Very interesting story on SPACE.com regarding currently unexplained anomalies in the velocities of spacecraft after their Earth flybys.
http://www.space.com/scienceastronomy/080229-spacecraft-anomaly.html
Perhaps the twisting of spacetime induced by Earth's rotation could be gently altering the spacecraft's velocity.
http://www.voanews.com/english/archive/2004-10/2004-10-21-voa131.cfm?CFID=266654923&CFTOKEN=51791561
In any case its pretty cool to have an unexplained force meddling with our best laid plans.
Mmm...don't forget that the gravitational constant G is the least precisely known of all the physical constants, and it's a direct coefficient for many trajectory calculations. I suspect that part of the answer lies in this uncertainty.
If anyone were to undertake a serious investigation of these anomalies, I'd suggest a very precisely balanced spin-stabilized vehicle (with operational mass known to the highest degree possible), minimal outgassing, and almost nothing ancillary but the basic bus functions needed to keep it stable & relay data that would do a high-perigee (to negate drag effects) Molinya style Earth orbit with supporting tracking.
Think we're really getting very deep into the weeds here; statistical uncertainties seem like the most probable causes for these observed effects.
According to one of Emily Lakdawalla's Planetary Society Blog entries,
at least some relativistic effects are already accounted for in spaceflight.
http://planetary.org/blog/article/00001329/
"It turns out that general relativity is routinely accounted for in
spacecraft navigation.... the NASA navigation software developed
at JPL....incorporates the Ted Moyer formulations for navigation
which includes mathematical expressions that describe the effects
of general relativity."
That's pretty much a validation of how far down you have to go in order to account for all the possible effects. Mercury's orbital velocity is way below any significant fraction of the speed of light; we're probably talking about mm/sec variations in acceleration at most, but of course this is cumulative.
Emily's article describes comparison between pure Newtonian calculations and that which includes general relativity effects for the first flyby:
"The flyby altitude at Mercury increased by about 10 km, but the closest approach time changed by about 13 seconds, which corresponds to about 65 km."
The relativistic effects is quoted as 0.5e-6 mm/s^2. Carried over a long period of time it makes a big difference.
Wow, did I ever overestimate!!! Same point applies, though; such things do add up, and presumably so does error in planetary mass estimates, the uncertainty in the value of G, drag from planetary atmospheres (however tenuous), drag effects from the extended solar atmosphere & localized gas concentrations such as those distributed along planetary orbits, and a whole lot of patently trivial effects that considered systemically do have a measurable impact.
Sorry to be an iconoclast, but the only way that the "Pioneer Effect" would have been surprising to me is if it wasn't vectored towards the Solar System's center of mass. I'm far from convinced that we need to invoke modifications of fundamental physics to explain it.
"The researchers looked at six deep-space probes — Galileo I and II to Jupiter[...]" Two flybys perhaps...
The author obviously meant the Voyagers...but the editor or somebody in the chain definitely should've caught that (this is space.com, after all!!!) Nice find, Rem.
There is a sort of "weirdness" to the whole thing that makes me very suspicious that something's been missed that should be "Oh Damn" obvious, something almost as obvious but missed as the nt/lb force units screwup on Mars Climate Orbiter.
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