Parameterize SimRelOrbit.jenkins to specify the repositories to compose.
diff --git a/orbit/SimRelOrbit.jenkinsfile b/orbit/SimRelOrbit.jenkinsfile
index 9e167d4..8dc51ca 100644
--- a/orbit/SimRelOrbit.jenkinsfile
+++ b/orbit/SimRelOrbit.jenkinsfile
@@ -26,6 +26,18 @@
         '''
     )
 
+    string (
+      name: 'ORBIT',
+      defaultValue: 'https://download.eclipse.org/tools/orbit/downloads/latest-I',
+      description: 'The Orbit repository to aggregate.<br/>Visit <a href="https://download.eclipse.org/justj/?file=tools/orbit/downloads/drops">https://download.eclipse.org/tools/orbit/downloads/drops/</a> for choices.'
+    )
+
+    string (
+      name: 'OOMPH_MAVEN',
+      defaultValue: 'https://download.eclipse.org/oomph/simrel-maven/nightly/latest',
+      description: 'The Oomph Maven repository to aggregate.<br/>Visit <a href="https://download.eclipse.org/oomph/simrel-maven/">https://download.eclipse.org/oomph/simrel-maven/<a/> for choices'
+    )
+
     booleanParam(
       name: 'PROMOTE',
       defaultValue: false,
@@ -38,9 +50,13 @@
       steps {
         echo "BUILD_TYPE=${params.BUILD_TYPE}"
         echo "PROMOTE=${params.PROMOTE}"
+        echo "ORBIT=${params.ORBIT}"
+        echo "OOMPH_MAVEN=${params.OOMPH_MAVEN}"
         script {
           env.PROMOTE = params.PROMOTE
           env.BUILD_TYPE = params.BUILD_TYPE
+          env.ORBIT = params.ORBIT
+          env.OOMPH_MAVEN = params.OOMPH_MAVEN
         }
       }
     }
@@ -80,6 +96,17 @@
       }
     }
 
+    stage('Modify Aggregation') {
+      steps {
+        script {
+          def contents = readFile( file: 'orbit/orbit.aggr' )
+          contents = contents.replaceAll('location="[^"]+" description="oomph-maven"', "location=\"${OOMPH_MAVEN}\"").replaceAll('location="[^"]+" description="orbit"', "location=\"${ORBIT}\"")
+          echo "$contents"
+          writeFile( file: 'orbit/orbit.aggr', text: contents)
+        }
+      }
+    }
+
     stage('Build SimRel Orbit') {
       steps {
         sshagent(['projects-storage.eclipse.org-bot-ssh']) {