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Hubble Space Telescope
Post-SM4 Internal CTE for WFC

WFC Parallel EPER

Old coefficients are given in Table 2 of ACS ISR 2005-03. Below is the table with the new coefficients. MJD limits are defined such that MJD1 <= MJD < MJD2. The discontinuities are an educated guess based on known temperature changes and observed CTE trends. Their fits are shown in the plots to follow.

MJD1 MJD2 n c p Notes about MJD2
52335 53552 8.086x10-5 2.329x10-6 -5.799x10-1 Aft shroud temperature test
53552 53918 -5.520x10-4 2.569x10-6 -5.616x10-1 -77C to -81C; Switched to Side-2
53918 58849 -6.947x10-4 2.739x10-6 -5.532x10-1 A distant future

CTE vs Signal

Here are the fit residuals:

Here is the legend:

CTE vs Time

"Problematic" point is as re-defined by M. Mutchler during SM4 SMOV (2009; private communication) based on initial prediction in ACS-R Multi-Parameter Optimization Constraints (ACS TIR 2008-04).

Here are the fit residuals:

Here is the legend:

These are no longer good fits

Least-square straight lines do not fit so well anymore without having to break the data into separate segments as above.

Here are the fit residuals for the plot above:

Predictions using fits from ACS ISR 2005-03 do not fit post-SM4 data well.

Here are the fit residuals for the plot above: