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.
|Order by Order||69,70,72,||67,72,73,75-82,||66-101|
|Order by Order||69,70,72||67,68,71,73,||66-101|