EGRAM- ECHELLE SPECTROGRAPH DESIGN AID

( NASA Goddard Space Flight Center )

     EGRAM aids in the design of spectrographic systems that utilize an
echelle-first order cross disperser combination. This optical combina-
tion causes a two dimensional echellogram to fall on a detector. EGRAM de-
scribes the echellogram with enough detail to allow the user to effectively
judge the feasibility of the spectrograph's design. By iteratively alter-
ing system parameters, the desired echellogram can be achieved without mak-
ing a physical model. EGRAM calculates system parameters which are accu-
rate to the first order and compare favorably to results from ray tracing
techniques.

     The spectrographic system modelled by EGRAM consists of an entrance
aperture, collimator, echelle, cross dispersion grating, focusing op-
tions, and a detector. The system is assumed to be free of aberrations and
the echelle, cross disperser, and detector should be planar. The EGRAM pro-
gram is menu driven and has a HELP facility. The user is prompted for in-
formation such as minimum and maximum wavelengths, slit dimensions, rul-
ing frequencies, detector geometry, and angle of incidence. EGRAM calcu-
lates the resolving power and range of order numbers covered by the echel-
logram. A numerical map is also produced. This tabulates the order number,
slit bandpass, and high/middle/low wavelengths. EGRAM can also compute the
centroid coordinates of a specific wavelength and order (or vice versa).

     EGRAM is written for interactive execution and is written in Microsoft
BASIC A. It has been implemented on an IBM PC series computer operating un-
der DOS. EGRAM was developed in 1985.

     COSMIC, and the COSMIC logo are registered trademarks of the National
Aeronautics and Space Administration. All other brands and product names
are the trademarks of their respective holders.



LANGUAGE: BASIC

MACHINE REQUIREMENTS: IBM PC SERIES

PROGRAM SIZE: APPROXIMATELY 794 SOURCE STATEMENTS

DISTRIBUTION MEDIA: 3.5 Inch IBM PC DOS Format Diskette

PROGRAM NUMBER: GSC-13016

DOMESTIC - DOCUMENTATION PRICE: $18.00    PROGRAM PRICE: $200.00

INTERNATIONAL - DOCUMENTATION PRICE: $36.00   PROGRAM PRICE: $400.00



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