diff --git a/definitions/mars/grib.elda.est.def b/definitions/mars/grib.elda.est.def
new file mode 100644
index 000000000..f877d1fa5
--- /dev/null
+++ b/definitions/mars/grib.elda.est.def
@@ -0,0 +1 @@
+alias mars.anoffset=offsetToEndOf4DvarWindow;