Submitting in response to email from Alison.
The 2 warnings are not serious issues.
We prefer the WFC3/UVIS setup for 3 orbits but provided the ACS setups as a backup.
ACS/WFC likely need a dither pattern, we require feedback on that.
We also want to ensure the debris trail spans the longest chip axis.
Debris trail has a PA of ~280 degrees East of North. The tail currently spans ~290 arc seconds from the object.
Ideally, we want to shift the object as close as possible to an edge so that we can image as much of
this tail as is feasbile while keeping the object in the FOV.
cut visit 2 to a 50 min visibility interval;
Keane: Jan 17
3 warnings are the same and relate to the position target which is offset to have the
target in the lower left.
I revised the setup to have dithers, resulting in 5 images. I adjusted the exposure
times to ensure each visit fits 1 orbit.
Keane: #15678-4: edited position target arcsecond offsets.
visit 1 is good.
visit 2 and 3 need checking
Ebeling: Following suggestions from Kailash Sahu, Visit 1 was updated to improve dithering and centering;
ORIENT constraint was added; Visits 2 and 3 still to be refined (removed ACS components)
Keane: Visit 2 & 3 edited: pattern using dither box, added Orient (U3 from email from Alison for appropriate date) and change pos-targ x,y values to place object
on CCD. Visit 2 and 3 now similar to Visit 1 (with appropriate pos-targ x,y values).
Keane: Changed Aperture to UVIS2 for Visit 3-WFC3/UVIS(03)492765978----- Attempting Submission 1 (Wed Jan 16 03:25:56 GMT 2019) -----
----- Attempting Submission 2 (Wed Jan 16 15:26:12 GMT 2019) -----
----- Attempting Submission 3 (Fri Jan 18 01:26:29 GMT 2019) -----
HST Phase II Proposal 15678 (Gault.apt) successfully submitted.
Receipt: # 15678-3
----- Attempting Submission 4 (Fri Jan 18 03:07:55 GMT 2019) -----
----- Attempting Submission 5 (Wed Jan 23 20:26:56 GMT 2019) -----
----- Attempting Submission 6 (Mon Jan 28 18:52:32 GMT 2019) -----
----- Attempting Submission 7 (Mon Mar 04 17:50:26 GMT 2019) -----Comet or break-up? The physical nature of Gault's dust trailThe past two decades have shown that the main asteroid belt contains a number of asteroids exhibiting mass loss. Main-belt comets show regular activity due to the excavation of revealed subsurface ices, either through intra-asteroid collisions which result in the explosive ejection of a debris cloud, or through rotational spin up due to thermal torques (the YORP effect) that can disrupt rubble-pile asteroids. As only some 20 such bodies have been detected so far, many physical aspects of their origin and subsequent evolution remain uncertain.
On 5 January 2019 we detected a dust tail / trail associated with the 5-10 km main belt asteroid (6478) Gault in images obtained by the ATLAS project; this is only the third discovery of a dust coma around a known main-belt asteroid. Archival data from ATLAS and Pan-STARRS show the Gault tail / trail already in early December 2018, but not in images taken between 2010 and January 2018. The tail / trail has significantly changed over one month; it is not clear whether this is due to pure dynamical evolution and changes in observing geometry, or because of continuous sublimation.
We propose a DD programme of WFPC3 imaging over four orbits. A two-orbit observation is requested as soon as possible to image the asteroid coma and near-asteroid dust structures at high angular resolution (about 40 km at the asteroid). The remaining two orbits would be used in February and March. Only HST will allow us to study the changing morphology of the dust structures and thus differentiate between continuous mass-loss and an impulsive event, and for the latter to decide between an impact and spin-up origin for this surprising discovery.Optical imaging observations to explore the dust surrounding asteroid Gault. We request a total time baseline for observations of approximately two months, with visits spaced roughly equally, to enable robust measurements of the evolution of the dust structure and of the velocity of any detected fragments.
While we would like to observe Gault as soon as possible, disruptive scheduling is not warranted.Solar System0falseSUPPORTEDSOLAR SYSTEMYESASTEROIDActive asteroidTYPE=ASTEROID,A=2.305298349567425,E=0.1942278713804378,I=22.79993887779855
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)true10Using ephemeris for target 15678-03-GAULTephemeris data for target 15678-03-GAULT does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 19.005 to 20.090. ephemeris interval: 19.059 to 21.060Timing link suitability includes constraints ([03 After 02 by 20.0 to 27.0 days])The scheduling data was generated by CASM 27.0.CASM was run in Phase II mode./private/var/folders/1b/dpbn10d57tqgshjqchxtrp8w0000gq/T/OPVisit7792232219145151975.xml(Tic-Visit
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