Calstis Version 2.15b was installed in the OTFR pipeline on 2003-Dec-16. It is available for download in the new STSDAS release Version 3.1 which can be found at the STSDAS Advisories page.

The following OPRs were implemented in the release of CALSTIS 2.15b:

OPR 47249:	CALSTIS populates the V_HELIO keyword
OPR 48084:	Support for new pseudo-aperture positions
OPR 48303:	CALSTIS should remove invalid WCS keywords from table header
OPR 48983:	CALSTIS should compare BIASFILE rather than WBIAFILE
OPR 49009:	Correct CCD spectroscopic data for Charge Transfer Efficiency
OPR 49010:	Correct the S/N of CCD spectroscopy for the Q correction
OPR 49045:	CALSTIS should allow missing row in TDS table in CALSTIS7
OPR 49159:	CALSTIS uninitialized memory in echelle scattered light correction
OPR 49670:	CALSTIS1 should provide an option to override the darkscale values

Below we give more details on the changes that are likely to be noticed by users in their data.

OPR 47249: CALSTIS populates the V_HELIO keyword in CALSTIS6 and CALSTIS7

CALSTIS will now populate the V_HELIO keyword with the value of the heliocentric correction applied. A positive value for V_HELIO means the Earth was heading away from the target at the time of the observation.

OPR 48084: Support for new pseudo-aperture positions Related OPRs: 48657, 48666, 48662, 48670, 48671, 48668, 48658,48677

CALSTIS and the X1D task now recognize when the new D1 or E2 pseudo-aperture positions (see the STIS Instrument Handbook) are used and will use appropriate rows from the reference tables for calibration of the data.

OPR 48303: CALSTIS should remove invalid WCS keywords from table header in CALSTIS6

The input file for 1-D spectral extraction is an image and has keywords for describing the transformation between pixel coordinates and "world" coordinates (i.e. wavelength and angle along the slit). These keywords are no longer copied to the output file, because that file is a table rather than an image.

OPR 48983: CALSTIS should compare BIASFILE rather than WBIAFILE

CALSTIS was modified to remove a test that compared the reference file names in the science and wavecal headers to check that the bias files were the same. CALSTIS already compares BIASFILE names when the science and wavecal exposures have the same binning and gain. If the binning or gain are not the same, no comparison can be made, since the bias files should be different. Therefore the WBIAFILE keyword is no longer necessary.

OPR 49009: Correct CCD spectroscopic data for Charge Transfer Efficiency

Extraction of fluxes for 1st-order CCD spectra now includes corrections for the losses caused by Charge Transfer Inefficiency (CTI). For spectra of faint sources, the correction to the flux at the present time can amount to 15% or more. A full description of the algorithm used can be found in the STIS ISR 2003-03R by Bohlin and Goudfrooij. Note that ehe correction is applied to the flux. The gross count rate G used in the computation should include dark counts and spurious charge. The background count rate per pixel is computed using a median; given by the MEANDARK keyword.

OPR 49010: Correct the S/N of CCD spectroscopy for the Q correction in CALSTIS6

The error estimate in 1-D extracted CCD data now includes a correction to handle the case where more than one electron may be generated from a single UV photon.
The follow algorithm will be used to correct the error array:

                         ((S + B_s) + B_d)*G*t + RN^2
  Q_correction = sqrt(----------------------------------)
                      ((S + B_s)/Q(wl) + B_d)*G*t + RN^2

where S is the source counts, B_s the sky background, B_d the mean dark background, G the gain, t the exposure time, RN the readnoise, and Q is the average number of electrons per photon at the measured wavelength (see the Special Case in Section 6.4.1 of the Instrument Handbook for an indication of how this expression is derived). For the UV band covered by the CCD, Q is typically in the range of 1 - 2. The Q correction becomes approximately sqrt(Q) when the gross counts (S + B_s) >> readnoise (RN^2).

OPR 49045: CALSTIS should allow missing row in TDS table in CALSTIS7

CALSTIS was failing when no grating entry was found on the TDSTAB reference file. It now just skips the TDS correction if the grating is not found. Calstis6 (x1d) prints a warning to that effect in the trailer file and continues with the tdscorr turned off.

OPR 49159: CALSTIS uninitialized memory in echelle scattered light correction in CALSTIS6

Two small arrays of wavelengths are defined for the echelle scattered light correction. The arrays are four elements long, and only the first three elements of each array are initialized since there are actually only three wavelengths. The fourth element is referenced, however, when comparing with the values in a reference table. This can fail if the value in the fourth element is not a valid double precision number. To avoid failures all elements were initialized.

OPR 49670: CALSTIS1 should provide an option to override the darkscale values

A temperature dependent scaling factor is automatically applied to the input dark file before correcting for exposure time. Because the CCD Side 2 temperature can be inaccurate in some circumstances, the user should have the option to override these values on the command line. In addition, the "darkscale" variable used for reading the optional list of scaling factors for dark subtraction in CALSTIS1 (or BASIC2D) was not initialized. This would normally be harmless, but it could result in the dark reference image being scaled by an arbitrary factor. The darkscale variable now is by default initialized to an empty string, since darkscale parsing routing expects it as input, and can be a list of floating point values.