pro readsat_overpass,arg,platform,sattime,viewzen
;-------------------------------------------------------------------------------
;Title:		readsat_overpass.pro
;
;Purpose:	To read in the satellite overpass times for all available 
;		platforms with viewing angles less than a designated angle.
;
;Inputs:	arg - Date of interest, string, 'YYYYMMDD'
;
;Outputs:	platform - the satellite platform name
;		sattime - the time of satellite overpass
;		viewzen - the zenith viewing angle from NSA site
;
;Author:	Matthew Shupe
;Date:		4/18/01
;--------------------------------------------------------------------------------


anglelimit=30
yyyy=strmid(arg,0,4)
yy=strmid(arg,2,2)
mm=strmid(arg,4,2)
dd=strmid(arg,6,2)

; The platforms
;---------------
platforms=['TERRA','NOAA_12','NOAA_14','NOAA_15','NOAA_16']
sattime=0.0
viewzen=99.0
platform='NONE'
v1=' ' & v2=v1 & v3=v1 & v4=v1 & v5=v1 & v6=v1 & v7=v1 & v8=v1

;Read in the data
;------------------
if long(arg) lt 20010130L then begin
	for p=0,n_elements(platforms)-1 do begin
		arg='BRW_'+platforms[p]+'.txt'
		file=findfile(arg)
		openr,lun,/get_lun,file[0]
		v1='80'
		while v1 ne yy and not(eof(lun)) do readf,lun,v1,v2,v3,v4,v5,v6,format='(1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,6X,A5)'
		if not(eof(lun)) then begin
			if fix(v2) lt 10 then v2f='0'+strmid(v2,1,1) else v2f=v2
			while v2f ne mm and not(eof(lun)) do begin
				readf,lun,v1,v2,v3,v4,v5,v6,format='(1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,6X,A5)'
				if fix(v2) lt 10 then v2f='0'+strmid(v2,1,1) else v2f=v2
			endwhile
			if not(eof(lun)) then begin
				if fix(v3) lt 10 then v3f='0'+strmid(v3,1,1) else v3f=v3
				while v3f ne dd  and not(eof(lun)) do begin
					readf,lun,v1,v2,v3,v4,v5,v6,format='(1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,6X,A5)'
					if fix(v3) lt 10 then v3f='0'+strmid(v3,1,1) else v3f=v3
				endwhile
				if not(eof(lun)) then begin
					tm=0.0
					vz=99.0
					while v3f eq dd do begin
						tm=[tm,float(v4)+float(v5)/60.0]
						vz=[vz,float(v6)]
						readf,lun,v1,v2,v3,v4,v5,v6,format='(1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,6X,A5)'
						if fix(v3) lt 10 then v3f='0'+strmid(v3,1,1) else v3f=v3
					endwhile
					sattime=[sattime,tm]
					viewzen=[viewzen,vz]
					platform=[platform,strarr(n_elements(tm))+platforms[p]]
				endif
			endif
		endif
		free_lun,lun
	endfor
endif else begin
	for p=0,n_elements(platforms)-1 do begin
		arg='yNSA_'+platforms[p]+'.txt'
		file=findfile(arg)
		openr,lun,/get_lun,file[0]
		v1='8000'
		while v1 ne yyyy and not(eof(lun)) do readf,lun,v1,v2,v3,v4,v5,v6,v7,v8,format='(1X,A4,1X,A3,1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,5X,A5)'
		if not(eof(lun)) then begin
			if fix(v3) lt 10 then v3f='0'+strmid(v3,1,1) else v3f=v3
			while v3f ne mm and not(eof(lun)) do begin
				readf,lun,v1,v2,v3,v4,v5,v6,v7,v8,format='(1X,A4,1X,A3,1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,5X,A5)'
				if fix(v3) lt 10 then v3f='0'+strmid(v3,1,1) else v3f=v3
			endwhile
			if not(eof(lun)) then begin
				if fix(v4) lt 10 then v4f='0'+strmid(v4,1,1) else v4f=v4
				while v4f ne dd  and not(eof(lun)) do begin
					readf,lun,v1,v2,v3,v4,v5,v6,v7,v8,format='(1X,A4,1X,A3,1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,5X,A5)'
					if fix(v4) lt 10 then v4f='0'+strmid(v4,1,1) else v4f=v4
				endwhile
				if not(eof(lun)) then begin
					tm=0.0
					vz=99.0
					while v4f eq dd and not(eof(lun)) do begin
						tm=[tm,float(v5)+float(v6)/60.0]
						vz=[vz,float(v8)]
						readf,lun,v1,v2,v3,v4,v5,v6,v7,v8,format='(1X,A4,1X,A3,1X,A2,1X,A2,1X,A2,1X,A2,1X,A2,5X,A5)'
						if fix(v4) lt 10 then v4f='0'+strmid(v4,1,1) else v4f=v4
					endwhile
					sattime=[sattime,tm]
					viewzen=[viewzen,vz]
					platform=[platform,strarr(n_elements(tm))+platforms[p]]
				endif
			endif
		endif
		free_lun,lun
	endfor
endelse

iwh=where(viewzen le anglelimit,num)
if num gt 0 then begin
	sattime=sattime[iwh]
	viewzen=viewzen[iwh]
	platform=platform[iwh]
endif else begin
	sattime=-1
	viewzen=''
	platform=''
endelse

end