How to find the orbital needle in the celestial haystack (Forwarded)

ESA News
http://www.esa.int

2 February 2006

How to find the orbital needle in the celestial haystack

Today experts from across the world meet at ESA to discuss how to best
calculate spacecraft orbits. Even though the space age is now 49 years
old, determining the optimal trajectories for spacecraft is a far from
easy task.

People often have trouble deciding which is the best route to take on a
car journey. In space the problems are much worse. Space missions are
constrained by certain factors such as the thrust of the rocket used to
launch the spacecraft, the celestial object you want to reach and the time
at which you want to get there. When working out the best trajectories
within such constraints, engineers all have different strategies.

"Ask ten engineers for the best orbit for a particular spacecraft and
you'll get ten different ideas," says Dr Dario Izzo, a researcher on
mission analysis in the Advanced Concepts Team at ESA's European Space and
Technology Research Centre (ESTEC) in the Netherlands. Each one of these
missions will be the best for a certain reason, so the question becomes:
what's the best of the best? One of the proposed trajectories or another
that no-one has thought of?

In other words, orbits are like needles in a haystack. Search hard enough
and you'll find one, but is it the best one in the haystack? That's where
the new technique of global optimisation comes in. It is a method of
handling complex problems with many variables that has lots of solutions.
But there are many techniques for global optimisation and they are
difficult to compare since they seldom use the same constraints when
applied.

To compare and contrast different techniques, ESA's Advanced Concepts
Team, supported by the European Space Operations Centre (ESOC), launched a
competition. They issued a challenge to space engineers across the world
to find an intercept trajectory that delivered as much energy as possible
to the asteroid 2001 TW229.

Twelve teams, from the US, China, Russia and Europe submitted their
respective best solution. Izzo's job was to rank the proposals according
to how much energy each mission could impart to the asteroid. "The
inspiration for this competition was asteroid deflection, a problem we
have been working on quite thoroughly" says Izzo. Whilst asteroid 2001
TW229 presents no danger to Earth, issuing a call for trajectories
simulated a step that would be taken in the event that a potentially
dangerous asteroid were to be discovered. The key to the mission would be
to deliver the largest push possible, in time for it to do the most good.

The top ranked trajectory went to a team from the United States' Jet
Propulsion Laboratory (closely followed by two Spanish teams). Their
amazing trajectory involved seven planetary flybys, mostly of the Earth
but including Venus, Jupiter and Saturn that literally smashed the
spacecraft into a head-on collision with the asteroid.

The teams will now meet in the Netherlands to discuss their individual
approaches to the problem. "The response to the competition was excellent.
At the meeting we will discuss the different methods used and identify the
ones that have proven the most promising," says Izzo.

In fact, the response to the competition was so good that the Advanced
Concepts Team also hope to run future competitions, to further stimulate
research in the exciting field of mission analysis.

For further information please contact:

Dr Dario Izzo
ESA Advanced Concepts Team
ESTEC
EUI-ACT
Keplerlaan 1
2201 AZ Noordwijk
The Netherlands
Tel: +31(0)71 565 3511
Fax: +31(0)71 565 8018

Related articles

* Designing the missions of the future
http://www.esa.int/esaCP/SEMU1CVLWFE_index_0.html
* ESA selects targets for asteroid-deflecting mission Don Quijote
http://www.esa.int/esaCP/SEML9B8X9DE_index_0.html

Related links

* Advanced Concepts Team
http://www.esa.int/gsp/ACT/index.htm
* ESOC
http://www.esa.int/esoc

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/esaCP/SEMWKINZCIE_index_1.html]
Best trajectory to intercept an asteroid

Artist's impression of the final moments before impact with asteroid 2001
TW229.

To compare and contrast different techniques of global optimisation, ESA's
Advanced Concepts Team, supported by the European Space Operations Centre
(ESOC), launched a competition in 2005. They issued a challenge to space
engineers across the world to find an intercept trajectory that delivered
as much energy as possible to the asteroid 2001 TW229.

Credits: ESA

[Image 2:
http://www.esa.int/esaCP/SEMWKINZCIE...html#subhead2]
The winning trajectory from JPL.

Credits: ESA