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The current ("new software") high dispersion extraction routines SPECHI, SORTHI and POSTHI were implemented in production processing at GSFC on 10 November 1981. Section 7.1 pertains solely to these programs, and no attempt is made to offer a detailed comparison between this software and the previous extraction software described in Versions 1.0 and 1.1 of this manual. Readers interested in a discussion of differences between the old and new software are referred to Turnrose, Thompson, and Bohlin, (1982) and Bohlin and Turnrose (1982). Design details of the programs SPECHI and POSTHI can be found in Lindler (1982b) and Lindler (1982c) respectively.


Following the spectral format registration step, an analyzing slit is passed numerically by the computer along each order of the photometrically corrected image (as determined by the dispersion relations described in Section 6), and entries in a table of slit-integrated instrumental spectral fluxes as a function of wavelength are accumulated.

In the point-source reduction mode the gross spectral flux of each order is extracted from the registered spectral image using an analyzing slit which is effectively SQRT(2)/2 pixels wide and with a length which increases linearly from 5 pixels at order 125 to 7 pixels at order 68, and then linearly to 10 pixels at order 66. The point-source reduction mode is appropriate for the extraction of data from spectra of very localized (i.e., significantly smaller in spatial extent than the 10 by 20 arcsec large aperture) or spatially unresolved objects when the large aperture is used, and for the extraction of all data taken through the small aperture.

In addition to the point-source reduction mode, IUESIPS provides a high reso lution full-aperture reduction mode for large-aperture observations of an extended object or trailed spectra. This would have the advantage of improved throughput and the disadvantage of substantial loss in wavelength resolution caused by the extent of the large aperture. (In the high resolution mode the large aperture is oriented with its long axis almost parallel to the disper sion line; see Figures 2-16 through 2-18.) In the full-aperture mode the extraction slit used is 10 pixels long for all orders and thus includes all flux from the large aperture, which is ~ 7 pixels long perpendicular to the dispersion. The total area covered by the slit is ~ 7.1 square pixels for the full-aperture extraction, compared to an area of from ~ 3.5 to 7.1 square pixels for the point-source extraction. Note that the only difference between the point-source and full-aperture processing modes is the slit length; the orientation of the slit is the same in both cases (i.e., the slit runs along diagonal rows of pixels).

In addition to the gross spectrum, an interorder or background spectral flux is also computed using data extracted with a 1-pixel-square analyzing slit approximately (to the nearest pixel center) halfway between each pair of spectral orders. For each extracted order the background flux is defined as the average of the background values measured on either side of the order, normalized to the total slit area used to extract the gross spectrum. It should be noted that apart from this normalization the measured interorder (background) spectrum is the same in both the point-source and full-aperture modes. The choice of full-aperture processing has two possible disadvantages which should be pointed out. First of all, the longer slit will extend across part of the adjacent orders when the closely-spaced orders are extracted. However, the need to keep the slit height shorter than the order separation is often outweighed by the need to measure substantially all of the flux, particularly since many extended objects are emission-line sources for which continuum contamination from adjacent orders is unimportant. The other possible disadvantage is that high dispersion full-aperture processing currently requires manual spectral registration which is generally less accurate than the automatic registration technique presently available (see Section 6.3.2).

7.1.2 EXTRACTION METHOD Extraction of Gross Flux

In order to extract fluxes from the photometrically corrected data in the raw image coordinate system, it is necessary to invoke both the geometric mapping function G-1 which gives raw image coordinates as a function of geometrically corrected coordinates (see Section 4) and the dispersion formulae which relate wavelength and order number to geometrically corrected coordinates (see Section 6). To decrease computation time, these functions are invoked only for selected points along the order separated by a constant, suitably small wavelength interval (e.g. 1 Å). Slit centerings and wavelength assignments between these points are then determined using linear interpolation, which is a very good approximation over such short distances. (Tests have shown that a typical error in slit centering due to this approximation is less than 0.007 pixels.) In either the point-source or full-aperture mode, the extraction slit is oriented such that its long axis runs along successive diagonal rows of pixels of the photometrically corrected image array (which is within ~ 9 degrees of the perpendicular to the dispersion line) and is bisected by the interpolated position as calculated above. The end pixels of the slit are weighted to give a constant effective slit height along each order as shown in Figure 7-1. Also shown is how the analyzing slit is stepped in the dispersion direction by an amount equal to SQRT(2)/2 pixels in raw image space. Note that this step size is about half the amount used in the old production software prior to 10 November 1981, but because the step size is constant in raw image space, not geometrically correct space, the corresponding wavelength interval is not constant along an order. Further note that because the current effective slit width is only one-half that of the old software, extracted fluxes are multiplied by a factor of 2 to normalize them to the former SQRT(2) pixel slit width. In this way, extracted fluxes are compatible with those derived from the old software (see Section

