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Accurate position of the Sun



 
 
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  #1  
Old March 8th 04, 02:45 AM
Graham
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Default Accurate position of the Sun

Greetings all,

I am looking for the most accurate way to determine the position of
the sun with respect to an orbiting satellite. I've searched on the
web and received conflicting information from our astronomy department
on whether the JPL solar ephemeris data is suitable. The problem with
using HORIZON is that I need the solar position relative to an
orbiting satellite and in reading the documentation, it isn't
particularly obvious how to do this. Moreover, I need to be able to
calculate the position accurately until 2005.

Any ideas or advice would be greatly appreciated!

Cheers,
Graham
  #3  
Old March 8th 04, 07:34 PM
Greg Neill
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Default Accurate position of the Sun

"Graham" wrote in message
om...
Greetings all,

I am looking for the most accurate way to determine the position of
the sun with respect to an orbiting satellite.


Orbiting what? Presumably the Earth...

I've searched on the
web and received conflicting information from our astronomy department
on whether the JPL solar ephemeris data is suitable. The problem with
using HORIZON is that I need the solar position relative to an
orbiting satellite and in reading the documentation, it isn't
particularly obvious how to do this. Moreover, I need to be able to
calculate the position accurately until 2005.

Any ideas or advice would be greatly appreciated!


Whoever owns the satellite should be able to provide
accurate ephemerides for it, presumably in an
Earth-centered frame of reference.

The Sun's position in an Earth-centered frame can be
had from HORIZONS. MICA 1.5 has been released. It
covers the time period to 2005:

http://aa.usno.navy.mil/software/mica/micainfo.html

The rest is just vector addition.


  #4  
Old March 9th 04, 05:19 AM
Alan Moore
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Default Accurate position of the Sun

On Mon, 8 Mar 2004 13:34:33 -0500, "Greg Neill"
wrote:

"Graham" wrote in message
. com...
Greetings all,

I am looking for the most accurate way to determine the position of
the sun with respect to an orbiting satellite.


Orbiting what? Presumably the Earth...

I've searched on the
web and received conflicting information from our astronomy department
on whether the JPL solar ephemeris data is suitable. The problem with
using HORIZON is that I need the solar position relative to an
orbiting satellite and in reading the documentation, it isn't
particularly obvious how to do this. Moreover, I need to be able to
calculate the position accurately until 2005.

Any ideas or advice would be greatly appreciated!


Whoever owns the satellite should be able to provide
accurate ephemerides for it, presumably in an
Earth-centered frame of reference.


But bear in mind that the satellite may have orbit under conditions
that make long term prediction of it's position impossible, or may be
subject to orbital adjustments. You may not be able to get a reliable
ephemeris for the satellite as far out as 2005.

Al Moore

  #5  
Old March 9th 04, 05:25 AM
Greg Neill
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Posts: n/a
Default Accurate position of the Sun

"Alan Moore" wrote in message
...

But bear in mind that the satellite may have orbit under conditions
that make long term prediction of it's position impossible, or may be
subject to orbital adjustments. You may not be able to get a reliable
ephemeris for the satellite as far out as 2005.


True enough. And many satellites do station keeping and
adjust their orbits dynamically to maintain nominal
orbit for their mission.

From now to 2005 is now less than a year. Surely the
owners of a satellite would have a handle on its
position for its working life?


 




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