[meteorite-list] Astronomers Plan Last Look at Asteroid 1999 RQ36 Before OSIRIS-REx Launch

[Ron Baalke]

FOR IMMEDIATE RELEASE

FROM THE UNIVERSITY OF ARIZONA

Sept. 13, 2011

This story and photos are online at: http://uanews.org/node/41796 .

Contact information follows this story.

Astronomers Plan Last Look at Asteroid Before OSIRIS-REx Launch

Every six years, asteroid 1999 RQ36 nears the Earth - by cosmic standards -
and researchers are launching a global observation campaign to learn as much 
as possible in preparation for the OSIRIS-REx, the first U.S.-led mission 
to bring back a sample of pristine asteroid material.

Astronomers working on the U.S.' first asteroid-sample return mission - the 
NASA mission named OSIRIS-REx - have begun a months-long observing campaign 
that is the last chance to study their target asteroid from Earth before 
the OSIRIS-REx spacecraft launches in 2016.

OSIRIS-REx is a quest to bring back to Earth a good-sized sample of an 
asteroid unaltered since solar system formation - a sample that very well 
could contain molecules that seeded life.

Discovered in 1999, the OSIRIS-REx target asteroid, designated 1999 RQ36, 
nears Earth once every six years.  During the 2011 closest approach in early
September, it will be 10.9 million miles (17.5 million kilometers) away. In 
1999, closest approach was 1.4 million miles (2.3 million kilometers).

"Six years sets the whole cadence for our mission," said Dante Lauretta of 
the University of Arizona Lunar and Planetary Laboratory, deputy principal 
investigator for the OSIRIS-REx mission.

"The next chance for ground-based telescopes to see this asteroid will be in 
2017, when it again nears Earth. Our spacecraft performs a gravity-assist
at this time, giving it the kick it needs to rendezvous with the asteroid 
in 2019-20. The next chance for ground-based astronomy is 2023, the year the 
spacecraft returns a sample of the asteroid to Earth."

1999 RQ36 last attracted astronomers' attention in 2005, when it passed 3.1
million miles (5 million kilometers) from Earth and appeared 30 times brighter 
than it does this year.

In 2005, Carl Hergenrother of the UA Lunar and Planetary Laboratory was 
searching with the 61-inch Kuiper telescope on Mt. Bigelow north of Tucson for
exciting targets for the proposed asteroid sample-return mission. He observed 
1999 RQ36.

"Looking at my data, I saw this was a B-type asteroid, which is carbonaceous 
and related to unusual outer main-belt asteroids that act like comets by 
outgassing volatiles," Hergenrother, who heads the OSIRIS-REx asteroid 
astronomy working group, said.

After a quick search of the scientific literature, which turned up nothing 
on the object, he did a Google search. Jackpot.

"Astronomers had been observing this asteroid, just not formally publishing
about it," Hergenrother said. "Their results were sitting on their personal 
Web pages. They had radar images of it, visible and near-infrared observations, 
confirmed it was a B-type (bluish) asteroid, got a pretty good light curve and 
a rotation period, although the rotation period was wrong."

Michael Drake of the UA Lunar and Planetary Laboratory, principal investigator 
for OSIRIS-REx, urged Josh Emery, one of Drake's former students, now of 
the University of Tennessee and a co-investigator on OSIRIS-REx, to observe 
1999 RQ36 with the Spitzer Space Telescope. Emery won the telescope time,
providing first observations of the asteroid at thermal infrared wavelengths.

"Coming out of 2006-07, 1999 RQ36 was probably the best-studied near-Earth 
asteroid out there that hadn't already been visited by a spacecraft," 
Hergenrother said. "We lucked out in that not only is this an asteroid that's 
relatively easy to get to, it is extremely interesting, exactly the kind of 
object that we want for this mission."

The international team of astronomers collaborating in the fall 2011-spring 
2012 observing campaign for 1999 RQ36 have time or are applying for time on 
a network of telescopes operating in Arizona, the Canary Islands, Chile, Puerto 
Rico and space.

The new observations will not only influence mission planning and development, 
but will directly address two key OSIRIS-REx mission goals, Lauretta said.

One goal is to check results from ground-based observations against results 
from OSIRIS-REx spacecraft observations that will be made in 2019-20 as the 
spacecraft circles the asteroid for about 500 days.

Another goal is to measure a slight force called the "Yarkovsky effect" to 
better understand the likelihood that potentially hazardous near-Earth 
asteroids, such as 1999 RQ36, will strike our planet, and when.

# # #

LINK:

The University of Arizona Lunar and Planetary Laboratory: http://www.lpl.arizona.edu

CONTACTS:

Dante S. Lauretta
UA Lunar and Planetary Laboratory
520-626-1138
lauretta at lpl.arizona.edu

Carl W. Hergenrother
UA Lunar and Planetary Laboratory
520-237-6432
chergen at lpl.arizona.edu

Daniel Stolte
University Communications
The University of Arizona
520-626-4402
stolte at email.arizona.edu