next up previous contents
Next: Shift + Add Mode Up: No Title Previous: Standards

Data Storage

  The exposures are written to an external hard disk as .SDF files, which should have up to 2 Gb (3.9 M blocks) free space at the start of your run. Each 256 tex2html_wrap_inline1163 256 frames is 270 kb (530 blocks) large, hence you should be able to store up to tex2html_wrap_inline1117 7000 full sized images on disk, although the amount of free space will often be less than as WHIRCAM data from previous runs are generally not deleted until after the D-tape has been varified. If your exposure times are short, you should consider using a number of exposures per integration to save disk space (see § 3.5.1).

The disk name, directory structure and filename nomenclature are:

where YYYYMMDD is the directory date (eg. 1996 Feb 29 = 19960229), YYMMDD is the filename date (eg. 1996 Feb 29 = 960229), and N is the run number. The IDIR directory contains the array+header data, and it is these files which are written to tape by AUTOFITS (see below). The files in the ODIR directory are just the header information for each frame, and the RODIR directory is where frames read in and/or produced by IRCAM_CLRED are stored (ie Reduced Observations).

At the beginning of each night's observing start AUTOFITS running, which will automatically back-up your data to a DAT D-tape and a C-tape (DAT or exabyte) as each frame is written to disk. AUTOFITS converts the .SDF files to FITS format as it writes them to tape. The C-tape is the observer's copy which you can take home with you.

To use AUTOFITS with WHIRCAM, log onto one of the VAXcluster machines (LPVE, LPVF or LPVG, usually from one of the VT220 terminals in the computer terminal room) as TPCOPY (no password required), type AUTOFITS, and answer all the questions. You can currently write up to four tape copies simultaneously (one D tape and up to 3 C tapes, but remember that more than one C tape must be paid for), and append files to previous nights' data tapes. AUTOFITS will write every file stored in the current IDIR directory, including vector maps (created in Shift+Add integrations) and any reduced data frames you may create there (if you don't want these written to your archive tape, then reduce your data in the RODIR directory).

If you wish to reduce your data at site using IRAF on the unix cluster, you can either re-read your C-tape copy using rfits in IRAF, or else create diskFITS copies using WDFITS in Figaro, and copy these to a unix disk using ftp, followed by rfits in IRAF.

next up previous contents
Next: Shift + Add Mode Up: No Title Previous: Standards

Shaun Hughes
Thu Mar 14 14:48:38 GMT 1996