I had a look at factors that impact our duty cycle, starting at midnight UTC Sept 10th until 2:43 UTC Sept 18th (the latest time available when I started downloading data.) I choose this time because there were fewer of the commisioning activities that maade it hard to get a good picture of the duty cycle in the earlier weeks of ER8.

• We were in the nominal low noise state for 68% of the week, although this includes about 10 hours of time when the data quality was very poor because of a beckhoff failure which introduced a 2Hz comb. (21530, 21555)
• We were not attempting to lock (in DOWN or READY) for 13.7% of the week.  This included earthquakes, alignment (at least 4% of the week), and time when we were down for beckhoff troubleshooting (about 9 hours or 5% of the week).
• We are still spending about 8% or our time locking DRMI. The median time to lock DRMI is still 5 minutes, and we still have a handfull of long attempts (2 and a half hours was the longest this week)
• Our lock acquistion sequence is more reliable than it was.  Out of 49 DRMI locks, 33 survived to resonance, 28 to DC readout, and 23 to nominal low noise.  This is an improvement over the situation durring ER7 when about 1 in 5 DRMI locks survived to the low noise state.
• The third plot shows a histogram of the length of our low noise locks.  Half of our locks have been less than 5 hours long, with the longest 25 hours. 

Ground motion

• Although we think that we have improved our ability to lock on windy days, the third attachment shows a plot of wind vs duty cycle which does not seem to have changed much since ER7 (see the equivalent plot for ER7 here).  The low wind speed and high wind speed points are based on small amounts of data. This week has been less windy than normal, with winds above 15 mph only 15% of the time.
• There is also a similar plot for the Z direction blrms of low frequency ground motion, which should help us understand the impact of earthquakes.  We've had many locklosses durring even small earthquakes this week and have had trouble relocking until the ground calms down.  I am not sure about the units on this channel, it is calibrated but it doesn't seem to agree with the DMT monitor on the wall.  I will update this entry when I know.  (hints?)

It seem that we've taken much of the low hanging fruit in making our locking sequence more robust, while there are still parts that could be speed easily up the gains to be had from doing that are pretty small.  Probably the most important thing we can do to improve the duty cycle now is to figure out why we are loosing lock durring relatively small earthquakes.  Another alog about that comming soon.