Re: precession of mercury

On Thu, 25 Dec 2008 04:22:32 -0800 (PST), Jerry
<Cephalobus_alienus@xxxxxxxxxxx> wrote:

On Dec 24, 3:24 pm, hw@..(Dr. Henri Wilson) wrote:
On Wed, 24 Dec 2008 01:54:01 -0800 (PST), Jerry
<Cephalobus_alie...@xxxxxxxxxxx> wrote:
On Dec 24, 12:42 am, hw@..(Dr. Henri Wilson) wrote:

Did you find anything about the orbit, Jerry?

(sigh)
As I have repeated AGAIN AND AGAIN, Hipparcos was stuck in
a highly elliptic geostationary transfer orbit because of
failure of the apogee boost engine. The original intent
was for a geostationary orbit "which would have kept the
satellite in a fixed position with respect to a single
ground station. From this orbit, as opposed to low-Earth
orbits, the Earth obscures only a small portion of the
celestial sphere being scanned."
http://www.rssd.esa.int/SA/HIPPARCOS/docs/vol2_all.pdf

The operational orbit was a far cry from what was intended:
? perigee height: 526 km
? apogee height: 35 900 km
? orbital period: 640 min
? eccentricity: 0.72
? inclination: 6.8 deg
? ascending node: 105 deg
? argument of perigee: 214 deg

In short, the whole thing was a complete stuff up.

On the contrary. The Hipparcos team did a remarkable recovery
starting from a bad situation.

You didn't mention that it eclipses every orbit.

Depends on the orientation of the orbit with respect to the Sun,
which changes during the year. But yes, thermal cycling was
hard on the equipment.

During the operational lifespan of the satellite, its orbit
decayed from due to repeated passages through the atmosphere
at perigee. This complicated the analysis considerably.
Repeated passage through the Van Allen belts was hard on the
equipment and the solar panels. The high speeds required
much greater precision in orbit determination because of the
fast changing aberration at perigee.

Now will you SNAP OUT OF YOUR FANTASYLAND WANDERINGS and
start paying attention to actual facts as opposed to your
imaginings?

The whole process could be simplified if the thing was sent into a circular
orbit in the ecliptic plane. However as long as the axis of precession of the
axis of rotation is perpendicular to that plane, a small tilt in the orbit
plane wont cause much of a problem or error.

A worthless suggestion inconsistent with your earlier posts
(you are obviously trying to make it fit the nominal Hipparcos
orbit) and quite clueless.

It should be obvious that what I said is correct. Placing it an ecliptic orbit
would allow for much simpler analysis and greater accuracy. An equatorial or
other orbit requires additional and very complcated corrections.
The Hipparcos telescope was meant to be sent into an ecliptic orbit.

Obvoiusly neither you nor Paul can get it into your head that aberration can be
virtually eliminated from parallax measurements if the telescope used does not
rotate around its own axis.

Not only inconsistent with the immediately preceding paragraph,
but utterly false and clueless. In the preceding paragraph, you
propose a telescope whose "axis of precession of the axis of
rotation is perpendicular to [the ecliptic] plane" while here
you propose a telescope that does not rotate, period.

Try thinking occasionally Crank.
As long as it is in the same orientation when specific stars are in view, that
constitutes 'NOT ROTATING'.
The scanning procedure is clearly quite ingenious and the same stars are viewed
a number of times during the year. They are identified by the direction in
which the telescope is pointing at the time. It is has the same angular
position at the time, aberration effects are avoided.

You haven't the foggiest idea what you propose, do you? It keeps
changing from post to post, and even within this single post, it
changes...

I have to explain it in more basic terms so you can understand what I said.
Aberration CAN EFFECTIVELY BE ELIMINATED.


If it is pointed at a particular star all year, the
positions of other stars in the vicinity change according to their relative
distances from the central star.

How quaint! You are proposing use of a GUIDE STAR. A technique
that has been in use since the birth of astronomical photography!

I am proud of you, Henri! You have FINALLY proposed a technique
that could possibly work...

I'm not proposing it..... you old dope. I'm just explaining how, with that
arrangement, the image does not rotate in the 'eyepiece' if the telescope does
not spin around. Hence aberration is not a factor in relative star displacement
over the year.

Except it won't work for truly high precision compensation for
aberration. HST has three fine guidance sensors used to point and
lock the telescope onto the target. Except the guide stars are
generally not in the near vicinity of the object being imaged.
HST often takes images of objects so faint that the CCD cameras
don't register more than a photon every several seconds (or in
the case of the famous Deep Field photos, every several minutes),
and so the target object itself cannot be tracked. Aberration for
any guide star located several degrees from the target object
will generally not be identical to the aberration of the target
itself.

It will be the same if the telescope is in an ecliptic orbit. The Earth's tilt
complicates the whole process.

I won't tell you how HST solves this problem (I have already
described the technique that HST employs in a previous post
several months ago) and await your proposed fantasy solution...

Light speed shold not affect the outcome.

That is because BaTh is false, and light therefore arrives at the
telescope with a constant speed of c.

BaTh cannot be false.

I am aware that Hipparcos does not operate like this directly because of its
scanning method...but the principle still exists.

The more I read about the Hipparcos mission, the less faith I have in its
published figures.

Jerry



Henri Wilson. ASTC,BSc,DSc(T)

www.users.bigpond.com/hewn/index.htm.

......
.

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