Comet Missions - The More The Merrier! Options

[SFJCody]

http://today.reuters.co.uk/news/newsArticl...SPACE-CHINA.xml

Who's next? My money's on India.

[tedstryk]

Looks like a pipe dream to me.

[djellison]

I'll say Europe.


COUGH*Rosetta*COUGH


Doug

[SFJCody]

I'll say Europe.
COUGH*Rosetta*COUGH


Doug

I meant unannounced missions. Rosetta has already launched.

[SFJCody]

Looks like a pipe dream to me.

I dunno. These pipe dreams have a funny habit of becoming reality:

http://firstnews.com.ua/en/science/science.html?id=68552

I'm sure China's comet mission (if there is one) will be more modest than they seem to be hinting at. I really hope so, anyway.

Has anyone here read Stephen Baxter's 'Titan'?

[Bob Shaw]

I dunno. These pipe dreams have a funny habit of becoming reality:

http://firstnews.com.ua/en/science/science.html?id=68552

I'm sure China's comet mission (if there is one) will be more modest than they seem to be hinting at. I really hope so, anyway.

Has anyone here read Stephen Baxter's 'Titan'?  

I think we're safe unless they put any squid aboard!

[tedstryk]

I dunno. These pipe dreams have a funny habit of becoming reality:

http://firstnews.com.ua/en/science/science.html?id=68552

I'm sure China's comet mission (if there is one) will be more modest than they seem to be hinting at. I really hope so, anyway.

Has anyone here read Stephen Baxter's 'Titan'?  

I believe the lunar thing. But sending a comet off course, when they haven't even launched a planetary probe? I think that is bluffing. I do hope they launch a cometary mission.

[Guest_BruceMoomaw_*]

"As opposed to NASA's 'impacting' method, China would use a 'more clever' method that could be called 'pasting', he said, explaining the plan was to soft-land a craft with an engine capable of pushing a comet or asteroid off a collision course."

This is utter hooey as a description of any comet mission in the reasonably near future -- there's a very strong argument for trying to push dangerous NEOs off their course gently instead of ramming them, but any craft capable of doing so would have to have a huge propulsion system (powered by a nuclear reactor).

He may just have been saying, in a sloppy way, that China has in mind a Rosetta-type comet mission involving a rendezvous with a comet followed by a landing on it -- but even that mission is so technolgically sophisticated that I think it will be out of China's technological and economic reach until the late 2020s. What we're seeing here, I'm convinced, is just more nationalistic hooey (encouraged by China's current government, which is frantically whipping up nationalism for all it's worth to try and distract the Chinese public from their discontent at its dictatorship).

[ljk4-1]

N° 41-2005 – Paris, 26 September 2005

ESA selects targets for asteroid-deflecting mission Don Quijote

Based on the recommendations of asteroid experts, ESA has selected two target
asteroids for its Near-Earth Object deflecting mission, Don Quijote.

Don Quijote is an asteroid-deflecting mission currently under study by ESA’s
Advanced Concepts Team (ACT). Earlier this year the NEO Mission Advisory Panel
(NEOMAP), consisting of well-known experts in the field, delivered to ESA a
target selection report for Europe’s future asteroid mitigation missions,
identifying the relevant criteria for selecting a target and picking up two
objects that meet most of those criteria. The asteroids’ temporary designations
are 2002 AT4 and 1989 ML.

With this input and the support of ESA’s Concurrent Design Facility (CDF)
experts, the Advanced Concepts Team has now completed an extensive assessment of
suitable mission architectures, launch strategies, propulsion system options and
experiments.

The current scenario envisages two spacecraft in separate interplanetary
trajectories. One spacecraft (Hidalgo) will impact an asteroid, the other
(Sancho) will arrive earlier at the target asteroid, rendezvous and orbit the
asteroid for several months, observing it before and after the impact to detect
any changes in its orbit.

Industrial studies are now about to start; it will be down to European experts
to propose alternative solutions for the design of the low-cost NEO precursor
mission. This will be the first step towards the development of a means to
tackle asteroid impacts – one of the few natural disasters that our technology
can prevent.

A near miss?

While the eyes of the world were on the Asian tsunami last Christmas, one group
of scientists were watching uneasily for another potential natural disaster –
the threat of an asteroid impact.

On 19 December 2004 MN4, an asteroid of about 400 m, lost since its discovery
six months earlier, was observed again and its orbit was computed. It
immediately became clear that the chances that it could hit the Earth during a
close encounter in 2029 were unusually high. As the days passed the probability
did not decrease and the asteroid became notorious for surpassing
all previous records in the Torino and Palermo impact risk scales - scales that
measure the risk of an asteroid impact just as the Richter scale quantifies the
size of an earthquake.

Only after earlier observations of the object were found and a more accurate
trajectory was computed did it become clear that it would not impact the Earth –
at least not in 2029. Impacts on later dates, though unlikely, have not been
totally ruled out. It is extremely difficult to tell what will happen unless we
come up with a better way to track this or other NEOs and if necessary take
steps to tackle them.

Most world experts agree that this capability is now within our reach. A mission
like ESA’s Don Quijote could provide a means to assess a threatening NEO and
take concrete steps to deflect it away from the Earth.

But every good performance needs rehearsing and in order to be ready for such a
threat, we should try our hardware on a harmless asteroid first. Don Quijote
would be the first mission to make such an attempt. The big question was: which
asteroid and what should it be like?

