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faq.md

@@ -10,13 +10,44 @@
 
 ### What is the impact of the Ionosphere on the accuracy of the time transfer?
 
+### Why the GPS receivers are installed on the surface?
+
 ## Fiber length calibration
 
 ### Why haven't you used fiber reflectometry to measure fiber lengths?
 
+We avoided using reflectometry to calibrate our delays for the following
+consideration:
+
+1.  Commercial reflectometers are known to be accurate at the ~10ns
+    level, whereas we know that our internal delay chain is stable at
+    the ~1ns level. 
+2.  Lab tests show that swapping the transmitter and receiver over a
+    ~5Km optical fibber roll induces a change in the delay at the order
+    of 0.1ns. Sagnac effects over an extended 10Km fibber would add an
+    additional asymmetry of only ~0.1ns on the earth equator. This means
+    that a simple two-way scheme over an spare fibber has the potential
+    to do a time-transfer between two points separated by 10Km with ~1ns
+    accuracy. 
+3.  Delay paths should include as many components as possible in order
+    to reduce any systematic error.
+
+
 ### These fibers are not length-compensated online. What is the length change throughout the year?
 
 ## Beam Current Transformer cable calibration
 
+### What does the BCT measure?
+
 ### You have calibrated using an LHC beam. How do those measurements apply to the CNGS beam?
 
+## Measurement set up.
+
+### How do you measure the neutrino speed?
+
+### How could you remove any systematics errors?
+
+### Is there anyone else measuring the neutrino velocity?
+
+## How could
+