pro read_sage2,dayno,latpos,lonpos,dir=dir

;+
; this routine reads the haloe data
;  dayno = the day number length L
;  latpos is the latitude vector (3,L) where latpos(1,L) is the overpass point
;  lonpos is the longitude vector (3,l) " "
; dir is the directory where the data is located
;-  
;
; sage read (4258)
;Variable 1:      1 sunrise; -1 sunset
;Variable 2:      Event date year
;Variable 3:      Event date month
;Variable 4:      Event date day
;Variable 5:      Event date hour
;Variable 6:      Event date minute
;Variable 7:      Event date seconds
;Variable 8:      Tangent point altitude (km)
;Variable 9:      Latitude 150 km from subtangent point to spacecraft
;Variable 10:     Longitude 150 km from subtangent point to spacecraft
;Variable 11:     Latitude of subtangent point
;Variable 12:     Longitude of subtangent point
;Variable 13:     Latitude 150 km from subtangent point toward sun
;Variable 14:     Longitude 150 km from subtangent point toward sun
;Variable 15:     Latitude of spacecraft projected on the surface
;Variable 16:     Longitude of spacecraft projected on the surface
;Variable 17:     Azimuth to spacecraft
;Variable 18:     Azimuth from spacecraft
;Variable 19:     Unknown
;-

get_lun,unit
sun=1 & year=1900. & mon=0. & day=0. & hour=0. & min=0. 
sec=0. & tanalt=0. & lat150=0. & lon150=0. & lats=0. & lons=0.
aztosp=0. & asfrsp=0. & lats150=0. & lonss150=0.
dayno=dblarr(4258)
latpos=fltarr(3,4258)
lonpos=fltarr(3,4258)
i=0
openr,unit,dir+'sage22.dat'
while not eof(unit) do begin
   readf,unit,sun,year,mon,day,hour,min,sec,tanalt,lat150,$
      lon150,lats,lons,lats150,lons150,aztosp,asfrsp
      if mon le 9 then strmon='0'+str(mon) else strmon=str(mon)
      if day le 9 then strday='0'+str(day) else strday=str(day)
      strdate=string(fix(year),format='(i4)')+strmon + strday
      dayno(i)=double(day1900(strdate))+ double((hour*3600.+min*60.+sec)/86400.)
      latpos(0,i)=[lat150,lats,lats150]
      lonpos(0,i)=[lon150,lons,lons150]
      i=i+1
      
      end
      free_lun,unit
      return
end