New commands for the timing analysis in EXSAS '97:

  
PLOT/PULSE_PROFILE:
        New command, producing a fancy plot of the binned pulse profile 
        deduced by a photon arrival time analysis using MAKE/FOLDING.

                                                          
CORRECT/BARYCENTER:
        The Julian days of the leap seconds which were used to compute 
        the number of leap seconds since 1972 were pointing to 12h rather 
        than to 0h, the actual time the leap second was introduced. This 
        results in errors for pulse arrival time measurements if the pulsar
        observation was performed at that day where the leap second was
        applied. The leap second reference times are now correct.

        Also: it is now using the first and last photon event time of the 
        given table to check for consistency with the orbit file. Before 
        only the first and last entry of the TIM_SEL descriptor was used. 
        This has caused trouble for low count rate objects and prompted 
        the warning: *Correction table and photon table not compatible. 
        Check the times* although the orbit file actually covered all 
        photon arrival times of the given table.

        Also: During the barycentring procedure the expire date of the 
        scc_to_utc calibration table is given in UTC and SCC for 
        information purpose.
                                                          

EXSAS_CAL:leap_sec.tbl
        Leap seconds are now read in from a file EXSAS_CAL:leap_sec.tbl
        The table has the descriptors: 
 
          VERSION:          1_97
          ORIGIN:           EXSAS
          LAST_UPDATED:     05-FEB-1997
        
        which presented for information purpose during the barycentring
        procedure CORRECT/ORBIT
                                                          

MAKE/FOLDING_SEARCH, FOLD/LIGHT_CURVE:
        The parameter EPOCH in the parameter file used for folding has 
        changed its unit. Epoch has now to be given in Julian Days while 
        before it was in seconds. Giving an epoch 0.0 takes the Julian 
        Day stored in the descriptor CORR_OFFSET (which is present after 
        barycenter correction) as the reference epoch (!) , that is
        epoch=0.0  is equivalent to epoch=corr_offset.

CONVERT/UTC_TDB
        New command. Converts the photon arrival times from the 
        Coordinated Universal Time scale (UTC) to the Barycentric 
        Dynamical Time scale (TDB)
                                                          

CORRECT/BINARY_ORBIT
        New command. Corrects the photon arrival times for a binary 
        motion of a pulsar following R. Blandford & S. Teukolsky, 
        Ap.J. 205, 580 (1976). After applying CORRECT/BINARY_ORBIT
        the file type is changed to PETB.
                                                          
TUTORIAL/TIMING
        New command. Demonstrates the functionality of the timing 
        routines and gives an introduction in the timing analysis 
        technics.                      
                                                          
CONVERT/GEO_SSB
        New command. Converts a geocentric pulse arrival time which 
        is in UTC to the solar system barycenter and the time scale TDB.
                                                          
 
New SCC to UTC calibration: Version 2_97
        The conversion of space craft clock times from SCC to UTC is now
        based on clock calibration data up to 08-JUN-1997. Conversion
        after this date is done by extrapolation. Plots showing the
        residuals of the scc/utc polynomial fits for the years 1990
        to 1997 as well as other timing related information (e.g. on
        leap seconds) can be found in the ROSAT service area under:

             /info_svc/rosat_svc/calibration/timing.

        or via the URL:

        http://ftp.rosat.mpe-garching.mpg.de/calibration/timing/readme.html

        A new descriptor (Origin) has been introduced with this release
        for identification purpose.