7.2.1 IUESIPS Quality Flags

The IUESIPS flags reseaux, saturated pixels, data points linearized by extrapolating the ITF, bright spots, and some other defects. Normally the quality flags are used by the IDL procedures to either mark questionable data (e.g., NSPLOT) or to control the correction process (e.g., PATCH). Once you have extracted IUE spectral data you may display the quality flags by plotting the epsilon vector as a function of wavelength, (i.e., PLOT,W,Q). You can manipulate these flags directly if you wish to control what these other procedures do to your data. The example below is an IDL assignment statement rather than a procedure. Note that the meaning and values of the quality flags were changed many years ago (see Table 7.1); the example below is for the current IUESIPS software (implemented on 3 November 1981 for low dispersion, and on 10 November 1981 for high dispersion).

Extrapolated points are assigned a value of -200. To flag them as good points (with values of 100), type

    Q = Q + 300 * (Q EQ -200)

The logical expression (Q EQ -200) is an array of the same size as Q for which all elements corresponding to extrapolated points (elements of Q that are equal to -200) are set equal to one. The other elements are set equal to zero. We multiplied this array by 300 and added it to Q. Therefore, Q elements equal to -200 have 300 added to them, resulting in values of 100, and the rest of the Q array is left unchanged.

Patching procedures will generally set $\epsilon$ values for user-interpolated data as -210, and for user-flagged data as -325.

 

 

$$\epsilon \epsilon \epsilon$$ D=distance from camera center in pixels.

$$\epsilon$$ -800 if gross is near reseaux, else 0.

$$\epsilon$$

-200 Extrapolated intensity transfer function.

-220 Microphonic noise.

-300 Bright spot.

-800 Reseau fiducial mark.

-1600 Saturated pixel.

-3200 Pixel outside target ring.