next up previous contents
Next: 12 Final Archive Data Up: 11.2 High-Dispersion Absolute Flux Previous: 11.2.2 Absolute Flux Calibration

11.2.3 Application of Calibrations and Corrections

High-dispersion absolutely-calibrated fluxes are obtained using a combination of the high-dispersion net fluxes, the ripple correction, the high-dispersion calibration function, the low-dispersion inverse sensitivity function, time- and temperature-dependent sensitivity corrections, effective exposure time normalization, and any overall gain correction factor (for non-standard exposure or read gain or LWR UVC voltage settings). The calibrations and corrections are applied as follows:

F_{calib} = FN_{\lambda} \times S_{\lambda}^{-1} \times
gain \times R_{T} \times C_{\lambda} / R_{m} / R_{t} /
t_{eff} \end{displaymath}

where $S_{\lambda}^{-1}$ is the low-dispersion inverse sensitivity including any necessary S/L response correction, gain is the cumulative UVC voltage and gain correction factor (if necessary), Rt and RT are the time- and temperature-dependent sensitivity correction factors, respectively, $C_{\lambda}$ is the high-dispersion calibration function, Rm is the ripple correction, and teff is the effective exposure time. Except for Rm and $C_{\lambda}$, all corrections are defined in the previous section concerning low-dispersion calibrations. No T/L response correction is used for high-dispersion trails, as they are obtained by slewing across the minor-axis (versus the major-axis for low-dispersion trails) of the aperture and therefore the low-dispersion T/L ratio is not applicable. The values for $S_{\lambda}^{-1}$ and Rt are evaluated at the wavelength of each pixel through quadratic and nearest neighbor interpolation, respectively, of their tabulated values. The resulting absolutely calibrated units are ergs/cm2/Å/sec.

Note: an error in the application of the time-dependent sensitivity degradation correction for LWP and LWR high-dispersion images was detected after the majority of these images were processed by GSFC. The error is such that it applies an incorrect solution to fluxes longward of approximately 2712Å and is on the order of several percent shortward of 3000Å, but can increase to 20% or more beyond 3200Å. LWP and LWR images affected by this error can be identified by a NEWSIPS version number of 3.3.1 or 3.3.2 in the processing history portion of the FITS header. It is the project's intent to correct this error by re-archiving corrected high-dispersion merged extracted image FITS files (MXHIs). Such corrected files will be identifiable by notations in the NEWSIPS processing history. Corrected LWP and LWR MXHIs will carry NEWSIPS version numbers of 3.3.1_A_C and 3.3.2_A_C, respectively. Additionally, the version numbers in these corrected files will be appended with the following text: ``(CORRECTED SENS. DEGRAD.)''. Data processed with the corrected NEWSIPS high-dispersion image processing pipeline system will be identifiable by a NEWSIPS version number of 3.3.3.

next up previous contents
Next: 12 Final Archive Data Up: 11.2 High-Dispersion Absolute Flux Previous: 11.2.2 Absolute Flux Calibration
Karen Levay