Crosstalk correction for WFC3/UVIS (alternative)

pkg/wfc3/Dates

@@ -1,3 +1,6 @@
+07-Feb-2026 - PLL - Version 3.8.0
+    - New crosstalk correction for WFC3/UVIS fullframe unbinned exposures.
+
 07-Jan-2026 - PLL - Version 3.7.3
     - Bug fix to remove per-second in BUNIT for CRREJ output for IR data.
 

pkg/wfc3/History

@@ -1,3 +1,6 @@
+### 07-Feb-2026 - PLL - Version 3.8.0
+    - New crosstalk correction for WFC3/UVIS fullframe unbinned exposures.
+
 ### 07-Jan-2026 - PLL - Version 3.7.3
     - Bug fix to remove per-second in BUNIT for CRREJ output for IR data.
 

pkg/wfc3/Updates

@@ -1,3 +1,6 @@
+Updates for Version 3.8.0 07-Feb-2026 - PLL
+    - New crosstalk correction for WFC3/UVIS fullframe unbinned exposures.
+
 Updates for Version 3.7.3 07-Jan-2026 - PLL
     - Bug fix to remove per-second in BUNIT for CRREJ output for IR data.
 

pkg/wfc3/include/doccd.h

@@ -23,6 +23,7 @@ int doFlash (WF3Info *, SingleGroup *, float *);
 int flashHistory (WF3Info *, Hdr *);
 int doBlev (WF3Info *, SingleGroup *, int, float *, int *, int *);
 int blevHistory (WF3Info *, Hdr *, int, int);
+int cross_talk_corr(WF3Info *, SingleGroup *);
 int CCDHistory (WF3Info *, Hdr *);
 int doDQI (WF3Info *, SingleGroup *, int overscan);
 int dqiHistory (WF3Info *, Hdr *);

pkg/wfc3/include/wf3version.h

@@ -4,7 +4,7 @@
 /* This string is written to the output primary header as CAL_VER. */
 
 
-# define WF3_CAL_VER "3.7.3 (Jan-07-2026)"
-# define WF3_CAL_VER_NUM "3.7.3"
+# define WF3_CAL_VER "3.8.0 (Feb-07-2026)"
+# define WF3_CAL_VER_NUM "3.8.0"
 
 #endif /* INCL_WF3VERSION_H */

pkg/wfc3/lib/CMakeLists.txt

@@ -85,6 +85,7 @@ add_library(${PROJECT_NAME} SHARED
 	wf32d/wf32d.c
 	wf3ccd/blevdrift.c
 	wf3ccd/blevfit.c
+	wf3ccd/crosstalk.c
 	wf3ccd/doatod.c
 	wf3ccd/dobias.c
 	wf3ccd/doblev.c

pkg/wfc3/lib/wf3ccd/crosstalk.c

@@ -0,0 +1,58 @@
+# include <math.h>		/* for sqrt */
+
+#include "hstio.h"
+#include "wf3.h"
+#include "wf3info.h"
+
+
+/* remove amplifier cross-talk */
+int cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
+    extern int status;
+    const int arr_rows = x->sci.data.ny;
+    const int arr_cols = x->sci.data.nx;
+    int i, j, cur_amp;  /* iteration variables */
+    float *y;
+    double corr_fac, cur_err;
+
+    /* Correction coefficients (ABCD) from WFC3 ISR 2012-02 */
+    const double intercept[NAMPS] = {0.0180206, 0.15501201,-0.038376406, 0.19124641};
+    const double slope[NAMPS] = {-6.0494304e-5, -2.0746221e-4, -7.9701178e-5, -2.3177171e-4};
+
+    /* Crosstalk correction in electrons but then converted back to DN */
+    for (i = 0; i < arr_rows; i++) {
+        /* Copy out original row for corr_fac calculation. */
+        if ((y = calloc(arr_cols, sizeof(float))) == NULL) {
+            return (status = OUT_OF_MEMORY);
+        }
+        for (j = 0; j < arr_cols; j++) {
+            y[j] = Pix(x->sci.data, j, i);
+        }
+
+        for (j = 0; j < arr_cols; j++) {
+            if (x->group_num == 1) {
+                if (j < wf3->ampx) {
+                    cur_amp = AMP_C;
+                } else {
+                    cur_amp = AMP_D;
+                }
+            } else {
+                if (j < wf3->ampx) {
+                    cur_amp = AMP_A;
+                } else {
+                    cur_amp = AMP_B;
+                }
+            }
+            corr_fac = intercept[cur_amp] + y[arr_cols - j - 1] * wf3->atodgain[cur_amp] * slope[cur_amp];
+            /* Only fix when we can recover the signal, not removing more signal */
+            if (corr_fac < 0) {
+                Pix(x->sci.data, j, i) = (y[j] * wf3->atodgain[cur_amp] - corr_fac) / wf3->atodgain[cur_amp];
+
+                /* Propagate error; assume ERR of correction is sqrt(corr_fac) */
+                cur_err = Pix(x->err.data, j, i) * wf3->atodgain[cur_amp];
+                Pix(x->err.data, j, i) = sqrt(cur_err * cur_err + fabs(corr_fac)) / wf3->atodgain[cur_amp];
+            }
+        }
+    }
+
+    return status;
+}

pkg/wfc3/lib/wf3ccd/doccd.c

@@ -101,6 +101,7 @@ int DoCCD (WF3Info *wf3, int extver) {
     int sizex, sizey;	/* size of output image */
 
     int i, j, x1, dx;		/* loop index */
+    int is_binned;
     int overscan;
     int blevcorr;
     char buff[SZ_FITS_REC+1];
@@ -319,6 +320,16 @@ int DoCCD (WF3Info *wf3, int extver) {
         if (biasHistory (wf3, x.globalhdr))
             return (status);
 
+    is_binned = checkBinned(&x);
+
+    /* Apply crosstalk correction after BIASCORR but before everything else. */
+    if (wf3->biascorr == PERFORM && wf3->blevcorr == PERFORM && !is_binned & !wf3->subarray) {
+        trlmessage("\nCrosstalk correction is being performed.");
+        if (cross_talk_corr(wf3, &x)) {
+            return (status);
+        }
+    }
+
     /* Apply the saturation image.
        Strictly speaking, the application of the full-well saturation image is
        not a calibration step (i.e., there is no SATCORR), but the application
@@ -346,7 +357,7 @@ int DoCCD (WF3Info *wf3, int extver) {
      BINNED IMAGES ARE NOT SUPPORTED AT ALL
     */
     if (wf3->dqicorr == PERFORM) {
-        if (checkBinned(&x)){
+        if (is_binned){
             trlmessage("Binned data not supported for Sink Pixel detection");
         } else {
             if (wf3->subarray){