J/AJ/156/20 Astrometry of (486958) 2014 MU69 with HST (Porter+, 2018)
High-precision orbit fitting and uncertainty analysis of (486958) 2014 MU69.
Porter S.B., Buie M.W., Parker A.H., Spencer J.R., Benecchi S., Tanga P.,
Verbiscer A., Kavelaars J.J., Gwyn S.D.J., Young E.F., Weaver H.A.,
Olkin C.B., Parker J.W., Stern S.A.
<Astron. J., 156, 20-20 (2018)>
=2018AJ....156...20P 2018AJ....156...20P (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Positional data ; Minor planets
Keywords: astrometry - celestial mechanics - Kuiper belt: general -
Kuiper belt objects: individual: 2014 MU69 - occultations
Abstract:
NASA's New Horizons spacecraft will conduct a close flyby of the
cold-classical Kuiper Belt Object (KBO) designated (486958) 2014 MU69
on 2019 January 1. At a heliocentric distance of 44 au, "MU69" will be
the most distant object ever visited by a spacecraft. To enable this
flyby, we have developed an extremely high-precision orbit fitting and
uncertainty processing pipeline, making maximal use of the Hubble
Space Telescope's Wide Field Camera 3 (WFC3) and pre-release versions
of the ESA Gaia Data Release 2 (DR2) catalog. This pipeline also
enabled successful predictions of a stellar occultation by MU69 in
2017 July. We describe how we process the WFC3 images to match the
Gaia DR2 catalog, extract positional uncertainties for this extremely
faint target (typically 140 photons per WFC3 exposure), and translate
those uncertainties into probability distribution functions for MU69
at any given time. We also describe how we use these uncertainties to
guide New Horizons, plan stellar occultions of MU69, and derive MU69's
orbital evolution and long-term stability.
Description:
2014 MU69 was discovered with the HST search program (GO 13633)
described in M. W. Buie et al. (2018DPS....5050906B). This program
was designed to take five full-frame 370 s Wide Field Camera 3 (WFC3)
UVIS images in one orbit with the F350LP broadband filter, skip an HST
orbit, and then repeat the same observation. The images were tracked
on a nominal cold-classical orbit, producing streaked stars, but
nonstreaked KBOs. To perform the search, the images were shift-stacked
at 20 different representative cold-classical shift rates. Objects
that appeared in both search orbits for one of the shift rates were
identified and targeted for follow up HST observations. The available
data set for 2014 MU69 has both a short temporal arc (2014 July-2017
October) and an extremely high data quality, making it ideal for the
analysis described below. MU69 is a very faint object, with V∼27.5
(S. Benecchi et al. 2018arXiv181204758B 2018arXiv181204758B) and is in an extremely crowded
star field (galactic longitudes from -8° to -12°). These
constraints have made it effectively impossible to detect with
ground-based telescopes, and all observations of MU69 have been with
the Hubble Space Telescope. A list of these HST observations is in Table 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 69 205 *2014 MU69 astrometry for "rd2b" solution
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Note on table3.dat: The "rd2b" orbit solution for 2014 MU69 (from Table 1
of this paper):
--------------------------------------------------
Value 1σ
--------------------------------------------------
x | +1.163133074444e+09 ± 2.80233e+02 km
y | -6.385039581373e+09 ± 1.52754e+03 km
z | +2.373261916929e+08 ± 5.87015e+01 km
vx | +4.461378977476e+00 ± 5.92714e-06 km/s
vy | +9.619622770583e-01 ± 2.45488e-05 km/s
vz | -1.066958207821e-01 ± 9.45150e-07 km/s
a | 44.23555350 ± 0.00003999 au
e | 0.03787388 ± 0.00000476
I | 2.44993086 ± 0.00000203 deg
Ω |159.04712465 ± 0.00006746 deg
ω |183.74800591 ± 0.00469779 deg
M |301.30454775 ± 0.00406885 deg
--------------------------------------------------
State vector and orbit are relative to the solar system barycenter and in
the ICRF ecliptic frame at the epoch 2014-06-01 00:00:00 UTC.
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See also:
J/AJ/154/62 : Orbital parameters of Kuiper Belt objects (Volk+, 2017)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID HST WFC3/UVIS dataset identifier
11- 25 F15.7 yr JD UTC Julian Date of observation
27- 40 F14.10 deg RAdeg Right Ascension in decimal degrees (J2000)
42- 55 F14.10 deg DEdeg Declination in decimal degrees (J2000)
57- 62 F6.3 mas e_RAdeg [3.997/12.89] 1-σ uncertainty in RAdeg
(J2000)
64- 69 F6.3 mas e_DEdeg [4.429/12.064] 1-σ uncertainty in DEdeg
(J2000)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 10-Jan-2019