;+
; NAME:
;  covp
; PURPOSE: (one line)
;  Return vapor pressure of CO from Brown & Ziegler 1980
; CATEGORY:
;  Volatile Transport
; CALLING SEQUENCE:
;  vp = covp(t)
; INPUTS:
;  t : temperature, K
; KEYWORD INPUTS
;  None
; OUTPUTS:
;  vp : vapor pressure in microbar
; OPTIONAL OUTPUT
;  None
; RESTRICTIONS:
; PROCEDURE:
;  This function implements the tables of Brown and Zeigler 
; MODIFICATION HISTORY:
;  Written 2009 Dec 7, by Leslie Young, SwRI
;-
function covp, t

; Return N2 vapor pressure, in microbar, as a function of temperature
a_liq  =[1.50598052e1, -6.27448768e2, -4.07696150e3, -7.02090082e4, 0,            0 ]
a_beta =[1.68655152e1, -7.48151471e2, -5.84330795e3,  3.93853859e4, 0,            0 ]
a_alpha=[1.80741183e1, -7.69842078e2, -1.21487759e4,  2.73500950e5, -2.90874670e6, 1.20319418e7]
a=a_beta
if t lt 61.544 then a=a_alpha
if t gt 68.127 then a=a_liq
p = exp( total((t^(-findgen(6))) * a))* 1.33322e3
return, p
end