Grism QA Guide (viewing JPEGs)

When viewing the *-ng-offset_grid_qa.jpg and the *-xg-offset_profile_qa_rtastar.jpg images watch for shifts in the photon data which show up as echoes in the grid image, profiles, and spectra.

Below, there are some tests on SIRTFFL_00_0033. Here is the large 2 color image: SIRTFFL_00_0033-xg-int_2color_large.jpg .

Here is are clean (successful run) JPEGs: (grid image) (profile and spectra) .

Example of a 30 arcsecond total shift of 10% of the photon data: (grid image) (profile and spectra) .

Example of a 10 arcsecond spatial (profile) direction (Y) shift of 10% of the photon data: (grid image) (profile and spectra) .

Example of a 10 arcsecond dispersion (spectral) direction (X) shift of 10% of the photon data: (grid image) (profile and spectra) . Small X offset shifts of 10% of less of the photon data are almost to detect. You might see a slight "washing-out" of the absorption lines and perhaps a bad fit to the synthetic spectrum, especially on the red edge of the spectrum.

Example of a -10 arcsecond dispersion (spectral) direction (X) shift of 10% of the photon data: (grid image) (profile and spectra) . In this case, you can see that the absorption line blueward of the big peak has been diluted.

Example of a +20 arcsecond dispersion (spectral) direction (X) shift of 20% of the photon data: (grid image) (profile and spectra) . In this case, notice the poor fit on the red side of the highest peak in the spectra.

Time-sliced spectra:
Nominal spectra divided into 100 second intervals: (sliced spectra plot) . Example of a +10 arcsecond dispersion (spectral) direction (X) shift of 10% of the photon data: (x+10 sliced spectra plot) .