Context: The three latest satellites will jointly undergo testing of a new system of navigation signaling and inter-satellite links, and start providing navigation services when ready.

Question: What will the three latest satellites provide after testing?
Answer: navigation services

Question: What kind of testing will be performed on the three latest satellites?
Answer: testing of a new system of navigation signaling and inter-satellite links

Question: How many satellites will be used to test a new system of navigation signaling?
Answer: three

Question: Four of the newest satellites will undergo what?
Answer: Unanswerable

Question: The satellites will individually undergo testing of an old system of what?
Answer: Unanswerable

Question: The three newest terminals will start providing what type of services when ready?
Answer: Unanswerable

Question: How many satellites will undergo separate testing for new signaling units?
Answer: Unanswerable

Question: How many terminals will be undergo testing of the new system?
Answer: Unanswerable