The Japanese lunar orbiter Kaguya was launched on September 14, 2007, by an H-IIA rocket from Tanegashima Space Center (Figure 1.1). Kaguya is also known as SELENE, the SELenological and ENgineering Explorer, and was developed by the Japan Aerospace Exploration Agency (JAXA). The nickname Kaguya, selected by a popular vote, is the name of a princess in Japanese medieval folklore who came from, and returned to, the Moon. The boxy main orbiter, 2.1 m wide and 4.8 m tall, weighed about 3 t with fuel (Figure 1.2). Two small satellites, Okina and Ouna, each about 50 kg, accompanied the main craft.