Activity of comets at large heliocentric distances pre-perihelion Posted on June 26, 2014 by UHNAI Webmaster in Meech, K. J., Pittichova, J., Bar-Nun, A., Notesco, G., Laufer, D., Hainaut, O. R., Lowry, S. C., Yeomans, D. K., Pitts, M. (). Activity of comets at large heliocentric distances pre-perihelion. , 201,