The Discovery Program was founded in 1990 to implement then-NASA Administrator Daniel S. Goldin's policy of "faster, better, cheaper" planetary science missions. Existing NASA programs had specified mission targets and objectives in advance, then sought bidders to construct and operate them. In contrast, Discovery missions are solicited through a call for proposals on any science topic, and assessed through peer review. Selected missions are led by a scientist called the Principal Investigator (PI) and may include contributions from industry, universities, or government laboratories.