Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations
Authors: Buie Marc W. , Porter Simon B. , Tamblyn Peter , Terrell Dirk , Parker Alex Harrison , Baratoux David , Kaire Maram , Leiva Rodrigo , Verbiscer Anne J. , Zangari Amanda M. , Colas François , Diop Baidy Demba , Samaniego Joseph I. , Wasserman Lawrence H. , Benecchi Susan D. , Caspi Amir , Gwyn Stephen , Kavelaars J. J. , Ocampo Uría Adriana C. , Rabassa Jorge , Skrutskie M. F. , Soto Alejandro , Tanga Paolo , Young Eliot F. , Stern S. Alan , Andersen Bridget C. , Arango Pérez Mauricio E. , Arredondo Anicia , Artola Rodolfo Alfredo , Bâ Abdoulaye , Ballet Romuald , Blank Ted , Bop Cheikh Tidiane , Bosh Amanda S. , Camino López Matías Aarón , Carter Christian M. , Castro-Chacón J. H. , Caycedo Desprez Alfonso , Caycedo Guerra Nicolás , Conard Steven J. , Dauvergne Jean-Luc , Dean Bryan , Dean Michelle , Desmars Josselin , Dieng Abdou Lahat , Bousso Dieng Mame Diarra , Diouf Omar , Dorego Gualbert Séraphin , Dunham David W. , Dunham Joan , Durantini Luca Hugo A. , Edwards Patrick , Erasmus Nicolas , Faye Gayane , Faye Mactar , Ferrario Lucas Ezequiel , Ferrell Chelsea L. , Finley Tiffany J. , Fraser Wesley C. , Friedli Alison J. , Galvez Serna Julián , Garcia-Migani Esteban A. , Genade Anja , Getrost Kai , Gil-Hutton Ricardo A. , Gimeno German N. , Golub Eli Joseph , González Murillo Giovanni Francisco , Grusin Michael D. , Gurovich Sebastian , Hanna William H. , Henn Santiago M. , Hinton P. C. , Hughes Paul J. , Josephs Jr John David , Joya Raul , Kammer Joshua A. , Keeney Brian A. , Keller John M. , Kramer Emily A. , Levine Stephen E. , Lisse Carey M. , Lovell Amy J. , Mackie Jason A. , Makarchuk Stanislav , Manzano Luis E. , Mbaye Salma Sylla , Mbaye Modou , Melia Raul Roberto , Moreno Freddy , Moss Sean K. , Ndaiye Diene , Ndiaye Mapathe , Nelson Matthew J. , Olkin Catherine B. , Olsen Aart M. , Ospina Moreno Victor Jonathan , Pasachoff Jay M. , Pereyra Mariana Belen , Person Michael J. , Pinzón Giovanni , Pulver Eduardo Alejandro , Quintero Edwin A , Regester Jeffrey R. , Resnick Aaron Caleb , Reyes-Ruiz Mauricio , Rolfsmeier Alex D. , Ruhland Trina R. , Salmon Julien , Santos-Sanz Pablo , Santucho Marcos Ariel , Sepúlveda Niño Diana Karina , Sickafoose Amanda A. , Silva José S. , Singer Kelsi N. , Skipper Joy N. , Slivan Stephen M. , Smith Rose J. C. , Spagnotto Julio C. , Stephens Andrew W. , Strabala Samuel D. , Tamayo Francisco J. , Throop Henry B. , Torres Cañas Andrés David , Toure Labaly , Traore Alassane , Tsang Constantine C. C. , Turner Jake D. , Vanegas Santiago , Venable Roger , Wilson John C. , Zuluaga Carlos A. , Zuluaga Jorge I. 
Published: February 2020

Abstract
We present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies.