From 8b6d7cc1b176189a7ec873df320f36b763f13914 Mon Sep 17 00:00:00 2001
From: Pey Lian Lim <2090236+pllim@users.noreply.github.com>
Date: Fri, 6 Feb 2026 18:27:32 -0500
Subject: [PATCH 1/6] Implement crosstalk correction for WFC3/UVIS following
 ACS/WFC style but adjusted for WFC3 pipeline flow.

---
 pkg/wfc3/Dates                  |   3 +
 pkg/wfc3/History                |   3 +
 pkg/wfc3/Updates                |   3 +
 pkg/wfc3/include/doccd.h        |   1 +
 pkg/wfc3/include/wf3version.h   |   4 +-
 pkg/wfc3/lib/CMakeLists.txt     |   1 +
 pkg/wfc3/lib/wf3ccd/crosstalk.c | 132 ++++++++++++++++++++++++++++++++
 pkg/wfc3/lib/wf3ccd/doccd.c     |  11 ++-
 8 files changed, 155 insertions(+), 3 deletions(-)
 create mode 100644 pkg/wfc3/lib/wf3ccd/crosstalk.c

diff --git a/pkg/wfc3/Dates b/pkg/wfc3/Dates
index de3acdf9e..460a8bceb 100644
--- a/pkg/wfc3/Dates
+++ b/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.
 
diff --git a/pkg/wfc3/History b/pkg/wfc3/History
index 751e0b30b..9c097a298 100644
--- a/pkg/wfc3/History
+++ b/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.
 
diff --git a/pkg/wfc3/Updates b/pkg/wfc3/Updates
index 2ef336487..e6475a71d 100644
--- a/pkg/wfc3/Updates
+++ b/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.
 
