Down Time

The down time statistics are based on individual fault reports. In Table 1 I give the general down time statistics for period 35. A total of 118 fault reports were submitted, with an average time lost of 11 min per fault, for a total down time of 1.4% ( % on scheduled observing nights). Of these, 80 reported no time lost, 34 reported $<$ 2 hrs lost, and 4 reported 2 or more hrs lost.

Table 1: Technical down time statistic period 35: 2007-04-01 to 2007-10-01

Night included	Time lost	Nights	Percentage$^a$	Last period
All nights	1320 min	183	1.4%	0.7%
Scheduled observing nights$^b$	1145 min	121	1.8%	0.8%
Technical nights	165 min	27	1.1%	0.3%
Service nights$^c$	335 min	24	2.6%	0.6%
Visitor instruments	10 min	17	0.1%	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

This compares to a down time of 0.7% over all nights (0.8% on scheduled observing nights) in period 34. For that period 117 faults reports were submitted with an average time lost of 7 min per fault. Of these, 82 reported no time lost, 35 reported $<$ 2 hr lost, and none reported 2 or more hrs lost.

Although significantly higher than the previous period, the down time is still not very high (it is just above the average over the past 6 semester, and below the average if you go further back). The down time in the last period was very low, and the occurrence of only a few problems makes a significant difference in the overall down time. Specifically, in period 34 there was no fault causing a relatively large ($\ge$2 hr) amount of down time compared to 4 in period 35.