He is said to be an electrical engineer, but I'm no expert on what exactly that means. Obviously it involved science and computers for a lot of his work. I don't think he was directly involved in astronomy, he was just helping to design the computer software being used in a radio telescope.
He was working odd jobs (packing boxes or being a janitor, etc.) until the end of book 5, which was the 2 year anniversary of his wife's "death." He then told Marco that he had finally decided to stop grieving and move on with his life and starting working again.