Dataset TYPE could be `1D', `2D' etc in the general case, but a range of standard TYPEs is also defined, as listed below. Note that the order of the axes in multidemensional cases is not generally fixed, though some software may insist on a particular order, as discussed in section 6.
SPECTRUM - count rate vs. channel, energy or
frequency
IMAGE - count rate vs. x,y position
TIME_SERIES - count rate vs. time
SPECTRAL_SET - set of concurrent spectra from
multiple detector instrument (2D)
Spectral axis must be dimension 1
SPECTRAL_SERIES - time series of spectra (2D array)
IMAGE_SERIES - time series of images (3D array)
SPECTRAL_IMAGE - 3D dataset representing a set of
spatially resolved spectra
SPEC_IM_SERIES - time series of spectral images
HARD_SERIES - hardness ratio vs. time
FOLDED_SERIES - 1D dataset folded at some period
DISTRIBUTION - frequency distribution
PROJECTION - projection of some object of higher
dimensionality
SCATTERGRAM - scattergram relating two sets of
quantities
POLAR - polar profile, surface brightness vs.
radius, azimuth
POWER_SPECTRUM - power vs. frequency, may also contain
a DATA_PHASE array
AUTOCORRELATION - autocorrelation function vs. lag
CROSS_CORR - cross-correlation function vs. lag
CROSS_SPECTRUM - cross-spectrum, includes coherency
and phase array structures
DYN_SPECTRUM - dynamical power spectrum, 2D dataset
giving a time sequence of power
spectra (calculated from successive
data segments)
GRAFIX - graphics display object
A brief description of the nature of a dataset can be included in the TITLE component. This is available for user information, and will also be displayed by graphics sofware, unless explicitly overridden by a graphics legend.