AAVSO: American Association of Variable Star Observers

The Challenge of Finding the Comet for the Deep Impact Extended Mission (Abstract)

Volume 36 number 2 (2008)

Karen Meech

Abstract

(Abstract only) The spectacular success of the Deep Impact mission coupled with adequate fuel reserves led to the authorization for the Deep Impact project to perform a maneuver on 2005 July 24 that would bring the flyby spacecraft back to the Earth’s neighborhood in late 2007 for an extended mission to another comet. The goal of the extended mission will be to explore the diversity of comets, exploring the range of cometary topography, activity, thermal properties and chemistry. There were two possible comets accessible to the spacecraft: 103P/Hartley and 85P/Boethin. Of the two, 85P/Boethin is a much more desirable target. In order to re-direct the spacecraft to the comet, preparations for the December Earth-flyby maneuver are to begin with deep space maneuvers in early November 2007. On January 4, 1975, one day prior to its perihelion passage, short period comet 85P/Boethin was discovered by Reverend Leo Boethin in the Philippines. The comet was followed until early June. With an orbital period of 11.23 years, the comet was expected at its next perihelion passage in January 1986. It was recovered by Alan Gilmore and Pam Kilmartin in New Zealand on October 11, 1985 and followed just beyond its perihelion passage (January 16) until March 1986. Due to very poor observing conditions when the comet reached perihelion near superior conjunction, the comet was not observed during its most recent return to perihelion in April 1997. This comet gets bright enough for small telescope observations right near perihelion and the dust and gas coma and tail becomes visible approximately three months before perihelion. In order to fully map the orbit, observations are needed at three apparitions. This paper will discuss the role that small telescopes can play and will report on our attempts to recover this comet for a third apparition, in what is turning out to be the most challenging comet recovery ever done, using most of the world’s largest telescopes. We will know by October 19 if we have a mission target!