Queued Service Observations with CFH12K:

Semester 2002B Report

02/03/03

 

A - Introduction

The Queued Service Observing (QSO) Project is part of a larger ensemble of software components defining the New Observing Process (NOP) which includes NEO (acquisition software), Elixir (data analysis) and DADS (data archiving and distribution). The semester 2002B was the last time CFH12K was used for the NOP system. Starting in 2003A, MegaPrime will replace CFH12K. Due to some delays in the MegaPrime engineering and commissioning, addtional nights were made available for QSO and CFH12K in 2002B. This report presents some statistics and comments on this fourth semester of the queued service observing mode.

B - General Comments

Contrary to the last semester, weather was better than usual during the semester 2002B. However, during certain periods, the seeing was highly variable and we experienced certain periods when the seeing was extremely bad (1.5" or even worse). This resulted in very good statistics for some of the snapshots programs. Fortunately, additional nights due to delays with Megaprime resulted in exceptional statistics for the completion level of programs. Grade A programs were 100% completed and B programs were finished at 94% ! Even C programs were completed at a level of 64%. As with the past semesters, all of the observations requesting photometry have been calibrated.

In October/November, we experienced a technical problem related to the chip#2 inCFH12K. Due to some bad connection within the camera, abnormal structures could be seen on the chip for about 10% of the data. This did not affect most of the programs and the problem was fixed later during the semester. One night was lost due to a problem with a motor in the prime focus bonnette.

1. Technically, the entire chain of operation, QSO --> NEO --> TCS, is very efficient and robust. This is a complex system and the time lost to glitches now is basically negligible. Almost 19000 exposures have been taken through the QSO/NEO system since 2001A...

2. The QSO concept is sound. With the possibility of preparing several queues covering a wide range of possible sky conditions in advance of an observing night, a very large fraction of the observations were done within the specifications. The ensemble of QSO tools allows also the quick preparation of queues during an observing night for adaptation to variable conditions, or in case of unexpected overheads. The observing tool offers the possibility to load a pending queue and prepare it (for instance, by including the focus sequences) while another one is being executed so that the transition between queues is done rapidly. The new version of the tool is also very flexible and allows the selection of specific observations within the queue resulting in a greater observing efficiency.

3. QSO is well-adapted for time-constrained programs. The Phase 2 Tool allows the PIs to specify time constraints. We had three difficult monitoring programs with those constraints during 2002B. Except for one program with special constraints, we were able to carry out the observations in a timely manner. However, the impact of these programs on the other regular QSO programs cannot be understated. The number of time-constrained programs should be restricted during a semester.

4. Very variable seeing and non-photometric nights represent the worse sky conditions for the QSO mode. During 2001A and 2001B, we did not have enough programs requesting bad seeing or non-photometric conditions. In 2002B, we had two "shapshot" programs available (programs requesting mediocre conditions) and we used them very frequently during the bad seeing conditions. In fact, one of the program was done at more than 90%. In total, about 32 hours of integration time was spent on snapshot programs, 10% of the total QSO time. This reflects an abnormal semester regarding seeing conditions. Unfortunately, we had very few programs requesting 1" this semester. The availability of Skyprobe and real-time measurements of the transparency is extremely valuable and regularly used do decide what observations should be undertaken.

C - Global and Program Statistics

The following table presents some general numbers regarding the queue observations for 2002B (C, F, H, K, time, excluding snapshot programs):

Parameter
Number
Total number of Nights
58
Nights fully lost to weather
6 (10%)
Nights lost to technical problems
~3
Nights considered photometric
32 (55%)
QSO Programs Requested
36
QSO Programs Started
36
QSO Programs Completed
28
Total I-time requested (hrs)
348
Total I-time validated (hrs)
314.2
Queue Validation Efficiency
~85%

Remarks:

 

D - Agency Time Accounting

Balancing of the telescope time between the different Agencies is another constraint in the selection of the programs used to build the queues. The figure below presents the Agency time accounting for 2002B. The top panel presents the relative fraction requested by the different agencies, according to the total I-time calculated from the Phase 2 database. The bottom panel represents the relative fraction for the different Agencies, that is, [Total I-Time Validated for a given Agency]/[Total I-Time Validated]. As showed in the plots, the relative distribution of the total integration time of validated exposures between the different was well balanced at the end of the 2002B. For the French Agency, the 3% fraction below what was requested was due to a voluntary decision from the QSO Team. The fraction validated for France has exceeded what was requested for previous semesters so a longer term balance was achieved. The discrepnacy comes from a long C program that was at 40%.

 

E - Additional Remarks

Our fourth semester with the queue mode with CFH12K was quite successful, with basically all A and B programs completed.