From: LARRY KLAES (ljk4_at_msn.com)
Date: Mon Sep 26 2005 - 13:58:39 UTC
>From: "ESA" <contactesa_at_esa.int>
>Reply-To: ContactESA_at_esa.int
>To: (Larry Klaes) Country: , Member of Media: , Media: <ljk4_at_msn.com>
>Subject: Press Release N° 41-2005-ESA selects targets for
>asteroid-deflecting mission Don Quijote
>Date: Mon, 26 Sep 2005 14:06:27 +0100
>
>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_at_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_at_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
>
>
>
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