Re: Question: r/e Orbital math (SGP4/SDP4?)

Kerry L. Bonin (kerry@probotics.com)
Thu, 25 Jul 1996 03:38:01 -0700

At 11:13 PM 7/25/96 +0200, Bjoern Gimle wrote:
>>Kerry L. Bonin wrote:
>>...), and I have been wanting to write a
>>good satellite package for quite some time.  (Yes, I know there are lots out
>>there!)  I am interested in putting together a Win32 ap, with the focus on
>>visual presenation.
>>
>
>In my opinion we don't need more prediction programs, since there already
>enough of them doing tabular or star map predictions, occultations,
>solar and lunar transits, ground tracks, stereographic space views...
>
>I would rather write (and I will) better interfaces to make use of
>existing programs, and satellite data/magnitude reference files.
>SkyMap, Quicksat, Seesat need no more improvement to participate in this,
>since they have manageable input files for everything, and output
>files that can be interpreted by other programs. TrakStar has good
>output, but needs a lot of cursor key input from menus, other programs
>seem to have greater problems.
>
>This is part of my line of work, and hobby, and of what I will discuss
>at Eurosom 2 in October.

While I would agree that there are plenty of prediction programs, that does
not preclude the creation of more for several reasons, such as (1) wanting
to write one for the sake of the technical challenge, or (2) I can locate no
software that allows me to easily meet an design spec in which satellite
info needs to be incorporated into an existing application.

I have an application request that I recently received that I find
technically interesting enough to complete the project for the fun of it.
Specifically, a avionics / telemetry display package that takes info from a
guidance package providing a realtime state vector, and displaying the
vehicle position in a 3D view of an earth map database.  (This is for
several [potential] X-prize entrants.)

In of itself, that is (relatively) simple.  However, I now wish to
superimpose on that display any satellite or debris objects for which a) I
have elements and b) meet display criteria (like gets within 25km of vehicle
track).

In looking around, I find several standalone applications which can draw
pretty screen shots, or in an offline batch mode generate data files which I
can parse and display.

What I WANT is a C++ class set that lets me write code like:

  // Get Keyhole current position
  CSatTrack sat( "data\\SSR06AEA.TXT" );
  CStateVec keyholePos = sat.CalcSatPos( "USA 86", CTime.GetTime() );
  cout << keyholePos;

Basically, I want a clean class (in C++, maybe port to Java) that lets me
integrate satellite information into any application.  And I want one that
is not tied to somebody's GUI, O/S, or compiler.  Just a simple mathematical
resource/tool that abstracts and encapsulates satellite orbital propogation
from orbital elements.  (Yes, I know that to perform the above application
requires a great deal of additional operations that are memory and database
intensive etc...)

If someone has written such a cleanly generic piece of code, and it's
available free of charge and license restrictions, please tell me about it!
In the mean time, back to the keyboard...

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Kerry L. Bonin                                http://www.probotics.com
Probotics, Inc.                                    kerry@probotics.com
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