Electronic Telegram No. 4305
Central Bureau for Astronomical Telegrams
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(441987) 2010 NY_65
[Editor's note:  this text replaces that on CBET 4304.]
     J. D. Giorgini, M. Brozovic, S. P. Naidu, L. A. M. Benner, Jet
Propulsion Laboratory (JPL); P. A. Taylor Arecibo Observatory; and A.
Greenberg, University of California at Los Angeles, report that a
non-gravitational acceleration has been detected influencing the motion
of minor planet (441987).  Recent Goldstone (8560-MHz, 3.5-cm) and Arecibo
(2380-MHz, 12.6-cm) radar imaging at 15-m resolution produced round-trip
delay measurement of the center-of-mass of (441987) to within 56-m over
2016 June 21, 22, and 26.  Consistently biased delay offsets were observed,
having a mean of -10.9 +/- 1.0 x 10^{-6} seconds relative to the prior
gravity-only prediction of JPL orbit solution 63.  This nominal ballistic
trajectory estimate was based on 220 initial plane-of-sky optical angle
measurements spanning 2010-2016 combined with four prior round-trip
time-delay measurements and two Doppler frequency shift measurements
reported by Arecibo in 2014 and 2015.  The systematic 2.5-sigma offset
observed is consistent with a mean heliocentric transverse non-gravitational
acceleration over the data arc of -9.2 +/- 2.3 x 10^{-13} m/s^2, as
subsequently estimated in JPL orbit solution 65 (dated 2016 July 29), with a
15-percent reduction in total dataset post-fit residual chi-square.  The
combined astrometric dataset consists of 228 optical angular measurements
spanning 2010-2016 and the three radar apparitions spanned by nine radar
delay and three Doppler-shift measurements.  This object will continue to
make yearly close approaches to the earth, and the authors anticipate future
measurements in 2017, 2018, 2019, and 2020 that will be at least as precise,
permitting ongoing refinement and characterization of the estimated force.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2016 CBAT
2016 August 22                   (CBET 4305)              Daniel W. E. Green