Header.md

@@ -33,4 +33,27 @@ The header is the first object of a CZML file, it describes for example what kin
 
 **name** - String : Name of the header, describes what have been used to build it
 
-**Clock** - [Clock]() : The clock object, describes when the study will be done.
+**Clock** - [Clock]() : The clock object, describes when the study will be done.
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+
+
+# Build
+
+A header can be build with  :
+
+* An Id, a name, and a [Clock]() :
+
+```Java
+Header header = new Header(id, name, clock);
+```
+
+* An id, a name, a version and a [Clock]() :
+
+```Java
+Header header = new Header(id, name, version, clock);
+```
+
+* A [Propagator](https://www.orekit.org/site-orekit-development/apidocs/org/orekit/propagation/Propagator.html) (from Orekit) and an [AbsoluteDate](https://www.orekit.org/site-orekit-development/apidocs/org/orekit/time/AbsoluteDate.html) (from Orekit) that represents the final date of the simulation.
+
+```Java
+Header header = new Header(propagator, finalDate);
+```
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