The complex spin state of 103P/Hartley 2: Kinematics and orientation in space

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 2013-02, Vol.222 (2), p.595-609
• Main Authors: Belton, Michael J.S., Thomas, Peter, Li, Jian-Yang, Williams, Jade, Carcich, Brian, A’Hearn, Michael F., McLaughlin, Stephanie, Farnham, Tony, McFadden, Lucy, Lisse, Carey M., Collins, Steven, Besse, Sebastien, Klaasen, Kenneth, Sunshine, Jessica, Meech, Karen J., Lindler, Don
• Format: Article
• Language: English
• Subjects: Comets; Comets, Nucleus; Lunar And Planetary Science And Exploration; Rotational dynamics
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2012.06.037

► We show how the nucleus of the comet wobbles as it spins. ► We deduce how the spin state is oriented in space. ► We show how the spin state evolves with time becoming more excited as it slows down. ► We calculate the length of daytime at places on the nucleus that show activity. We derive the spin state of the nucleus of Comet 103P/Hartley 2, its orientation in space, and its short-term temporal evolution from a mixture of observations taken from the DIXI (Deep Impact Extended Investigation) spacecraft and radar observations. The nucleus is found to spin in an excited long-axis mode (LAM) with its rotational angular momentum per unit mass, M, and rotational energy per unit mass, E, slowly decreasing while the degree of excitation in the spin increases through perihelion passage. M is directed toward (RA, Dec; J2000)=8±4°, 54±1° (obliquity=48±1°). This direction is likely changing, but the change is probably