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: http://www.stsci.edu/instrument-news/handbooks/nicmos/c14_calplan.doc5.html
Дата изменения: Thu Aug 7 20:42:47 1997 Дата индексирования: Tue Feb 5 12:21:35 2013 Кодировка: Поисковые слова: arp 220 |
The Cycle 7 calibration plan consists of routine monitoring and special calibration programs as well as of contingency calibration programs that will be executed only in the event the cameras show large physical displacements. NIC3 specific calibration programs are also included in the calibration plan. These programs will be executed when scientific observations with NIC3 are enabled.
http://www.stsci.edu/ftp/instrument_news/NICMOS/nicmos_doc.html
The calibration programs may each be examined by using the ID number and the HST Program and Schedule Information Page:http://presto.stsci.edu/public/propinfo.html
Detector Performance
All three detectors will be characterized to the same extent. High quality darks will be obtained for all requested MULTIACCUM sequences during June and early July 1997 (proposals ID 7703 to 7710). Changes in the detectors performance will be monitored with a monthly periodicity (proposal ID 7596). Darks will also be obtained for a limited subset of ACCUM exposure times (proposal ID 7688). Other ACCUM exposure times will require interpolated dark current subtraction that may be less satisfactory. Flat Fields
High quality internal lamp flat-fields for all NIC1 and NIC2 polarizers, broad- and medium-band filters will be obtained in July 1997 (proposal ID 7690). The temporal evolution of the pixel-to-pixel response as a function of camera and wavelength will be monitored once a month using a subset of NIC1 and NIC2 filters. No data will be taken for NIC3 filters until the camera is back into PAM focus range, or close enough to enable NIC3 science observations. Photometry
A preliminary photometric calibration of NICMOS filters, based on a limited set of observations, has been achieved during SMOV. Photometric observations of standard stars will be obtained in all NIC1 and NIC2 filters as part of the Cycle 7 calibration plan (proposal ID 7691). Images of two HST absolute standards, one white dwarf (G191-B2B) and one solar analog (P330E) will be obtained as part of this program. The spectral and photometric characteristcis of G191-B2B and P330E are fully described in Bohlin, Colina & Finley (1995) and in Colina & Bohlin (1997), respectively. In addition, images of a bright red star (OPH-S1) will be obtained to measure possible red-leaks in the filters, in particular the narrow filters at the short wavelength range of NICMOS. Thermal Background
The absolute level and stability of the thermal background as seen by the NICMOS cameras has already been measured as part of the SMOV program. The Cycle 7 calibration program will extend the SMOV program with images obtained in NIC2/F237M and NIC3/F222M filters (proposal ID 7611). Images will be taken during June and July 1997 as pointed parallel observations to map possible changes in the thermal backgorund as a result of temperature changes in HST optics. An extended program is on hold and would only be executed if additional measurements are required to fully characterize the stability of the thermal background. Polarizers
The instrumental polarization and zero position angle of NIC1 and NIC2 polarizers will be measured by taking images of two bright near-infrared polarized standards HDE283812 and CHA-DC-F7. The photometric and polarization characteristics of these two standards are found in Whittet et al. (1992). Changes in the polarization as a function of position within the chip will also be measured by moving one of the polarized targets in a spiral pattern across the chip. Additional images of the HST unpolarized standards HD64299 and BD+32d3739 will also be taken. The photometric and polarization properties of these two standards are found in Turnshek et al. (1990). Grisms
The wavelength calibration and absolute sensitivity of the grisms will be measured once NIC3 science observations are enabled. The wavelength dispersion solutions for each grism will be obtained by observing a compact planetary nebula (proposal ID 7695). Changes in the dispersion solution as a function of location in the detector will also be measured by taking spectra of the planetary nebula at four different positions within the chip, i.e., one per quadrant. Coronograph
The ability to position a star behind the coronographic mask will be enabled during SMOV. The PSF within the coronograph will also be characterized during SMOV. A contingency program designed to measure the stability of the coronograph performance will be executed as part of the cycle 7 calibration plan if large physical motions in the NIC2 camera are detected (proposal ID 7694). This program focuses on measuring the possible change in the scattering and diffracted energy rejection patterns as a function of target decentration in the mask. Point Spread Function
No calibration program specifically designed to measure the point spread function of the three cameras will be executed as part of the Cycle 7 calibration plan. Observers requiring PSFs in specific filters and/or locations within the field of view are advised to include these in their own program. NICMOS PSFs can however be modeled quite well using Tiny Tim V4.3. Focus Monitoring
Since the NICMOS camera focii will continue to change as cryogen vents, the focus of all three cameras will be monitored throughout the entire Cycle 7 (prop ID 7608). During the first few months, focus measurements will be obtained every other week with the three cameras. The frequency of the monitoring will be decreased to once a month, after the first few months. The focus and physical motion of the cameras will be measured using phase retrieval, encircled energy and plate scale techniques. Updates to best focus positions will most likely occur a few times during Cycle 7. Information regarding these focus updates will be posted on the NICMOS focus Web page.