This document does not allow you to go to mission.
It is a basis for the people who take care of your mission, so that they can handle your mission order as closely as possible to reality, as far as finance is concerned.
The mission order, signed by both the authorising officer and your superior, is the only document that authorises your mission. That is why, it has to be formalised before leaving. Furthermore, it sets the conditions of reimbursement of your mission.
You have to take take your mission order with you when you're abroad.
If you wish more information, you can check the the « guide des déplacements professionnels », that is on the intranet of the Université Le Havre Normandie in the square « les missions ». In this guide, you will find what you can expect for reimbursement matters. However, the autorising officer can decide, for financial matters, to limit the reimbursement when the mission order is established.