diff --git a/pkg/wfc3/include/doccd.h b/pkg/wfc3/include/doccd.h
index 5b3c0dd3f..e70e632cd 100644
--- a/pkg/wfc3/include/doccd.h
+++ b/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);
+void cross_talk_corr(WF3Info *, SingleGroup *);
 int CCDHistory (WF3Info *, Hdr *);
 int doDQI (WF3Info *, SingleGroup *, int overscan);
 int dqiHistory (WF3Info *, Hdr *);
diff --git a/pkg/wfc3/include/wf3version.h b/pkg/wfc3/include/wf3version.h
index 3a7c5e050..e0248af95 100644
--- a/pkg/wfc3/include/wf3version.h
+++ b/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 */
diff --git a/pkg/wfc3/lib/CMakeLists.txt b/pkg/wfc3/lib/CMakeLists.txt
index a59725724..c7c288190 100644
--- a/pkg/wfc3/lib/CMakeLists.txt
+++ b/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
diff --git a/pkg/wfc3/lib/wf3ccd/crosstalk.c b/pkg/wfc3/lib/wf3ccd/crosstalk.c
new file mode 100644
index 000000000..24806b92a
--- /dev/null
+++ b/pkg/wfc3/lib/wf3ccd/crosstalk.c
@@ -0,0 +1,132 @@
+# include <math.h>		/* for sqrt */
+
+#include "hstio.h"
+#include "wf3.h"
+#include "wf3info.h"
+
+static void dn_to_e (SingleGroup *, int, int, int, float *);
+static void e_to_dn (SingleGroup *, int, int, int, float *);
+
+
+/* remove amplifier cross-talk */
+void cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
+    double temp;
+    const int arr_rows = x->sci.data.ny;
+    const int arr_cols = x->sci.data.nx;
+    int i, j;  /* iteration variables */
+
+    /* cross talk scaling constant */
+    double cross_scale = 9.1e-5;
+
+    /* Convert to electrons */
+    for (i = 0; i < arr_rows; i++) {
+        dn_to_e(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
+    }
+
+    for (i = 0; i < arr_rows; i++) {
+        for (j = 0; j < arr_cols; j++) {
+            temp = Pix(x->sci.data, arr_cols-j-1, i) * cross_scale;
+            Pix(x->sci.data, j, i) += (float) temp;
+
+            /* Propagate error */
+            Pix(x->err.data, j, i) = (float) sqrt(Pix(x->sci.data, j, i));
+        }
+    }
+
+    /* Convert back to DN */
+    for (i = 0; i < arr_rows; i++) {
+        e_to_dn(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
+    }
+}
+
+
+static void dn_to_e (SingleGroup *a, int line, int ampx, int ampy, float *gain) {
+
+/* arguments:
+SingleGroupLine *a	io: input data; output product
+int line		i: line number of input line
+int ampx, ampy		i: amp parameters
+float *gain		i: atogain parameter
+
+Adapted from multgn1d for fullframe only.
+*/
+	int i;
+	int dimx=a->sci.data.nx;
+
+    /* Since both the science and error arrays operate on the
+       same line of data, we will combine them into one loop over
+       X values.
+    */
+	if (line < ampy) {
+        /* This line has 2-AMP readout */
+        /* Apply gain for first amp to first part of line */
+        for (i = 0;  i < ampx;  i++) {
+            Pix(a->sci.data, i, line) = gain[AMP_C] * Pix(a->sci.data, i, line);
+	        Pix(a->err.data, i, line) = gain[AMP_C] * Pix(a->err.data, i, line);
+        }
+        /* Apply gain for second amp over remainder of line */
+        for (i = ampx;  i < dimx;  i++) {
+            Pix(a->sci.data, i, line) = gain[AMP_D] * Pix(a->sci.data, i, line);
+	        Pix(a->err.data, i, line) = gain[AMP_D] * Pix(a->err.data, i, line);
+        }
+
+    } else {
+        /* This line has 2-AMP readout */
+        /* Apply gain for first amp to first part of line */
+        for (i = 0;  i < ampx;  i++) {
+            Pix(a->sci.data, i, line) = gain[AMP_A] * Pix(a->sci.data, i, line);
+	        Pix(a->err.data, i, line) = gain[AMP_A] * Pix(a->err.data, i, line);
+        }
+        /* Apply gain for second amp over remainder of line */
+        for (i = ampx;  i < dimx;  i++) {
+            Pix(a->sci.data, i, line) = gain[AMP_B] * Pix(a->sci.data, i, line);
+            Pix(a->err.data, i, line) = gain[AMP_B] * Pix(a->err.data, i, line);
+        }
+    }
+}
+
+
+static void e_to_dn (SingleGroup *a, int line, int ampx, int ampy, float *gain) {
+
+    /* arguments:
+    SingleGroupLine *a	io: input data; output product
+    int line		i: line number of input line
+    int ampx, ampy		i: amp parameters
+    float *gain		i: atogain parameter
+
+    Adapted from multgn1d for fullframe only.
+    */
+    int i;
+    int dimx=a->sci.data.nx;
+
+    /* Since both the science and error arrays operate on the
+       same line of data, we will combine them into one loop over
+       X values.
+    */
+    if (line < ampy) {
+        /* This line has 2-AMP readout */
+        /* Apply gain for first amp to first part of line */
+        for (i = 0;  i < ampx;  i++) {
+            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_C];
+            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_C];
+        }
+        /* Apply gain for second amp over remainder of line */
+        for (i = ampx;  i < dimx;  i++) {
+            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_D];
+            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_D];
+        }
+
+    } else {
+        /* This line has 2-AMP readout */
+        /* Apply gain for first amp to first part of line */
+        for (i = 0;  i < ampx;  i++) {
+            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_A];
+            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_A];
+        }
+        /* Apply gain for second amp over remainder of line */
+        for (i = ampx;  i < dimx;  i++) {
+            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_B];
+            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_B];
+        }
+    }
+}
diff --git a/pkg/wfc3/lib/wf3ccd/doccd.c b/pkg/wfc3/lib/wf3ccd/doccd.c
index de336435a..330d7efe2 100644
--- a/pkg/wfc3/lib/wf3ccd/doccd.c
+++ b/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 +320,14 @@ 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.");
+        cross_talk_corr(wf3, &x);
+    }
+
     /* 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 +355,7 @@ 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){

From 0752fa81bbad7b382e383f14c612fd324cb6d598 Mon Sep 17 00:00:00 2001
From: Pey Lian Lim <2090236+pllim@users.noreply.github.com>
Date: Tue, 10 Feb 2026 20:39:27 -0500
Subject: [PATCH 2/6] Implement WFC3 ISR 2012-02 coefficients

