* BROADLY USED PARAMETERS:
*_________________________________________________
* i/o file unit numbers
      INTEGER kout, kin 
* output
      PARAMETER(kout=53)
* input
      PARAMETER(kin=12)
*_________________________________________________
* altitude, wavelength, time (or solar zenith angle) grids
      INTEGER kz, kw, kt
* altitude
      PARAMETER(kz=125)
* wavelength
      PARAMETER(kw=1000)
* time/sza
      PARAMETER(kt=100)	
*_________________________________________________
* number of weighting functions
      INTEGER ks, kj
*  wavelength dependent
      PARAMETER(ks=60)
*  wavelength and altitude dependent
      PARAMETER(kj=150)

* delta for adding points at beginning or end of data grids
      REAL deltax
      PARAMETER (deltax = 1.E-5)

* some constants...

* pi:
      REAL pi
      PARAMETER(pi=3.1415926535898)

* radius of the earth, km:
      REAL radius
      PARAMETER(radius=6.371E+3)

* Planck constant x speed of light, J m

      REAL hc
      PARAMETER(hc = 6.626068E-34 * 2.99792458E8)

* largest number of the machine:
      REAL largest
      PARAMETER(largest=1.E+36)

* small numbers (positive and negative)
      REAL pzero, nzero
      PARAMETER(pzero = +10./largest)
      PARAMETER(nzero = -10./largest)

* machine precision
	
      REAL precis
      PARAMETER(precis = 1.e-7)

* More physical constants:
*_________________________________________________________________
* Na = 6.022142E23  mol-1       = Avogadro constant
* kb = 1.38065E-23  J K-1       = Boltzmann constant 
* R  = 8.31447      J mol-1 K-1 = molar gas constant
* h  = 6.626068E-34 J s         = Planck constant 
* c  = 2.99792458E8 m s-1       = speed of light in vacuum 
* G  = 6.673E-11    m3 kg-1 s-2 = Netwonian constant of gravitation
* sb = 5.67040E-8   W m-2 K-4   = Stefan-Boltzmann constant
*_________________________________________________________________
* (1) From NIST Reference on Constants, Units, and Uncertainty
* http://physics.nist.gov/cuu/index.html Oct. 2001.
* (2) These constants are not assigned to variable names;  in other 
* words this is not Fortran code, but only a text table for quick 
* reference.  To use, you must declare a variable name/type and
* assign the value to that variable. Or assign as parameter (see
* example for pi above).