In actually performing the extraction, the image is brought into the computer a few lines at a time. Within wavelength limits defining the useful spectral region of the image, one entry (i.e., a slit-integrated spectral flux value) for each order is generated per line of the photometrically corrected image, and up to 1022 entries per echelle order may be accommodated. As each on- order gross flux measurement is made, the corresponding background or interorder flux is also accumulated as described below.

Figure 7-1. Adjacent Extraction Slits for Obtaining the Gross Flux (After Lindler, 1982b) Extraction and Processing of Background Flux

The background present on IUE images is composed of contributions from several sources, including the null, particle radiation, radioactive decays within the detector phosphor, halation within the UV converter, background skylight, and scattered light. The integrated effect of the last three sources varies in a complicated manner across the target depending on the spectral flux distribution of the object observed, whereas the general radiation and null components vary slowly across the vidicon tube. Currently the only correction for the background applied to the gross spectrum to obtain a net spectrum is the subtraction of a smoothed (filtered) version of the extracted interorder signal from the gross spectrum, as explained below.

The interorder region and also to a certain extent the echelle orders themselves tend to be contaminated by light from adjacent echelle orders. This phenomenon is referred to as "order overlap" and is discussed in Bianchi and Bohlin (1983). The flux profile perpendicular to an order is approximately Gaussian with a full width at half maximum (FWHM) of ~ 2.3 - 4 pixels (de Boer, Preussner, and Grewing, 1982; see also Section, while the spacing between orders varies from about 12 to 5 pixels from the long to the short wavelength end of the echelle format. The order overlap problem is therefore most severe at the short wavelength end of the echelle format (high orders) and for cases where an extended source is placed in the large aperture.

In approximating the background by an extracted interorder signal, the current software positions a 1-pixel-square extraction slit midway between orders. This midpoint is calculated on the diagonal for each point along the order computed as described in Section and rounded off to the nearest integral pixel. To compute the background flux value corresponding to slit position (s,l) on order M, the extracted interorder flux from both sides of the order (pixels at (s1, l1) and (s2, l2)) are averaged together as shown in Figure 7-2. If one of the two interorder pixels is found to be

  1. within 2 pixels in the line or sample direction from a reseau, or
  2. on a line containing microphonic noise (LWR only), or
  3. saturated or excessively extrapolated, or
  4. in a region not photometrically corrected, or
  5. on a flagged bright spot
then the background flux from the other extracted interorder pixel will be used. If both points are unacceptable the background flux will be determined by interpolating between values at neighboring wavelengths.

Figure 7-2. Background Pixel Positions (After Lindler, 1982b)

Before the background flux is subtracted from the gross extracted flux, the background is processed with a 63-point median filter followed by two mean filters each with a default width of 31 points (see Turnrose, Bohlin, and Harvel, 1979). The filtered background flux values are then normalized through multiplication by the slit area used in the extraction of the corresponding gross flux for that order. This normalized, smoothed background is used in the computation of the net spectrum as described in Section 7.1.3.


The net spectral flux is calculated by subtracting the smoothed and normalized background flux (see Section from the gross extracted flux (see Section on a point-by-point basis. The following sections describe further processing applied to the net fluxes in high dispersion. The corrections are described in the order of their application. Noise-Conditioning Filter

Whereas the "old" IUESIPS reduction software, which performed an explicit geometric correction, artificially suppressed point-to-point noise in extracted spectra (see Bohlin and Turnrose, 1982), the current high dispersion software does not. Schiffer (reported in Bohlin and Turnrose, 1982) demonstrated that the correlated camera noise present in raw images and preserved by the current extraction software has a characteristic power spectrum which dominates the observed power spectrum of the extracted data at high spatial frequencies (typically, at frequencies greater than about 0.25 cycles per pixel).

