Down Time

The down time statistics are now based on individual fault reports instead of what was reported in the general end-of-night reports. To keep in line with previous reports, I give in Table 1 the general down time statistics for period 27.

A total of 107 fault reports were submitted, with an average time lost of 28 min per fault, for a total down time of 3.5% (2.3% on scheduled observing nights). Of these, 67 reported no time lost, 31 reported $<$ 2 hr lost, and 9 reported 2 or more hrs lost.

Table 1: Technical down time statistic period 27: 2003-04-01 to 2003-09-31

Night included	Time lost	Nights	Percentage$^a$	Last period
All nights	3042 min	183	3.5%	1.5%
Scheduled observing nights$^b$	1267 min	114	2.3%	2.1%
Technical nights	370 min	23.5	3.3%	0.4%
Visitor instruments	1405 min	45.5	6.4%	0.0%
Service nights$^c$	746 min	22	7.1%	$-$
$^a$ Assuming an average of 8 hr per night
$^b$ Excluding technical nights and visitor instruments
$^c$ Not included are the 23.5 SOFIN nights

This compares to a down time of 1.5% over all nights (2.1% on scheduled observing nights) in period 26 (2002-01-10 to 2002-03-31). For that period the numbers were based on the End-Of-Night reports where in 50 End-Of-Night faults were reported with an average time lost of 32 min per fault. Of these, 29 reported no time lost, 19 reported $<$ 2 hr lost, and 2 reported 2 or more hrs lost.

Comparing the two periods, there are two things to note. In general, the number of fault reports is more than double that of the number of End-Of-Night reports which reported problems in the last semester. This is at least partly because in the past some of the End-Of-Night reports contained more than one fault, but we also believe that the system has made it easier to submit problems (as is also indicated by the fact that twice as many fault reports with no time lost were reported compared to the End-Of-Night reports which reported faults with no time lost). The second thing to note is that the number of cases with 2 or more hrs lost has increase a lot with respect to last semester, which largely explains the significant increase in down time.