Re: Space Geography

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On Fri, Sep 23, 2011 at 2:16 AM, Tom B <kaladorn@gmail.com> wrote:

> Roger replied to me:
>
> > "Orbital inclination" is the term you're after here.
>
> TomB: Yes. I wasn't sure what that inclination was relative too so I
> avoided the term.
>
> > Inclination of orbital plane relative to the ecliptic, which is what
you
> > described in 2), isn't the same thing as eccentricity.
>
> TomB: I meant eccentric in the sense of 'not conforming to the common
way'
> versus mathematically eccentric orbits. Sort of how you might describe
an
> eccentric Englishman. :0)
>
> > But all the planets' planes are within 7 degrees of Earth's orbit,
and
> > all except Mercury within about 3.5 degrees. To a first
approximation,
> > the smaller the body, the more inclined its orbit is likely to be -
> > Pluto's at 17 degrees, Pallas at 34, Eris at 44.
>
> TomB: That gives me a reasonably idea for Earth's system. What I'm
sort of
> wondering is if this sort of data is readily available from an online
> catalog
> of any sort. (By readily, I also mean 'without mind bending math tools
to
> apply to the data').
>

Most basic astronomy books that cover the solar system have appendices
in
the back that have much/all of the orbital information for the planets,
and
probably now the dwarf planets. A bit of googling about should also
dredge
up tables online as well.

For extra solar planets, try exoplanets.org or exoplanet.eu

>
> > >Would that sort of approach help? Does background clutter matter?
> >
> > With realistic sensors, yes, but to a limited extent - remembering
how
> > sparse real-life asteroid fields are, unless you're willing to bury
your
> > ship in a comet and wait for several years, it _is_ going to be
spotted.
>
> TomB: I'm not talking about hiding behind planets or comets, although
those
> sorts of things are valid. I'm talking about using background
radiation
> from
> the systems of your galaxy and perhaps from bodies in your system to
make
> it harder to pick you out.
>

There are a whole slew of assumptions (which you the list) that would
have
to be taken into account in order to answer this question. Given that
you're
probably thinking near or medium future tech, you can probably safely
PSB it
out yourself.  :-)   But note that in general the background radiation
is
pretty low to begin with. On the flip side, contemporary technology has
challenges just detecting Earth-crossing asteroids. It's pretty much all
passive and optical.

On the flip-flip side, contemporary technology is on the cusp of imaging
planets (gas giants) in other solar systems. It wouldn't be much of a
stretch to have a two-layered detection system in place in a
starship-traveling future: one an area detector covering a chunk of sky
for
unknown objects moving in-system, and a second with powerful
detectors/sensors/telescopes to zoom in and look at said unknown objects
in
detail. To stealth against optical detection, you'd have to have very
black
ships. Near 75% of the known asteroids have albedos of 0.03 (which means
they reflect only 3% of the radiation that hits them; by comparison,
Ceres
is 0.11, the Moon 0.12, and Earth is 0.35), which is pretty damned dark.
But
albedo is also a function of the host star, so...

Mk