Limits on Pluto’s ring system from the June 12 2006 stellar occultation and implications for the New Horizons impact hazard

• Published in: Icarus (New York, N.Y. 1962) Vol. 246; pp. 345 - 351
• Main Authors: Throop, Henry B., French, Richard G., Shoemaker, Kevin, Olkin, Cathy B., Ruhland, Trina R., Young, Leslie A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.2015
• Subjects: Hazards; Hubble Space Telescope; New Horizons mission; Occultation; Occultations; Photometry; Planetary rings; Pluto; Small satellites; Spacecraft; Occultations; Planetary rings; Pluto
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2014.05.020

•Deep search for rings around Pluto system using stellar occultation.•No rings detected at optical depth 0.06 for narrow rings.•Limits from these observations and Hubble Space Telescope non-detections can be used to help assure mission safety for upcoming New Horizons flyby of Pluto. The Pluto system passed in front of a 15th magnitude star on 12 June 2006. We observed this occultation from the 3.9m Anglo-Australian Telescope (AAT), and took photometric observations every 100ms for 3h. Our three-hour baseline of data provides among the longest and highest-quality occultation dataset of the Pluto system ever taken. Results on Pluto’s atmospheric structure from these data have been previously reported (Young, E.F. [2008]. Astron. J. 136, 1757–1769). Here we report on limits for rings, ring arcs, and small satellites within the system. We find a 3σ upper limit on the normal optical depth of τ<0.07 for narrow rings of width 2.4km, and τ<5×10-3 for rings of width 1500km. We also detect no discrete objects of radius 220m or larger along the occultation path. Motivated by the upcoming flyby of New Horizons through the Pluto system, we estimate the dust impact hazard to the spacecraft based on our optical depth limits and those derived from imaging with the Hubble Space Telescope.