Comet Hopper (CHopper) was a proposed lander to NASA's Discovery Program that, had it been selected, would have orbited and landed multiple times on Comet Wirtanen as it approached the Sun.

[1] The Comet Hopper mission was one of three Discovery Program finalists that received US$3 million in May 2011 to develop a detailed concept study.

[3] The CHopper mission had three primary science goals for the 7.3 years of its lifetime.

At roughly 4.5 AU the spacecraft would have rendezvoused with Comet Wirtanen to map the spatial heterogeneity of surface solids as well as gas and dust emissions from the coma - the nebulous envelope around the nucleus of a comet.

The remote mapping would also allow for any nucleus structure, geologic processes, and coma mechanisms to be determined.