EJS 9/9/98
SCORE AND ASPECT FILE FORMATS
SIMULATED SCORE FILE
The score simulations are stored in fits files with a header like the
following:
SIMPLE = T / Written by IDL: Mon Aug 31 16:43:32 1998
BITPIX = 32 /
NAXIS = 2 /
NAXIS1 = 3 /
NAXIS2 = 5830 /
DATE = 'Mon Aug 31 16:43:32 1998' /Date of Simulation
OBJECT = '/hessi/.pro/model_1pt.sav' /FLARE SIMULATION
INSTRUME= 'HESSI SIMULATION' /E. Schmahl, GSFC
CTYPE1 = 'Time Tag' /
CTYPE2 = 'Sub-Collimator' /
CTYPE3 = 'Pulse-Height' /
CDELT1 = 1.00000 /MICRO SECONDS
CDELT2 = 1.00000 /SUB-COLLIMATORS 1 TO 9
CDELT3 = 1.00000 /PULSE HEIGHTS 0 TO 16383
TSTART = 0.00000 /Start of score (relative time)
TSTOP = 4.00000 /End of score (relative time)
CREATOR = 'model_to_score.pro' /Program creating this FITS file
SAS-FILE= 'aspect904596211.sav' /Aspect simulation used
END
Each score is named uniquely in the form
"scorennnnnnnnn.fits", where
nnnnnnnnn is the 9-digit time returned by
IDL's long(systime(1)). The associated aspect savefile, whose name appears
in the score header,
is named in parallel form: "aspectnnnnnnnnn.sav",
where the 9-digit
"magic number" is the same as that for its associated score.
THE SIMULATED ASPECT FILE
The simulated aspect save files are created at the same time as the
scores (in model_to_score.pro), and consist of a 3 x N floating-point
array (t_dxdy) of times (µsec) and dx, dy displacements (arc sec) of
the telescope axis from sun center:
time=t_dxdy(0,*) (micro seconds from start of score)
dx=t_dxdy(1,*) (arc sec from sun center)
dy=t_dxdy(2,*) (arc sec from sun center)
Each of the dx and dy values are for a simulated event
time appearing in the score fits file, so there is a one-to-one
agreement of times in both the score fits file and the associated
aspect save file.
The angular orientation of the (dx,dy) frame is parallel to the x,y
coordinate system of the modulation patterns. The orientations of the
latter are defined only relative to the flare site through its x,y
coordinates. No orientation relative to solar north is defined.
In the August 1998 version of the program "model_to_score.pro", it is
assumed that there is a perfect linear relationship between telescope
rotation angle phi and time. Thus dphi/dt is exactly constant. This may
well not be the case on the actual satellite.
The (dx,dy) pairs in the aspect save file are used in the Monte Carlo
process (model_to_score.pro) which selects or rejects photons for the
score. The aspect save file retains only those pairs for which
photons are accepted, These dx,dy values are required for subsequent
image reconstruction, and are used by score_bproj.pro to shift the
modulation patterns by the appropriate amounts.
Written Sept. 9, 1998.