Linearity correction

[Michael Collins]

Among the calibration parameters supported by the Data Processor module are coefficients for a higher-order linearity correction. I've done some searching for published data pertaining to characterization of various sensors, derivation of coefficients, and effectiveness of the correction process, but have so far come up empty. I would be particularly interested in knowing if linearity correction as supported by AIJ is useful in expanding the useful range of CCDs with anti-blooming gates. I have some ideas about performing characterizations on a couple of available cameras, but it would be best to learn from others before setting off on my own.

References to reports or descriptions of any direct experience in this realm would be appreciated.

[karenacollins]

Hi Michael,

As it turns out, my Ph.D. adviser, John Kielkopf, who is still a close collaborator, is actively looking into linearity corrections at this time. I know of two general methods to measure non-linearity.

The first is to use a stabilized lamp and set it up to smoothly illuminate the field of view and then use different exposure times to give a range of measurements from dim to bright, to map out the the detector non-linearity.

The second method is to use exposures of a field that contain stars to cover the faint to saturated limits on the detector. Then the measured brightnesses can be compared to known brightnesses (which can be done fairly nicely now with Gaia DR2 data) to measure the non-linearity. My adviser is currently working on the Gaia DR2 method, but his work is not completed and written up yet, which I believe he will be willing to share with the AIJ user base.

I have attached two related documents from John, and a third document that describes the stabilized lamp method from me. The stabilized lamp method also includes an outline of how to fit the non-linearity measurements to produce the coefficients needed for AIJ's DP process.

I don't have experience with anti-blooming CCDs, so I don't know how well they can be corrected. If you figure it out, please let us know here.

kielkopf_gain_20200601.pdf

kielkopf_light_scattering_section_gain_pp22-27_20200601.pdf

CCD_Nonlinearity_Test_Process.pdf 

If you'd like to contact John kielkopf, he can be reached at jkielkopf atatat gmail dotdotdot com.

Karen