Down Time

The down time statistics are based on individual fault reports. In Table 1 I give the general down time statistics for period 31.

A total of 101 fault reports were submitted, with an average time lost of 24 min per fault, for a total down time of 2.8% (2.3% on scheduled observing nights). Of these, 58 reported no time lost, 38 reported $<$ 2 hrs lost, and 5 reported 2 or more hrs lost.

Table 1: Technical down time statistic period 31: 2005-04-01 to 2005-10-01

Night included	Time lost	Nights	Percentage$^a$	Last period
All nights	2430 min	183	2.8%	1.2%
Scheduled observing nights$^b$	1390 min	128	2.3%	0.9%
Technical nights	90 min	26	0.7%	4.1%
Service nights$^c$	790 min	28	6.3%	3.4%
Visitor instruments	950 min	29	6.8%	0.4%
$^a$ Assuming an average of 8 hr per night
$^b$ Excluding technical nights and visitor instruments
$^c$ Excluding service nights with SOFIN

This compares to a down time of 1.2% over all nights (0.9% on scheduled observing nights) in period 30. For that period 84 faults reports were submitted with an average time lost of 16 min per fault. Of these, 58 reported no time lost, 24 reported $<$ 2 hr lost, and 2 reported 2 or more hrs lost.

Comparing to the last few semesters the overall downtime is significantly higher. The main difference with the last few period is that the 2 main problems that occurred were difficult to solve and caused downtime over several nights. One of these problems occurred during a service observing run and one during an observing run with a visiting instrument, which caused the down time for these categories to be very high.