Down Time

The down time statistics are based on individual fault reports. In Table 1 I give the general down time statistics for period 40. A total of 87 fault reports were submitted, with an average time lost of 6 min per fault, for a total down time of 0.5% (0.5% on scheduled observing nights). Of these, 58 reported no time lost, 29 reported $<$ 2 hrs lost, and none reported 2 or more hrs lost.

This compares to a down time of 0.7% over all nights (0.8% on scheduled observing nights) in period 39, and 0.2% over all nights (0.2% on scheduled observing nights) in period 38. Of the 93 fault reports reported in period 39, 63 reported no time lost, 30 reported $<$ 2 hrs lost, and none reported 2 or more hrs lost. Of the 88 fault report in period 37, 66 reported no time lost, 22 reported $<$ 2 hrs lost, and none reported 2 or more hrs lost.

Table 1: Technical down time statistic period 40: 2009-10-01 to 2010-04-01

Night included	Time lost	Nights	Percentage$^a$	Last semester	Last winter
All nights	555 min	182	0.5%	0.7%	0.2%
Scheduled observing nights$^b$	455 min	132	0.5%	0.8%	0.2%
Technical nights	35 min	23	0.2%	1.1%	0.2%
Service nights$^c$	120 min	39	0.5%	0.9%	0.2%
Visitor instruments	65 min	27	0.4%	0.2%	0.0%
$^a$ Taking the average length of time within nautical twilight. Exact numbers for each night
are used when looking at ``All nights''
$^b$ Excluding technical nights and visitor instruments
$^c$ Excluding service nights with SOFIN

Also with reference to Table 2, the general conclusion is that the level of downtime is rather stable with similar amounts of fault reports and no major failures during the past 3 semesters (at the time of writing the last fault report listing more than 2 hours down time is from more than 2 years ago).