Accordingly, Schiffer developed a so-called "optimal" filter, applied in direct convolution with the net extracted flux points, to flatten the power spectrum of the net fluxes at frequencies where the noise dominates. Application of this filter, which is seven points wide (see Table 7-1), suppresses the high frequency camera noise sufficiently to allow the true noise characteristics of the actual spectral data to be seen. This filtering is in fact rather mild, because the filter window is so heavily center- weighted (see Table 7-1). Note that for the SWR camera, an optimal filter has not been determined.

Table 7-1: Optimal Weights Currently Used For Filtering High Dispersion Net Spectra
 Element Value
7.0017.0016-.00210 Echelle Blaze ("Ripple") Correction

Net high dispersion IUE spectra are corrected for the response of the sharply blazed IUE echelle gratings. This blaze function is commonly referred to as the echelle "ripple" function because uncorrected spectra have a character istic rippled or arch-like appearance. The current ripple correction algorithm applied to net spectra was implemented at GSFC on 27 August 1982 and is based on the work of Ahmad (1981) and the more detailed studies of Ake (1981, 1982). Note that this implementation date is considerably later than the implementation date of the current high dispersion software, so that many images were processed with the current software using the ripple correction described in Versions 1.0 and 1.1 of this manual.

The studies cited above conclude that the parameterized sinc function, which Ake (1981) showed was justified by optical theory, was indeed an appropriate functional form for the ripple correction if the grating constant was allowed to vary with order number so as to align the peak of the blaze pattern with the observed values. The ripple-corrected net flux is therefore calculated in production processing as follows:


Fcorr( lambda ) = F( lambda )filtered extracted net / R( lambda )
R( lambda ) = sin2x/x2
x = pi m alpha abs( lambda - lambda c) / lambda c
lambda c = K/m
m = echelle order number
K = echelle grating constant
alpha = adjustable parameter

The value for the grating constant K is currently represented by the empirical formula
K = Al +A2m + A3m2.

According to Ake (1981) the K values change with time (as well as camera temperature) and may therefore require periodic revision. The currently implemented A1, A2, A3 and a parameters are listed in Table 7-2. Note that the LWP and LWR K coefficients used in production refer to vacuum wavelengths and therefore differ from the LWR values given by Ake (1982) which are designed to be used in after-the-fact applications. Ake's published coefficients apply to wavelengths converted to air values, as are all wavelengths longer than 2000 Å on Guest Observer tapes (see Section 7.1.4).

The ripple correction described above is only applied within a given order at vacuum wavelengths for which x <= 2.61. Wavelengths outside this range are assigned a net ripple-corrected flux value of zero.
Table 7-2: Echelle Ripple Parameters
alpha .896.896.856.856
* Same as for complementary camera; actual values for these cameras have not yet been determined.


There are two types of wavelength corrections applied to the high dispersion extracted spectra (gross, background, net and ripple-corrected net). The first is the Doppler correction to compensate for the Earth's motion about the Sun and the satellite's motion about the Earth; the second is the correction from vacuum wavelengths to air wavelengths, longward of 2000 Å. The algorithms currently used in production processing to apply these corrections are described in Sections 6.4.1 and 6.4.2. Note that these corrections are not applied to the wavelength scales which are overlaid on processed photowrite images described in Section

Note also that CalComp plots of the net ripple-corrected flux versus wavelength (see Section allow only a restricted wavelength range for each extracted order. These wavelength limits are empirically determined values which prevent wavelength regions containing excessive noise at the ends of the orders from being plotted. This is done to improve plot legibility and applies only to the plots; data written to tape in the merged extracted spectra (MEHI) file (see Sections 8.1 and 8.2) are unaffected by this plotting wavelength restriction.


