Down Time

As in the last report, the down time statistics are now based on individual fault reports instead of what was reported in the general end-of-night reports. In Table 1 I give the general down time statistics for period 28.

A total of 63 fault reports were submitted, with an average time lost of 29 min per fault, for a total down time of 1.7% (2.6% on scheduled observing nights). Of these, 37 reported no time lost, 24 reported $<$ 2 hr lost, and 2 reported 2 or more hrs lost.

Table 1: Technical down time statistic period 28: 2003-10-01 to 2004-04-01

Night included	Time lost	Nights	Percentage$^a$	Last period
All nights	1815 min	183	1.7%	3.5%
Scheduled observing nights$^b$	1555 min	98	2.6%	2.3%
Technical nights	180 min	32	0.9%	3.3%
Visitor instruments	80 min	53	0.3%	6.4%
$^a$ Assuming an average of 10 hr per night
$^b$ Excluding technical nights and visitor instruments

This compares to a down time of 3.5% over all nights (2.3% on scheduled observing nights) in period 27 (2003-01-04 to 2003-09-31). For that period 107 faults reports were submitted with an average time lost of 28 min per fault. Of these, 67 reported no time lost, 31 reported $<$ 2 hr lost, and 9 reported 2 or more hrs lost.

Comparing the two periods, there are two things to note. In general, the total number of fault reports has decrease by more than 40%. Secondly, the number of cases with 2 or more hrs lost has decrease a lot with respect to last semester, which largely explains the significant decrease in down time. One could also say that the last semester was in that respect rather out of the ordinary in both the number of faults with more than 2 hrs lost and the total amount of downtime.