SSSARF (Feb96)               ftools.caltools              SSSARF (Feb96)



NAME
    sssarf  --  creates  an  Ancilliary Response File (ARF) for Einstein
    SSS PHA data
    
    
USAGE
    phafile  calfexp  outfile1  (arfversn)  (oddeven)  (icef)  (chatter) 
    (mode)
    
    
DESCRIPTION
    
     This  task  creates  an  Ancilliary Response File (ARF) appropriate
    for a user-defined PHA file from the Solid State Spectrometer  (SSS)
    onboard  the  Einstein  Observatory.  The  task  calculates the ARF,
    taking  into  account  the  area  of  the   X-ray   telescope,   AND 
    corrections  for  the  time-dependent  build  up of water ice on the
    front of the detector.
    
    The Solid State Spectrometer was a  croygenically  cooled  detector.
    Cooling  was obtained by attatching the SSS to a cold plate within a
    cryostat   containing   methane   and    ammonia.    Unfortunantely,  
    cryopumping  of  outgassing  material lead to a time-dependant build
    up of water-ice on the detector surface, giving a much lower  energy
    response  than  expected.  A  heater  attatched  to  the  cold plate
    enabled the SSS to be periodically de-frosted. After  each  defrost,
    a  fraction  of  the  defrosted  water  ice  escaped  out of a small
    opening in the cryostat to outer space; however ice  returned  after
    12-24  hrs  due  to  the  residual water.  As the number of defrosts
    performed increased, the total  amount  of  ice  return  after  each
    defrost  was  reduced,  until  after 10 months (Dec 1978 - Oct 1979)
    the amount of ice on the front of the detector was  negligable.  Two
    efforts,  in  1979  and  1990,  have been made to understand the SSS
    response matrix. Many observations between Dec 1978 and Oct 1979  of
    sources  with  simple, well-known spectra were used to determine the
    variation in the amount of ice as a function of time. This  lead  to
    the   development   of  an  ice-model  consisting  of  two  distinct 
    components with e-folding return times of 0.25  and  10  days  (D.J.
    Christian  et al., "The Einstein SSS Calibration", Legacy, 1992, No.
    1, p38-42). The model includes  the  effects  of  the  defrosts  and
    produces  an  estimate of the amount of ice accumulated at any given
    epoch.
    
    SSSARF calculates the epoch of every sub SSS observation within  the
    input  source  PHA  file,  and  enters  this  value  into  the above
    ice-model   to   determine   the   amount   of   ice.   Using   this  
    'ice-parameter'  and  the energy bounds read from the input RMF, the
    level of ice absorption at each energy is determined.  All i/p  must
    be  in  an  OGIP-approved  FITS  file format (i.e. PHAVERSN = 1992a,
    RMFVERSN = 1992a) and therefore consist of:
    
    (i) an EINSTEIN SSS PHA file for a given source observation.
    
    (ii)  an  EINSTEIN  SSS  Detector  Restribution  Matrix  File  (RMF) 
    containing  information  concerned  with  the  photon redistribution
    process ONLY (i.e.  detector gain and energy resolution).  Two  RMFs
    are   currently   available   via   anonymous  ftp  to  the  HEASARC 
    Calibration                                                 database                                                
    (ftp://heasarc.gsfc.nasa.gov/caldb/data/einstein/sss/cpf/*.rmf).
    The  recommended  RMF  for use with this task is that which has been
    corrected for the 'odd/even' effect (whereby the  original  elements
    in   the  SSS  detector  redistribution  matrix  are  multiplied  by 
    1.000000 for odd-numbered channels, and 1.029390  for  even-numbered
    channels).  A  corresponding  dataset,  without  corrections for the
    `odd/even' effect may also be  used.  It  should  be  stressed  that
    neither  RMF contains any corrections for the water ice on the front
    of the detector.
    
    An output Ancilliary Response File (ARF) appropriate to  the  source
    observation  is generated. This dataset contains a 1-D (energy) FITS
    extension  containing  the  product  of  the  SSS   geometric   area 
    (180cm**2)  and  the  ice-absorption  at  each  energy. Finally, the
    source PHA file is updated by writing the names  of  the  input  RMF
    and   the   output   ARF  to  the  keywords  RESPFILE  and  ANCRFILE 
    respectively. Comment lines are also  written  giving  overall  mean
    epoch and mean ice values for the observation.
    
    
    
PARAMETERS
    
    phafile [character string]
         The  user-supplied  string  for  the Einstein SSS PHA filename,
        required  if QOVERRIDE=Y
    
    calfexp [character string]
         The user-supplied string for the calibration information to  be
        used   (either  caldb or CALDB or pathname of calibration file),
        required  if QOVERRIDE=Y
    
    outfile1 [character string]
         The name of the output file (an ARF).
    
    (arfversn='1992a') [character string]
         OGIP version number of the ARF format to be created.
    
    (oddeven=.true.) [logical]
         calibration information (.RMF) is to  be  used  which  accounts
        for the 'odd/even'  effect.
    
    (icef=1) [integer] 
         user-defined ice-fraction.
    
    (chatter = 9) [integer]
         Flag  to  indicate how chatty the task is at execution. A value
        of  9  is  the   default,  with  lower/higher  values  producing 
        quieter/verbose output  respectively.
    
    (mode = "ql") [character string]
        
    
    
    
    
    
BUGS
    None known
    
    
    
LOG OF SIGNIFICANT CHANGES
    
    
    
    v1.0.0 (1996 Feb)
            original version (Lorraine Breedon)
    
    
    
PRIMARY AUTHOR
    
    Lorraine Breedon
    HEASARC
    NASA/GFSC
    http://heasarc.gsfc.nasa.gov/cgi-bin/ftoolshelp
    (301) 286-1364