``I've Got This FITS Tape''

Certain combinations of magnetic tape produced on one model of tape drive but read on a different model seem to generate parity errors that are detected by the MAG_ library that FITSIN uses. However, this doesn't mean that you won't be able to read your FITS tape. The UNIX tape-reading commands seem less sensitive to these parity errors.

Thus you should first attempt to convert the inaccessible FITS files on tape to disc files using the UNIX dd command, and then use the FITSDIN application to generate the output NDF or foreign format. For example to convert a FITS file from device /dev/nrst0 to an NDF called ndfname, you might enter

     % dd if=/dev/nrst0 ibs=2880 of=file.fits
     % fitsdin files=file.fits out=ndfname
     % rm file.fits

where file.fits is the temporary disc-FITS file. The 2880 is the length of a FITS record in bytes. Repeated dd commands to a no-rewind tape device (those with the n prefix on OSF/1 and the n suffix on Solaris) will copy successive files. To skip over files or rewind the tape, use the mt command. For example,

     % mt -f /dev/rmt/1n fsf 3
           :       :       :
     % mt -f /dev/rmt/1n asf 4

moves the tape on device /dev/rmt/1n forward three files, then moves to the fourth file,

     % mt bsf 2

moves back two files on the default tape drive (defined by the environment variable TAPE), and

     % mt -f /dev/nrmt0h rewind

rewinds to the start of the tape on device /dev/nrmt0h. Thus it is possible to write a script for extracting and converting a series of files including ranges, just like FITSIN does.

If the above approach fails, try another tape drive.