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Summary of Most Significant IUESIPS Reduction Changes

The IUESIPS software was used to process IUE data over a nearly 19 year time span. During that time, there were many changes to the processing algorithms and calibrations. When requested by researchers, images were reprocessed with more up-to-date software but most of the data were never reprocessed with IUESIPS. The IUESIPS archive is thus rather heterogeneous, reflecting the many changes made to the processing system over time. (This is of course one of the reasons for the creation of the IUE Final Archive using the NEWSIPS software.)

The following list summarizes the most signficant changes to the IUESIPS data reduction procedures that are of interest to archival data users. Data processed before the dates given will be affected by the problems or limitations described. Since some data have been reprocessed, it is important to check the processing date, not just the obesrvation date, to see how the data were processed. Changes in extraction techniques, calibrations, etc. can obviously affect comparisons of data processed at different times. The references given at the end of the summary give more detailed discussions of the software and software changes.

Low Dispersion Images:

  • 7 July 1979 GSFC; 7 August 1979 VILSPA. SWP ITF error corrected. Removed photometric error at 20% exposure level of SWP ITF.

  • 4 November 1980 GSFC; 10 March 1981 (VILSPA). Implementation of IUESIPS "new software". Doubled spectral extraction frequency, geometric resampling handled differently, increased (but more realistic) point-to-point noise, better background handling.

  • 1 October 1985 GSFC & VILSPA. Extended line-by-line file. Increased spatial resolution, perpendicular to dispersion.

  • 22 December 1987 GSFC & VILSPA. New LWP photometric calibrations. Improved fluxes and signal-to-noise.

High Dispersion Images:

  • 19 May 1981 GSFC; 11 March 1982 VILSPA. Time and temperature corrected geometric and wavelength calibrations. Reduced residual internal wavelength errors (sigma < 2-3 km/s).

  • 28 August 1981 GSFC; 11 March 1982 VILSPA. Improved spectral registration at crowded orders. Better background placement, better net fluxes.

  • 10 November 1981 (LWR, SWP), 7 January 1982 (LWP) GSFC; 11 March 1982 VILSPA. Implementation of IUESIPS "new software". Doubled spectral extraction frequency, explicit geometric resampling eliminated, increased (but more realistic) point-to-point noise, improved background placement and handling, better photometry (increased net fluxes at short wavelengths, due to lower background; better stability).

  • 22 December 1987 GSFC & VILSPA. New LWP photometric calibrations. Improved fluxes, signal-to-noise.

  • 29 August 1990 GSFC; 22 December 1987 VILSPA. New absolutely calibrated data file. Absolute fluxes explitictly given.

REFERENCES

Chronologies of Modifications to IUESIPS Output Products:

  • Turnrose, B.E., Thompson, R.W., and Gass, J.E. 1982, "Techniques of Reduction of IUE Data: Time History of IUESIPS Configurations", NASA IUE Newsletter No. 25, p. 40.

  • Gass, J.E., and Thompson, R.W. 1985, "Techniques of Reduction of IUE Data: Time History of IUESIPS Configurations - 1984 Supplement", NASA IUE Newsletter No. 28, p. 102.

  • Martz, A., and Imhoff, C. 1993, "Chronology of Modifications to IUESIPS Output Products: 1985-1993", NASA IUE Newsletter No. 50, p. 22.

  • Thompson, R., Martz, A., and Imhoff, C. 1996, "Techniques of Reduction of IUE Data: Time History of IUESIPS Configurations - 1996 Supplement", NASA IUE Newsletter No. 56, p. 114.

Image Processing Manual and Updates:

  • Turnrose, B.E., and Thompson, R.W., 1984, "IUE Image Processing Information Manual (Version 2)", CSC/TM-84/6058.

  • Munoz Peiro, J.R. 1985, "Generation of the New Extended Line-by-Line Spectrum (ELBL)", NASA IUE Newsletter No. 27, p. 27.

  • Cassatella, A., Lloyd, C., and Riestra, G. 1988, "Absolute Calibration of the LWP with ITF2", NASA IUE Newsletter No. 35, p. 225.

  • Cassatella, A., Gonzalez-Riestra, R., Imhoff, C., Oliversen, N., and Lloyd, C. 1992, "Photometric Calibration of the International Ultraviolet Explorer (IUE) at Low Resolution: the LWP Camera", Astron. Ap. 256, p. 309.

  • Martin, T. 1990, "High Resolution Absolute Calibration: Data Format Changes", NASA IUE Newsletter No. 41, p.147.