STUDY SUMMARY - IPMU

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<strong>SUMMARY</strong> REPORT WIDE FIELD FIBER-FED OPTICAL MULTI-OBJECT SPECTROMETER (WFMOS) Figure 3.13-3: Read noise versus dwell time for three DECam CCDs manufactured by LBNL/DALSA. Courtesy of Juan Estrada, Fermi Lab. Fabrication and testing of 84 CCDs has been budgeted to produce 6 science-grade devices, safely more than the yield experienced by the 62 CCD Dark Energy Survey Camera. Images will be dithered in the spatial direction so that cosmetic defects will be removed along with cosmic rays, allowing specifications for cosmetic defects to be relaxed. Three hundred-μm thick Hamamatsu CCDs without delta doping (but possibly with JPL’s multilayer coating design) are offered as a technology fallback option, although this route appears to be more expensive (unless wavelength coverage or multiplex advantage is sacrificed) and delivers lower performance at both wavelength extremes. 3.14 System Software The WFMOS software is responsible for: • Preparing and managing WFMOS observations in advance. • Selecting the observations to be made each night. • Top-level control of WFMOS observations at the Subaru observatory. • Providing engineering and test software. • Batch processing of WFMOS data in real time to monitor survey data quality. 3.14.1 Observation Preparation WFMOS will be capable of observing 2,400 science targets simultaneously in a single observation and, in total, a given WFMOS survey will yield data for up to 4 million science targets. Observers need a means of automating the generation of their surveys. The WFMOS observation preparation software will provide the observer with facilities for selecting the science targets that make up a WFMOS survey and arranging those targets into a collection of schedulable observations. It will also provide configuration software for matching targets efficiently to fibers. The end product of the observation preparation software is a database of observation commands waiting to be scheduled. 3.14.2 Observation Management The WFMOS software provides facilities for managing prepared observations. Priorities can be assigned, extra science targets can be added to observations that have spare fibers, and obser- 53
<strong>SUMMARY</strong> REPORT WIDE FIELD FIBER-FED OPTICAL MULTI-OBJECT SPECTROMETER (WFMOS) vations can be modified to bring them up to date with any changes in instrument capabilities. Nights of WFMOS observations are scheduled by the Subaru observatory. 3.14.3 Observation Execution The WFMOS control software runs at the Subaru observatory and interacts with the local computer infrastructure through Subaru’s SOSS software. Descriptions of the WFMOS observation descriptions required for a particular night are extracted from the database created by the observation preparation software and may be executed by the observer or observatory staff member. The WFMOS control software is responsible for coordinating all the underlying WFMOS subsystems. The control hierarchy and block diagram are shown in Figures 3.14-1 and 3.14-2, respectively. The control software manages the sequence of operations needed to make each observation, acquire the data and save it to the data store. A typical sequence would be: • Acquire the target field with the telescope and configure the spectrograph. • Use the feedback provided by the metrology camera to configure the fiber positioner. • Acquire guide stars using the autoguiders. • Acquire data with the science detectors. • Collect and store FITS header information. • Send the data to the data pipeline. The sequencing steps are overlapped wherever possible to maximize the survey efficiency; for example, the next target can be acquired while the science detectors are still reading out. The WFMOS control software will manage the subsystem interfaces shown in the block diagram and ensure all the interfaces meet the required standards of maintainability. A Pythonbased communication infrastructure will be provided. 3.14.4 Engineering and Test Software Engineering software will be used to set up and calibrate the instrument during integration and testing, and when WFMOS is installed on the Subaru telescope. The end product of the instrument calibration software is an instrument description that is shared with all the WFMOS software systems. The engineering software will allow the instrument description to be kept up to date; for example, if any fibers or positioners break or if the spectrograph has new components installed. The WFMOS software will provide diagnostic and testing facilities that can be used throughout the development and testing phases of the instrument. Automatic test scripts will ensure that instrument components are tested frequently and rigorously. The engineering facilities will remain after delivery to provide diagnostic tools for investigating any faults and problems. 54
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STUDY SUMMARY - IPMU

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