As extracted, the IUE spectral fluxes are in time-integrated flux number (FN) units, representing the exposure value measured within the extraction slit. As mentioned in Section 7.1.2, because the current effective slit width (SQRT(2)/2) is only one-half of that used by the "old" IUESIPS high dispersion software, the new extracted fluxes are multiplied by a factor of 2 before further output operations are performed. This scaling is done to keep the flux levels comparable with those obtained from the old software by renormalizing them to the same effective slit width. Absolute Calibration

In contrast to low dispersion (see Section, there is no officially adopted absolute calibration for IUE in the high dispersion mode. Cassatella, Ponz, and Selvelli (1981 and 1982) have described a methodology for calculating an absolute calibration for high dispersion and have presented absolute calibrations derived from spectra reduced with the old and new IUESIPS software. Because of the differences in the net high dispersion fluxes determined with the new and old software at high orders (m >= 100; see Bohlin and Turnrose, 1982), two different calibration curves were found necessary.


The current ("new software") low dispersion extraction routines SPECLO and POSTLO were implemented in production processing at GSFC on 3 November 1980. As is the case with Section 7.1, Section 7.2 describes only the current extraction software without attempting a detailed comparison with the old software. Comparisons of the old and new low dispersion software may be found in Turnrose, Bohlin, and Lindler (1981) and Bohlin, Lindler and Turnrose (1981). Details of the programs SPECLO and POSTLO are given in Lindler (1979).


As described in Section 7.2.2, the algorithm used to extract spectral fluxes in low dispersion first performs a resampling of the pixel values in the photometrically corrected image and is therefore unlike the high dispersion extraction method discussed in Section 7.1.2. In this resampling, spatially resolved or line-by-line spectra are produced (see Section from which slit-integrated spectra are then computed (see Section For the slit-integrated spectra a point-source reduction mode is used under the same circumstances as it is used for the high dispersion case (see Section 7.1.1). The on-order analyzing slit has an effective length of 9*SQRT(2) pixels and an effective width of SQRT(2)/2 pixels, while the background is extracted using two 5*SQRT(2)-pixel-long slits (again SQRT(2)/2 pixels wide) placed a distance 8*SQRT(2) or 11*SQRT(2) pixels to either side of the order. The distance of 11*SQRT(2) pixels is used when the data are taken through the large aperture; the distance of 8*SQRT(2) pixels is used for small-aperture data.

In those cases where the large aperture is used and the source is multiply exposed or extended, or the spectrum is trailed, a larger slit height is recommended. In these modes the on-order slit has an effective height of 15*SQRT(2) pixels and the background flux is obtained with a 5*SQRT(2)-pixel-long slit a distance 11*SQRT(2) pixels from the order. Again the effective slit widths are SQRT(2)/2 pixels.

For the extended-source or trailed-spectrum mode the on-order analyzing slit has an effective area of 15 square pixels while for the point-source mode its effective area is 9 square pixels. As is the case in high dispersion, however, the extracted fluxes are normalized to the old software slit width of SQRT(2) pixels by multiplication by a factor of 2. In this way, the extracted fluxes are on a scale which is compatible with that appropriate for data reduced by the old software (see Section

7.2.2 EXTRACTION METHOD Spatially Resolved (Line-by-Line) Spectra

To extract the spectral fluxes from the photometrically corrected image it is necessary to use dispersion formulae which relate wavelength to geometrically corrected coordinates (see Section 6). As is true in high dispersion, this is done by computing the position of a given wavelength in geometrically correct space and then using the geometric mapping function G-1 (see Section 4) to compute the position in raw-image coordinates. Unlike the high dispersion extraction, the mapping into raw space is done at every extraction point.

Flux values are extracted every SQRT(2)/2 pixels (relative to the geometrically correct coordinates) along and approximately perpendicular to the dispersion using bilinear interpolation between the appropriate pixels in the photometrically corrected image. As shown schematically in Figure 7-3, a given extracted flux value is equivalent to a weighted average of the surrounding four pixels in the photometrically corrected image, with weights proportional to the area of each pixel under the cross hatching.

