[meteorite-list] NASA Mars Spacecraft Prepare for Close Comet Flyby (C/2013 A1 Siding Spring)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 25 Jul 2014 15:54:19 -0700 (PDT)
Message-ID: <201407252254.s6PMsJ7K006810_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2014-244

NASA Mars Spacecraft Prepare for Close Comet Flyby
Jet Propulsion Laboratory
July 25, 2014

NASA is taking steps to protect its Mars orbiters, while preserving opportunities
to gather valuable scientific data, as Comet C/2013 A1 Siding Spring heads
toward a close flyby of Mars on Oct. 19.

The comet's nucleus will miss Mars by about 82,000 miles (132,000 kilometers),
shedding material hurtling at about 35 miles (56 kilometers) per second,
relative to Mars and Mars-orbiting spacecraft. At that velocity, even
the smallest particle -- estimated to be about one-fiftieth of an inch
(half a millimeter) across -- could cause significant damage to a spacecraft.

NASA currently operates two Mars orbiters, with a third on its way and
expected to arrive in Martian orbit just a month before the comet flyby.
Teams operating the orbiters plan to have all spacecraft positioned on
the opposite side of the Red Planet when the comet is most likely to pass
by.

"Three expert teams have modeled this comet for NASA and provided forecasts
for its flyby of Mars," explained Rich Zurek, chief scientist for the
Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena,
California. "The hazard is not an impact of the comet nucleus, but the
trail of debris coming from it. Using constraints provided by Earth-based
observations, the modeling results indicate that the hazard is not as
great as first anticipated. Mars will be right at the edge of the debris
cloud, so it might encounter some of the particles -- or it might not."

During the day's events, the smallest distance between Siding Spring's
nucleus and Mars will be less than one-tenth the distance of any known
previous Earthly comet flyby. The period of greatest risk to orbiting
spacecraft will start about 90 minutes later and last about 20 minutes,
when Mars will come closest to the center of the widening dust trail from
the nucleus.

NASA's Mars Reconnaissance Orbiter (MRO) made one orbit-adjustment maneuver
on July 2 as part of the process of repositioning the spacecraft for the
Oct. 19 event. An additional maneuver is planned for Aug. 27. The team
operating NASA's Mars Odyssey orbiter is planning a similar maneuver on
Aug. 5 to put that spacecraft on track to be in the right place at the
right time, as well.

NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft is on
its way to the Red Planet and will enter orbit on Sept. 21. The MAVEN
team is planning to conduct a precautionary maneuver on Oct. 9, prior
to the start of the mission's main science phase in early November.

In the days before and after the comet's flyby, NASA will study the comet
by taking advantage of how close it comes to Mars. Researchers plan to
use several instruments on the Mars orbiters to study the nucleus, the
coma surrounding the nucleus, and the tail of Siding Spring, as well as
the possible effects on the Martian atmosphere. This particular comet
has never before entered the inner solar system, so it will provide a
fresh source of clues to our solar system's earliest days.

MAVEN will study gases coming off the comet's nucleus into its coma as
it is warmed by the sun. MAVEN also will look for effects the comet flyby
may have on the planet's upper atmosphere and observe the comet as it
travels through the solar wind.

Odyssey will study thermal and spectral properties of the comet's coma
and tail. MRO will monitor Mars' atmosphere for possible temperature increases
and cloud formation, as well as changes in electron density at high altitudes.
The MRO team also plans to study gases in the comet's coma. Along with
other MRO observations, the team anticipates this event will yield detailed
views of the comet's nucleus and potentially reveal its rotation rate
and surface features.

Mars' atmosphere, though much thinner than Earth's, is thick enough that
NASA does not anticipate any hazard to the Opportunity and Curiosity rovers
on the planet's surface, even if dust particles from the comet hit the
atmosphere and form into meteors. Rover cameras may be used to observe
the comet before the flyby, and to monitor the atmosphere for meteors
while the comet's dust trail is closest to the planet.

Observations from Earth-based and space telescopes provided data used
for modeling to make predictions about Siding Spring's Mars flyby, which
were in turn used for planning protective maneuvers. The three modeling
teams were headed by researchers at the University of Maryland in College
Park, the Planetary Science Institute in Tucson, Arizona, and JPL.

For more information about the Mars flyby of comet Siding Spring, visit:

http://mars.nasa.gov/comets/sidingspring

For more information about NASA's Mars Exploration Program, visit:

http://www.nasa.gov/mars

Dwayne Brown
NASA Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster at jpl.nasa.gov

244-2014
Received on Fri 25 Jul 2014 06:54:19 PM PDT