Format description of GaussFit data files generated by td2gf

The *.gf files are text files with two header lines followed
by one data line per transit.  There are 16 columns separated
by (blanks and) the tabulator character (ASCII code 9).

The first header line contains the names of the variables,
'obs', 'ip', etc, one per column.

The second header line contains the word 'double' in each 
column.  (This is the only numerical format used by GaussFit.)

The third and following lines contain 16 numerical values in
'free format', i.e. with or without the decimal point and
decimal exponent (E).  The meaning of these values are
explained in the table below.

See Section 2.9 in Vol. 1 of the Hipparcos and Tycho Catalogues
(ESA SP-1200) for further explanation.

-------------------------------------------------------------
Name		Explanation
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obs		sequential numbering of the transits
ip		target position index (=JT1)
t		epoch of the transit in years from 1991.25 (=JT2)
fx		spatial frequency in rad/rad (JT3)
fy		spatial frequency in rad/rad (JT4)
fp		parallax phase factor in rad/rad (JT5)
b1		DC component of signal in counts/sample
b2		AC Fourier component of signal (counts/sample)
b3		"
b4		"
b5		"
b1_b1		variance of b1 in (counts/sample)^2
b2_b2		variance of b2 "
b3_b3		variance of b3 "
b4_b4		variance of b4 "
b5_b5		variance of b5 "
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