subroutine TLE_Subset( nIn, nOut, ClsLvl, IntlNo, EltSet, EphTyp,
     &   Orbit, EpochJD, dNdT, d2NdT2, bStar, Incl, Node, E,
     &   Omega, M, N, Status )
!
!     Select a "consistent" subset of the input NORAD (USSPACECOM)
!     two-line orbit element sets.  The input arrays are overwritten
!     by the output.
!
!     B. Knapp, 2000-05-26
!
      implicit none
!
!     Input
      integer*4 nIn
!
!     Input/Output
      real*8 EpochJD(nIn), dNdT(nIn), d2NdT2(nIn), Incl(nIn), Node(nIn),
     &   E(nIn), Omega(nIn), M(nIn), N(nIn), bStar(nIn)
      character*8 IntlNo(nIn)
      integer*4 EltSet(nIn), Orbit(nIn)
      character*1 ClsLvl(nIn), EphTyp(nIn)
!
!     Output
      integer*4 nOut, Status
!
!     Externals
      external TLE_Filter
!
!     Static: none
!
!     Local
      integer*4 j !, nGood1
!
!     Verify that elements are sorted in ascending order of Epoch
      do j=1,nIn-1
         if ( EpochJd(j+1) .le. EpochJd(j) ) then
            Status = 98
            return
         endif
      enddo
!
!     Perform one round of internal consistency checking (select
!     a consistent subset)
      call TLE_Filter( nIn, nOut, ClsLvl, IntlNo, EltSet, EphTyp,
     &   Orbit, EpochJD, dNdT, d2NdT2, bStar, Incl, Node, E,
     &   Omega, M, N, Status )
!     call TLE_Filter( nGood1, nOut, ClsLvl, IntlNo, EltSet, EphTyp,
!    &   Orbit, EpochJD, dNdT, d2NdT2, bStar, Incl, Node, E,
!    &   Omega, M, N, Status )
      if ( Status .ne. 0 ) then
         Status = 97
         return
      endif
!
!     We must have at least four TLE sets
      if ( NOut .lt. 4 ) then
         Status = 96
         return
      endif
!
!     All is well!
      Status = 0
      return
      end