Chindi (Academy - Book 3) by Jack McDevitt
'A writer who is a storyteller first and a science fiction writer second. In his ability to absolutely rivet the reader, it seems to me that he is the logical heir to Isaac Asimov and Arthur C. Clarke' Stephen King
The universe has been explored - and humanity has all but given up on finding other intelligent life.
Then an alien satellite orbiting a distant star sends out an unreadable signal.
Is it the final programmed gasp of an ancient, long-dead race? Or the first greeting of an undiscovered life form?