The extraction of points in the spatial direction is done along lines of constant wavelength, which because of spectrograph geometry are not always normal to the dispersion. For this reason, the software extracts points and assigns constant wavelengths along lines which make an angle w with the dispersion direction. For trailed exposures, w = 90 degrees since the trail axis is very close to being normal to the dispersion. For multiple exposures in the large aperture, it is recommended that the trailed-exposure reduction mode (w = 90) be selected since the offsets used to make the multiple exposures are along the trail axis. For large-aperture untrailed exposures, however, w is the angle of the major axis of the large aperture. For small-aperture exposures, w is defined by the line which joins the centers of the large and small apertures (see Figure 7-4 and Bohlin, Lindler, and Turnrose, 1981). Once 110 points spaced every SQRT(2)/2 pixels have been extracted along the line of angle w, adjacent points are added in the spatial direction resulting in a set of 55 spatially resolved gross flux points, each separated from the next by SQRT(2) pixels in geometrically correct space. This process is repeated for each sampled wavelength (see Figure 7-5). Notice that because the effective slit width of each extraction is only SQRT(2)/2 pixels, a multiplication by a factor of 2 is applied as mentioned in Section 7.1.1 (see also Section to create a line-by-line gross flux element scaled similarly to that produced by the old software.

Figure 7-3: Bilinear Interpolation for Obtaining Low Dispersion Flux Values at the Position "x".

Figure 7-4: w angles for LWP, LWR, SWP Cameras (Bohlin, Lindler and Turnrose (1981).
w L = angle of constant wavelength for large-aperture point-source or extended-source exposures.
w S = angle of constant wavelength for small-aperture exposures. Note for trailed exposures (and recommended for multiple exposures in the large aperture) w = 90.

Figure 7-5: Section of Spatially Resolved Extracted Spectrum. The bilinear interpolation shown in Figure 7-3 is initially performed at each point shown above. Adjacent points in the spatial direction are added together resulting in an effective line-by-line slit height of SQRT(2) pixels and a slit width of SQRT(2)/2 pixels. The set of extracted points at angle w to the dispersion are assigned the same wavelength. Rows of extracted points parallel to the dispersion are treated as separate "pseudo-orders."

The extraction procedure described above is continued for successive sampled wavelengths as long as (a) the wavelength is between hardcoded minimum and maximum values (1000 Å and 1990 Å in the short wavelength spectrograph, and 1700 Å. and 3400 Å in the long wavelength spectrograph), and (b) the central 9 rows of extracted flux are inside the photometrically corrected area. The spatial separation of each row of extracted flux corresponds to SQRT(2) pixels in geometrically correct space and each row is treated as a separate spectral "pseudo-order". The 28th or central row is centered on the dispersion line and assigned an order number of 100; each of the other 54 spectra are assigned an order number equal to 100 ± n, where nSQRT(2) pixels is the distance of the extracted spectrum from the dispersion line (hence, order numbers 73-127 are assigned). The order numbers increase in the direction from the large aperture toward the small aperture for SWP and LWR; for LWP the order numbers increase in the opposite direction. As described in Section 8 the resulting data file is output to the Guest Observer tape and defined as the "line-by-line spectrum" (LBLS) file. Slit Integrated Spectra

The slit integrated gross and background flux values outlined in Section 7.2.1 are computed directly from the spatially resolved line-by-line spectral file (normalized to a SQRT(2) slit width as described in Section by a direct summation in the spatial direction (i.e., at constant wavelength) as shown in Figure 7-6. The on-order analyzing slit has an effective length of 9SQRT(2) pixels for point-source reduction and 15SQRT(2) for trailed or extended-source reduction. The background flux is extracted using an effective slit length of 5SQRT(2) pixels with the analyzing slit placed on each side of the order at a distance of 8SQRT(2) pixels for small-aperture spectra and 11SQRT(2) pixels for all large-aperture spectra.

Figure 7-6. Extraction of Gross and Background Fluxes from Spatially Resolved File (From Lindler 1979).

In the background spectrum, all points with negative epsilon values (i.e., saturated or extrapolated points, flagged bright spots, points within a 3-pixel-square area centered on a reseau, points within lines containing microphonic noise and points outside the photometrically corrected area; see Section 7.3) are excluded prior to the summation of values within the background slit. If all the background data points for a particular wavelength are excluded, the background flux is set equal to its nearest "good" neighbor. Following the normalization of the background to the slit area for the gross spectrum, the background is filtered as in high dispersion using a 63-point median filter followed by a 31-point mean filter which is applied twice, simulating a triangular filter. The smoothed normalized background is subtracted from the gross flux on a point-by-point basis to generate the net flux spectrum.


