Reading and Writing FITS Files

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Reading and Writing FITS Files General tools In
IDL fits_info Summarizes FITS file primary
data and extensions Example fits_info,
'hsi_spectrum_20020421_004040.fits' mrdfits
Reads an extension in a FITS file Calling
sequence data mrdfits(file, ext,
header) Example data mrdfits('hsi_spectrum_200
20421_004040.fits, 0, header) headfits Reads
header from an extension of a FITS file Example
header headfits('hsi_spectrum_20020421_004040.fi
ts', exten1) mwrfits Writes an extension in a
FITS file FITS object Under construction SSW/g
en/fits directory contains many IDL tools to
read/write FITS files Astronomy Library at GSFC
documentation on SSW FITS I/O FV tool from
HEASARC at GSFC Free software tool you can
download Graphical interface for examining FITS
files easily Allows for plotting of rows/columns
in FITS files
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IDLgt fits_info,'hsi_spectrum_20020421_004040.fits
hsi_spectrum_20020421_004040.fits has 3
extensions Primary header 26 records No
data Extension 1 -- 'RATE ' /
Header 67 records
Binary Table ( 792 820 ) Extension 2 -- 'ENEBAND
' /Extension name Header
52 records Binary Table ( 970 1
) Extension 3 -- 'HESSI Spectral Object
Parameters' / Header 300
records Binary Table ( 173821 1 )
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IDLgt data mrdfits('hsi_spectrum_20020421_004040.
fits', 1, header) MRDFITS Binary table. 5
columns by 820 rows. IDLgt help,data DATA
STRUCT -gt ltAnonymousgt Array820 IDLgt
help,data,/st Structure lt3c6dce0gt, 5 tags,
length800, data length792, refs1 RATE
FLOAT Array97 ERROR
FLOAT Array97 LIVETIME FLOAT
0.910374 TIME DOUBLE
52385.028 TIMEDEL FLOAT
4.62963e-005 IDLgt help, header HEADER
STRING Array67 IDLgt prstr, header
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XTENSION 'BINTABLE' /Written by IDL
Mon Jul 12 104249 2004 BITPIX
8 /
NAXIS 2 /

NAXIS1 792 /Number of bytes
per row NAXIS2
820 /Number of rows
PCOUNT 0
/Random parameter count
GCOUNT 1 /Group count
TFIELDS
5 /Number of columns
COMMENT

COMMENT End of mandatory fields
COMMENT

DATE '2004-07-12' /

ORIGIN 'HESSI ' /High Energy
Solar Spectroscopic Imager OBSERVER
'unknown ' /Usually the name of the
user who generated file TELESCOP 'HESSI '
/High Energy Solar Spectroscopic Imager
OBJECT 'Sun ' /
DATE_OBS
'2002-04-21T004040.000' /
DATE_END '2002-04-21T01352
0.000' /
GEOAREA 356.310 /
DETUSED
'SEGMENTS 1F2F3F4F5F6F7F8F9F' /
SUMFLAG
1 /Spectra summed over detectors
SUMCOINC 0 /
COINCIDE
0 /Anti-coincident spectra
RESPFILE 'hsi_srm_20020421_004040.f
its' /
TIMESYS 'MJD ' /
TIMEUNIT 'd
' /
MJDREF ' '
/Undefined for HESSI.
TIMEZERI 52385 /
TIMEZERF
0.028240741 /

