FUNCTION iter_eph,date,t0,t1

; PoCaRun returns 0 at t0, 1 at t1

iter=0
dt0=DOUBLE(t0)
dt1=DOUBLE(t1)
REPEAT BEGIN
    t=0.5*(dt0+dt1)
    run=PoCaRun(sec2hms(t),date)
    IF run THEN dt1=t ELSE dt0=t
    iter=iter+1
    ENDREP UNTIL (iter EQ 8)
RETURN,FLOAT(t)
END

PRO PoCa_ops,date,debug=dbg

dates=STRTRIM(date,2)
obs=BYTARR(24)
FOR j=0,23 DO obs(j)=BYTE(PoCaRun(sec2hms(3600.*j),dates))

c=obs-SHIFT(obs,1) ; change of operational status if c <> 0
IF N_ELEMENTS(WHERE(c NE 0)) GT 2 THEN STOP,obs
IF KEYWORD_SET(dbg) THEN PRINT,c,FORMAT='(12I4)'

IF MAX(c) GT 0 THEN BEGIN
    e=WHERE(c EQ 255)  ; end of operations
    b=WHERE(c EQ 1)    ; beginning of ops

    ; first find end of operations
    t0=e*3600.
    t1=(e-1)*3600.
    tend=iter_eph(dates,t0,t1)
    PRINT,"Operations ended at " $
          +STRTRIM(sec2hms(tend,/round),2) $
          +" UT, "+dates

    ; then find subsequent start of operations
    t0=(b-1)*3600.
    t1=b*3600.
    tstart=iter_eph(dates,t0,t1)
    PRINT,"Operations restarted at " $
          +STRTRIM(sec2hms(tstart,/round),2) $
          +" UT, "+dates
    ENDIF ELSE PRINT,'Polar Camera non-operational less than 1 hour."

RETURN
END