The only wavelength correction applied to low dispersion spectra is the vacuum-to-air conversion for wavelengths greater than 2000 Å, as described in Section 6.4.2. This correction is applied in the initial extraction of the spatially resolved, line-by-line spectrum prior to computation of the slit- integrated spectra.


As is the case for high dispersion, extracted IUE spectral fluxes are in time- integrated flux-number (FN) units, representing the exposure value measured within the extraction slit. As mentioned in Section 7.2.1 and elsewhere, fluxes as extracted with the SQRT(2)/2 slit width by the new software are multiplied by a factor of 2 in order to keep the flux levels comparable to those obtained with the old software which used a SQRT(2) pixel slit width. Absolute Calibration

Through IUE observations of ultraviolet photometric standard stars, absolute flux calibrations for low dispersion may be defined as described by Bohlin et al. (1980), Bohlin and Holm (1980), and Cassatella and Harris (1983). The absolute calibrations as published consist of inverse sensitivity functions S lambda -1 for the SWP, LWR, and LWP cameras. The absolute flux at a given wavelength F lambda (ergs cm-2 sec-1 /-1) may be computed from the extracted time- and-slit-integrated IUE flux number at that wavelength, FN lambda , as follows:
F lambda = FN lambda S lambda -1/t ,
where t is the exposure time in seconds.

In production processing the S lambda -1 function is multiplied by the flux numbers FN lambda representing the net spectrum and the result is referred to as the absolutely calibrated net spectrum. Note that the absolutely calibrated net spectrum is still time-integrated. Division by the exposure time is left to the user since actual exposure times cannot be extracted from the image header records in an automatic way with sufficient reliability. Hence the units of the absolutely calibrated net spectrum as provided to the user are ergs cm-2 Å-1. The gross, background, and net components of the merged extracted spectral (MELO) file are left in FN units, as are the line-by-line fluxes comprising the LBLS file (see Sections, 8.1, and 8.2).

The inverse sensitivity function S lambda -1 adopted for SWP and LWR production processing at GSFC as of 3 November 1980 are those known as the "May 1980 calibration" (Bohlin and Holm, 1980), with the exception that at the wavelength extremes ( lambda < 1190 Å or > 1950 Å for SWP; lambda < 1900 Å or lambda > 3200 A for LWR) S lambda -1 is set to zero because of uncertainty in the published values (see further discussion below). This same truncation at wavelength extremes is also used for the LWP absolute calibration of Cassatella and Harris (1983) implemented in production at GSFC on 19 October 1983. Note that although the absolutely calibrated net spectrum is thus though, the net spectrum in the MELO file on tape is not, so that users may at their discretion apply calibrations over the full extracted wavelength range.

The May 1980 LWR and SWP calibrations are reprinted from Bohlin and Holm (1980) in Tables 7-3 and 7-4. The October 1983 LWP calibration is listed in Table 7-5. In production these S lambda -1 functions are interpolated to intermediate wavelengths using quadratic interpolation of the natural logarithm of the values listed in the above tables. Also presented in Tables 7-3 and 7-4 are the "original" calibrations used in production at GSFC prior to 3 November 1980 (see Turnrose, Bohlin, and Harvel, 1980), as well as the factors by which the May 1980 values differ from the original. Between 1375 Å and 2540 Å, the internal scatter in the determination of S lambda -1 by individual stars is typically 3 percent (Bohlin and Holm, 1980). Longward of 3200 Å this internal scatter exceeds 10 percent; shortward of 1250 Å the derivation of S lambda -1 is complicated and uncertain.

Note that although the occasion of implementing the new software in November 1980 was taken to begin the use of the improved May 1980 calibration, the reasons for the changes from the original calibration (see Bohlin and Holm, 1980) are unrelated to the reduction software change, and in fact no reduction-software-induced changes were required.


