Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2691c Report Date: 09-May-96:17:17 Version: ********** Check-in Date: ********** 1.Proposal Title: PRECISION PARALLAXES OF CEPHEIDS AND RR LYRAES USING THE WF/PC ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR POPULATIONS GO 1 Long Term yrs Sub Category ASTROMETRY ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Douglas K. Duncan STSCI USA 301-338-4935 ------------------------------------------------------------------------------------ 7. Abstract A new technique using the WF/PC should allow astrometric positions to be determined with an accuracy of 0.0002 arcsec 0.2 m.a.s. from two PC frames. We propose an initial test of the technique. Our new technique involves trailing HST during exposures to help alleviate the problem of undersampling inherent in the WF/PC. Once our technique of precision astrometry is proven, it should have numerous applications. ------------------------------------------------------------------------------------ 8. Scientific Key Words: STARS: CEPHEIDS, ASTROMETRY, PARALLAXES. ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 2.50 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2691c PI: Dr. Douglas K. Duncan Proposal Title: PRECISION PARALLAXES OF CEPHEIDS AND RR LYRAES USING THE WF/PC ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Ronald L. Gilliland STSCI USA Dave Van Buren CANADIAN INST. FOR THEORETICAL CANADA ASTROPHYSICS P.I. Douglas K. Duncan STSCI USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. Description of observations: This is a test of precision astrometry capability of WF/PC. In this case we observe a rich field of 14th magnitude stars in the globular cluster 47 Tuc. Goal is simply to measure the separation of all stars in the field of view in one dimension. In order to increase signal-to-noise, and obviate problems due to undersampling of the point-spread-function the images are trailed over about 75 pixels. The trailing is done at an angle of 35 degrees with respect to CCD coords to provide trails that are not degenerate in pixel sampling. In a science experiment to measure parallax, the trailing would be done perpendicular to the ecliptic, so that parallax offsets would be normal to the trails. Observations would be taken at epochs to maximize parallax displacements. For this test the trail direction in celestial coords is arbitrary. We require several independent observations to determine precision with which separation of trails can be measured. The TAC report requested that observations cover a solar UV flood of WF/PC as this might alter the shape of the chip -- this drives time critical aspect of these observations. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Only HST will have the capability of pursuing this program. We should attain precisions a factor of 5 better than is now contemplated from the ground. While images obtained with ground-based observations can be centroided to the requisite sub-milli-arcsec level (with trailing and high S/N exposures) the atmosphere introduces offsets of apparent position which cannot be controlled to the accuracy we propose to measure. HST will provide relative image separations unaffected by the atmosphere. The large aperture of HST is required to reach high signal-to-noise on stars of mV = 17-18. Only at this level can an adequate number of background stars of similar magnitude be found. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Spacecraft time required is primarily driven by the overhead components for this test experiment. We need guided exposures at two different S/N to allow identification of all stars in the field (required for subsequent analysis of trail separation) -- we request a total of three. The remaining exposures are all to generate trailed images, a sufficient number over two epochs have been requested to allow a determination of measurement precision. Independent trails at two different positions on the PC chips are used to determine the level of chip nonuniformity, and its potential impact on this project. In 47 Tuc the horizontal branch is at 14th mag, with the brightest stars being two magnitudes brighter. We have two constraints: 1) want to reach S/N a little better than 100 for the common 14th mag objects, 2) need to keep count rate in central pixels of brightest objects well under 80,000 cts to avoid any charge bleeding problems. At an exposure time of 0.4s (guided, or average per pixel in a trailed image) the S/N over full image will be about 135, with maximum cts per pixel of brightest stars at 43,000. This will produce ideal conditions for the test. At 0.4s per pixel exposure a trail over 75 pixels requires a 30s exposure. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Observations must all be taken with stars at precisely the same positions (includes roll angle) on the chip. The TAC request that we sample two epochs before and after a solar UV flood coupled with need for same roll angle, requires that first set of observations be taken within one week before a UV flood, and the second set taken within one week following the UV flood. We need good flat fielding, of order S/N=200, for all of our F555W exposures. We request that sufficient calibration exposures for cycle 1 be scheduled by the Institute such that this goal is met. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. We anticipate the 2-D CCD image data set will first be carefully reduced for overscan, bias, preflash, dark and flat-field. The primary reduction step for each frame will be to determine the relative separation of the program star trail with respect to each background star trail. The trails will in general be at an angle to the CCD rows and columns. Since the trail length is < 10% of CCD size, the trails generally will not overlap in the trail direction. Each trail (line segment) can be characterized by: x,y position, length and slope. The length and slope will be determined as a common global parameter for all trails in an exposure (if necessary length and slope could be generalized to a template curve common to each trail). The x,y position (in CCD row, columns) will be set for each trail by a full point-spread- function fit over the about 5x75 pixels involved. This can be thought of as performing a full simulation of each trail, using both analytic and empirical information on the PSF, with the x,y position adjusted via