You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
BeiDou_Navigation_Satellite_System

Context:
In 2015, the system began its transition towards global coverage with the first launch of a new-generation of satellites, and the 17th one within the new system.

Question:
When did the BeiDou system begin transitioning to global coverage?

2015