Looking for the perfect target

The NEO population contains a confusing variety of objects, and deciding which
physical parameters are most relevant for mitigation considerations is no
trivial task. But the NEOMAP experts took on the challenge and in February 2005
provided ESA with their recommendations on the asteroid selection criteria for
ESA’s deflection rehearsal.

People might wonder whether performing a deflection test, such as that planned
for Don Quijote, represents any risk to our planet. What if things go wrong?
Could we create a problem, rather than learn how to avoid one?

Experts world-wide say the answer is no. Even a very dramatic impact of a heavy
spacecraft on a small asteroid would only result in a minuscule modification of
the object’s orbit. In fact the change would be so small that the Don Quijote
mission requires two spacecraft – one to monitor the impact of the other. The
second spacecraft measures the subtle variation of the object’s orbital
parameters that would not be noticeable from Earth.

Target objects can also be selected so that all possible concerns are avoided
altogether, by looking into the way the distance between the asteroid’s and the
Earth’s orbits changes with time. If the target asteroid is not an ‘Earth
crosser’, as is the case with NEOs in the ‘Amor’ class (which have orbits with
perihelion distance well in excess of 1 AU), testing a deflection manoeuvre
represents no risk to the Earth.

Other considerations related to the orbit of the target asteroid are also
important, especially the change of orbital velocity that is required by the
spacecraft to ‘catch up’ with the target asteroid – the so-called ‘delta V’.
This should be sufficiently small to minimise the required amount of spacecraft
propellant and enable the use of cheaper launchers, but high enough to allow the
same spacecraft to be used with a number of possible targets.

Navigation and deflection measurements requirements set some heavy constraints
on the target selection. The shape, density, and size are all important factors,
but are often poorly known. A spacecraft orbiting an asteroid needs to know
about the object’s gravitational field in order to navigate. The ‘impactor
spacecraft’ must know the position of the centre of mass to define the point it
is aiming for.

Asteroids come in all sort of flavours, but as far as composition is concerned
two main types dominate. Our still rudimentary knowledge of the abundance of
asteroids of different types in the near-Earth asteroid population indicates
that the next hazardous asteroid is more likely to be a ‘C-type’, than an
‘S-type’. C-types have dark surfaces with a carbonaceous spectral signature,
while S-types have brighter surfaces, their spectra matching closely that of
silicates. The surface properties of the target asteroid -and in particular the
percentage of light that it reflects - are a critical factor in the final phase
of the impactor spacecraft navigation. The brighter it looks the easier it is to
aim at. However for a rehearsal the target should not be too easy.

ESA has selected asteroids 2002 AT4 and (10302) 1989 ML as mission targets
because they represent best compromise among all the (sometimes conflicting)
selection criteria. A decision on which of the two will become the final
destination of both Sancho and Hidalgo spacecraft will be made in 2007.

Don Quijote – the knight errant rides again

The phase of internal studies on the Don Quijote mission is now over, and it is
time for the space industry to suggest suitable design solutions. ESA has made
an open invitation to European space companies to submit proposals on possible
designs. The selection of the most promising ones will take place towards the
end of the year. In early 2006, two teams should start working on their
interpretations of this technology demonstration mission. A year later, once the
results are available, ESA will select the final design to be implemented, and
then Don Quijote will be ready to take on an asteroid!

Note for editors:

Don Quijote is a NEO deflection test mission based entirely on conventional
spacecraft technologies. It would comprise two spacecraft - one of them
(Hidalgo) impacting an asteroid at a very high relative speed while a second one
(Sancho) would arrive earlier at the same asteroid and remain in its vicinity
before and after the impact to measure the variation on the asteroid’s orbital
parameters, as well as to study the object.

Asteroid 2004 MN has now been given an official designation, (99942) Apophis.
Recent observations using Doppler radar using Arecibo radio telescope in Puerto
Rico have reduced the impact probability during future encounters to very small
levels, though they have not totally ruled out an Earth impact. In 2029, the
asteroid will have the closest approach ever witnessed for an object of this
size, swinging by the Earth at a distance of around 32,000 kilometres. Its
trajectory will be well within the geosynchronous orbit used by most
telecommunications and weather satellites, and the object will be visible to the
naked eye. Further radar measurements are expected in 2013.

Don Quijote target asteroids 2002 AT4 and (10302) 1989 ML do not represent any
danger to our planet.

For more information, please contact

ESA Media Relations Division
Tel: + 33(0)1.53.69.7155
Fax: + 33(0)1.53.69.7690
Email: media@esa.int
Andrés Gálvez
Advanced Concepts Team
ESTEC
Noordwijk
The Netherlands
Tel +31 –71-565-3118
Fax: +31-71-565-8018
E-mail: Andres.Galvez@esa.int

Links:

NEO Space Mission Preparation:
http://www.esa.int/gsp/NEO

Advanced Concepts Team:
http://www.esa.int/ACT

CDF NEO Study:
http://www.esa.int/SPECIALS/CDF/SEMOC4D3M5E_0.html

[mike]

Don Quijote? I suppose maybe ole Don could have taken out a windmill eventually, but why not call the mission 'It'll Never Work'?

[hendric]

2002 AT4 is 160 - 370 m in diameter:
http://earn.dlr.de/nea/K02A04T.htm

(10302) 1989 ML is 600 m in diameter:
http://earn.dlr.de/nea/10302.htm