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Completion expectations for queue programs

Here we give a guide to expectations for the completion of Band 1, 2 and 3 programs. The three bands are best described as (i) top priority, intended to be executed and if possible completed (ii) lower priority, but intended to be executed to some reasonable completion rate and (iii) fillers, which should, in order to get data, be able to take worse observing conditions and be particularly aware of other constraints that may affect their execution.


We fill the queue to a level consistent with the above descriptions in a semester with reasonable weather. In case of a semester with poorer-than-normal conditions or significant instrumental or telescope problems, we attempt to protect programs in Band 1 as best we can (in the sense that any good weather will go to those programs). It is a clear signature of bad weather that Band 3 completions exceed those in the other two bands, and in such cases, programs in Band 2, which still tend to have tight observing conditions requirements, often lose out. The above analysis excludes target of opportunity programs, for which the completion rate depends on the rate of triggers and which we cannot therefore control, and block-scheduled instruments or observing modes, where statistics vary a lot (up and down) due to coincidences between observing blocks and weather.


The figures below show completion statistics in the three bands, north and south, over the period since the commencement of multi-instrument queue observing in 2005. In all cases, the grey line is the fraction of time lost to technical faults, and the red line is the ratio of the advertised available time to the actually usable time in the semester (which has a mean level corresponding to weather loss). The histogram in all cases represents the fraction of programs in the band which achieved a completion rate of 80% or above. These figures should serve as a guide to what to expect in terms of completion rate.



Gemini North 

The significant recent feature at Gemini North was the shutter failure of 2013B and 2014A; Band 1 completions were protected against this, but Band 2 suffered badly. 




Gemini South 

The significant recent feature at Gemini South has been a combination of weather loss, earthquakes and laser problems in 2015B and 2016A; even Band 1 was not immune to these problems. 






Breakdown: good and bad semesters


As seen above, Gemini North in 2014A presented a particularly bad semester, with shutter failure and weather reducing the amount of available time significantly.  2014B represented a more "average" semester, with good Band 1 completion rate and an understandable distribution between Band 1,2 and 3. Note that in a "reasonable" semester, a good fraction of programs reach 100% completeness.