pro aksm,wn,fnu,wns,fnus,sigma

; take a spectrum (wn,fnu) and return a gaussian smoothed
; version sampled on the grid wns

dwn = abs(wn[1] - wn[0])

nx = n_elements(wn)

if ( abs ((wn[nx-1] - wn[0])/(nx-1)) - dwn  gt 0.1 ) then begin
   print,'wn grid is not uniform'
   stop

endif

; make a kernel that is +/- 5-sigma

nk = floor(10.0*sigma/dwn)
if ( nk mod 2 eq 0 )  then nk = nk + 1


kx = dwn*(findgen(nk)-nk/2)

kernel = exp(-0.5*(kx/sigma)^2)   
kernel = kernel/total(kernel)	; normalze the kernel to 1

; convolve with the kernel 

fnuc = convol(fnu,kernel,/EDGE_WRAP)

; interpolate onto the output grid over valid data range

w = where(wns ge min(wn) and  wns le max(wn))



fnus = fltarr(n_elements(wns))

fnus(w) = interpol(fnuc,wn,wns(w))


end