! Proposal 6938, submission 2 ! PI: Andy Fruchter ! Received Fri Aug 1 16:10:23 EDT 1997 ! From: shireen@stsci.edu Proposal_Information Title: PSF Characterization Proposal_Category: CAL/WF2 Scientific_Category: Cycle: 6 Investigators PI_Name: Andy Fruchter PI_Institution: STScI CoI_Name: Chris O'dea CoI_Institution: STScI Contact: N Abstract: Provide a subsampled PSF over the full field to allow PSF fitting photometry, test PSF subtraction as well as dithering techniques (cf. effects of the OTA breathing and CCD gain). Questions Observing_Description: Measure PSF over full field in photometric filters in order to update the TIM and TINYTIM models and to allow accurate empirical PSFs to be derived for PSF fitting photometry. These observations will also be useful in order to test PSF subtraction and dithering techniques at various locations on the CCD chips. With one orbit per photometric filter, a spatial scan is performed over a 4X4 grid on the CCD. The step size is 0.025 arcseconds. This gives a critically sampled PSF over most of the visible range. The crowded Omega Cen field is used. 40 (with gain = 15) sec images are taken through each of the photometric filters (F336W, F439W, F555W, F675W and F814W). Effects of the OTA breathing (1 additional orbit) and CCD gain (1 additional orbit) onto the dithering and PSF subtraction techniques will also be investigated. Based partially on cycle 4 program 5575 and cycle 5 program 6193 which used a similar field. Note however that most observations in this program use the same specially chosen field in Omega Cen as the cycle 5 proposal 6193, but with a few arcsec shift in order to better map the PSF variation across the field. The proposal also allows a check for subpixel phase effects on the integrated photometry. Output -- Subsampled PSFs for photometry codes. Data for comparison with PSF and dithering codes. Provides measurement of pixel phase effect on photometry (sub pixel QE variations exist). The chosen field will have tens of well exposed stars in each chip. Each star will be measured 16 times per filter at different pixel phase. The proposal therefore provides, in principle, a high signal to noise, critically sampled PSF. This will leave PSF fitting photometrists in a much better position than now, where pixel undersampling clearly limits the results. The result will be largely limited by breathing variations in focus. It is hard to judge the PSF accuracy that will result. If breathing is less than 5 microns peak to peak, the resulting PSFs should be good to about 10% in each pixel. Breathing effects will be investigated (1 additional orbit) as well as the gain dependence (1 additional orbit). PSF fitting results using this calibration would of course be much more accurate. In addition, the test gives a direct measurement of sub-pixel phase effects on photometry, which should be measured to better than 1%. Real_Time_Justification: Calibration_Justification: Additional_Comments: SCHEDULING COMMENTS: - Proposal currently written as several single visits requiring in total 7 orbits for easier scheduling (same orientation should of course be maintai- ned for all visits except F336W). Because of a desirable comparison between the PSFs derived for the different filters, we should like the entire proposal to be executed within 2 weeks. This is necessary to minimize the spacecraft temperature differences t hat result from orbital precession effects. Fixed_Targets Target_Number: 1 Target_Name: OMEGA-CEN-A Alternate_Names: NGC5139 Description: CALIBRATION,PHOTOMETRIC Position: RA = 13H 26M 41.48S +/- 0.1S, DEC = -47D 31' 7.4" +/- 1",PLATE-ID=ZZZR Equinox: 2000 RV_or_Z: RA_PM: Dec_PM: Epoch: Annual_Parallax: Flux: V=20.0 +/- 1.2, B-V=-0.4 +/- 0.2 Comments: target position from dataset u2ssa203t (proposal 6053) Target_Number: 2 Target_Name: OMEGA-CEN-B Alternate_Names: Harris1461 Description: CALIBRATION,PHOTOMETRIC, Position: RA=13H 25M 31.5S +/- 0.1S, DEC=-47D 35' 33.6" +/- 1.00" Equinox: J2000 RV_or_Z: RA_PM: 0.0 Dec_PM: 0.0 Epoch: Annual_Parallax: 0.0 Flux: V = 16.4 Comments: target position from dataset u3890401t (proposal 6193) Target_Number: 3 Target_Name: OMEGA-CEN-C Alternate_Names: NGC5139 Description: CALIBRATION,PHOTOMETRIC Position: XI-OFF=0.25" +/- 0.01",ETA-OFF=0.25" +/- 0.01",FROM 2 Equinox: J2000 RV_or_Z: RA_PM: 0.0 Dec_PM: 0.0 Epoch: Annual_Parallax: 0.0 Flux: V = 16.4 Comments: position offset to study effects of breathing Scan_Data Scan_Number: 1 FGS_Scan: Cont_or_Dwell: D Dwell_Points: 4 Dwell_Secs: 40 Scan_Width: 0.375 Scan_Length: 0.375 Sides_Angle: 90.0 Number_Lines: 4 Scan_Rate: First_Line_PA: 270 Scan_Frame: S/C Length_Offset: 0.0 Width_Offset: 0.0 Visits !---------------------------------------------------------- Visit_Number: 01 Visit_Requirements: ORIENT 5D TO 75D; GROUP 1-7 WITHIN 14D On_Hold_Comments: Visit_Comments: orient 185d to 255d also acceptable. Orient based on pa_v3=217 for u2ssa203t, +/-35d Exposure_Number: 10 Target_Name: OMEGA-CEN-A Config: WFPC2 Opmode: IMAGE Aperture: WFALL-FIX Sp_Element: F336W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=15,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: UV PSF observations, rich field in prop 6053 Visit_Number: 02 Visit_Requirements: ORIENT 45D TO 115D On_Hold_Comments: Visit_Comments: orient 225d to 295d also acceptable. Orient based on pa_v3=263d for u3890401t (from cyc 5 psf proposal 6193), +/- 35d Exposure_Number: 20 Target_Name: OMEGA-CEN-B Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F439W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=15,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: same field as prop 6193, same orient (+/- 35d) Visit_Number: 03 Visit_Requirements: SAME ORIENT AS 02 On_Hold_Comments: Visit_Comments: Exposure_Number: 30 Target_Name: OMEGA-CEN-B Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=15,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: same field as prop 6193, same orient (+/- 35D) Visit_Number: 04 Visit_Requirements: SAME ORIENT AS 02 On_Hold_Comments: Visit_Comments: Exposure_Number: 40 Target_Name: OMEGA-CEN-B Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F675W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=15,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: same field as prop 6193, same orient (+/- 35D) Visit_Number: 05 Visit_Requirements: SAME ORIENT AS 02 On_Hold_Comments: Visit_Comments: Exposure_Number: 50 Target_Name: OMEGA-CEN-B Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=15,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: same field as prop 6193, same orient (+/- 35D) Visit_Number: 06 Visit_Requirements: SAME ORIENT AS 02; GROUP 6-7 WITHIN 2D On_Hold_Comments: Visit_Comments: Exposure_Number: 60 Target_Name: OMEGA-CEN-C Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=15,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: To study breathing effects Visit_Number: 07 Visit_Requirements: SAME ORIENT AS 02 On_Hold_Comments: Visit_Comments: Exposure_Number: 70 Target_Name: OMEGA-CEN-B Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO,ATD-GAIN=7,SCAN-READ=ALL Number_of_Iterations: 1 Time_Per_Exposure: 40S Special_Requirements: SPATIAL SCAN 1 Comments: To study gain=7 effects Data_Distribution ! Defaults indicated; change if desired Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS Recipient_Email: !num_orbits: 14