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1 total messages Started by Lowell Herr Thu, 02 Mar 1995 04:49
Re: How to calculate the Mass of Mars.
#583
Author: Lowell Herr
Date: Thu, 02 Mar 1995 04:49
83 lines
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Phil,

Here might be a very simple, but nevertheless problem with trying to track
one satellite.  How would we be assured we were seeing the same satellite?
 In the spring of 1958 there were few pieces moving around the
earth.  I do recall seeing one Soviet Union (t'was a Union then <g>)
rocket on its last orbit around the earth.  The rocket (it was not the pay
load) was tumbling to the extent that the reflected light off the
object gave the viewer the illusion there was a point of light
describing a sine curve in the sky.  To be sure, the amplitude was quite
small but it was easy to recognize.  It was the most amazing sight I ever
witnessed while viewing orbiting bodies.  [Of course one needs to
eliminate those full moon nights with a lovely .....well you get the
picture.]

To set up the sites I described is very easy to do.  Just know the
latitude and longitude of your location, mount a large metal cross at that
location and have eight to twelve students with moniculars lined up in a
straight line so a wide arc of the sky can be observed.  Not much to it.
The hard work would come when the data arrives.  I was not
involved in any of that as the analysis took place in Washington, D.C.

Lowell
 On
Wed, 1 Mar 1995, Phil Kline (Guest) wrote:

> Lowell,
>
>   Your satellite project from the early days might well be a super on-line
> project for current physics teachers and their students.  With the current
> prediction software and daily keplarian elements updates available also
> on-line from NASA, observations could be made from a good portion of the
> US, weather permitting, and reported through this listserv.  Could be
> interesting.
>
> -Phil Kline,
>  Chemistry/Physics Teacher
>  Mohawk HS
>  Sycamore, OH 44882
>  email: pkline@nike.heidelberg.edu
>
>
>  On Tue, 28 Feb 1995, Lowell Herr wrote:
>
> > > >
> > > > Lowell
> > > >
> > >  You are right about the value of G=6.67 x 10^-11, It was my typo. I did
> > >  try to look up a couple of Physics books, but did not get any info. How
> > >  accurate can the data be if such a technique(timing the moon(s) of
> > >  Mars) to calculate the mass is used. So does that mean that the timing
> > >  of the planets can be used to calculate the mass of the sun. Thanks for
> > >  your reply....
> >
> > Yes.  The mass of the Sun can accurately be measure by knowing the orbital
> > time and mean radius.  The mass of the Earth was accurately measured back
> > in the late '50's and early '60's using satellites.  I forget the name of
> > the project but can get it as my brother worked on it.  I was part of a
> > team that helped to determine orbits of the early satellites.  It is much
> > too long to explain here but readers would sure get a kick out of how it
> > was done.
> >
> > Briefly, we would sit out at night looking up at the sky until we would
> > spot a satellite.  Remember, there were very few objects moving around the
> > earth in 1958!  Once we spotted a satellite we would look into a monicular
> > scope - all 16 spotters looking into scopes as we formed a line of
> > viewers, eight on each side of a large metal cross.  When the satellite
> > came into view we would press on a buzzer that was connected to a tape
> > that recorded WWV time.  If and when the satellite crossed behind the
> > large cross we would release the buzzer and then depress it again as the
> > satellite emerged from behind the cross.
> >
> > Knowing the latitude and longitude of our position and the time the
> > satellite crossed the position, plus the viewers position in the straight
> > line (difficult to explain without a diagram), the tape was sent to the
> > Smithsonian as I recall.  Using triangulation with other sites, the orbit
> > of the satellite could be determined.  That is the crux of what it was
> > like in the early days.
> >
> > It was a lot of fun.
> >
> > Lowell
> >
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