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.
|Night included||Time lost||Nights||Percentage||Last period|
|All nights||1815 min||183||1.7%||3.5%|
|Scheduled observing nights||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%|
|Assuming an average of 10 hr per night|
|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.