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New FITS object Use is similar to RHESSI
objects Use SET, GET, GETDATA to read FITS
file Under construction basics are available
now, more methods will be added Example o
fitsread( filename 'test_cube_small.fits'
) print, o-gtgetstatus() print, o-gt getfield(
extension 1, 'cbe_det_effavg' ) o-gtset,
extension 1 print, o-gtget( /extension
) print, o-gtgetdata( /header ) data
o-gtgetdata() obj_destroy, o
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RHESSI Spectrum FITS files GUI In the Spectrum
Widget, set up your parameters, press the Write
Output File Button. Youll see this
widget CLI Create and set parameters in
a spectrum object and call filewrite method.
Options to filewrite are /buildsrm If set,
write an SRM file in addition to the spectrum
file /autoname If set, autoname FITS files
based on time of data all_simplify 0, 1, 2, or
3. Specifies type of SRM to calculate 0 full
matrix 1 off diagonal terms are an
approximation 2 diagonal terms only 3
diagonal terms only and all are set to 1 srmfile
name of SRM FITS file to write specfile name
of spectrum FITS file to write Example o -gt
filewrite, /buildsrm, /autoname, all_simplify2
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RHESSI Spectrum FITS Files (cont) Spectrum and
SRM FITS files are used as input to OSPEX and
SPEX to proceed with spectroscopy
analysis Detectors must be summed (sum_flag set
to 1 in object) in FITS files for use in OSPEX,
SPEX To analyze separate detectors, write a
separate file for each detector (for now) Energy
bins must be defined in terms of keV, not channel
numbers, for use in OSPEX, SPEX SRM file will
contain SRM for all attenuator states during
spectrum time interval OSPEX will automatically
choose the correct one for each fit time
interval SPEX will only use first one
(corresponding to attenuator state at start of
spectrum time interval) Use hsi_break_srm to
break up the SRM file into separate SRM files for
each attenuator state for use in SPEX. No
mechanism for using a FITS file to create a
spectrum object currently
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IDLgt fits_info,'hsi_srm_20020421_004040.fits' hsi
_srm_20020421_004040.fits has 5
extensions Primary header 12 records No
data Extension 1 -- 'SPECRESP MATRIX'
/Extension name Header 61
records Binary Table ( 402 107
) Extension 2 -- 'EBOUNDS ' /Extension
name Header 49 records
Binary Table ( 1164 1 ) Extension 3 -- 'SRM
Object Parameters' / Header 95
records Binary Table ( 2093 1
) Extension 4 -- 'SPECRESP MATRIX' /Extension
name Header 61 records
Binary Table ( 402 107 ) Extension 5 --
'SPECRESP MATRIX' /Extension name
Header 61 records Binary Table
( 402 107 )
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IDLgt srm1 mrdfits('hsi_srm_20020421_004040.fits'
, 1, header1) MRDFITS Binary table. 6 columns
by 107 rows. IDLgt help,srm1 SRM
STRUCT -gt ltAnonymousgt Array107 IDLgt
help,srm1,/st Structure lt3247e80gt, 6 tags,
length404, data length402, refs1 ENERG_LO
FLOAT 3.00000 ENERG_HI
FLOAT 4.00000 N_GRP INT
1 F_CHAN INT
0 N_CHAN INT 97 MATRIX
FLOAT Array97 IDLgt
print,fxpar(header1, 'FILTER') 0 IDLgt
srm4 mrdfits('hsi_srm_20020421_004040.fits', 4,
header4) MRDFITS Binary table. 6 columns by
107 rows. IDLgt print,fxpar(header4, 'FILTER')
1 IDLgt srm5 mrdfits('hsi_srm_20020421_00
4040.fits', 5, header5) MRDFITS Binary table. 6
columns by 107 rows. IDLgt print,fxpar(header5,
'FILTER') 3
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• RHESSI Image FITS files with GUI
• GUI
• Writing Image FITS file
• In the Image widget, select option to create
  FITS file when generating image
• Select any RHESSI image panel in the GUI, and
  click File /Export Data / Write Fits file
• Reading Image FITS file
• Click File / Import FITS file

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• RHESSI Image FITS files with CLI
• Writing Image FITS Files
• Create an image object, set parameters, and call
  fitswrite method
• Example o -gt fitswrite, fitsfilexxx.fits
• Currently for single images only, image cube
  requires use of hsi_multi_image object
• Reading Image FITS Files
• hsi_image_fitsread returns image data, object,
  info/control parameters, plots images. Many
  options.
• Example image hsi_image_fitsread()
• hsi_fits2map reads image file and creates an
  array of map structures
• Example hsi_fits2map, fitsfile, map
• However
• New and improved image object software will be
  online very soon

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• OSPEX FITS Files
• OSPEX stores results of analysis in FITS files
• OSPEX GUI
• Click File / Save Fit Results / In FITS file to
  write FITS file
• Click File / Import Fit Results to read FITS file
  
• OSPEX CLI
• Use savefit method to write FITS file
• Example ospex_obj -gt savefit
• Use restorefit method to restore import results
  in FITS file into OSPEX object
• Example ospex_obj -gt restorefit
• Use spex_read_fit_results to read FITS file into
  structure
• Example structure spex_read_fit_results(file)