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;
diff --git a/definitions/mars/grib.rfsd.go.def b/definitions/mars/grib.rfsd.go.def
new file mode 100644
index 000000000..6aff32403
--- /dev/null
+++ b/definitions/mars/grib.rfsd.go.def
@@ -0,0 +1,14 @@
+# rfsd Gridded observations
+
+alias mars.step = endStep;
+
+alias mars.date = dateOfForecast;
+alias mars.time = timeOfForecast;
+
+alias mars.origin = inputOriginatingCentre;
+
+alias mars.anoffset=anoffset;
+
+# We need this because 'postProcessing' is defined later
+meta efas_model sprintf("%s", postProcessing) : no_copy;
+alias mars.model = efas_model;
diff --git a/definitions/mars/grib.rfsd.sfo.def b/definitions/mars/grib.rfsd.sfo.def
new file mode 100644
index 000000000..dd53fa1d5
--- /dev/null
+++ b/definitions/mars/grib.rfsd.sfo.def
@@ -0,0 +1,14 @@
+# Simulation forced with observations
+
+alias mars.step = endStep;
+
+alias mars.date = dateOfForecast;
+alias mars.time = timeOfForecast;
+
+alias mars.origin = inputOriginatingCentre;
+
+alias mars.anoffset=anoffset;
+
+# We need this because 'postProcessing' is defined later
+meta efas_model sprintf("%s", postProcessing) : no_copy;
+alias mars.model = efas_model;