The linear mapping of high-dispersion images from pixel space to Å
ngstroms was carried out with the *IRAF* routine *identify*.
This task identifies the emission lines for a single order in a
reference WAVECAL spectrum and generates a dispersion solution which is
a one-dimensional fitted function (Chebyshev polynomial) of wavelength
versus pixel number. The next step involves the use of the IRAF task
*reidentify* which maps the reference-image Chebyshev solution
derived from the *identify* step to an ensemble of images. The final
dispersion solution for a given order is averaged from several hundred
individual solutions output from *reidentify* and consists of a
starting wavelength and wavelength increment per pixel. This process is
repeated for every order to yield a set of order-by-order solutions.

Some orders, particularly those at the shorter wavelengths, have too few
Pt-Ne lines in the WAVECAL spectra for valid individual dispersion
solutions. In these cases the IRAF tasks *ecidentify* and *
ecreidentify* were used to determine two-dimensional dispersion
solutions (as a function of wavelength and order number versus pixel)
for a specified block of orders; thus the Chebyshev solutions for these
orders are coupled. The types of IRAF solutions used for the wavelength
linearization and the time and temperature correlation steps are listed
in Tables 8.5 and 8.6. The block solution
simultaneously solves for three contiguous orders and is applied only to
the central order of the block. The global solution solves for all
orders and usually is utilized only (with the exception of the LWR) for
the higher orders.