South have been challenging , especially 2015B , which we discuss later ). Semester 2014A at Gemini North was unusually poor , as bad weather and dome shutter failures hit us hard ; but we recovered and are now back at roughly average performance compared to the last five years .
The two charts in Figure 18 show histograms of queue program completion at Gemini South 2012A and Gemini North 2014A .
The very sparse tail of programs below the 100 % -complete bin in the “ exceptional ” semester compares with large numbers of programs ending at 90 % and below in the “ bad ” semester . Numerous programs were not started at all in 2014A at Gemini North .
Note that the queue preferentially protects Band 1 observations in a “ bad ” semester , as it should . In the “ exceptional ” semester at Gemini South the Band 1 completion exceeded that of Band 2 , which in turn exceeded that of Band 3 . In a “ normal ” semester ( neither exceptional nor terrible ) results lie somewhere between these extremes , with Band 1 completion higher than that in the other two bands .
While Band 2 completion usually exceeds that in Band 3 during a “ normal ” semester , it is a signature of bad weather that in some semesters Band 3 , in which programs can typically take poorer conditions , does
January 2017 | 2016 Year in Review
better . As you can see in Figure 18 , in recent semesters , Band 3 has done well relative to the others at Gemini South ; again , this is a symptom of weather adversity .
Addressing Weather Loss at Gemini South
Weather conditions at Gemini South repeat themselves fairly regularly across each semester . In the past we didn ’ t make any allow-
GeminiFocus
Figure 18 . In 10 % bins , the fraction of programs ending the semester at a given completeness level . Top : an unusually good semester ( Gemini South 2012A ). Bottom : an unusually bad semester ( Gemini North 2014A ).
Figure 19 . Percentage of time lost to weather at Gemini South . This pattern is quite reproducible from year to year . We now take better account of it in the time allocation process ; we no longer overload the mid-year months ( May-September ), and allow more programs into the southern summer time .
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