---
 pkg/wfc3/lib/wf3ccd/crosstalk.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/pkg/wfc3/lib/wf3ccd/crosstalk.c b/pkg/wfc3/lib/wf3ccd/crosstalk.c
index 24806b92a..92cf3ab1d 100644
--- a/pkg/wfc3/lib/wf3ccd/crosstalk.c
+++ b/pkg/wfc3/lib/wf3ccd/crosstalk.c
@@ -10,25 +10,41 @@ static void e_to_dn (SingleGroup *, int, int, int, float *);
 
 /* remove amplifier cross-talk */
 void cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
-    double temp;
     const int arr_rows = x->sci.data.ny;
     const int arr_cols = x->sci.data.nx;
     int i, j;  /* iteration variables */
 
-    /* cross talk scaling constant */
-    double cross_scale = 9.1e-5;
-
     /* Convert to electrons */
     for (i = 0; i < arr_rows; i++) {
         dn_to_e(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
     }
 
+    /* WFC3 ISR 2012-02 */
     for (i = 0; i < arr_rows; i++) {
-        for (j = 0; j < arr_cols; j++) {
-            temp = Pix(x->sci.data, arr_cols-j-1, i) * cross_scale;
-            Pix(x->sci.data, j, i) += (float) temp;
+        if (i < wf3->ampy) {
+            for (j = 0; j < wf3->ampx; j++) {
+                // c_corr = c - (-0.038376406 + np.flip(d, 1) * -0.079701178)
+                Pix(x->sci.data, j, i) -= -0.038376406 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.079701178;
+            }
+            for (j = wf3->ampx; j < arr_cols; j++) {
+                // d_corr = d - (0.19124641 + np.flip(c, 1) * -0.23177171)
+                Pix(x->sci.data, j, i) -= 0.19124641 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.23177171;
+            }
+        } else {
+            for (j = 0; j < wf3->ampx; j++) {
+                // a_corr = a - (0.0180206 + np.flip(b, 1) * -0.060494304)
+                Pix(x->sci.data, j, i) -= 0.0180206 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.060494304;
+            }
+            for (j = wf3->ampx; j < arr_cols; j++) {
+                // b_corr = b - (0.15501201 + np.flip(a, 1) * -0.20746221)
+                Pix(x->sci.data, j, i) -= 0.15501201 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.20746221;
+            }
+        }
+    }
 
-            /* Propagate error */
+    /* Propagate error */
+    for (i = 0; i < arr_rows; i++) {
+        for (j = 0; j < arr_cols; j++) {
             Pix(x->err.data, j, i) = (float) sqrt(Pix(x->sci.data, j, i));
         }
     }

From 5e58f1656492fd7f925933c34145371a22fbd5af Mon Sep 17 00:00:00 2001
From: Pey Lian Lim <2090236+pllim@users.noreply.github.com>
Date: Tue, 10 Feb 2026 20:54:21 -0500
Subject: [PATCH 3/6] Fix sqrt calc for ERR

---
 pkg/wfc3/lib/wf3ccd/crosstalk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/wfc3/lib/wf3ccd/crosstalk.c b/pkg/wfc3/lib/wf3ccd/crosstalk.c
index 92cf3ab1d..9c45a0c63 100644
--- a/pkg/wfc3/lib/wf3ccd/crosstalk.c
+++ b/pkg/wfc3/lib/wf3ccd/crosstalk.c
@@ -45,7 +45,7 @@ void cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
     /* Propagate error */
     for (i = 0; i < arr_rows; i++) {
         for (j = 0; j < arr_cols; j++) {
-            Pix(x->err.data, j, i) = (float) sqrt(Pix(x->sci.data, j, i));
+            Pix(x->err.data, j, i) = (float) sqrt(fabs(Pix(x->sci.data, j, i)));
         }
     }
 

From f5afd9c7555e284bf165707750d742676da6611b Mon Sep 17 00:00:00 2001
From: Pey Lian Lim <2090236+pllim@users.noreply.github.com>
Date: Wed, 11 Feb 2026 11:25:32 -0500
Subject: [PATCH 4/6] Clean up logic, fix ERR propagation

