I just re-watched the Nova episode about Cassini/Huygens. Remember that mission planners did not account for the 12,000 (kph or mph, don't remember which) difference in relative speeds after Huygens was to be launched. Well into the mission they found that Cassini could not "read" the Doppler-shifted radio transmission as it arrived from Huygens. It took six months just to discover why Huygens and Cassini couldn't communicate with each other and another two years(!) to design the fix. They had to do something with Cassini's receiver to adjust for the shifted frequency. Chuck, now you've got me curious to know at what velocities relativistic effects become an issue. I would be surprised to learn if at the velocities of current interplanetary travel relativistic effects make any difference. But that hunch is based on my weak memory of college physics, taken some 30 years ago. (I know, I don't even look that old...) Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Friday, June 20, 2008 12:56 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Relativistic orbital effects Without doing the math, it's still fun to think about. The time frame of reference of a probe landing on such a planet would be out-of-sync with mission control, or another spacecraft orbiting further from the star in a more leisurely orbit. Would the computers on the two craft even be able to communicate with each other? Recall that NASA has had troubles with orbiter-lander communication in the past, thanks to Doppler-shifted lander transmission frequencies induced by velocity. Might relativistic effects pose similar problems? The longer the mission, the further "ahead" in time mission control gets from the probe's frame of reference. How different would a frame dragging have to be, before human perceptions would notice it, let alone computers? Are you reaching for the Excedrin, Rich? *;o) * On Thu, Jun 19, 2008 at 5:06 PM, Richard Tenney <retenney@yahoo.com> wrote:
This post reminds me of a fellow I took some programming classes in college with. He was interning for Huges Aircraft, doing a project to calculate liquid fuel sloshing effects on satellite trajectories -- gives me a math headache just thinking about it!
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