Control commands allowed in free-format headers:

CLK    Terrestrial time standard  
       Allowed values: 'UNCORR' (default), 'UTC(NIST)', 'UTC(BIPM)', 
                       'TT(BIPM)', 'PTB', 'AT1'

COORD  Input coordinate system
       Allowed values: 'B1950', 'J2000' (default)

EPHEM  Solar system ephemeris
       Allowed values:  First five characters of file names listed
                        in tempo.cfg file (see below).  Typically
                        'DE200' and 'DE405'

IBOOT  Bootstrap error analysis, with 2^n iterations
       Allowed values:  integers n

NDDM   Model DM as an n-th order polynomial expansion in time
       Allowed values:  integers n

NITS   Iterate solution n times, or fewer if it converges.
       Allowed values:  integers n
       Special case: n=9: iterate until convergence

NPRNT  Print every 10^n TOA line in file tempo.lis
       Allowed values:  integers n

PSR    Pulsar name (normally without the leading B or J)
       Allowed values:  up to 12 characters

BINARY Binary model to use (see BINARY MODELS, below)
       Allowed values:  'NONE', 'BT', 'EH', 'DD', 'DDGR', 'H88',
                        'BT+', 'DDT', 'MSS', 'ELL1', 'BT1P', 'BT2P'

START  Ignore TOAs before this date (MJD) (if flag is nonzero)
       Allowed values:  single-precision real numbers
       Allowed flags:  integers; START will be used only if flag is nonzero

FINISH Ignore TOAs after this date (MJD) (if flag is nonzero)
       Allowed values:  single-precision real numbers
       Allowed flags:  integers; FINISH will be used only if flag is nonzero

GAIN   Fraction of correction added to each parameter on each iteration
       Allowed values:  positive real numbers
       Default value: 1