diff --git a/src/RemoteTech2/NetworkManager.cs b/src/RemoteTech2/NetworkManager.cs
index 84f8499..e44ef84 100644
--- a/src/RemoteTech2/NetworkManager.cs
+++ b/src/RemoteTech2/NetworkManager.cs
@@ -108,12 +108,14 @@ public void FindPath(ISatellite start, IEnumerable<ISatellite> commandStations)
 
         public IEnumerable<NetworkLink<ISatellite>> FindNeighbors(ISatellite s)
         {
-            if (!s.Powered) return Enumerable.Empty<NetworkLink<ISatellite>>();
+            if (!s.Powered || !Graph.ContainsKey(s.Guid)) return Enumerable.Empty<NetworkLink<ISatellite>>();
             return Graph[s.Guid].Where(l => l.Target.Powered);
         }
 
         private void UpdateGraph(ISatellite a)
         {
+			if (!Graph.ContainsKey(a.Guid)) return;
+
             var result = new List<NetworkLink<ISatellite>>();
 
             foreach (ISatellite b in this)
diff --git a/src/RemoteTech2/VesselSatellite.cs b/src/RemoteTech2/VesselSatellite.cs
index fd3638a..3f355e5 100644
--- a/src/RemoteTech2/VesselSatellite.cs
+++ b/src/RemoteTech2/VesselSatellite.cs
@@ -8,7 +8,7 @@ namespace RemoteTech
     public class VesselSatellite : ISatellite
     {
         public bool Visible { 
-            get { return SignalProcessor.Visible; }
+            get { return SignalProcessor != null ? SignalProcessor.Visible : false; }
         }
 
         public String Name { 
@@ -43,7 +43,7 @@ public ISignalProcessor SignalProcessor
             get {
                 return RTUtil.CachePerFrame(ref mSignalProcessor, () =>
                 {
-                    return SignalProcessors.FirstOrDefault(s => s.FlightComputer != null) ?? SignalProcessors[0];
+                    return SignalProcessors.FirstOrDefault(s => s.FlightComputer != null) ?? SignalProcessors.FirstOrDefault();
                 });
             }
         }