f/48 Special Calibrations
The recent successful operation of the f/48 relay has prompted some effort to characterize the long-slit spectrograph and detector in support of f/48 long-slit spectroscopy. These calibration proposals will provide some measurements of the slit location, detector sensitivity, slit throughput, and geometric distortion with the expected accuracies summarized in the f/48 calibration summary [Postscript, 55kb].
The performance of the FOC+COSTAR system has been characterized in detail using a combination of ground-based and in-flight tests. After COSTAR deployment, an extensive calibration program was carried out (SMOV) to describe the performance of what could be considered, to all intents and purposes, a new instrument. At that point, the scientific program was enabled. The Cycle 4 calibration program then completed this initial effort and fully characterized the FOC+COSTAR performance. In Cycle 6, we are in a routine situation, and our calibration program is divided into two parts:
- a set of monitoring tests, whose aim is to maintain the calibration level previously achieved (e.g. pointing accuracy, geometric distortion, flat fields), or
- to discover possible variations in performance a number of dedicated tests designed to maximize the scientific output of the instrument.
These tests were designed after having carefully reviewed the observing proposals to be executed during the current cycle, and would, for example, provide accurate PSFs and check the detector response at certain wavelengths, or characterize special capabilities not previously calibrated. In the calibration summary table [PostScript, 55 kb], we provide a list of the calibration tests which are being performed in Cycle 6, with their objective outlined. An extensive calibration program has been designed, after checking all the individual requirements, to ensure that the best science is achieved with the FOC.
- The Routine Calibration Programs
- The routine calibration programs are designed to monitor those aspects of FOC performance that are believed to be subject to time variation. Typically, observations are made at 3 month intervals to verify that the performance has not changed significantly, and then warn users if a significant difference is found.
- The Special Calibration Programs
- The special calibration programs are designed to offer a more detailed calibration of modes or observation types and represent a class of calibration observations that may be executed once with the results expected to be valid over a long time base. Previous special calibrations, as well as monitoring programs, have resulted in calibration accuracies as discussed in Section 11.2 of the FOC Instrument Handbook.
Should your program require calibration accuracies that are not obviously satisfied by the values listed in the FOC Handbook, then you should contact STScI for guidance. Individual GO programs requiring special calibrations must directly request these observations as part of their Phase I proposal.