Time Correlation File (TCF) task

Background

The On-Board Time (OBT) needs to be adjusted/changed on occasion. There are three types of OBT changes: coarse, phase and frequency. The first two are only done after emergencies where our OBT is interrupted. A frequency adjustment is done every few months when necessary to avoid OBT drift away from actual time. When any of the three are done, the information is logged into the Time Correlation Log file (the .DAT file in the ecs@soc:/ftp/ancillary_data/tcf), which also needs to be submitted for serving on the web at URL http://sohowww.nascom.nasa.gov/data/ancillary/time/.

Doing the task

The file should be checked every workday, even though the file is usually only updated every three months. The task is best done on ecs@soc, although the daily checkup can also be done from a mcsoc account. The task workflow is as follows:

1. Change current working directory to /ftp/ancillary_data/tcf. The shortcut for this is the command tcf.
2. Give the command tail *.DAT. This will display the last 10 lines of the Time Correlation File:

   soc $ tail *.DAT                                                  
   2006-096-19:37:04.9 OBT FREQ ADJUST:        Delete 1 tick every     425449 cycles (   -11061.674 secs)   KNK11000 FFF98217       
   2006-115-16:11:21.5 OBT FREQ ADJUST:        Delete 1 tick every     438276 cycles (   -11395.176 secs)   KNK11000 FFF94FFC       
   2006-158-17:09:37.6 OBT FREQ ADJUST:        Delete 1 tick every     458498 cycles (   -11920.948 secs)   KNK11000 FFF900FE       
   2006-297-20:05:00.4 OBT FREQ ADJUST:        Delete 1 tick every     442631 cycles (   -11508.406 secs)   KNK11000 FFF93EF9       
   2007-186-16:17:27.3 OBT FREQ ADJUST:        Delete 1 tick every     538784 cycles (   -14008.384 secs)   KNK11000 FFF7C760       
   2007-316-20:30:22.5 OBT FREQ ADJUST:        Delete 1 tick every     457361 cycles (   -11891.386 secs)   KNK11000 FFF9056F       
   2008-093-17:28:54.5 OBT FREQ ADJUST:        Delete 1 tick every     540272 cycles (   -14047.072 secs)   KNK11000 FFF7C190       
   2009-078-19:47:51.3 OBT FREQ ADJUST:        Delete 1 tick every     595166 cycles (   -15474.316 secs)   KNK11000 FFF6EB22       
   2009-084-19:31:21.5 OBT FREQ ADJUST:        Delete 1 tick every     727099 cycles (   -18904.574 secs)   KNK11000 FFF4E7C5       
   2009-215-18:07:12.0 OBT FREQ ADJUST:        Delete 1 tick every     804931 cycles (   -20928.205 secs)   KNK11000 FFF3B7BD       
       

3. Compare the Day-of-the-Year (DOY; 215 in the above example) with the DOY/date of the latest change date logged on the SOC logbook's inside cover. If the change displayed on the file is more recent, do the following (otherwise no actions are needed):
4. Log the date from the file to the SOC logbook. Include both the date and the DOY for easier comparison.
5. On the soc_interface toolbar at the top of (usually) the socop1 workstation's screen click on the CDHF Support button.

   

6. Left-click once on the button that says Time Correlation Log -- SEND...

   

7. A window will pop up with the name of the .DAT file, the word YES or NO (probably NO if the date/DOY was different), and a box next to the word INCLUDE that may or may not be checked.

   

8. Make sure the box is checked and left-click once on the Send button at the bottom of the window.
9. After a minute or two, the word NO should change to YES. At this point, click the Cancel button; you are done with this window.
10. Close the CDHF Support Functions menu by double-left-clicking on the symbol in the upper left-hand corner.