| Description: | The MPL PC clock was noted to be off (slow) by more than an hour over a several day
period. It has previously been noted that the time synchronization program "D-4" fails to
update the PC clock under certain circumstances. As a result, the program "D-4" was replaced
by "AboutTime" on 2/5/2004.
The specifics of this problem are not well understood. It turns out that the instrument
has TWO clocks on the instrument computer display - one being displayed by the MPL
software and the other being the PC clock displayed in the lower right-hand corner of the
screen. The MPL software clock was the one that is noted on daily rounds and was never off by
any amount. Apparently the only clock that was off was the computer clock.
What is clear is that between the time the MPL computer was installed on 11-11-2003 and
the CM log on 1-06-2004 the MPL clock exhibited a discrepancy of over 1 hour and 20
minutes. What is not clear is whether this clock discrepancy was also applied to the data time
stamps. Furthermore, seven days later the MPL clock exhibited only a 1.77 second drift.
Not exceptional at all, and not in line with the previous discrepancy of more than 4800
seconds over a span of 57 days.
Attempts to identify gradual correctible clock drift in the MPL data were not successful.
As a worst-case scenario, the MPL data may be inappropriately time-stamped by as much a
1 hour 20 minutes and 41 seconds slow relative to UTC between the dates of 2003-11-11 and
2004-01-06. After this time until 2004-02-05 time synchronization was maintained within
a few seconds a day with local observer assistance. |