Tweet

# How exactly are space probes trajectories calculated?

## After answering a question a few minutes ago about the location of Voyager 1, and playing around with Celestia, I started wondering -- how exactly are these "gravitational slingshot" trajectories set up anyway? We have numerous examples of those. For example, the 6-year-long voyage of the Messenger probe to Mercury had some 6 or 7 such maneuvers to gradually lose energy and allow it to enter an orbit around Mercury. This has to be very carefully planned, otherwise too much fuel is spent in course correction, or the probe gets ejected or even passes too close to the atmosphere of a planet and crashes. So, while at first it might be "eyeballed" when preparing the orbit solution for a mission, in the end it has to be selected exactly -- at what instant to make an attitude correction so it passes at the closest approach at a certain minute and thusly picks up/loses delta-V. My question is specifically if, on these moments the interaction is treated as a 2-body interaction, or something more complicated. For example, the Celestia simulator shows Voyager 1 making a pass near Titan en route to Saturn, and after passing near Saturn it gets ejected towards the northern celestial hemisphere. To me, this suggests some careful planning prior to launch -- they knew how to plan the orbit. And given that computers have limited digit precision (which might not matter in face of some tiny uncertainties such as radiation pressure), there is always some room for uncertainty in the orbits. Does anyone know of comprehensive textbooks detailing this subject? Whether more sophisticated approaches than mere 2-body approximations (a la Newton law of gravitation) is done? Whether relativistic corrections are considered ("turned on") or ignored ("turned off") when the trajectory crosses some boundary distance to the Sun? Whether cutoffs are applied at some instances (for example, radiation pressure is ignored up until some point and then used in the calculations beyond a certain distance from the Sun)?

Asked By: Satan Claws - 12/24/2012
The calculations are way beyond 2-body interactions. First, the engineers start with a high-precision ephemeris of the plants, such at JPL's DE-421. Then they add in the ephemeris of any moons (or asteroids) the probe will come close to. That gives a gravity map of the solar system... More

When we did simpler problems like this in my Celestial Mechanics class, we worked backwards from where we wanted to end up. We had no zippy little computers in the classroom, so we just set them up, no graphics, no fun little dotted line trajectories... boo hoo.

Try this: http://www.tauzero.aero... More

Textbooks... More
Source(s):

\$47/hour Part-Time Job Openings. Requirements: Must Have Computer.
www.eworkerportal268.org
Over 483 Local Jobs Now Hiring In Your Area. \$18-\$87/Hr - Apply Today!
Jobs.Quick-com
\$47/hour Part-Time Job Openings. Requirements: Must Have Computer.
www.eworkerportal268.net
Shop Online or Sign Up To Sell AVON & Earn Fast Cash Today!
www.youravon.com

## Mechanical Engineering Job Security?

Do most mechanical engineering jobs offer job security?

## Job survey: for everyone with a job?

What is your current job? Why did you choose this job? What do you enjoy about your job? What do you dislike about your job? What would be your perfect job? Would you rather have this j...

## Where are the jobs?

Where are the jobs? Is productivity and globalization creating a permanent “recession” of jobs? My main issue is I am doing a paper for school and have no idea where to begin. I was hoping suggestions...
 Content is not owned or controlled by Monster. Any content concerns should be addressed with Yahoo! Yahoo! Does not evaluate or guarantee the accuracy of any Yahoo! Answers content. Yahoo! Disclaimer.

### Popular Articles

Best-Paying Work-from-Home Jobs
It’s easier than ever to work from home. Of course, not every job is a mobile job, and some companies aren’t interested in having their employees work from home.
2013 Marketing Jobs Outlook
The US may be facing another year of anemic hiring overall, but that won't be the case in the high-orbit world of multichannel, digital media marketing.

### Popular Job Searches

Explore Photonic Engineer Jobs and Career Opportunities
For Employers: Post Jobs | Search Resumes | Advertise
About Monster | Work for Monster | Advertise with Us | AdChoices | Partner with Us | Investor Relations | Social Media