OAA computing section circular NK 830 90P/Gehrels 1
The following improved orbital elements, by S. Nakano, are from 52 observations 1972 to 2001. Perturbations by Mercury to Neptune and three minor planets, Ceres, Pallas and Vesta, were taken into account. The mean residual is +/- 0.92 arc second. Note; Rejected observations are not bad. Comet shows some non- gravitational effects (A1 = +8.6 and A2 = -2.1). But we can't solve this since comet has a large perihelion distance. Epoch = 2002 June 15.0 TT T = 2002 June 22.96847 +/- 0.00516 (m.e.) TT Peri. = 28.19349 +/- 0.00070 Node = 13.52583 +/- 0.00021 (2000.0) Inc. = 9.61601 +/- 0.00006 q = 2.9656622 +/- 0.0000100 AU e = 0.5088350 +/- 0.0000015 a = 6.0380163 +/- 0.0000045 AU n' = 0.06642976 +/- 0.00000007 P = 14.837 +/- 0.0000166 years T = 1973 Jan. 24.67121 TT Epoch = 1973 Feb. 7.0 TT Peri. = 28.94267 e = 0.5065113 Node = 15.31256 (2000.0) a = 5.9480543 AU Inc. = 9.64984 n'= 0.06794253 q = 2.9352976 AU P = 14.506 years T = 1987 Aug. 10.21321 TT Epoch = 1987 July 24.0 TT Peri. = 28.49156 e = 0.5100002 Node = 13.55152 (2000.0) a = 6.0992689 AU Inc. = 9.61895 n'= 0.06543158 q = 2.9886408 AU P = 15.063 years The predicted orbit for the 2017 return is as follows: T = 2017 June 19.20241 TT Epoch = 2017 June 16.0 TT Peri. = 29.25548 e = 0.5097330 Node = 13.25172 (2000.0) a = 6.0681335 AU Inc. = 9.63526 n'= 0.06593582 q = 2.9750058 AU P = 14.948 years The following residuals in seconds of arc are from the above orbital elements: Date Code Residual(") Date Code Residual(") Date Code Residual(") 1972/ 870831 691 (2.2- 3.2-) 010916 704 0.0 0.7+ 721011 675 1.4- 2.6- 870831 691 (1.7- 3.2-) 010916 704 1.7- 1.0+ 721014 675 (1.3- 3.0-) 870920 691 1.1- 1.0- 010919 809 0.0 0.2+ 721110 675 0.7+ 1.7- 870920 691 1.0- 0.2- 010919 809 0.0 0.2+ 721113 675 0.5+ 2.1- 870920 691 1.2- 0.2- 011010 644 0.2- 0.3+ 721202 801 0.6- 0.4- 871016 691 0.3- 2.1+ 011010 644 0.1+ 0.5+ 721203 693 1.3+ 0.4- 871016 691 0.0 0.1- 011010 644 0.1- 0.4+ 721203 693 1.3+ 0.0 871016 691 0.3+ 0.1+ 011017 644 0.4- 0.3+ 721203 688 (0.9- 3.5-) 871116 691 0.1+ 0.8+ 011017 644 0.4- 0.8+ 721204 688 (1.0- 4.2-) 871116 691 0.3- 0.9+ 011017 644 0.2+ 1.6+ 721211 801 1.2- 0.0 1988/ 011116 402 0.2+ 0.9- 721213 691 1.6+ 0.3- 880115 691 1.4+ 1.0+ 011116 402 0.5- 0.3- 721213 691 1.8+ 0.2- 880115 691 1.2+ 1.1+ 011116 402 0.6+ 0.9+ 1973/ 880115 691 1.6+ 1.2+ 011120 699 0.6- 0.4+ 730101 693 0.7+ 0.2- 880212 691 (3.2+ 2.1+) 011120 699 0.8+ 0.3- 730101 693 0.2+ 0.5- 880212 691 (3.4+ 2.2+) 011120 699 1.3- 0.3+ 730103 801 (3.0- 1.7+) 880212 691 (3.4+ 2.2+) 011120 699 0.5- 0.4+ 730129 691 0.4+ 1.8+ 880313 691 (4.9+ 0.8+) 011205 704 0.2- 0.0 730129 691 0.4+ 1.6+ 880313 691 (5.5+ 1.4+) 011205 704 1.2+ 0.2+ 730923 691(20.5+ 1.1-) 2001/ 011205 704 0.6- 0.3- 730923 691(18.8+ 3.2-) 010810 809 0.3+ 0.5+ 011205 704 0.3+ 0.4- 1987/ 010810 809 0.4+ 0.6+ 011205 704 0.1+ 1.5- 870829 691 1.7- 1.6- 010810 809 0.5+ 0.4+ 870829 691 2.2- 0.8- 010916 704 0.6- 0.2+ ( ) -------- Rejected Obs.
Director, Computing Section Syuichi Nakano 2001 Dec. 22