non-linear least-squares until an optimal match occurs with each trail. The two parameters x,y carry useful information only on the normal separation between line segments, not true 2-D position of stars on sky -- orthogonal trailing required for latter. ------------------------------------------------------------------------------------ 11. Address Information Name: DOUGLAS K. DUNCAN Category: PI Institution: SPACE TELESCOPE SCIENCE INSTITUTE Address: 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2691c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC0104 STAR CLUSTER; GLOBULAR RA=00H 23M 58.00S +/-5.00S, 1984 1 V=14 +/- 3 47TUC CLUSTER DEC=-72D 3' 14.4" +/-5.00" Comments: WE HAVE ONLY ONE FIELD. LOCATION IN FIRST ACQUISITION DOES NOT NEED TO BE BETTER THAN +/- 5". IN SUBSEQUENT ACQUISITION POSITIONING SHOULD BE AS CLOSE TO ORIGINAL AS POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2691c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 0.4S 100 1 1 GROUP 1-4 WITHIN CR-SPLIT=NO 0.4S 7D ORIENT 25D +/- 0D FROM NOMINAL / 1- 4.5 CYCLE 1 / 1-8 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 4 78S 100 1 1 SPATIAL SCAN CR-SPLIT=NO 30S SINGLE-EXP SAME ORIENT FOR 2- 4.2 AS 1 SAME POS FOR 2-8 AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 3 78S 100 1 1 SPATIAL SCAN CR-SPLIT=NO 30S SINGLE-EXP ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 80S 100 1 2 SPATIAL SCAN CR-SPLIT=NO 260S SEQ 4-4.2 NON-INT READ=NO SEQ 4-5 Comments: SEQ 4-5 (AND AFTER 4 ON LINE 5) MAY BE DELETED IF TRANS BREAKS ON THIS, BUT CHANGE THE GROUP 1 -4 TO SEQ 1-5 ON LINE 1. ------------------------------------------------------------------------------------------------------------------------------------ 4.1 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 80S 100 1 2 SPATIAL SCAN CR-SPLIT=NO 260S POS TARG -5.404, READ=NO 9.190 Comments: DELTA = 1.893,-2.703 ------------------------------------------------------------------------------------------------------------------------------------ 4.2 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 80S 100 1 2 SPATIAL SCAN CR-SPLIT=NO 260S POS TARG -8.107, READ=YES 7.297 Comments: DELTA = 4.596, -0.810 ------------------------------------------------------------------------------------------------------------------------------------ 4.3 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 80S 100 1 2 SPATIAL SCAN CR-SPLIT=NO 260S SEQ 4.3-4.5 NON- READ=NO INT ------------------------------------------------------------------------------------------------------------------------------------ 4.4 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 80S 100 1 2 SPATIAL SCAN CR-SPLIT=NO 260S POS TARG -5.404, READ=NO 9.190 Comments: DELTA = 1.893,-2.703 ------------------------------------------------------------------------------------------------------------------------------------ 4.5 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 80S 100 1 2 SPATIAL SCAN CR-SPLIT=NO 260S POS TARG -8.107, READ=YES 7.297 Comments: DELTA = 4.596, -0.810 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2691c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 2.0S 250 1 1 AFTER 4.2 BY 45D CR-SPLIT=NO 2.0S SAME ORIENT FOR 5- 8 AS 1 Comments: SEE COMMENTS ON LINE 4 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 4 78S 100 1 1 SPATIAL SCAN CR-SPLIT=NO 30S SINGLE-EXP GROUP 6-7 WITHIN 7D AFTER 5 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 3 78S 100 1 1 SPATIAL SCAN CR-SPLIT=NO 30S SINGLE-EXP SEQ 7-8 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC0104 PC IMAGE ALL F555W 5479 PRE-FLASH=15 1 2.0S 250 1 2 AFTER 7 CR-SPLIT=NO 2.0S ------------------------------------------------------------------------------------------------------------------------------------ Scan Paramters Form Proposal ID: 2691c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 2, 6 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 3.3000 Angle between sides (degrees) 0.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0423 PA of first scan line (degrees) 35.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0000 Width Offset (arc-sec): 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 2 Exposure Logsheet lines: 3, 7 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 3.3000 Angle between sides (degrees) 0.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0423 PA of first scan line (degrees) 35.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0000 Width Offset (arc-sec): 2.2000 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 3 Exposure Logsheet lines: 4, 4.3 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 3.3000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0423 PA of first scan line (degrees) 35.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0000 Width Offset (arc-sec): 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 4 Exposure Logsheet lines: 4.1,4.4 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 3.3000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0423 PA of first scan line (degrees) 125.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0000 Width Offset (arc-sec): 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 5 Exposure Logsheet lines: 4.2,4.5 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 3.3000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0423 PA of first scan line (degrees) 215.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.0000 Width Offset (arc-sec): 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2691c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations PC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PRE-FLASH=15 CR-SPLIT=NO READ=NO READ=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 2.50 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ASTROMETRY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 1-4 WITHIN 7D; ORIENT 25D +/- 0D FROM NOMINAL / 1-4.5; CYCLE 1 / 1-8; SPATIAL SCAN SINGLE-EXP; SAME ORIENT FOR 2-4.2 AS 1; SAME POS FOR 2-8 AS 1 SPATIAL SCAN SINGLE-EXP SPATIAL SCAN;SEQ 4-4.2 NON-INT; SEQ 4-5 SPATIAL SCAN; POS TARG -5.404,9.190 POS TARG -8.107, 7.297 SEQ 4.3-4.5 NON-INT; AFTER 4.2 BY 45D; SAME ORIENT FOR 5-8 AS 1; GROUP 6-7 WITHIN 7D; AFTER 5 SEQ 7-8 AFTER 7 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC0104 47TUC ------------------------------------------------------------------------------------------------------------------------------------