For both high and low dispersion, each extracted flux point is assigned a data quality flag, or epsilon, value which is intended to indicate the presence of exceptional pixels. The epsilon values are included within the MEHI, MELO, and LBLS files on tape (see Section 8.2) and are also used to generate special plotting characters on the IUESIPS CalComp plots. The epsilon values and the conditions to which they correspond are contained in Table 7-6. Note that under the new software the epsilons are no longer the sum of a positive term, and a negative term for special conditions, as in the old software. Also, note that if more than one of the exceptional (i.e. negative-epsilon) conditions applies to a given flux point, the most negative flag is used. Since reseaux, LWR microphonics, bright spots, and saturated pixels are not used in the background determination (see Sections 7.l.2.2 and, the presence of such conditions in the background is flagged only in the CalComp plots of the unsmoothed background. Specifically, this means such points are not flagged in the smoothed background plots nor in the MELO or MEHI tape files. The epsilons associated with the MELO and MEHI files refer to conditions affecting the gross flux only.

Table 7-3: Original and May 1980 Calibrations for LWR from Bohlin and Holm (1980)
lambda (Å)S lambda -1 (Original) *Corr.S lambda -1(May 1980)*
2300 1.10 .912 1.00
2350 .90 .913 .822
2400 .76 .915 .695
2450 .63 .923 .581
2500 .54 .932 .503
2550 .47 .947 .445
2600 .42 .957 .402
2650 .38 .962 .366
2700 .35 .969 .339
2750 .34 .971 .330
2800 .34 .969 .329
2850 .35 .967 .338
2900 .38 .963 .366
2950 .43 .957 .412
3000 .51 .949 .484
3050 .64 .944 .604
3100 .91 .935 .851
3150 1.4: .924 1.29
3200 2.3: .915 2.10:
3250 4.2: .908 3.81:
3300 8.9: .900 8.01:
3350 19.: .89 16.9:
* The units of S lambda -1 are 10-14 erg cm-2 Å-1 FN-1
** Changed November 1979
: Uncertain value

Table 7-4: Original and May 1980 Calibrations for SWP from Bohlin and Holm (1980)
lambda (Å)S lambda -1 (Original) *Corr.S lambda -1(May 1980)*
1150 20: 1.035 20.7:
1175 6.65: 1.191 7.92:
1200 3.65: 1.189 4.34:
1225 2.68: 1.089 2.92:
1250 2.23 1.081 2.41
1275 2.06 1.087 2.24
1300 2.02 1.079 2.18
1325 2.03 1.079 2.19
1350 2.07 1.092 2.26
1375 2.19 1.096 2.40
1400 2.36 1.102 2.60
1425 2.56 1.094 2.80
1450 2.75 1.105 3.04
1475 2.97 1.111 3.30
1500 3.19 1.110 3.54
1525 3.33 1.123 3.74
1550 3.43 1.120 3.84
1575 3.31 1.118 3.70
1600 3.16 1.108 3.50
1625 3.00 1.107 3.32
1650 2.85 1.095 3.12
1675 2.70 1.081 2.92
1700 2.53 1.079 2.73
1725 2.39 1.063 2.54
1750 2.22 1.063 2.36
1775 2.05 1.073 2.20
1800 1.97 1.066 2.10
1825 1.91 1.079 2.06
1850 1.87 1.091 2.04
1875 1.85 1.103 2.04
1900 1.84 1.103 2.03
1925 1.84 1.098 2.02
1950 1.84 1.098 2.02
1975 1.83 1.093 2.00
* The units of S lambda -1 are 10-14 erg cm-2 Å-1 FN-1
: Uncertain value

Table 7-5: October 1983 Calibration for LWP from Cassettella and Harris (1983)
lambda (Å) S lambda -1 *
335015.46 **
* The units of S lambda -1 are 10-14 erg cm-2 Å-1 FN-1
** extrapolated value

Table 7-6: Data Quality Flag (Epsilon) Values
100No special conditions
-200Extrapolated at upper end of ITF
-220Microphonic noise
-250Filtered bright spot *
-300Unfiltered bright spot
-800Reseau in extracted spectral region
-1600Saturated pixel or excessive ITF extrapolation
-3200Pixel outside photometrically corrected region (low dispersion LBLS file only)
* Feature possibly to be implemented in the future, to flag filtered bright-pixel artifacts).

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