;+
; NAME:
;   oclc_epq03_AAREADME
; PURPOSE
;   Print the file 'oclc_epq03_AAREADME.pro'
; CATEGORY:
;  Occultation lightcurve (oclc)
; CALLING SEQUENCE:
;  oclc_ey92_AAREADME
;
; PROCEDURE
;
; README_oclc_epq03
; 
; These routines implement the model of Elliot, Person and Qu 2003.
; Analysis of stellar occultation data for planetary atmospheres. II - 
; Inversion, with application to Pluto and Triton.  Ap J 126: 1041-1079.
; 
; The routines are called oclc_epq03_*.  oclc stands for OCcultation
; LightCurve.  EPQ03 refers to the paper cited above.
; Other occultation lightcurves can be implemented, and will be prefixed
; oclc_<other>_.pro.
; 
; ---------------------------------------------------------------------------
; OVERVIEW
; ---------------------------------------------------------------------------
; 
; This formulation is a numerical implementation of the Abel transform,
; integrating the bending angle along the line of sight through the
; atmosphere. 
; 
; It is a challenge to keep track of the shells on which the variables are
; defines, since some are tabulated at shell centers and others at shell
; boundaries.
; 
; We begin by reproducing Figure 2 and caption from EPQ03:
; 
; ======================================================================================================================
;           .
;  Boundary {############################## r ^#######                     y ^
;  Integral {#################################|#######                       |
;    Region {#################################|#######                       |
;            _ r_b = r_{i_b-1/2}  _ _ _ _ _ _ ________________...............|
;           {                    {            |               \_______________ y_b = y_{i_b-1/2} _ _
;           {                    {            |                              |                      }
;           {       Delta r_i_b  {      r_i_b +                              |                      }
;           {                    {            |                              |                      }
; Inversion {                    {            |                              + y_i_b                } Delta y_i_b
; Summation {        r_{i_b+1/2}  _ _ _ _ _ _ ___________....................|                      }
;    Region {                    {            |          \____theta_{i_b+1/2}|                      }
;           {                    {            |                    \__________ y_{i_b+1/2} _ _ _ _ _
;           {    Delta r_{i_b+1} {  r_{i_b+1} +                              |                      }
;           {                    {            |                              |                      }
;           {                    {            |                              |                      }
;           {        r_{i_b+3/2}  _ _ _ _ _ _ _______........................+ y_{i_b+1}            } Delta y_{i_b+3/2}
;           {                                 |      \_____   theta_{i_b+3/2}|                      }
;           {                                 |            \_____            |                      }
;           {                                 |                  \_____      |                      }
;            _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ \______ y_i_{b+3/2} _ _ _ _ _
;                                             |                              |
;                                            //                             //
;                                         Body Plane                Observer Plane
;                                            //                             //
;                                            |                               |
;                                      r = 0 +                         y = 0 +
;                                      
;                                            <--------------- D ------------->
;                                            
; EPQ03 Figure 2. Shells used in inversion summations.  This magnified
; view of the body section of Fig 1 shows our scheme for the inversion
; shells.  Note that the integral shell indeices, i, occur at shell
; midpoints, while the index of i-1/2 denotes the upper boundary of the
; shell i and i+1/2 denotes its lowerboundary.  Corresponding values on
; the y-axis are determined by the ray paths for the refracted
; starlight, and the shaded area above is the inersion boundary integral
; region. The first shell of the inversion region ("boundary shell")
; begins at radius r=r_b and has an index i = i_b
; 
