11231( 2) - 05/02/07 13:11 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11231 Version: 2 Check-in Time: 02-May-2007 17:11:00 STScI Edit Number: 0 Title Calibration of the WFPC2 HeII and [SII] Filters. ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. C. Robert O'Dell Vanderbilt University ------------------------------------------------------------------------------------ Abstract Observations of NGC 6720 (the Ring Nebula) will be used to determine the calibration constants for the important emission-line filters that isolate nebular HeII (F469N) and [SII] (F673N) emission. The pre-launch calibrations are inadequate because of possible temporal changes and the fact that these interference filters are used in a different configuration from that of the ground calibration. The Ring Nebula is a nearly ideal reference source as multiple 2.4"x4.0" samples have been accurately measured spectro-photometrically and five of the six samples can be imaged with one pointing of the HST. The method of derivation of the calibration constants will be the same as previously employed to calibrate the primary emission-line filters for the WFPC2 (F487N, F502N, F656N, F658N) and ACS (F502N, F658N, F660N) using the Orion Nebula as a reference source. However, Orion cannot be used for this calibration because the targeted lines are weak ([SII]) or absent (HeII) and the scattered-light continuum is strong. The Ring Nebula has strong HeII emission in its middle, strong [SII] emission in its main ring, and a weak (atomic only) continuum. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will make WFPC2 observations of the Ring Nebula (NGC 6720) in the F469N, F547M, and F673N filters for the purpose of calibrating the F469N and F673N filters. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11231( 2) - 05/02/07 13:11 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6720 ISM, EMISSION LINE RA=18H53M35.5400S +/- 1", J2000 V = 15.0+/-1.0 NEBULA, PLANETARY DEC=+33D01'48.00" +/- 1" NEBULA Reference Frame: ICRS 11231( 2) - 05/02/07 13:11 - [ 3] Visit: 01 Visit Priority: Visit Requirements: ORIENT 258.0D TO 260.0 D On Hold Comments: Additional Comments: This visit uses the same target and orientation as the PI's Visit 1 of program 11232 and optimally would be executed immediately before Visit 1 of program 11232. If that is done, then the exposure times of 11232 should be increased to take advantage of not having to do a new guidestar acquisition. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6720 WFPC2 IMAGE WF3-FIX F469N CR-SPLIT=NO 3 600 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6720 WFPC2 IMAGE WF3-FIX F547M CR-SPLIT=NO 3 200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6720 WFPC2 IMAGE WF3-FIX F673N CR-SPLIT=NO 3 260 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC6720 1 WFPC2 IMAGE WF3-FIX F469N none none 1 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F469N none none 2 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F469N none none 3 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F547M none none 1 none 2 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F547M none none 2 none 2 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F547M none none 3 none 2 N/A NGC6720 3 WFPC2 IMAGE WF3-FIX F673N none none 1 none 2 N/A NGC6720 3 WFPC2 IMAGE WF3-FIX F673N none none 2 none 2 N/A NGC6720 3 WFPC2 IMAGE WF3-FIX F673N none none 3 none 2 N/A 11231( 2) - 05/02/07 13:11 - [ 4] Summary Form for Proposal 11231 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 258.0D TO 260.0 D; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F469N F547M F673N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6720 ------------------------------------------------------------------------------------------------------------------------------------