FORCED PRECESSION MODEL FOR 3 PERIODIC COMETS - 30P REINMUTH-1, 37P/FORBES, AND 43P/WOLF-HARRINGTON/

The nongravitational motion of three short-period comets-discovered in the twenties and running on similar heliocentric orbits-has been inve stigated. We used the Sekanina's forced precession model of the rotati ng cometary nucleus to include the nongravitational terms into equatio ns of the comet's motion. Values of six precessional parameters: A, et a, I, phi, f(p) and s have been determined along with corrections to o rbital elements from astrometric observations of the comets. We were a ble to link successfully all the observations of each comet over inter val of time spanning about seventy years. According to our solutions, the nucleus of comet Reinmuth 1 is oblate whereas those of comets Forb es and Wolf-Harrington are prolate along the spin-axis.