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From: tomyee3@gmail.com (ProkaryoticCaspaseHomolog)
Newsgroups: sci.physics.relativity
Subject: Re: Weakness in the results of the three tests of GR shown in rhe lasr
 century,.
Date: Mon, 4 Nov 2024 07:45:22 +0000
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On Mon, 4 Nov 2024 3:06:47 +0000, rhertz wrote:

> Take the example below, which I extracted for the first three minutes of
> today (now). One minute is the best resolution available.
>
> The data, a Vector Table (xyz position and velocity from SSB), would
> allow you to compute the orbital path of Venus, if you download the full
> data for the orbital period of 224.7016 days (323,571 minutes), if you
> ask to generate data for the entire period.
>
>
> The resolution, as you can see, is about 1 part in 10E+16 (almost
> hundred of micrometers).

As I stated before, the display of 16 figures merely provides the best
decimal representation of the binary output of the ephemeris program,
and is not intended to imply that the numbers are actually accurate to
that level of accuracy.

> BUT, THERE IS A CATCH: TO USE THIS DATA (323,571 BLOCKS) FOR POSITION
> AND SPEED ///IN A CLOSED ORBIT///, YOU HAVE TO KNOW EXACTLY THE 3D DATA
> OF THE PERIMETER OF THE ELLIPSE THAT DEFINE THE ORBIT OF VENUS.

Venus does not follow a closed elliptical orbit.

> BUT, TILL TODAY, THE PERIMETER OF AN ELLIPSE IS UNKNOWN.

There is no simple, exact closed-form solution for the perimeter of an
ellipse.

> ONLY
> APPROXIMATIONS EXIST, BEING THE RAMANUJAN ALGORITHM THE BEST.
>
> THEN, IT MEANS THAT THE STATE VECTOR METHOD USING THE DATA THAT HORIZONS
> PROVIDES, DON'T LEAD YOU TO A CLOSED ORBIT.

It shouldn't.

> IT MEANS THAT THE RESULTS
> ARE APPROXIMATED. AND THIS IS EVEN WORSE WITH MERCURY AND OTHERS.
>
> THE ONLY WAY TO HAVE AN ACCURACY OF 10E-10 (NOT TO MENTION 10E-16) WOULD
> REQUIRE EXPERIMENTAL MEASUREMENTS FROM A DEDICATED SPACECRAFT ORBITING
> VENUS IN A HIGHLY KNOWN ORBIT,

The last three Venus obiters were Akatsuki (Dec 2015-Apr 2024), Venus
Express (2006-1014) and Magellan (1990-1994). So yes, up until quite
recently, we would have had tracking data to the "handful of meters"
level.

> WHICH WOULD HAVE TO RELAY STATE VECTORS
> DATA TO EARTH WITH VERY PRECISE TIME SLICING, LOWER THAN 1 SECOND. MORE
> THAN 19,414,219 BLOCKS OF DATA, AND FOR SEVERAL ORBITS (TO OBSERVE
> PERTURBATIONS AND DEVIATIONS).
>
> AFAIK, there is only ONE project to do such measurements for Mercury
> (Japan, two spacecrafts, being ready by the end of 2025).
>
> Meanwhile, all the data available IS THEORETICAL, with some corrections
> introduced by several spacecrafts in the past. Not now.
>
> And if it is done as it's being thought with Mercury in 2026, you'd be
> surprised of the ACTUAL ORBITAL PATH in a long period of time (say one
> year or two). There are many perturbations that simplistic models don't
> consider, in particular asynchronous perturbations and random anomalies.

What random anomalies?

> Because of the above comments, I would LOWER the expectations of current
> accuracy available for the general public. I'm quite sure that JPL has a
> model with better accuracy, but they reserve that data for US only.
>
> After all, it's not a matter of giving to other countries such
> information FOR FREE, being some of them competitors in the field of
> planet ranging (China, India, Russia, EU ESA, Japan, etc.).
>
> Would you help to your competitors for nothing, so they can beat you?

I really don't understand the point that you are trying to make. Sure,
data may be held in embargo until the research teams involved get to
process the data and publish their work, but the general practice
nowadays, once the embargo period is over, is to allow open
dissemination of the data.

Science is not a solo effort. So long as there are no commercial
proprietary concerns or national security issues involved, data are
freely shared.