How to Archive Yohkoh Tapes

Tape Codes

The Yohkoh exabyte tapes are received in discrete brown packages from Lockheed. The person there most responsible for getting the tapes to us is probably Greg Slater (slater@sxt.space.lockheed.com). The tapes arrive, usually two or three per envelope, at randomn intervals. They are mailed to Dick Canfield, who passes them on to the designated person. They arrive in roughly, but not strictly, chronological order, approximately two to three months after the data was aquired.

Each tape contains one week of Yohkoh data, and is either data for a new week, or is a re-reformatted version of some previous week. Each tape has label with a code like the following written on it:

                         95_22a.01-1.220
                         /  |    |    |
                       year | version |
                           week    reformatter

The "a" after the week and the "1." before the version number are reserved for future, unknown use and never change. The version indicates whether this is the first version of tape produced for the indicated week, or whether it is an updated version of the data for that week (i.e. a different version of the reformatter program was used). The reformatter number simply indicates which release of the reformatter software was used to process the data. The reformatter release numbers increment by 10. Sometimes a version number of "22" or "17" is written on the label instead of the proper "220" or "170". Thus if a tape was received at a later date with the code 95_22a.02-1.240, this tape would replace the tape above. The tape version number has been known to increase by more than one (from .01 to .03, for example), with no intermediary valued tape having been produced. A Lockheed mystery. The reformatter seems pretty stable now (Nov 95) and most tapes now are only for new weeks.

Logging Recevied Tapes

A list of the latest version of Yohkoh tapes received is stored in /solar/daily/Mees/tape_logs/yohkoh.tape_logs This file is merely a list of the tape codes (as described above) and the date of production that is also written on each tape. There is also room for listing when and if a backup was made or for making comments about a particular tape (e.g. "replacement for corrupted tape"). Currently, the tapes are not checked to see if they are readable or even if there is data on the tape (in the past, we have received at least one tape that was blank).

As each batch of tapes are received, the new tape code and production date are added to the list. If the tape is an updated version of an older tape already on the list, the tape code and date from the new tape are substituted for the older tape on the list. I also make a backup of the current list of tapes (current.yohkoh.tape_logs.backup) and a copy of the latest version before the most recent update (previous.yohkoh.tape_logs.backup). First edit the yohkoh.tape_logs file, adding the new tapes. Then copy the "current" file onto the "old" file. Then copy yohkoh.tape_logs onto the current file. Or in UNIX speak:

akala>% cd /solar/daily/Mees/tape_logs
akala>% vi yohkoh.tape_logs		#add new tapes 
akala>% cp current.yohkoh.tape_logs.backup previous.yohkoh.tape_logs.backup
akala>% cp yohkoh.tape_logs current.yohkoh.tape_logs.backup

This way there are always got one or two backups in case things really get munged up and someone can always figure out which were the most recent tapes to arrive.

Tape Storage

When the tapes have been catalogued on the the list, they are put in the data archives, presently upstairs in the C-building. The tapes are filed in different drawers according to year and sorted by week within a given drawer. Any new tapes are added in the appropriate place in the sequence in the appropriate drawer. Replacement or new versions of a given week take the place in the sequence of the tape which they are replacing. The superceded tape is put in a drawer of old Yohkoh tapes in different drawer (currently at the bottom of the MCCD cabinet in the back row of exabyte/card filing cabinets).

This page written by Kevin Reardon - 06 November, 1995
The current Yohkoh data archivist is Litao Jiao.
Last Updated - 13 November, 1995