Dusk til Dawn: An Odd Orbit

Would it be possible to set up a circular, polar orbit around Mercury
such that it always followed Mercury's terminator?

Also, could such a "dawn tracking orbit" pass over the same point at
the north and south poles each orbit?

Mike Miller, Materials Engineer

a écrit :
Would it be possible to set up a circular, polar orbit around Mercury
such that it always followed Mercury's terminator?


if you want to follow the noon instead, just drop your sat on the sun
;-)

" writes:

Would it be possible to set up a circular, polar orbit around Mercury
such that it always followed Mercury's terminator?

Sun-synchronous orbits like that are possible if the planet has a
sufficient equatorial bulge to supply the necessary perturbing force.
Earth, for example, has such a bulge, and sun-synchronous orbits
are frequently used for a variety of purposes. Not necessarily
following the terminator, though.

Mercury, may not have enough of an equatorial bulge to make this
sort of thing work. I can't find any data on the matter right this
moment, alas, but the planet's slow rotation rate does not make me
optimistic.


Also, could such a "dawn tracking orbit" pass over the same point at
the north and south poles each orbit?

It can't pass *precisely* over the poles, because it needs to be
inclined just a bit off the pure polar case in order to exploit
the equatorial perturbations. Sun-synchronous orbits about the
Earth, for example, tend to be at about 98 degrees inclination.


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John Schilling wrote:


Mercury, may not have enough of an equatorial bulge to make this
sort of thing work. I can't find any data on the matter right this
moment, alas, but the planet's slow rotation rate does not make me
optimistic.

I'd be surprised if we knew Mercury's gravitational field well
enough to design orbits that require fine-tuning precession
yet. The planet has no natural satellites, and the only
mission to visit it, Mariner 10, just did three fly-bys.