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  1. GMAT
  2. GMT-2454

Conversion errors for AOP and TA

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      Description

      I am using the September 16 build of GMAT.

      To duplicate this bug, open GMAT and open the DefaultSC. With the Cartesian state type, enter the following state:
      X Y Z VX VY
      -5975.575286 480.1471983 -3416.424837 3.800269068 0.916073412

      VZ
      -6.518201013

      Then select the state type to be Keplerian. The state should change to:
      SMA ECC INC RAAN AOP TA
      6900 0 98 360 0 210

      But it changes to:
      SMA ECC INC RAAN AOP TA
      6900 0 98 0 248.7517740275628 321.2482259726179

      Now change the state type to Modified Keplerian and the state should change to:
      RadPer RadApo INC RAAN AOP TA
      6900 6900 98 360 0 210

      But it changes to:
      RadPer RadApo INC RAAN AOP TA
      6900 6900 98 0 248.7517740275628 321.2482259726179

      AOP and TA are way off from the expected value. The conversion algorithm probably has an error in it somewhere.

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            Hide
            gmat_wcs Wendy Shoan added a comment -

            Is there anything unusual or special about this orbit, other than it being circular?

            Show
            gmat_wcs Wendy Shoan added a comment - Is there anything unusual or special about this orbit, other than it being circular?
            Hide
            shoffman Shawn Hoffman added a comment -

            Aside from it being a circular orbit, no I dont think there is anything special about the orbit.

            Show
            shoffman Shawn Hoffman added a comment - Aside from it being a circular orbit, no I dont think there is anything special about the orbit.
            Hide
            gmat_wcs Wendy Shoan added a comment -

            This is a tolerance issue. Switching to P3.

            Show
            gmat_wcs Wendy Shoan added a comment - This is a tolerance issue. Switching to P3.
            Hide
            shughes Steven Hughes added a comment -

            The tolerance causing the problem here is the tolerance on eccentricity value that defined to transition from circular to elliptic orbit to avoid divide by zero in the code.

            Show
            shughes Steven Hughes added a comment - The tolerance causing the problem here is the tolerance on eccentricity value that defined to transition from circular to elliptic orbit to avoid divide by zero in the code.
            Hide
            shughes Steven Hughes added a comment -

            This is not a bug, the issue is that not enough precision was used in the Cartesian state which results in an eccentricity that is not small enough to fall into GMAT's definition of a circular orbit. Here is the full precision required.

            Shawn, if you are using Test Complete for this, can you update the test with the more precise data?

            GMAT DefaultSC.X = -5975.575286112627;
            GMAT DefaultSC.Y = 480.1471983122256;
            GMAT DefaultSC.Z = -3416.424837158419;
            GMAT DefaultSC.VX = 3.800269067037762;
            GMAT DefaultSC.VY = 0.9160734111800484;
            GMAT DefaultSC.VZ = -6.518201013391741;

            Show
            shughes Steven Hughes added a comment - This is not a bug, the issue is that not enough precision was used in the Cartesian state which results in an eccentricity that is not small enough to fall into GMAT's definition of a circular orbit. Here is the full precision required. Shawn, if you are using Test Complete for this, can you update the test with the more precise data? GMAT DefaultSC.X = -5975.575286112627; GMAT DefaultSC.Y = 480.1471983122256; GMAT DefaultSC.Z = -3416.424837158419; GMAT DefaultSC.VX = 3.800269067037762; GMAT DefaultSC.VY = 0.9160734111800484; GMAT DefaultSC.VZ = -6.518201013391741;
            Hide
            shoffman Shawn Hoffman added a comment -

            Spreadsheet updated

            Show
            shoffman Shawn Hoffman added a comment - Spreadsheet updated
            Hide
            shughes Steven Hughes added a comment -

            Fixed in 4 July 2012

            Show
            shughes Steven Hughes added a comment - Fixed in 4 July 2012

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                  Updated:
                  Resolved: