Featured Research

from universities, journals, and other organizations

Genetic Algorithms "Naturally Select" Better Satellite Orbits

Date:
October 16, 2001
Source:
Purdue University
Summary:
Some Earth-orbiting satellites will be able to keep in touch longer with controllers on the planet's surface thanks to computer programs that mimic Darwin's evolutionary model of survival-of-the-fittest.

WEST LAFAYETTE, Ind. — Some Earth-orbiting satellites will be able to keep in touch longer with controllers on the planet's surface thanks to computer programs that mimic Darwin's evolutionary model of survival-of-the-fittest.

Purdue University engineers used "genetic algorithms" to design innovative constellations, or collections, of satellites orbiting the Earth. The algorithms are helpful in designing low-cost constellations that save money by placing a small number of satellites around the Earth at relatively low altitudes, said William Crossley, an associate professor at Purdue's School of Aeronautics and Astronautics and a faculty member of the university's Center for Satellite Engineering.

Such low-altitude satellite constellations are expected to bring a boon to mobile computing by making it more possible for people to use wireless communication devices. The constellations also may have military applications because they make it possible to quickly reposition satellite constellations for specific surveillance purposes.

However, the constellations have a key disadvantage. To maintain contact with stations on Earth, the satellites must be in a line of sight with antennas on the planet. Because the constellations contain only a few satellites orbiting at low altitudes, there are times when none of the satellites can be seen by ground stations; they are blocked by the Earth's curvature, temporarily cutting off communications. The conventional method for designing constellations containing three or four satellites in low-altitude orbits results in the satellites being out of touch with Earth for about four orbital periods out of each day. Each period represents a single orbit around the Earth, which takes about 90 minutes. During those four orbits, a base on Earth would not have a line of sight to any of the satellites, making communication to or from the Earth base impossible.

The Purdue-designed constellation, however, reduced the blackout time to three orbital periods, keeping the satellites in touch 90 minutes longer. The design is now being considered for defense-related satellites. A research paper about the findings is in the July-September issue of the Journal of Astronautical Sciences, published by the American Astronautical Society.

Genetic algorithms, or computer instructions, adapt Charles Darwin's evolutionary model, interchanging design elements in hundreds of thousands of different combinations. Only the best-performing combinations are permitted to survive, and those combinations "reproduce" further, progressively yielding better and better results. The most profound impact of such algorithms is that they sometimes find solutions that researchers would ordinarily have missed. An added bonus is that they run continuously, overnight and for days at a time, sometimes working faster than would have been humanly possible.

"The genetic algorithm can provide a good starting point," Crossley said. "Once the genetic algorithm has generated a solution, fine tuning or refinement needs to be done to obtain the best final solution."

The genetic algorithm developed by Crossley and former graduate student Edwin Williams has been used to design a constellation of satellites for a possible defense mission, and research collaborators at The Aerospace Corporation in El Segundo, Calif., are currently using the approach to investigate other possible constellation designs.

"For small numbers of satellites, at low altitude, we find constellations that outperform significantly the ones that you would find using the traditional approach," Crossley said.

If money is no object, then satellites can be kept in constant communication with Earth by placing constellations of three satellites in orbit 20,000 miles above Earth. Because they are high above Earth, each satellite can see a large portion of the surface. But the satellites are more expensive to design and build because they must withstand higher radiation than lower-altitude satellites, they require larger on-board power supplies to send and receive signals, and placing them in the proper orbits requires a larger launch vehicle and takes more time.

In comparison, the lower altitude satellites are placed in orbits only a few hundred miles above Earth.

Genetic algorithms are helpful in designing lower-cost constellations by sorting through the multitude of possible configurations and coming up with a design that minimizes the amount of time that the satellites are out of touch with links on the ground. The genetic algorithm designed at Purdue naturally selected the best-performing constellations by interchanging variables such as how far apart the satellites are from each other, the heading of the satellites as they cross the equator, and how high they are above the Earth's surface.

The results were unexpected. Normally, in constellations containing small numbers of satellites, the satellites are spaced at equal distances from each other as they track across the globe's equator. But in the best-performing constellations discovered by the genetic algorithm, the satellites were not spaced at equal distances.

"For example, the constellations might have two satellites spaced very far apart, and the third one will be very close to the second one," Crossley said, noting that engineers with years of aerospace experience were surprised by the higher performance offered by the unconventional design.

Williams, who earned a master of science degree in December 1999, currently works for the Pratt & Whitney Division of United Technologies Corp., in East Hartford, Conn.


Story Source:

The above story is based on materials provided by Purdue University. Note: Materials may be edited for content and length.


Cite This Page:

Purdue University. "Genetic Algorithms "Naturally Select" Better Satellite Orbits." ScienceDaily. ScienceDaily, 16 October 2001. <www.sciencedaily.com/releases/2001/10/011016070234.htm>.
Purdue University. (2001, October 16). Genetic Algorithms "Naturally Select" Better Satellite Orbits. ScienceDaily. Retrieved September 16, 2014 from www.sciencedaily.com/releases/2001/10/011016070234.htm
Purdue University. "Genetic Algorithms "Naturally Select" Better Satellite Orbits." ScienceDaily. www.sciencedaily.com/releases/2001/10/011016070234.htm (accessed September 16, 2014).

Share This



More Space & Time News

Tuesday, September 16, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA’s Curiosity Rover Finally Reaches Long-Term Goal

NASA’s Curiosity Rover Finally Reaches Long-Term Goal

Newsy (Sep. 15, 2014) — After more than two years, NASA’s Mars Curiosity Rover reached Mount Sharp, its long-term destination. Video provided by Newsy
Powered by NewsLook.com
SpaceX's Elon Musk Really Wants To Colonize Mars

SpaceX's Elon Musk Really Wants To Colonize Mars

Newsy (Sep. 14, 2014) — Elon Musk has been talking about his goal of colonizing Mars for years now, but how much of it does he actually have figured out, and is it possible? Video provided by Newsy
Powered by NewsLook.com
International Space Station Crew Returns Safely To Earth

International Space Station Crew Returns Safely To Earth

Newsy (Sep. 11, 2014) — The three-man crew touched down in Kazakhstan Wednesday after more than five months of science experiments in orbit. Video provided by Newsy
Powered by NewsLook.com
Solar Storm To Hit This Weekend, Scientists Not Worried

Solar Storm To Hit This Weekend, Scientists Not Worried

Newsy (Sep. 11, 2014) — Two solar flares which erupted in our direction this week will arrive this weekend. The resulting solar storm will be powerful but not dangerous. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins