Do space probes need to account for any relatavistic effects?

Have any of the probes sent out to the edges of or beyond the solar system reached velocities where relativistic effects would have to be calculated for in plotting their courses?

For instance, I have heard the terms “slingshot” or “gravity assist” to describe an orbit that has a probe approach the gravity well of a planet and adjusts its obit and greatly increases its velocity. Would the 2nd or 3rd or 4th time this happens leave them with such a velocity and mass that they have to be steered a little farther away the next time?

All long-range spacecraft that I am aware of use only Newtonian physics for their navigation, which is sufficient. However, it may interest you to know that GPS satelites do take relativistic problems into account. Here is an article about it.

The space craft are going only .01% of the speed of light. The relativistic equations are barely affected at that slow a speed.

My question is, is “barely” enough that it has to be figured in?

Time dilation can be measurable on aircraft going less 0.001% the speed of light.

The Cassini-Huygens mission did four slingshot maneuvers to get to Saturn: two past Venus, one past Earth, and one past Jupiter.

There was a paper on using relativistic methods on gravity assists in the May issue of the American Journal of Physics, on pages 619-621. It can be done with enirely Newtonian math. The error in position due to inexact firing of rockets would far overwhelm any difference due to relativistic effects.

As Wikkit notes, being measurable and being meaningful are two different things.

Being measurable and being influential are two different things, as demonstrated on the 2nd.

Oh, and it’s better for everyone to link directly to the Wikipedia raticle, rather than one of its copies: http://en.wikipedia.org/wiki/Hafele-Keating_experiment

I really ought to get a faster browser. Thanks, Exapno.

That suggests to me that it might need to be accounted for in the very 1st “slingshot”. What kind of v do you need to get free of earth orbit? Something like 25,000 moh, IIRC? So maybe 50x the airdraft speed in your link, 100-200x the distance.

Or maybe not, if mass doesn’t increase at a comparable rate to time dilation at lower speeds.

But that introduces yet another question. Maybe the correction wouldn’t need to be for mass, but for just plain position. If there are relativistic effects on the probe, doesn’t that mean the target planet will be in a slightly different posiition relative to the craft than otherwise predicted, when the probe is as it’s point of closest approach?

Oh, jeez, while composing my last post, there were several more posts that provided more details. Thanks.

Using extremely rough calculations, I figure:

A probe moving at 0.01c feels a relativistc effect of 1.0000500730132313, i.e. a second on Earth is ~1.00005 seconds to the time-slowed probe.

If the probe was using some kind of synchronous communications with Earth at 20Khz or higher (i.e. the speed of a slow dialup connection), it would be difficult or impossible to “sync up” correctly.

However, space probes don’t use synchronous commuications (simple lag prevents it; a message from Mars takes a minimum of four minutes to reach Earth) so the matter is kinda moot.

My WAG is that the boffins trying to figure out the “Pioneer anomaly” have to factor in relativistic effects since the effect of the anomaly (if it exists) seems pretty tiny

Most spacecraft do use synchronous communications. The ground stations use receivers and bit synchronizers with phase-locked loops to compensate for frequency/rate changes due to doppler and other effects.

Thank you, that’s a very interesting story, though I’m not at all sure whether it addresses my OP.

It would be fascinating to discover if some rules or constants in physics changed out of a heavy gravitational influence like the sun. What if the speed of light itself changed?

Well, now I’m gonna have to go look that up.

I was just about to ask a similar question - instead of asking about relativistic effects for deep space probes, what about probes at the other end of our system’s gravity well, near the Sun, like the proposed Mercury probe?

If I remember correctly, at the beginning of the 20th century, astronomers noticed various anomalies in their observations of star light that passed near the Sun, and postulated a planet even closer to the Sun than Mercury to explain the anomalies. Then Einstein produced his theory of relativity, which explained that the gravitational effect of the Sun is so large that light from other stars bends going around the Sun, and that was the cause of the anomalies.

Would this be the sort of thing that planners of the Mercury probe would have to take into account?

There is, in fact, a detectable anomoly in Mercury’s orbit, which is due to General Relativity. However, that anomoly is only 43 seconds of arc per century, and furthermore, it’s an anomoly in the precession of the planet’s perihelion, which means that any effects on the position of the planet are going to be even more suppressed. Toss in the fact that the spacecraft is going to have to make small course corrections anyway, and that those corrections are presumably going to be based in part on observations of the current measured position of Mercury, and it becomes a complete nonissue.

Welcome, Master Chronos. That’s pretty definite of you. I’m always a little suspicious of that level of certainty but hell, IANA Mr. Science-type guy.

What do you think of the Pioneer Anomaly link by Capt B. Phart? Not to suggest that it’s in any way linked to the issues in my OP.

I would think they could have ruled out a few things in the years they’ve been studying this. Shouldn’t the course deviation be an indicator of the axis along which the force is being applied? Wouldn’t a “dark matter” stimulus at the galactic core result in a considerably different orbit change than a force of solar origin?

Just to pick a nit, probes don’t go 0.01c. They go 0.01%c or 0.0001c. That would make the time correction even less noticeable or significant.