---
 pkg/wfc3/include/doccd.h        |  2 +-
 pkg/wfc3/lib/wf3ccd/crosstalk.c | 61 +++++++++++++++++++--------------
 pkg/wfc3/lib/wf3ccd/doccd.c     |  4 ++-
 3 files changed, 40 insertions(+), 27 deletions(-)

diff --git a/pkg/wfc3/include/doccd.h b/pkg/wfc3/include/doccd.h
index e70e632cd..4e04a0d2d 100644
--- a/pkg/wfc3/include/doccd.h
+++ b/pkg/wfc3/include/doccd.h
@@ -23,7 +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);
-void cross_talk_corr(WF3Info *, SingleGroup *);
+int cross_talk_corr(WF3Info *, SingleGroup *);
 int CCDHistory (WF3Info *, Hdr *);
 int doDQI (WF3Info *, SingleGroup *, int overscan);
 int dqiHistory (WF3Info *, Hdr *);
diff --git a/pkg/wfc3/lib/wf3ccd/crosstalk.c b/pkg/wfc3/lib/wf3ccd/crosstalk.c
index 9c45a0c63..a2b622210 100644
--- a/pkg/wfc3/lib/wf3ccd/crosstalk.c
+++ b/pkg/wfc3/lib/wf3ccd/crosstalk.c
@@ -9,43 +9,52 @@ static void e_to_dn (SingleGroup *, int, int, int, float *);
 
 
 /* remove amplifier cross-talk */
-void cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
+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;  /* iteration variables */
+    int i, j, cur_amp;  /* iteration variables */
+    float corr_fac, cur_err, *y;
+
+    /* Correction coefficients (ABCD) from WFC3 ISR 2012-02 */
+    const float intercept[NAMPS] = {0.0180206, 0.15501201,-0.038376406, 0.19124641};
+    const float slope[NAMPS] = {-0.060494304, -0.20746221, -0.079701178, -0.23177171};
 
     /* Convert to electrons */
     for (i = 0; i < arr_rows; i++) {
         dn_to_e(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
     }
 
-    /* WFC3 ISR 2012-02 */
+    /* Crosstalk correction */
     for (i = 0; i < arr_rows; i++) {
-        if (i < wf3->ampy) {
-            for (j = 0; j < wf3->ampx; j++) {
-                // c_corr = c - (-0.038376406 + np.flip(d, 1) * -0.079701178)
-                Pix(x->sci.data, j, i) -= -0.038376406 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.079701178;
-            }
-            for (j = wf3->ampx; j < arr_cols; j++) {
-                // d_corr = d - (0.19124641 + np.flip(c, 1) * -0.23177171)
-                Pix(x->sci.data, j, i) -= 0.19124641 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.23177171;
-            }
-        } else {
-            for (j = 0; j < wf3->ampx; j++) {
-                // a_corr = a - (0.0180206 + np.flip(b, 1) * -0.060494304)
-                Pix(x->sci.data, j, i) -= 0.0180206 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.060494304;
-            }
-            for (j = wf3->ampx; j < arr_cols; j++) {
-                // b_corr = b - (0.15501201 + np.flip(a, 1) * -0.20746221)
-                Pix(x->sci.data, j, i) -= 0.15501201 + Pix(x->sci.data, arr_cols - j - 1, i) * -0.20746221;
-            }
+        /* 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);
         }
-    }
 
-    /* Propagate error */
-    for (i = 0; i < arr_rows; i++) {
         for (j = 0; j < arr_cols; j++) {
-            Pix(x->err.data, j, i) = (float) sqrt(fabs(Pix(x->sci.data, j, i)));
+            if (i < wf3->ampy) {
+                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] * slope[cur_amp];
+            Pix(x->sci.data, j, i) = y[j] - corr_fac;
+
+            /* Propagate error; assume ERR of correction is sqrt(corr_fac) */
+            cur_err = Pix(x->err.data, j, i);
+            Pix(x->err.data, j, i) = (float) sqrt(cur_err * cur_err + fabs(corr_fac));
         }
     }
 
@@ -53,6 +62,8 @@ void cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
     for (i = 0; i < arr_rows; i++) {
         e_to_dn(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
     }
+
+    return status;
 }
 
 
diff --git a/pkg/wfc3/lib/wf3ccd/doccd.c b/pkg/wfc3/lib/wf3ccd/doccd.c
index 330d7efe2..44eeade6e 100644
--- a/pkg/wfc3/lib/wf3ccd/doccd.c
+++ b/pkg/wfc3/lib/wf3ccd/doccd.c
@@ -325,7 +325,9 @@ int DoCCD (WF3Info *wf3, int extver) {
     /* 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.");
-        cross_talk_corr(wf3, &x);
+        if (cross_talk_corr(wf3, &x)) {
+            return (status);
+        }
     }
 
     /* Apply the saturation image.

