diff --git a/Code/Mantid/instrument/Facilities.xml b/Code/Mantid/instrument/Facilities.xml
index 8bee7a11e9ecb1e3749c70b96b224b0f2c473f2b..fc6af65a4a504371ee656128b8c137575a63cc41 100644
--- a/Code/Mantid/instrument/Facilities.xml
+++ b/Code/Mantid/instrument/Facilities.xml
@@ -543,6 +543,11 @@
     <technique>Muon spectroscopy</technique>
   </instrument>
 
+  <instrument name="GPS">
+    <zeropadding size="3"/>
+    <technique>Muon spectroscopy</technique>
+  </instrument>
+  
 </facility>
 
 <!--  Reactor Orphee (France) -->
diff --git a/Code/Mantid/instrument/GPS_Definition_5detectors.xml b/Code/Mantid/instrument/GPS_Definition_5detectors.xml
new file mode 100644
index 0000000000000000000000000000000000000000..13c99260e01f19e60aaddb0dbfa9659c88123cc2
--- /dev/null
+++ b/Code/Mantid/instrument/GPS_Definition_5detectors.xml
@@ -0,0 +1,123 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- For help on the notation used to specify an Instrument Definition File 
+     see http://www.mantidproject.org/IDF -->
+<instrument xmlns="http://www.mantidproject.org/IDF/1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mantidproject.org/IDF/1.0 Schema/IDFSchema.xsd" 
+ name="GPS" valid-from   ="1900-01-31 23:59:01"
+		       last-modified="2013-06-27 00:00:00">
+  <defaults>
+    <length unit="meter"/>
+    <angle unit="degree"/>
+    <reference-frame>
+      <!-- The z-axis is set parallel to and in the direction of the beam. the 
+           y-axis points up and the coordinate system is right handed. -->
+      <along-beam axis="z"/>
+      <pointing-up axis="y"/>
+      <handedness val="right"/>
+    </reference-frame>
+  </defaults>
+
+  
+  <!-- BRIEF DESCRIPTION OF THE PSI GPS INSTRUMENT: 
+  
+      Data provided by Stephen Cottrell - dimensions of pixels are incorrect!
+  -->
+  
+  <parameter name="Default grouping file" type="string">
+    <value val="Grouping/GPS_Detector_Grouping_LF_5.xml"/>
+  </parameter>     
+  
+  <!-- LIST OF PHYSICAL COMPONENTS (which the instrument consists of) -->
+  
+  <!-- dummy components added for visualisation purposes. 
+       To easy spot what geometry the instrument is in -->
+       
+  <!-- source and sample-position components -->
+
+  <component type="source">
+    <location z="-10.0" />
+  </component>
+  
+  <type name="source" is="Source" />
+  
+  <component type="some-sample-holder">
+    <location />
+  </component>
+  
+  <type name="some-sample-holder" is="SamplePos" />
+ 
+  <!-- detector components --> 
+  
+  <component type="GPSdetector"  idlist="all">
+       <location />  
+  </component>  
+
+  <type name="GPSdetector" >
+     <component type="front" >
+       <location />
+     </component>
+     <component type="back" >
+       <location />     
+     </component>    
+	 <component type="up" >
+       <location />     
+     </component>
+	 <component type="down" >
+       <location />     
+     </component>
+	 <component type="right" >
+       <location />     
+     </component>    	 
+  </type>
+
+  <type name="front" >
+     <component type="pixel">
+        <location z="-0.1" name="front" />
+     </component>
+  </type>
+  
+  <type name="back" >
+     <component type="pixel">
+        <location z="0.1" name="back" />
+     </component>
+  </type>
+  
+  <type name="up" >
+     <component type="pixel">
+        <location y="0.1" name="top" />
+     </component>
+  </type>
+  
+  <type name="down" >
+     <component type="pixel">
+        <location y="-0.1" name="bottom" />
+     </component>
+  </type>
+  
+  <type name="right" >
+     <component type="pixel">
+        <location x="0.1" name="right" />
+     </component>
+  </type>
+     
+  <type name="pixel" is="detector">  
+    <!-- It is implicitely assumed here that the front y-z plane (looking down
+         the x-axis) is the surface that see the neutron beam.
+         This surface is 36mm along y and 30mm along z and the dept along x is 5mm.  -->
+    <cuboid id="inner-shape">
+      <left-front-bottom-point x="0.0" y="-0.04" z="-0.04"  />
+      <left-front-top-point  x="0.0" y="0.04" z="-0.02"  />
+      <left-back-bottom-point  x="0.010" y="-0.04" z="-0.02"  />
+      <right-front-bottom-point  x="0.0" y="-0.04" z="0.02"  />
+    </cuboid>
+    <algebra val="inner-shape" />     
+  </type>
+      
+  <!-- DETECTOR ID LISTS -->
+  
+  <idlist idname="all">
+    <id start="1" end="5"/>            
+  </idlist>
+
+
+  
+</instrument>
diff --git a/Code/Mantid/instrument/Grouping/GPS_Detector_Grouping_LF_5.xml b/Code/Mantid/instrument/Grouping/GPS_Detector_Grouping_LF_5.xml
new file mode 100644
index 0000000000000000000000000000000000000000..79361b2f7076f116cc75c415bbf38e7e19681178
--- /dev/null
+++ b/Code/Mantid/instrument/Grouping/GPS_Detector_Grouping_LF_5.xml
@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<detector-grouping instrument="GPS" description="GPS (5 detectors)"> 
+
+<group name="fwd"> <ids val="1"/> </group> 
+<group name="bwd"> <ids val="2"/> </group> 
+<group name="up"> <ids val="3"/> </group> 
+<group name="down"> <ids val="4"/> </group> 
+<group name="right"> <ids val="5"/> </group> 
+
+<pair name="long"> 
+  <forward-group val="fwd"/> 
+  <backward-group val="bwd"/>                              
+  <alpha val="1"/> 
+</pair> 
+
+<default name="long"/>
+
+
+
+</detector-grouping> 
+