From: Norman Rioux 	 
 Sent:  Fri 3/16/2007 9:05 AM
 To: Siskind, E. J.; Victor J. Sank; J. Eric Grove; Smith, David A.; Erik Andrews; Donald.R.Glenn
 Subject:   Absolute Time Accuracy Solution

Team,

We are working on setting up a discussion with GD on observatory absolute
timing accuracy at the next ISET meeting Tuesday afternoon. GD has a good
handle on causes for the timing errors with GPS on, off, as well as the
incorrect offset with respect to UTC. There are FSW explanations for all of
the behaviors observed. A key feature is that the sub-second information
from the GPS receiver being used in the control algorithm does not have the
tight accuracy associated with the GPS PPS signal and this is propagating
into the errors observed. GD is developing fixes for this. The agenda for
the meeting will be to support GD in reviewing their findings and ensure
that root causes have been completely identified and that the proposed
fixes and verification tests have the highest possible chances of quickly
resolving the problems on the first try.

Stay tuned for a follow up message.

Thanks,

Norman