From 3926f98d4fda8540162715ff173d8a658ba6f1b7 Mon Sep 17 00:00:00 2001
From: Pey Lian Lim <2090236+pllim@users.noreply.github.com>
Date: Wed, 11 Feb 2026 22:58:43 -0500
Subject: [PATCH 5/6] Bug fix rabbit hole

---
 pkg/wfc3/lib/wf3ccd/crosstalk.c | 124 +++-----------------------------
 1 file changed, 10 insertions(+), 114 deletions(-)

diff --git a/pkg/wfc3/lib/wf3ccd/crosstalk.c b/pkg/wfc3/lib/wf3ccd/crosstalk.c
index a2b622210..51fe93bb1 100644
--- a/pkg/wfc3/lib/wf3ccd/crosstalk.c
+++ b/pkg/wfc3/lib/wf3ccd/crosstalk.c
@@ -4,9 +4,6 @@
 #include "wf3.h"
 #include "wf3info.h"
 
-static void dn_to_e (SingleGroup *, int, int, int, float *);
-static void e_to_dn (SingleGroup *, int, int, int, float *);
-
 
 /* remove amplifier cross-talk */
 int cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
@@ -14,18 +11,14 @@ int cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
     const int arr_rows = x->sci.data.ny;
     const int arr_cols = x->sci.data.nx;
     int i, j, cur_amp;  /* iteration variables */
-    float corr_fac, cur_err, *y;
+    float *y;
+    double corr_fac, cur_err;
 
     /* Correction coefficients (ABCD) from WFC3 ISR 2012-02 */
-    const float intercept[NAMPS] = {0.0180206, 0.15501201,-0.038376406, 0.19124641};
-    const float slope[NAMPS] = {-0.060494304, -0.20746221, -0.079701178, -0.23177171};
-
-    /* Convert to electrons */
-    for (i = 0; i < arr_rows; i++) {
-        dn_to_e(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
-    }
+    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 */
+    /* 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) {
@@ -36,7 +29,7 @@ int cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
         }
 
         for (j = 0; j < arr_cols; j++) {
-            if (i < wf3->ampy) {
+            if (x->group_num == 1) {
                 if (j < wf3->ampx) {
                     cur_amp = AMP_C;
                 } else {
@@ -49,111 +42,14 @@ int cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
                     cur_amp = AMP_B;
                 }
             }
-            corr_fac = intercept[cur_amp] + y[arr_cols - j - 1] * slope[cur_amp];
-            Pix(x->sci.data, j, i) = y[j] - corr_fac;
+            corr_fac = intercept[cur_amp] + y[arr_cols - j - 1] * wf3->atodgain[cur_amp] * slope[cur_amp];
+            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);
-            Pix(x->err.data, j, i) = (float) sqrt(cur_err * cur_err + fabs(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];
         }
     }
 
