The New York Times: Heidi B. Hammel, 48, an M.I.T.-educated planetary astronomer, has two professional missions. The first is to learn everything possible about those icy planets, Neptune and Uranus. The second is to communicate knowledge about space to ordinary citizens. In 1994, when the Shoemaker-Levy 9 comet crashed into Jupiter, Dr. Hammel was the leader of the ground team that analyzed photos of the event from the Hubble Space Telescope. At the same time, she was the National Aeronautics and Space Administration’s public face, explaining the science to television audiences worldwide. We spoke at her home in Ridgefield, Conn., and later by telephone. An edited version of the conversations follows.