FITS File Formats

The table below summarizes the different FITS formats used for data sets archived within MAST. The notation used for the "format" column is described below. For more information on file formats, click on the mission names.

Mission	File Type	Sample Filename	Format^*	Description / Comments
BEFS	Extrcted Spectral Files	befs2223.spc1	1-2Bf	12 columns, fluxes given in both photons & ergs/cm2/... units
BEFS	Photon-list Files	befs2223.lst1	B	6715226 rows! Not widely used.
Copernicus	Raw	c084.pep	Bv	Binary table containing variable-length vectors, with each row containing data from one scan.
	Coadded Scans	c084-001.bu1	Bf	Binary table with fixed-length vectors.
	Spectral Atlas Files	alphacma2.fts	B	Binary table with scalar fields; each row contains data for one wavelength.
EUVE	Image	hz_43__9303101242N_img.fits	1-4I,1-5B	Images and filter limits for one EUVE observation.
EUVE	Event	hz_43__9303101242N_evt.fits	5-11B	Event and monitor data for one EUVE observation.
FOS	Calibrated Wavelengths	y3lg0107t_c0f.fits	PA	2064xn primary array of wavelength vectors (A)
	Calibrated Fluxes	y3lg0107t_c1f.fits	PA	Primary array of fluxes (ergs/cm2/s/A)
	Calibrated Sigmas	y3lg0107t_c2f.fits	PA	Primary array of sigmas (ergs/cm2/s/A)
GHRS	Calibrated Wavelengths	z0ex021vt.c0f	PA	2000x1 primary array of wavelengths (A)
	Calibrated Fluxes	z0ex021vt.c1f	PA	Primary array of fluxes (ergs/cm2/s/A)
	Calibrated Sigmas	z0ex021vt.c2f	PA	Primary array of Sigmas (ergs/cm2/s/A)
HUT	Flux Calibrated	0833p652_100_01_d_ph.fits	Pnh	non-homogeneous primary array of fluxes and sigmas
IUE	Raw file	swp12345.rilo	P	8-bit 768x768 image.
	Linearized image	lwp12345.lilo	P,I	16-bit 768x768 array.
	Resampled low dispersion	swp12345.silo	P,I	16-bit 640x80 primary array, and a 16-bit 640x80 image extension
	Resampled high dispersion	lwr97095.sihi	P,Bf,2I	16-bit 768x768 primary array, and auxillary data.
	Merged extracted spectral files	lwp12345.mxlo	Bf	binary table with fixed-length vectors containing fluxes and wavelengths (in high dispersion, each row is one echelle order)
NICMOS	mosaiced image	n43u050_mos.fits	P
NICMOS	2-d spectra	.fits	I
STIS	Preview Spectra	o4qa91929_p.fits	B	wavelengths in A, fluxes in ergs/cm2.. units.
	1-d spectra	o4mt02030_x1d.fits	Bf	18 fields including wavelgenths & calibrated fluxes
	summed 1-d spectra	o4mt02030_sx1.fits	Bf	18 fields including wavelgenths & calibrated fluxes
TUES	Single order	tues6003_3_ord40.fits	B	format similiar to BEFS, fluxes in both photons & ergs/cm2.. units.
TUES	Multiple Order	tues6003_3_spectrum.fits	B	20 row binary table, fluxes in both photons & ergs/cm2.. units.
UIT	Raw density	fuv0123d.fit	P	16-bit 2048x2048 (ASTRO-1) or 4096x4096 (ASTRO-2) image.
	Linearized flat-fielded (e,f,fc)	fuv0123f.fit	P	16-bit 2048x2048 (e,f) or 512x512 (fc) image.
	Undistorted, rotated (g,gc)	fuv0123g.fit	P	16-bit 2048x2048 (g) or 512x512 (gc) image.
	Point-source (pph)/Aperture (aph) Photometry	fuv0123aph.fit	A	ASCII Table of photometric measurements.
WUPPE	Halfwave Level 1 Data	ss-cyg_322731_1_hw.fits	P,0-1B	fluxes stored in primary array, polarimtery data in binary table

^*Format Notation:
The following abbreviations are used for the various types of FITS header and data units (HDUs):

P- Primary array,
Pnh- Non-homogeneous primary array where each row of the array represents an independent vector (e.g., wavelength, flux, & error vectors),
B- Binary Table extension using only scalar fields,
Bf- Binary Table with fixed-length vector fields,
Bv- Binary Table with variable-length arrays,
I- Image extension,
A- ASCII Table extension.

If a number precedes the letter, it represents the number of occurrences of that particular HDU within the file. In some cases, the number of extensions may vary for a given file type. As an example, "P,Bf,2-4I" would describe a FITS file containing a primary HDU, followed by a binary table extension using fixed-length vector fields, followed by two to four image extensions.