Index: trunk/ppSub/src/ppSubArguments.c
===================================================================
--- trunk/ppSub/src/ppSubArguments.c	(revision 20492)
+++ trunk/ppSub/src/ppSubArguments.c	(revision 20506)
@@ -214,4 +214,5 @@
     psMetadataAddS32(arguments, PS_LIST_TAIL, "-iter", 0, "Number of rejection iterations", -1);
     psMetadataAddF32(arguments, PS_LIST_TAIL, "-rej", 0, "Rejection thresold (sigma)", NAN);
+    psMetadataAddF32(arguments, PS_LIST_TAIL, "-sys", 0, "Relative systematic error in kernel", NAN);
     psMetadataAddU8(arguments,  PS_LIST_TAIL, "-mask-bad", 0, "Mask value for bad pixels", 0);
     psMetadataAddU8(arguments,  PS_LIST_TAIL, "-mask-poor", 0, "Mask value for poor pixels", 0);
@@ -302,4 +303,5 @@
     VALUE_ARG_RECIPE_INT("-iter",         "ITER",            S32, -1);
     VALUE_ARG_RECIPE_FLOAT("-rej",        "REJ",             F32);
+    VALUE_ARG_RECIPE_FLOAT("-sys",        "SYS",             F32);
     VALUE_ARG_RECIPE_FLOAT("-badfrac",    "BADFRAC",         F32);
     VALUE_ARG_RECIPE_FLOAT("-penalty",    "PENALTY",         F32);
Index: trunk/ppSub/src/ppSubReadout.c
===================================================================
--- trunk/ppSub/src/ppSubReadout.c	(revision 20492)
+++ trunk/ppSub/src/ppSubReadout.c	(revision 20506)
@@ -93,4 +93,5 @@
     int iter = psMetadataLookupS32(NULL, recipe, "ITER"); // Rejection iterations
     float rej = psMetadataLookupF32(NULL, recipe, "REJ"); // Rejection threshold
+    float sys = psMetadataLookupF32(NULL, recipe, "SYS"); // Relative systematic error in kernel
     bool reverse = psMetadataLookupBool(NULL, config->arguments, "REVERSE"); // Reverse sense of subtraction?
     psVector *widths = psMetadataLookupPtr(NULL, recipe, "ISIS.WIDTHS"); // ISIS Gaussian widths
@@ -181,5 +182,5 @@
     if (!pmSubtractionMatch(inConv, refConv, inRO, refRO, footprint, regionSize, spacing, threshold, sources,
                             stampsName, type, size, order, widths, orders, inner, ringsOrder, binning,
-                            penalty, optimum, optWidths, optOrder, optThresh, iter, rej, maskVal,
+                            penalty, optimum, optWidths, optOrder, optThresh, iter, rej, sys, maskVal,
                             maskBad, maskPoor, poorFrac, badFrac, subMode)) {
         psError(PS_ERR_UNKNOWN, false, "Unable to match images.");