[meteorite-list] UK Plans to Track Apophis (Apex)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 31 Aug 2007 15:36:05 -0700 (PDT)
Message-ID: <200708312236.PAA21342_at_zagami.jpl.nasa.gov>

http://news.bbc.co.uk/1/hi/sci/tech/6971216.stm

UK plan to track asteroid threat
BBC News
August 31, 2007

UK space scientists and engineers have designed a mission to investigate
a potentially hazardous asteroid.

The 300m-wide (980ft) rock, known as Apophis, will fly past Earth in
April 2029 at a distance that is closer than many communications
satellites.

Astrium, based in Stevenage, Herts, wants a probe to track the asteroid
so its orbit can be better understood.

The concept will compete for a $50,000 (?25,000) Planetary Society
prize, but a full mission would cost millions.

The British design calls for a small, remote-sensing spacecraft, dubbed
Apex (Apophis Explorer), which could rendezvous with Apophis in January
2014.

It would then spend the next three years tracking the rock, sending data
back to Earth about the object's size, shape, spin, composition and
temperature.

>From this information, orbit modelling would enable a more accurate
prediction of the risk of any future collision.

Astrium says that if its concept won the prize, it would donate the
money to charity.

"The real prize for us would be if the European or US space agencies
thought there was merit in our proposal and asked us to carry the
feasibility study forward," said Dr Mike Healy, the company's space
science director.

A full mission would be expected to cost about $500m (?250m) dollars to
develop, launch and operate.

Early warning

Apophis caused some consternation in 2004 when initial observations
suggested there was an outside chance it might hit Earth in 2029.

Further study by ground-based telescopes indicated there was virtually
no possibility of this happening, and the expectation is that the object
will whiz past the Earth at a close but comfortable distance of just
under 36,000km (22,400 miles).

Talk of a possible strike on another visit in 2036 has also been
dampened by astronomers who have kept a careful watch on the rock's
progress through space.

However, there is always some uncertainty associated with an asteroid's
orbit.

One reason is the Yarkovsky effect. This describes what happens when an
asteroid radiates energy absorbed from the Sun back into space.

Releasing heat in one direction nudges the object in the opposite
direction. The resulting acceleration is tiny, but over the centuries
acts like a weak rocket and could make the difference between a hit or a
miss in some circumstances.

The close encounter with Earth in 2029 will also perturb Apophis' orbit
gravitationally.

A mission like Apex to track and study the rock would help reduce
uncertainties and give solid predictions about the rock's course long
into the future.

Political support

At the moment, scientists stress Apophis is not thought to be a serious
danger to Earth.

But were such a rock to hit the planet, it could cause devastation on a
country-wide scale, leading possibly to the deaths of many millions of
people.

An Apophis-like object striking at about 20km/s (45,000mph) would gouge
a crater 5km (three miles) wide. Even standing 30km (18 miles) away from
the impact site, a thermal blast would ignite your clothes and the
ground would shudder with an earthquake measuring more than six on the
Richter Scale.

Rocks thrown up into the air by the impact would rain down - many of
them huge lumps a metre wide.

Given sufficient warning, though, a potential impactor could be
deflected out of Earth's path, scientists believe.

Some have suggested such a rock might be nudged on to a safe trajectory
by hitting it with a small mass. Others have proposed flying a
spacecraft next to the object, to use gravity to tug the asteroid clear
of the planet.

The issue of asteroid or comet strikes is a topical one as researchers
continue to gather more information about their frequency during Earth
history.

At least one of the planet's mass extinction events - which included the
demise of the dinosaurs 65 million years ago - has been attributed to
the impact of a large space object.

Liberal Democrat MP Lembit Opik has campaigned for the research area to
be given more funding. His grandfather, renowned Estonian astronomer
Ernst Opik, did much to raise science's understanding of Earth-crossing
comets and asteroids.

The politician told the BBC News website: "The question isn't whether
Earth is hit by an asteroid - it is when.

"Good luck to Astrium; they are showing that if we have the political
will, we certainly have the technical know-how to do something about
threatening objects."

The US-based Planetary Society has organised its competition in
co-operation with the European Space Agency (Esa), the US space agency
(Nasa), the Association of Space Explorers (ASE), the American Institute
of Aeronautics and Astronautics (AIAA), and the Universities Space
Research Association (USRA).

The winning entry will be submitted to space agencies to see if they
want to carry the ideas through.
Received on Fri 31 Aug 2007 06:36:05 PM PDT