Heidi Hammel improvements to the adaptive optics systems of the Keck telescope, astronomers became able to capture "unbelievably crisp images" and view many details that could not be seen before. Hammel's planetary research with Hubble and Keck has demonstrated that both Uranus and Neptune are dynamic worlds. Hammel primarily studies the outer planets and their satellites, focusing on observational techniques. She was a member of the Imaging Science Team for the Voyager 2 encounter with the planet Neptune in 1989. In 1994, Hammel led the team that investigated Jupiter's visible wavelength response to the impact of comet Shoemaker-Levy 9 using the Hubble
Comet Shoemaker–Levy 9 Despite published predictions, astronomers had not expected to see the fireballs from the impacts and did not have any idea in advance how visible the other atmospheric effects of the impacts would be from Earth. Observers soon saw a huge dark spot after the first impact. The spot was visible even in very small telescopes, and was about (one Earth radius) across. This and subsequent dark spots were thought to have been caused by debris from the impacts, and were markedly asymmetric, forming crescent shapes in front of the direction of impact. Over the next six days, 21 distinct impacts