

In this section, we give a brief overview of the rather complicated CIRS file structure.

  • A summary of the various file types is given in the DATAINFO.TXT file in the DATA directory of each volume.

  • A comprehensive description of the file structure and various data ‘fragments’ is given in the Data Product and Label SIS, found in the DOCUMENTS directory on every volume:

2. Directory Structure

  • All of the data is in subdirectories of the DATA directory. Sub-directories typically are named for the type of fragment they contain (e.g., FRV contains FRV files, HSK contains HSK tables, etc.). See the next section for more details on fragments.

3. File Structure Overview

  • The CIRS data set is conceptually one huge table, with time-ordered records (‘rows’), containing many fields (‘columns’). In practice, this large ‘virtual’ table is stored in multple files, known as fragments. The ‘physical’ table is fragmented both in the row and column sense.

  • For a given filename stem (‘fragment’), the data may consist of fixed-length records or a combination of fixed-length and variable-length fields. In the latter case the ‘fragment’ will be composed of two files with the same filename stem but different extensions:

    • .VAR - the file containing variable-length records.
    • .DAT - the file containing fixed-length records. This file contains the location within the ‘.VAR’ file of the variable length data.

Each ‘fragment’ is accompanied by a PDS detached label with the same filename stem and ‘.LBL extension. In the case of a variable length fragment, the two files are described in a single detached label file.

  • Table fragments have name stems of the form: AAAAYYMMDDHH, where AAAA is one of the following fragment type identifiers.

    • **OBS **- Information relating to the instrument data taking settings and the values of warning or indicator flags.
    • **FRV **- Voltages of the central fringe of the white-light interferometer.
    • IFGM- Raw interferogram data.
    • ISPM- Interpolated (resampled) calibrated spectra.
    • **HSK **- Housekeeping data including temperature information required for calibration.
    • IHSK- Interpolated housekeeping data.
    • DIAG- Diagnostic information regarding the raw interferograms.
    • **GEO **- Geometry information.
    • **POI **- Pointing information.
    • **RIN **- Ring-specific information.
    • **TAR **- Targets in the field of view.

YYMMDDHH is time at the start of the data period covered. CIRS data typically is divided into 4-hour blocks at the uncalibrated level and 24-hour blocks at the calibrated level.

4. Where to go next

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