IRCAL Data and FITS Files
Data File Names and Directory
IRCAL data are written as FITS files to ircalbox2 directory /data/today/ (which is a link to /data/ircal/YYYY.MM.DD, e.g. /data/ircal/2007.02.16/). This directory is accessible from gouda and karnak by the directory path /data/ircal/. Each day at noon, a new directory is created for the coming night's data.IRCAL file names are ircalxxxx.fits where xxxx is 0000 through 9999. For example, exposure number 51 will be in a file named ircal0051.fits. If you take data in imstream mode, the filename is imstreamX where X is the first number of the 100 exposure block. For example, if you start a 200 frame exposure sequence in imstream with exposure file number 349, the output filenames will be imstream349 and imstream449. imstream files are specially formatted FITS files designed for fast readout and writing to disk. For more information about imstream files, contact a support astronomer.
The data are automatically copied to the on-line data archive, http://mthamilton.ucolick.org/data/, shortly after being acquired. If you need to set or reset your data archive password, contact a Support Astronomer.
Data Format
Data are written to FITS files. The recorded value of each pixel is the product of the counts per coadd exposure time, number of reads, and number of coadds.total counts per pixel = counts/coadd * coadds * nreads
Reference Biases
Reference biases are stored dark frames for the most often used exposure times and number of reads. If you take an exposure using the same exposure time and number of reads as a reference bias, that reference bias frame is subtracted from the data before writing the FITS file and being displayed in the ircaldisplay window.Reference bias files are archived in case you wish to add them back into your data. The reference bias file name is listed in the FITS header under the BIASFILE keyword.
FITS Header Keywords
IRCAL FITS files have some unique header keywords to describe the data, state of the IRCAL instrument, and the state of the Adaptive Optics system.| Keyword | Description |
|---|---|
| Exposure Parameters | |
| EXPTIME | Exposure time per coadd (seconds) |
| COADDTIM | Exposure time per coadd (milliseconds) |
| NREADS | Number of reads |
| NRESETS | Number of resets |
| NCOADDS | Number of coadds |
| Motor Positions | |
| FILTER1 | Filter wheel 1 contents |
| FILTER2 | Filter wheel 2 contents |
| APERTURE | Aperture wheel contents |
| WHEELS | Wheels by index position |
| Readout Mode Details | |
| BIASFILE | Reference bias file subtracted |
| MODE | Mode summary string from ircalui: COADDTIM:NREADS |
| READMODE | Detector Readout Mode (1=3us,2=1us,3=Fast,4=Hybrid) |
| READMD_S | Detector Readout Mode Description |
| SUBARRX | Subarray X size (per quadrant) |
| SUBARRY | Subarray Y size (per quadrant) |
| CCDSEC | Subarray location in IRAF CCDSEC notation |
| IMSTREAM | Imstream mode? (0=no, 1=yes) |
| AO Parameters | |
| AO_MODE | AO Guide Star Mode: NGS or LGS |
| TTMODE | tipTilt Mode, ngs or lgs |
| AOLOOP | AO loop status |
| TTLOOP | Tip/Tilt loop status |
| AOGAIN | AO loop gain |
| AOINT | AO integrator gain |
| AORATE | AO frame rate |
| TTGAIN | Tip/Tilt loop gain (NGS TT loop, or LGS laser uplink) |
| LTTRATE | Tip/tilt sensor frame rate |
| LTTFOV | Tip/tilt sensor field of view |
| LTTGAIN | Tip/tilt sensor gain |
| WFSND | AO WFS ND wheel |
| TTSDN | Tip/Tilt sensor ND wheel |
| NOD_NS | Cumulative nod north-south, arcsec |
| NOD_EW | Cumulative nod east-west, arcsec |
| FIBER | Cassegrain focus fiber position |
| WPLAT | Waveplate angle |
| WPLIN | Waveplate insertion |
Elinor Gates Last modified: Thu Jan 19 11:53:12 PST 2012