;%=====================================================================
; dd 10/7/97 Copied from aciss_geometry, modified for ACIS I
;----------------------------------------------------------------------
pro acisi_geometry, aciss_rgaps, aciss_lgaps

   aciss_offset =  1.52        ; mm from aim-point to array geometric center (y,z)=0
   
   d_aciss_offset =  0.0     ;     offset aim-point
   aciss_offset = aciss_offset+d_aciss_offset

   aciss_segment =  1024.*0.024       ; mm length of ACIS-S array segment
   aciss_gap = 0.43             ; mm

;   aciss_segment = mm size of ccd side
;   aciss_gap = mm separation of ccds
;   aciss_offset = mm aimpoint from chip edge
;   theta_heg

; OUTPUTS:
;   aciss_rgaps = mm array right-side gap boundaries:
;     0=> left edge of first
;     1=> right edge of first
;     2=> left edge of second
;     3=> right edge of second
;     4=> right edge of array
;
;   aciss_lgaps = mm array left-side gap boundaries
;     0=> right edge of first
;     1=> left edge of first
;     2=> right edge of second
;     etc
;     6=> left edge of array

; gaps are positions are along dispersion direction; 

; allocate storage
; 
aciss_rgaps = fltarr(5)
aciss_lgaps = fltarr(7)

for ii = 0,4 do begin
  aciss_rgaps(ii) = (ii/2+1)*aciss_segment + ( (ii+1)/2)*aciss_gap - aciss_offset
endfor
; collapse gaps for ACIS-I:
aciss_rgaps(2) = aciss_rgaps(0)
aciss_rgaps(3) = aciss_rgaps(1)
aciss_rgaps(4) = (aciss_rgaps(1)+aciss_rgaps(0))/2.

for ii = 0,6 do begin
  aciss_lgaps(ii) = (ii/2)*aciss_segment + ( (ii+1)/2 )*aciss_gap + aciss_offset
endfor
; collapse gaps for ACIS-I:
aciss_lgaps(4) = aciss_lgaps(2)
aciss_lgaps(5) = aciss_lgaps(3)
aciss_lgaps(6) = (aciss_lgaps(3)+aciss_lgaps(2))/2.

;; assume symmetric - not strictly correct!
message, 'Assumes clocking angles symmetric!', /info
message, 'Clocking angle used is average of HEG and MEG', /info
; sysvar from startup AXAF_Params
ave_angle = 0.5*( ABS(!HEG_angle) + ABS(!MEG_angle) )
aciss_rgaps = aciss_rgaps / cos(ave_angle)
aciss_lgaps = -aciss_lgaps / cos(ave_angle)

END