; ======================================================================================================================
; 
; To maintain the strictest 1-to-1 correspondence with the cited paper, we
; will use the shell index scheme so defined.  
; 
; The scheme tabulates some values on shell centers and others on shell boundarys.
; 
; shell center (integer i): y, Delta y, phi, sigma(phi), Delta r, Delta theta
; shell edge (half-integer i): r, theta, nu, n, p, T, H
; 
; ---------------------------------------------------------------------------
; VARIABLES
; ---------------------------------------------------------------------------
; 
; ch
; EPQ03 notation: none
; flag - 1 to include an analytic approximation to the integral from
; the top of the highest shell to infinity.; (Not well tested)
;
; distobs       
; EPQ03 notation: D 
; Distance between target and observer
; scalar
; cm
; 
; deltathetamid
; EPQ03 notation: Delta theta_i
; change in theta over one shell (effectively at shell midpoint)
; negative for an isothermal atmosphere.
; radian
; 
; deltaymid
; EPQ03 notation: Delta y_i
; width of the shadow radius shell, defined as y_{i+1/2} - y_{i-1/2}
; so delta_y is negative for an isothermal atmosphere.
; 
; 
; i
; EPQ03 notation: i
; index of shells ranging from 0 (topmost) to imax-1
; EPQ02 is 1-based, and we use the native IDL 0-based arrays.
; This has no practical impact
; 
; ib
; EPQ03 notation: i_b
; index of first (highest) shell for the inversion.
; 1 <= i < ib      shells of boundary integral region
; ib <= i <= imax  shells of inversion
; scalar
; unitless
; 
; iminus
; EPQ03 notation: i - 1/2
; index of top of shell i
; unitless
; 
; imax
; largest shell index (closest to surface)
; scalar
; unitless
; 
; j
; EPQ03 notation: j
; summation shell index for calculating r_i, theta_i, nu_i, p_i, 
; ranging from ib to i.
; scalar
; unitless 
;
; mp
; EPQ03 notation: M_p (Eq 21)
; Mass of planet (or other occulting body
; gm
;
; mu
; EPQ03 notation: mu (Eq 31)
; molecular weight
; unitless (eg 12 for C)
;
; nbot
; EPQ03 notation: n_{i+1/2} (Eq. 55)
; number density at shell bottom
; molecule/cm^3
; 
; nu
; EPQ03 notation: nu_{i+1/2} (Eq. 54)
; Refractivity. 
; Unitless
; 
; nustp
; EPQ03 notation: nu_STP (Eq. 17)
; Refractivity at STP (1.01325 bar, 273.15 K)
; Unitless
; 
; phimid
; EPQ03 notation: phi_i
; normalized stellar flux at shell center
; unitless.
; 
; r
; EPQ03 notation: r
; planet radius (distance from planet center).
; cm
;
; rbot
; EPQ03 notation: r_{i+1/2}
; planet radius (distance from planet center) at shell bottom
; cm
; 
; rtop
; EPQ03 notation: r_{i-1/2}
; planet radius (distance from planet center) at shell top
; cm
; 
; thetabot
; EPQ03 notation: theta_{i+1/2}
; bending angle, negative for an isothermal atmosphere, at shell bottom
; radians.
; 
; thetamid
; EPQ03 notation: theta_i
; bending angle, negative for an isothermal atmosphere.
; radians.
; 
; yb
; shadow radius at beginning of inversion
; equivalent to y_{i_b - 1/2} or ytop[ib]
;
; ybot
; EPQ03 notation: y_{i+1/2} (eg eq. 33)
; shadow radius array tabulted at shell bottom, 
; [same as rho in oclc_ey92]
; indexed from 0 to imax-1,
; cm
;
; ymid
; EPQ03 notation: y_i (eg eq. 34)
; shadow radius array tabulted at shell mid, 
; [same as rho in oclc_ey92]
; indexed from 0 to imax-1,
; cm
; 
; ytop
; EPQ03 notation: y_{i-1/2} (eg eq. 33)
; shadow radius array tabulted at shell top, 
; [same as rho in oclc_ey92]
; indexed from 0 to imax-1,
; cm
; 
; ---------------------------------------------------------------------------
; LOW-LEVEL FUNCTIONS
; ---------------------------------------------------------------------------
; 
;   bnubot = oclc_epq03_bnu(rbot, rtop, thetamid, deltathetamid, ib, ch)
;   bpbot = oclc_epq03_bp(rbot, rtop, thetamid, deltathetamid, ib, ch)
;   deltathetamid = oclc_epq03_deltathetamid(thetabot)
;   deltaymid = oclc_epq03_deltaymid(ymid)
;   nbot = oclc_epq03_n(rbot, rtop, thetamid, deltathetamid, ib, ch, nustp)
;   pbot = oclc_epq03_p(rbot, rtop, thetamid, deltathetamid, ib, ch, mp, mu, nustp)
;   oclc_eqp03_r,ymid, deltaymid, phimid, ib, imax, rbot
;   snubot = oclc_epq03_snu(rbot, rtop, deltathetamid, ib)
;   spbot = oclc_epq03_sp(rbot, rtop, deltathetamid, ib)
;   thetabot = oclc_epq03_theta(ybot,rbot, distobs)
;   ybot = oclc_epq03_ybot(ymid)
;   ytop = oclc_epq03_ytop(ymid)
; 
;-

pro oclc_epq03_AAREADME

    findpro, 'oclc_epq03_AAREADME', dirlist=dirlist, /noprint
    
    tmp = ' '
    openr, lun, dirlist[0]+'/oclc_epq03_AAREADME.pro', /get_lun
    while not eof(lun) do begin
        readf,lun,tmp
        print, tmp
    endwhile
    free_lun,lun
end