-    /* Convert back to DN */
-    for (i = 0; i < arr_rows; i++) {
-        e_to_dn(x, i, wf3->ampx, wf3->ampy, wf3->atodgain);
-    }
-
     return status;
 }
-
-
-static void dn_to_e (SingleGroup *a, int line, int ampx, int ampy, float *gain) {
-
-/* arguments:
-SingleGroupLine *a	io: input data; output product
-int line		i: line number of input line
-int ampx, ampy		i: amp parameters
-float *gain		i: atogain parameter
-
-Adapted from multgn1d for fullframe only.
-*/
-	int i;
-	int dimx=a->sci.data.nx;
-
-    /* Since both the science and error arrays operate on the
-       same line of data, we will combine them into one loop over
-       X values.
-    */
-	if (line < ampy) {
-        /* This line has 2-AMP readout */
-        /* Apply gain for first amp to first part of line */
-        for (i = 0;  i < ampx;  i++) {
-            Pix(a->sci.data, i, line) = gain[AMP_C] * Pix(a->sci.data, i, line);
-	        Pix(a->err.data, i, line) = gain[AMP_C] * Pix(a->err.data, i, line);
-        }
-        /* Apply gain for second amp over remainder of line */
-        for (i = ampx;  i < dimx;  i++) {
-            Pix(a->sci.data, i, line) = gain[AMP_D] * Pix(a->sci.data, i, line);
-	        Pix(a->err.data, i, line) = gain[AMP_D] * Pix(a->err.data, i, line);
-        }
-
-    } else {
-        /* This line has 2-AMP readout */
-        /* Apply gain for first amp to first part of line */
-        for (i = 0;  i < ampx;  i++) {
-            Pix(a->sci.data, i, line) = gain[AMP_A] * Pix(a->sci.data, i, line);
-	        Pix(a->err.data, i, line) = gain[AMP_A] * Pix(a->err.data, i, line);
-        }
-        /* Apply gain for second amp over remainder of line */
-        for (i = ampx;  i < dimx;  i++) {
-            Pix(a->sci.data, i, line) = gain[AMP_B] * Pix(a->sci.data, i, line);
-            Pix(a->err.data, i, line) = gain[AMP_B] * Pix(a->err.data, i, line);
-        }
-    }
-}
-
-
-static void e_to_dn (SingleGroup *a, int line, int ampx, int ampy, float *gain) {
-
-    /* arguments:
-    SingleGroupLine *a	io: input data; output product
-    int line		i: line number of input line
-    int ampx, ampy		i: amp parameters
-    float *gain		i: atogain parameter
-
-    Adapted from multgn1d for fullframe only.
-    */
-    int i;
-    int dimx=a->sci.data.nx;
-
-    /* Since both the science and error arrays operate on the
-       same line of data, we will combine them into one loop over
-       X values.
-    */
-    if (line < ampy) {
-        /* This line has 2-AMP readout */
-        /* Apply gain for first amp to first part of line */
-        for (i = 0;  i < ampx;  i++) {
-            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_C];
-            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_C];
-        }
-        /* Apply gain for second amp over remainder of line */
-        for (i = ampx;  i < dimx;  i++) {
-            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_D];
-            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_D];
-        }
-
-    } else {
-        /* This line has 2-AMP readout */
-        /* Apply gain for first amp to first part of line */
-        for (i = 0;  i < ampx;  i++) {
-            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_A];
-            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_A];
-        }
-        /* Apply gain for second amp over remainder of line */
-        for (i = ampx;  i < dimx;  i++) {
-            Pix(a->sci.data, i, line) = Pix(a->sci.data, i, line) / gain[AMP_B];
-            Pix(a->err.data, i, line) = Pix(a->err.data, i, line) / gain[AMP_B];
-        }
-    }
-}

From 663a364a007b717d3a7b8232b91d9f7f6950cf3a Mon Sep 17 00:00:00 2001
From: Pey Lian Lim <2090236+pllim@users.noreply.github.com>
Date: Mon, 16 Feb 2026 13:22:26 -0500
Subject: [PATCH 6/6] Only add back signal

---
 pkg/wfc3/lib/wf3ccd/crosstalk.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/pkg/wfc3/lib/wf3ccd/crosstalk.c b/pkg/wfc3/lib/wf3ccd/crosstalk.c
index 51fe93bb1..099fd0d9c 100644
--- a/pkg/wfc3/lib/wf3ccd/crosstalk.c
+++ b/pkg/wfc3/lib/wf3ccd/crosstalk.c
@@ -43,11 +43,14 @@ int cross_talk_corr(WF3Info *wf3, SingleGroup *x) {
                 }
             }
             corr_fac = intercept[cur_amp] + y[arr_cols - j - 1] * wf3->atodgain[cur_amp] * slope[cur_amp];
-            Pix(x->sci.data, j, i) = (y[j] * wf3->atodgain[cur_amp] - corr_fac) / wf3->atodgain[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];
+                /* 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];
+            }
         }
     }