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NASA orbit simulation software



 
 
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  #41  
Old May 24th 09, 03:05 AM posted to sci.space.tech
Kevin Willoughby
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Posts: 220
Default NASA orbit simulation software

Dr J R Stockton wrote:
In sci.space.tech message
, Wed, 20 May 2009 23:50:28, kevin willoughby .

invalid posted:
Pat Flannery wrote:
kevin willoughby wrote:
If two of three versions agree, that doesn't mean those two are correct.
Though in this case you do get feedback by observing where exactly
the satellite's orbit ended up in reality versus what one or more
programs predicted.

That works, but it can be a *very* expensive way to debug a program...



Not necessarily expensive; it depends on the brightness of the satellite
and the magnitude of the error.


I'll stand by my statement. The test plan for a moderately complex
program will specify several hundred test cases, minimum. Launching
several hundred satellites. Until the cheap-access-to-space miracle
occurs, we're talking a significant chunk of a gigabuck.
--
Kevin Willoughby lid

It doesn't take many trips in Air Force One
to spoil you. -- Ronald Reagan

  #42  
Old May 24th 09, 04:16 AM posted to sci.space.tech
Pat Flannery
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Posts: 18,465
Default NASA orbit simulation software



kevin willoughby wrote:

I'll stand by my statement. The test plan for a moderately complex
program will specify several hundred test cases, minimum. Launching
several hundred satellites. Until the cheap-access-to-space miracle
occurs, we're talking a significant chunk of a gigabuck

Ah, but there is something slick we can do here...we don't need to use
satellites that are _going_ to be launched; we can backtrack and use
ones that were _already_ launched.
Unfortunately, we probably can't get our hands on all the detailed data
for all that thousand or so Soviet optical and Signit recon satellites
that were launched, but with some digging we certainly can come up with
the details on the hundreds of satellites the US has launched since
1958, and enter those into the programs to see how accurately they
predicted what would happen to them versus what really did.
In the case of the numerous Corona satellites, they never did end up in
exactly the intended orbits in the early days, and had to have their
event clocks reset once on-orbit to tell them when to photograph things
and when to release their film return capsules.

Pat

  #43  
Old May 25th 09, 04:48 AM posted to sci.space.tech
Kevin Willoughby
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Posts: 220
Default NASA orbit simulation software

Pat Flannery wrote:
kevin willoughby wrote:

I'll stand by my statement. The test plan for a moderately complex
program will specify several hundred test cases, minimum. Launching
several hundred satellites -- until the cheap-access-to-space miracle
occurs -- we're talking a significant chunk of a gigabuck

Ah, but there is something slick we can do here...we don't need to use
satellites that are _going_ to be launched; we can backtrack and use
ones that were _already_ launched.


That would certainly be useful. But it wouldn't come close to filling in
all the required test cases for a universal-orbit-calculator program.
You'd need custom launches into extreme and/or weird orbits to complete
the test plan. Perhaps the trickiest would be placing a satellite in
(not orbiting) each of the Lagrange points. As far as I know, no one has
ever done a sun-synchronous polar orbit around the moon. Buzz Aldrin
hypothesized a cyclic traveler orbit between Earth and Mars. So I still
say: we're talking a significant chunk of a gigabuck.


Unfortunately, we probably can't get our hands on all the detailed data
for all that thousand or so Soviet optical and Signit recon satellites
that were launched,


It wouldn't surprise me if that information was available. Perhaps the
former USSR would be willing to sell that data. Or may NORAD could be
convinced to declassify the data.

But again, that doesn't eliminate the need to lots of launches to
validate the software. The Soviet launches were all from high latitudes,
and flew into a limited number of orbital planes.
--
Kevin Willoughby lid

It doesn't take many trips in Air Force One
to spoil you. -- Ronald Reagan

 




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