0Assigned ID: 1243
----- Attempting Submission 1 (Mon Sep 26 18:58:16 GMT 2016) -----
HST Phase I Proposal 1243 (288P-DD_160926.apt) successfully submitted.
Receipt: # 1243-1
----- Attempting Submission 2 (Mon Sep 26 19:11:14 GMT 2016) -----FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser
FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser
FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser0----- Attempting Submission 1 (Tue Oct 11 06:55:23 GMT 2016) -----We checked that the flash level warning disappears if we use the zodiacal light background predicted for the time of observation rather than the generic value used by the APT (ETC request ID WFC3UVIS.im.839937). The same observation strategy has also already been used successfully in our GO 14790.Tracing rotational fission in the first known active binary asteroid system 288P/300163We request six orbits of DD time to monitor the recently discovered, first known active binary asteroid system 288P/300163, using WFC3. The key aim is to establish the Keplerian elements of the mutual orbit, to constrain the individual rotational periods of the nuclei, and to follow up on indications that tidal effects support the activity. The observations will help us to determine if the 288P system has recently formed by rotational fission (in which case we expect a highly eccentric mutual orbit and rotation periods of 2-4h), or if the dust activity is independent of the binary nature. For the first time, we are seeing two important consequences of rotational break-up in a single object: binary formation and dust ejection. This highlights the importance of the YORP-effect in re-shaping the asteroid belt. In addition, 288P is the first known binary asteroid system having both a high mass ratio (~1) and a large component separation (semi-major axis to radius ~70). A precise characterisation of its orbit is essential to put 288P in context with models of the formation of such systems. As 288P is receding from Earth, the two nuclei will not be resolvable by HST after the end of November 2016, which triggers our request for DD time. The next opportunity to carry out such observations will be in 2021.We purpose of this proposal is to observe active asteroid 288P during October and November of 2016 in three visits, each consisting of one orbit. The visits should be separated by 8-12 days and start as soon as possible.
The magnitude of a single component is V~22. The orbital visibility for a solar system target near the ecliptic plane is 54 min (Section 6.3 of the HST Primer document). We will follow the same successful observation strategy as for our program GO 14790, ensuring a maximum comparability of the data.
In each orbit, we will take 8 exposures of 230s using the 1k subarray of WFC3. We will perform a subsampling dither box pattern, obtaining 2 exposures at each dither point. We will carefully drizzle our subsampled images to a finer output pixel scale to extract the extra spatial information gathered by our subsampling strategy. This enhanced resolution will allow us to determine the relative position of the nuclei at the highest possible accuracy. The dithering will also enable us to reject hot pixels and cosmic ray hits.
This strategy gives us a total exposure time of 1800s = 30min per orbit, and estimated overheads of 6min for guide-star acquisition, 2.6min for the first exposure, a total of 14.7min for the subsequent 7 exposures, and 1.5min for the three spacecraft maneuvers required for dithering, which adds up to a total execution time of 54min per orbit.
We will use the wide bandpass filter F606W for an optimum trade-off between sensitivity and highest resolution: the bandpass (475 -- 700 nm) covers the maximum of the solar spectrum, and is in the wavelength range where the PSF is smallest (FWHM<0.07 arcsec, from the WFC3 instrument handbook for Cycle 24), such that we can optimally exploit our subsampling dither strategy. In addition, F606W is the same filter we used to observe 288P in GO 12597 and 14790, enabling a direct comparison of the data sets.
The WFC3 exposure time calculator returns for a solar-spectrum point source at V=21, exposure time of 230s, F606W filter, and default background values (using zodiacal light conditions of 2016-Nov-01) a signal-to-noise-ratio of 86 within a circle of 0.2 arcsec (ETC Request ID: WFC3UVIS.im.839937).Solar System0SUPPORTEDSOLAR SYSTEMNOASTEROIDactive asteroidTYPE=COMET,Q=2.437997636061935,E=.2002773126787514,I=3.239254302184838,O=83.22502588733704,W=281.9669249151093,T=18-JUL-2011:22:51:20,TTimeScale=UTC,EQUINOX=J2000,EPOCH=19-JUN-2010:00:00:00,EpochTimeScale=TDBEARTHWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WPOS-TARGDITHER0.173LINE0.112falsefalse81.785423.884WFC3-UVIS-DITHER-BOX1false/tmp/OPVisit2620730298287608662.xmlUsing ephemeris for target 14864-01-288Pephemeris data for target 14864-01-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.274 to 18.274Timing link suitability includes constraints ([02 After 01 by 8.0 to 12.0 days])The scheduling data was generated by CASM 24.2.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 14864
:visit-id "01"
:proposal-version -1
:trans-version "20160601"
:date "11-Oct-2016 08:50:07.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 1
:saa-model "29"
:si-bright-earth-limb-angle 20.0
:data-volume 142608
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 14864
:visit-id "01"
:obset-id "01"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 14864
:visit-id "01"
:orbit-number 1
:pcs-time 333
:si-vis-utilization 2674
:al-overhead-at-end 0
:internal-dur-at-end 192
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3140
:pcs-gap 0
)true10/tmp/OPVisit8174464918683213494.xmlUsing ephemeris for target 14864-02-288Pephemeris data for target 14864-02-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.274 to 18.274Timing link suitability includes constraints ([02 After 01 by 8.0 to 12.0 days] [03 After 02 by 8.0 to 12.0 days])The scheduling data was generated by CASM 24.2.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 14864
:visit-id "02"
:proposal-version -1
:trans-version "20160601"
:date "11-Oct-2016 08:50:47.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 1
:saa-model "29"
:si-bright-earth-limb-angle 20.0
:data-volume 142608
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 14864
:visit-id "02"
:obset-id "02"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 14864
:visit-id "02"
:orbit-number 1
:pcs-time 333
:si-vis-utilization 2674
:al-overhead-at-end 0
:internal-dur-at-end 192
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3140
:pcs-gap 0
)true10/tmp/OPVisit7737897498242337272.xmlUsing ephemeris for target 14864-03-288Pephemeris data for target 14864-03-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.274 to 18.274Timing link suitability includes constraints ([03 After 02 by 8.0 to 12.0 days])The scheduling data was generated by CASM 24.2.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 14864
:visit-id "03"
:proposal-version -1
:trans-version "20160601"
:date "11-Oct-2016 08:50:52.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 1
:saa-model "29"
:si-bright-earth-limb-angle 20.0
:data-volume 142608
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 14864
:visit-id "03"
:obset-id "03"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 14864
:visit-id "03"
:orbit-number 1
:pcs-time 333
:si-vis-utilization 2674
:al-overhead-at-end 0
:internal-dur-at-end 192
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3140
:pcs-gap 0
)true10