git grep -l 'Cluster-Tango' Observatory | xargs  sed -i 's/Cluster-Tango/Cluster4/g' 
git grep -l 'Cluster-Tango' Instrument | xargs  sed -i 's/Cluster-Tango/Cluster4/g' 
git grep -l 'Cluster-Tango' NumericalData | xargs  sed -i 's/Cluster-Tango/Cluster4/g'