ObserverSourcePairUpdateOneStep Subroutine

  Subroutine ObserverSourcePairUpdateOneStep(self)

      implicit none
      class(ObserverSourcePairClass)                      :: self

      !local variables
      integer                                             :: M

      M = size(self%Pacc, dim=1)
      if (allocated(self%tInterp)) self % tInterp(1:M-1) = self % tInterp(2:M)
      self % Pacc(1:M-1,:) = self % Pacc(2:M,:)

  End Subroutine ObserverSourcePairUpdateOneStep