C/2016 U1 NEOWISE
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Comet C/2016 U1 was discovered on 21 October 2016 by Near-Earth Object Wide-field Infrared Survey Explorer, that is less than 3 months before its perihelion passage, and was astrometrically observed until 12 January 2017. Comet had closest approach to the Earth on 13 December 2016 (0.709 au, about a month before the perihelion passage).
Sekanina (2019) concluded that this comet was a rare example of a comet that survived its perihelion passage despite a small distance from the Sun at that moment (see his Tables 2 and 6).

Despite short data arc this is a comet with NG effects determinable using positional data fitting. Both solutions (GR and NG) are based on data spanning over 0.227 yr in the pre-perihelion orbital leg, in a range of heliocentric distances from 1.86 au to 0.321 au.

GR assumption gives original hyperbolic orbit; however, NG orbit results in original semimajor axis of about 1900–3300 au (uncertainty of one sigma is used). C/2016 K1 suffers moderate/large planetary perturbations while passing through the planetary system; these perturbations probably lead to escape the comet from the planetary zone on a hyperbolic orbit (see future barycentric orbits).
solution description
number of observations 382
data interval 2016 10 21 – 2017 01 12
data type observed only before perihelion (PRE)
data arc selection entire data set (STD)
range of heliocentric distances 1.86 au – 0.321au
detectability of NG effects in the comet's motion comet with determinable NG~orbit
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 757
RMS [arcseconds] 0.85
orbit quality class 2b
orbital elements (barycentric ecliptic J2000)
Epoch 2306 02 22
perihelion date 2017 01 13.79211804 ± 0.00016312
perihelion distance [au] 0.31937399 ± 0.00000329
eccentricity 1.00023656 ± 0.00000928
argument of perihelion [°] 162.730741 ± 0.000812
ascending node [°] 61.503004 ± 0.000389
inclination [°] 46.409978 ± 0.000292
reciprocal semi-major axis [10-6 au-1] -740.70 ± 29.06
file containing 5001 VCs swarm
2016u1a5.bpl
Upper panel: Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line — the moment of perihelion passage.
Middle panel(s): O-C diagram for a given solution (sometimes in comparison to another solution available in CODE), where residuals in right ascension are shown using magenta dots and in declination by blue open circles.
Lowest panel: Relative weights for a given data set(s).
Six 2D-projections of the 6D space of future swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.