----- Attempting Submission 1 (Thu May 10 20:43:24 GMT 2007) -----
Phase II Proposal 11234 (CrabPM_ph2_newest) successfully submitted.
----- Attempting Submission 2 (Thu Jul 19 17:22:22 GMT 2007) -----
I had to designate a slightly longer exposure (430s) in visit 2, for it to break to
the correct (260s+160s) CR-split sub-exposures. Specifying 420s did not work. Accordingly I
have warning flags about the reductions of the two sub-exposures. I don't think that this
is a problem and, indeed, I found phase II exxamples doing the same thing in on-line
documentation. Let me know if this is really a problem or if there is a simple work-around.
Thanks -- RWR Assigned ID: 1085
----- Attempting Submission 1 (Tue Feb 06 21:42:25 GMT 2007) -----
Phase I Proposal 1085 (CrabPM) successfully submitted.
A Brief Revisit of the CrabWe propose using WFPC2 to obtain continuum-dominated images of the Crab pulsar and environs closely duplicating archival exposures from 1994 and 1995. By matching the archival data we can realize ~3mas precision astrometry with a minimum of systematic effects over a maximum (~13.5y) baseline. This determines the Crab proper motion to better than 0.3mas/yr (3km/s) accuracy and measures its position angle to better than 1.5degrees, i.e. reducing the errrors of the best present (HST archive) measurement by a factor of three. Most importantly, this provide a nearly systematic-free result. This proper motion measurement would match the precision of the CXO-measured angular momentum vector. Comparison of these vectors is the foundation of an effort to understand the physical origin of the large momentum kick at pulsar birth.Although careful PSF fitting and distortion mapping make enormous improvements, WFPC2 astrometry is still limited by systematics for moderately bright stars. We can however, make proper motion measurements largely free of these systematics by accurately reproducing the position and orientation of archival exposures, achieving ~3mas differential astrometry. We seek here to take advantage of the stable WFPC2 platform, duplicating Crab pulsar/nebula observations of 1995 and 1995. These observations are somewhat challenging to schedule, but offer a unique opportunity to make a measurement that is a fundamental constraint on models for the 'kicks' that give pulsars their high speeds. The observations must be made during cycle 16, before SM4.
Visit 1 is a duplication of WFPC2/F547M images taken on 1995-08-14 with the pulsar on the PC chip. Here we can achieve an exact match to the original roll angle for a wide range of dates -- we request dates from a 1 month window around the day-of-year of the original exposure to minize any parallactic shift of foreground comparison stars. After duplicating the 2000s CR-split 7e-gain exposure of the original pointing, we use the remaining visibility to obtain an unsaturated 120s image of the pulsar, which allows improved PSF centroiding.
Visit 2 matches the earliest available image, 1994-03-09 with the pulsar on the WF2 chip. Here the target is only available for a limited period near the required roll angle, and with low (18min) orbit visibility. This observation is, however, very valuable as the larger WF image provides more reference stars on the single chip containing the pulsar (which gives the most stable astrometry). Although the PSF is more poorly sampled, the larger number of stars compensates and we can get an accurate astrometric frame-tie even with shorter exposures. We have requested a 260s/160s exposure pair at 15e-gain, where the second exposure avoids saturation for the pulsar. The combined exposure suffices to reach systematics-dominated astrometry for all but our faintest reference stars. Since this is a single orbit visit, the low visibility is not a serious efficiency hit, as HST is free to move after occultation.
The science goals can be partly achieved with visit 1 alone. However, a key aspect is to demonstrate the lack of systematics in the measured proper motion vector; comparison between the visit 1 and visit 2 observations is an important addition, showing independance of chip, orient and season. The program produces a small data set, but very careful analysis will be needed to exploit the full astrometric potential of these frames.HOT STARS12false0.0falsefalsefalsefalsefalsefalseSUPPORTEDEXT-STARNEUTRON STARJ200005 34 30.3100+22 01 29.00J2000EXT-STARNEUTRON STARJ200005 34 29.2000+22 00 50.00J2000WFPC2ImagingNoF547MWFPC2ImagingNoF547M/tmp/OPVisit400.xml
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:date "19-Jul-2007 09:59:45.0"
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:pcs-visibility 3147
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true10/home/rwr/APT1622/OP-cache/CrabPM_ph2_newest-v02.xmlchecking gain/tmp/OPVisit402.xml
(Tic-Visit
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:trans-version "20070325"
:date "19-Jul-2007 10:03:07.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
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:saa-model "26"
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:data-volume 134448
:tdrss-contact-duration 0
:coron NIL
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(Tic-Obset
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(Tic-Orbit
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:pcs-time 355
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:internal-dur-at-end 0
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:pcs-visibility 3147
:pcs-gap 0
)
true10/home/rwr/APT1622/OP-cache/CrabPM_ph2_newest-v01.xml