Asteroids

Searching for the Grandest Asteroid Tour

Asteroids are Earth's closest celestial neighbors, sometimes passing closer to Earth than even the Moon. And yet, to date, only two spacecraft have ever remained in proximity to one of these bodies. Last month, orbit mechanics experts from around the world met to discuss methods for finding the best possible spacecraft trajectory, or flight path, for visiting a sequence of asteroids. The gathering was part of the second Global Trajectory Optimisation Competition, organized by JPL.
Ida and its small satellite Dactyl are main belt asteroids located between Mars and Jupiter

Ida and its small satellite Dactyl are main belt asteroids located between Mars and Jupiter

The idea of an asteroid grand tour is a celestial analogue to the Grand Tour embarked upon by Renaissance travelers seeking to further their cultural knowledge of Europe. Just as the traveler had to judge carefully which cities to visit based on his or her available resources, so must designers of a spacecraft flight path contend with limited resources and constraints. Such restrictions include the rocket's ability to launch the spacecraft into space, the strength of the spacecraft's thruster, orbital positions of the various asteroids over time, and the spacecraft's longevity.

Determining the best possible trajectory within these constraints, out of the many good ones, is not a trivial matter. It requires a big-picture, or global, view of all the possibilities, that is, it requires global optimization. There are many possible approaches, each with its own strengths and weaknesses.

The inspiration for this problem was the need to study closely different types of asteroids. By visiting a member of each of four different asteroid groups, a spacecraft would provide insights into their chemical composition, their structural characteristics, how they formed, and which might be suitable for future space mining operations. Such insights would also be critical should the need ever arise to deflect an asteroid that is found to be on an Earth-threatening trajectory.

The problem posed by JPL's Outer Planets Mission Analysis Group for the second competition was to design a flight path for visiting four asteroids-- one from each group -- in the shortest amount of flight time and with the least amount of propellant. With almost 1,000 asteroids to choose from, more than 41 billion asteroid sequences could be considered. That's far too many to study individually in the short time allocated for the competition, even with the fastest computers, largest computer clusters and best algorithms.

Fourteen teams - from Europe, Russia, China and the U.S. - sought the elusive best possible trajectory. Their search took place over a period of four weeks late last year, at the end of which they submitted their top solution to be ranked against those of the other teams.

The winning trajectory was found by a team from the Polytechnic of Turin, Italy. Two professors, Lorenzo Casalino and Guido Colasurdo, along with Ph.D. student Matteo Rosa Sentinella and graduate student Francesco Cacciatore, successfully and quickly screened out billions of possible asteroid sequences to focus on the most practical ones. Their winning trajectory, involving visits of four different asteroids in just over nine years, was followed by trajectories from a Russian team (the Moscow Aviation Institute and the Khrunichev State Research and Production Space Center), and a team from the European Space Agency's Advanced Concepts Team.

The workshop where the various teams convened for their discussions took place in Sedona, Ariz., in conjunction with the Space Flight Mechanics Meeting of the American Astronautical Society and the American Institute of Aeronautics and Astronautics.

Did the competition yield the best possible trajectory? With such complexity, it is likely impossible to say, but an educated guess, and the insights gained by comparing the various teams' methods, would suggest that there is still some room for improvement. The Turin team, as winners of this year's competition, will now be organizing the Third Global Trajectory Optimisation Competition, where various teams will again have the opportunity to test their mettle in solving the most challenging problems currently faced by spacecraft trajectory designers.

The Global Trajectory Optimisation Competition was instituted in 2005 by Dario Izzo of the European Space Agency's Advanced Concepts Team. As winners of the first competition, the JPL team organized this latest one, with support from NASA's In-Space Propulsion Program.

Source: NASA
» print article
Related articles:
Illustration of a binary asteroid
New International Study

Some Asteroids Live in Own 'Little Worlds'

» go to article
This artist's concept depicts the Hayabusa spacecraft (left) and sample return capsule (right) entering the atmosphere over South Australia.
June 13 circled on the calendar

NASA Helps in Upcoming Asteroid Mission Homecoming

» go to article
A new infrared image from NASA's Wide-field Infrared Survey Explorer, or WISE, showcases the Tadpole nebula, a star-forming hub in the Auriga constellation about 12,000 light-years from Earth. As WISE scanned the sky, capturing this mosaic of stitched-together frames, it happened to catch an asteroid in our solar system passing by. The asteroid, called 1719 Jens, left tracks across the image, seen as a line of yellow-green dots in the boxes near center (Figure 1). A second asteroid was also observed cruising by, as highlighted in the boxes near the upper left (the larger boxes are blown-up versions of the smaller ones).
Asteroid caught in the act

Asteroid Caught Marching Across Tadpole Nebula

» go to article
An artist impression of the Asteroid Themis
Water Ice in the solar system

Scientists Say Ice Lurks in Asteroid's Cold Heart

» go to article
A full-context view of P/2010 A2.
Cosmic Crash

Hubble Sees Asteroid Collision

» go to article
The asteroid 243 Ida does not pose a threat to Earth right now
Danger from Space

How can we prevent an asteroid impact?

» go to article
951 Gaspra is an S-type asteroid (of silicaceous or stony composition, hence the name) that orbits very close to the inner edge of the main asteroid belt. Gaspra was the first asteroid ever to be closely approached, when it was visited by NASA's Galileo spacecraft, which flew by on its way to Jupiter in 1991.
Looming catastrophes in the sky

Can we predict when an asteroid will impact Earth?

» go to article
Artist’s impression of how the solar wind makes young asteroids look old. After undergoing a catastrophic collision, the color of an asteroid gets modified rapidly by the solar wind so that it resembles the mean color of extremely old asteroids. After the first million years, the surface “tans” much more slowly. At that stage, the color depends more on composition than on age.
Solar wind tans young asteroids

Asteroids get sunburned

» go to article
Search
Astronomy Software

Redshift 8 Premium

Redshift 8 Premium - Download Edition (Multilingua Edition)

Explore the universe from your PC with the award-winning and professional planetarium software - Languages: German, English, French
 » more

Redshift 8 Premium DL deutsch/engl 2

Redshift 8 Premium - Update from older versions

Update from Redshift 7 or older to the current version of the professional planetarium software - Languages: German, English, French
 » more

Redshift Discover Astronomy

Redshift Discover Astronomy

The beginners version of the leading astronomy App Redshift » more

Redshift iphone Neu

Redshift for iPhone, iPad and iPod touch

The award winning Astronomy Software Redshift is now available for iPhone, iPod touch and iPad. » more