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TOPIC: Asteroid (101955) 1999 RQ36


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Asteroid (101955) Bennu
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Title: Bifurcation of equilibrium points in the potential field of asteroid 101955 Bennu
Author: Xianyu Wang, Junfeng Li, Shengping Gong

The stability and topological structure of equilibrium points in the potential field of the asteroid 101955 Bennu have been investigated with a variable density and rotation period. A dimensionless quantity is introduced for the nondimensionalization of the equations of motion, and this quantity can indicate the effect of both the rotation period and bulk density of the asteroid. Using the polyhedral model of the asteroid Bennu, the number and position of the equilibrium points are calculated and illustrated by a contour plot of the gravitational effective potential field. The topological structure and the stability of the equilibrium points are also investigated using the linearized method. The results show that there are nine equilibrium points in the potential field of the asteroid Bennu, eight in the exterior of the body and one in the interior of the body. Moreover, bifurcation will occur with a variation of the density and rotation period. Different equilibrium points will encounter each other and mix together. Thus, the number of equilibrium points will change. The stability and topological structure of the equilibrium points will also change because of the variation of the density and rotation period of the asteroid. When considering the error of the density of Bennu, the range of the dimensionless quantity covers the critical values that will lead to bifurcation. This means that the stability of the equilibrium points is uncertain, making the dynamical environment of Bennu much more complicated. These bifurcations can help better understand the dynamic environment of an irregular-shaped asteroid.

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Asteroid Bennu
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Title: The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu
Author: D.C. Reuter, A.A. Simon, J. Hair, A. Lunsford, S. Manthripragada, V. Bly, B. Bos, C. Brambora, E. Caldwell, G. Casto, Z. Dolch, P. Finneran, D. Jennings, M. Jhabvala, E. Matson, M. McLelland, W. Roher, T. Sullivan, E. Weigle, Y. Wen, D. Wilson, D.S. Lauretta

The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm-1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.

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Asteroid (101955) Bennu
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MITs REXIS is bound for asteroid Bennu

An SUV-sized spacecraft, loaded with instruments and an extendable robotic arm, will soon be barreling toward a space rock, on a round-trip journey that promises to return an unprecedented souvenir: extraterrestrial soil, taken directly from an asteroid, that could hold clues to the very early universe.

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RE: Asteroid (101955) Bennu (1999 RQ36)
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NASA Spacecraft Will Visit Asteroid with New Name

An asteroid that will be explored by a NASA spacecraft has a new name, thanks to a third-grade student in North Carolina.
NASA's Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer (OSIRIS-REx) spacecraft will visit the asteroid now called Bennu, named after an important ancient Egyptian avian deity. OSIRIS-Rex is scheduled to launch in 2016, rendezvous with Bennu in 2018 and return a sample of the asteroid to Earth in 2023.
The name for the carbon-rich asteroid, designated in the scientific community as (101955) 1999 RQ36, is the winning entry in an international student contest. Nine-year-old Michael Puzio suggested the name because he imagined the Touch-and-Go Sample Mechanism (TAGSAM) arm and solar panels on OSIRIS-REx look like the neck and wings in drawings of Bennu, which Egyptians usually depicted as a gray heron. Puzio wrote the name suits the asteroid because it means "the ascending one," or "to shine."
 
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RE: Asteroid (101955) 1999 RQ36
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New Observations Confirm NASA Mission's Target Asteroid As Sample-Friendly Rubble Pile

New observations of the asteroid in the sights of NASAs 2016 OSIRIS-REx mission - due to take an actual physical sample of the near-earth asteroid 1999 RQ36 and return it safely to a Utah desert by 2023 - confirm that its an ideal target from which to secure some of the solar systems most primitive matter.
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Title: Physical Properties of OSIRIS-REx Target Asteroid (101955) 1999 RQ36 derived from Herschel, ESO-VISIR and Spitzer observations
Authors: T. G. Mueller, L. O'Rourke, A. M. Barucci, A. Pal, C. Kiss, P. Zeidler, B. Altieri, B. M. Gonzalez-Garcia, M. Kueppers

In September 2011, the Herschel Space Observatory performed an observation campaign with the PACS photometer observing the asteroid (101955) 1999 RQ36 in the far infrared. The Herschel observations were analysed, together with ESO VLT-VISIR and Spitzer-IRS data, by means of a thermophysical model in order to derive the physical properties of 1999 RQ36. We find the asteroid has an effective diameter in the range 480 to 511 m, a slightly elongated shape with a semi-major axis ratio of a/b=1.04, a geometric albedo of 0.045 +0.015/-0.012, and a retrograde rotation with a spin vector between -70 and -90 deg ecliptic latitude. The thermal emission at wavelengths below 12 micron -originating in the hot sub-solar region- shows that there may be large variations in roughness on the surface along the equatorial zone of 1999 RQ36, but further measurements are required for final proof. We determine that the asteroid has a disk-averaged thermal inertia of Gamma = 650 Jm-2s-0.5K-1 with a 3-sigma confidence range of 350 to 950 Jm-2s-0.5K-1, equivalent to what is observed for 25143 Itokawa and suggestive that 1999 RQ36 has a similar surface texture and may also be a rubble-pile in nature. The low albedo indicates that 1999 RQ36 very likely contains primitive volatile-rich material, consistent with its spectral type, and that it is an ideal target for the OSIRIS-REx sample return mission.

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Asteroid-Naming Contest for Kids Involves UT Professor's Work

Josh Emery, assistant professor in earth and planetary sciences at the University of Tennessee, Knoxville, works on the OSIRIS-REx asteroid sample return mission, which is now hosting a contest that will allow kids under the age of 18 to name an asteroid.
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Asteroid-naming contest for children

Students worldwide have an opportunity to name an asteroid from which an upcoming NASA mission will return the first samples to Earth.
The competition is open to students under age 18 from anywhere in the world. Each contestant can submit one name, up to 16 characters long. Entries must include a short explanation and rationale for the name. Submissions must be made by an adult on behalf of the student. The contest deadline is Sunday, December 2, 2012.

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NASA Scientist Figures Way to Weigh Space Rock

A scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., has accurately determined the mass of a nearby asteroid from millions of miles away. The celestial equivalent of "guess your weight" was achieved by Steve Chesley of JPL's Near-Earth Object Program Office by utilising data from three NASA assets - the Goldstone Solar System Radar in the California desert, the orbiting Spitzer Space telescope, and the NASA-sponsored Arecibo Observatory in Puerto Rico.
Chesley presented his findings this past Saturday, May 19, at the Asteroids, Comets and Meteors 2012 meeting in Niigata, Japan.
For Chesley to define the asteroid's mass, he first needed to understand its orbit and everything that could affect that orbit -- including neighbouring celestial bodies and any propulsive force (however minute) the asteroid could generate.
Incorporating extraordinarily precise observations collected by astronomer Michael Nolan at Arecibo Observatory in September 2011, Arecibo and Goldstone radar observations made in 1999 and 2005, and the gravitational effects of the sun, moon, planets and other asteroids, Chesley was able to calculate how far the asteroid deviated from its anticipated orbit. He found that 1999 RQ36 had deviated from the mathematical model by about 160 kilometres in the past 12 years. The only logical explanation for this orbital change was that the space rock itself was generating a minute propulsive force known in space rock circles as the Yarkovsky effect.

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Google earth file: Asteroid (101955) 1999 RQ36 - 2012.kmz (18kb, kmz)



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