double precision function DCPVAL ( P, N, T )
C
C
C*******************************************************************************
C
C       Copyright (C) 1993, California Institute of Technology.  U.S.
C       Government Sponsorhip under NASA Contract NAS7-918 is
C       acknowledged.
C
C*******************************************************************************
C
C	emulates DCPVAL to remove GTARG's dependence on MATH-77
C	restriction: N < 10
C			(not tested for N>2 ,since GTARG only uses N=2)
C			will cause program to halt of p(2) = 0
C	reference:  "MATH77 Release 3.0: A library of Mathematical 
C			Subprograms for FORTRAN 77", JPL Applied
C			Mathematics Group, May 1989, JPL D-1341
C
C	DCPVAL evaluates a polynomial which is represented by 
C	coefficients relative to a Chebyshev basis.  
C
C	B. Shapiro 11/18/92
C
C	Only enough of DCPVAL is emulated to evaluate the atmospheric
C	density polynomial.  This is not a complete emulation of DCPVAL.
C
        integer n
	double precision p(*)
        double precision t, u, z(10)

        if (n.gt.10) n=10

	if (p(2).eq.0.0d0) then
	  write(8,*) 'Invalid value p(2) = 0.'
	  stop ' Error Exit.'
        end if
 
        u = ( t-p(1) ) / p(2)
        z(n) = p(n+3)
	z(n-1) = 2*u*z(n)+p(n+2)
        if (n.gt.2) then
	    do i = n-2,1,-1
	        z(i) = 2*u*z(i+1) - z(i+2) + p(i+3)
            end do
	end if
  
	dcpval = u * z(1) - z(2) + p(3)

        return
        end