NASA/CR–2004-212754

May 2004

Greenbelt, Maryland 20771

Support the Design of Improved IUE NEWSIPS High 

Dispersion Extraction Algorithms:

Improved IUE High Dispersion Extraction Algorithms

Final Report

Pat Lawton
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Support the Design of Improved IUE NEWSIPS High 

Dispersion Extraction Algorithms:

Improved IUE High Dispersion Extraction Algorithms

Final Report

Pat Lawton

L-3 Communications Government Services, Inc., Chantilly, Virgina

NASA/CR–2004-212754

May 2004
NASA Center for Aerospace Information 

7121 Standard Drive 

Hanover, MD 21076-1320 

Price Code: A1 7 

Available from: 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22 1 61 

Price Code: A10 
FINAL REPORT 

FOR 

NASA PURCHASE ORDER NUMBER S-50690-G 

May 30,2001 - May 29,2004 

Submitted By 

L3 Communications Government Services, Inc. 

\‘For@;erly EER System, Inc) 

3750 Centerview Drive 

Chantilly, VA 20151 

The objective of this work was to support the design of improved IUE NEWSIPS high 

dispersion extraction algorithms. The purpose of this work was to evaluate use of the 

Linearized Image (LIHI) file versus the Re-Sampled Image (SIHI) file, evaluate various 

extraction methods, and design algorithms for evaluation of IUE High Dispersion spectra. 

It was concluded the use of the Re-Sampled Image (SMI) file was acceptable. Since the 

Gaussian profile worked well for the core and the Lorentzian profile worked well for the 

wings, the Voigt profile was chosen for use in the extraction algorithm. It was found that 

the gamma and sigma parameters varied significantly across the detector, so gamma and 

sigma masks for the SWP detector were developed. Extraction code was written. 

Improved IUE High Dispersion Extraction Algorithms 

The objective of this work, which was done in collaboration with the the US Naval 

Observatory, was to support the design of improved IUE NEWSIPS high dispersion 

extraction algorithms. This work was from the peer reviewed and accepted Astrophysics 

Data Program (NRA 99-OSS-01 ADP) proposal: “Improved IUE High Dispersion 

Extraction Software for NEWSIPS Data”. 

The purpose of this work was to: 

- evaluate use of the Linearized Image &MI) file versus the Re-Sampled Image 

(SIHI) file, 

evaluate various extraction methods, and 

design algorithms for evaluation of IUE High Dispersion spectra. 

- 

- 

It was concluded that the problems associated with the IUE high dispersion spectra are in 

the extraction - not in the geometric resampling. Therefore, starting with the Re-Sampled 

Image (SMI) file instead of the early processing stage Linearized Image (LIHI) file was 

acceptable. 

Several extraction algorithms were tried - including Gaussian and Lorentzian. The 

Gaussian worked well for the core, but not always for the wings. The Lorentzian was 
Final Report 

P.O. S-50690-G 3 * 

promising for the wings. This information lead to a Voigt profile. Although the Voigt 

profile works well for the detector, values - that were being assumed to be fixed 

parameters - where showing significant inconsistencies for different locations on the 

detector. 

A more methodical - and rather computer intensive - analysis was done using 

SWP SMI files of BD +28 421 1 and HD 60753. The fits were done with 3 orders at 

once with a Voigt function for the wings. The two stars each had 80+ images processed 

individually to get a better sampling of the point spread function perpendicular to the 

dispersion direction. Exh image Wiis divided intG smd!! re@cns (8 pixels wide) by 3 

orders for each order. A three Voigt profile with a linear background was then fit to each 

region. The sigma and gamma were set to be the same for all three but allowed to vary, 

the parameters of the fit are: A(n-1), A(n), A(n+l), slope, intercept, sigma, and gamma 

where the As are the peak height for each of the 3 orders. 

The results of each image were then set to a common centroid (delta x) for each region 

and then combined. This combined set of regions was then fit producing gamma and 

sigma masks for each star. Those masks were compared with each other. If for one star 

the mask value was pegged at the high end of the allowed range, the value for the other 

star at that location on the detector was substituted. Then the mask values for each 

variable at each location were averaged to create gamma and sigma masks to use in the 

extraction procedure. Error estimates were included. 

Interactive Data Language (IDL) code was written to use the gamma and sigma masks 

and extract the spectrum from an IUE SWP SIHI image. A README file was written to 

assist the PI when he is ready to deliver the code to MAST for use with the lUE RDAF 

library. Contributed to a paper being prepared for submission to "The Publications of the 

Astronomical Society of the Pacific". 

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