In 1981 , a proposal for an asteroid mission was submitted to the European Space Agency ( ESA ) . Named the Asteroidal Gravity Optical and Radar Analysis ( AGORA ) , this spacecraft was to launch some time in 1990 – 1994 and perform two flybys of large asteroids . The preferred target for this mission was Vesta . AGORA would reach the asteroid belt either by a gravitational slingshot trajectory past Mars or by means of a small ion engine . However , the proposal was refused by ESA . A joint NASA – ESA asteroid mission was then drawn up for a Multiple Asteroid Orbiter with Solar Electric Propulsion ( MAOSEP ) , with one of the mission profiles including an orbit of Vesta . NASA indicated they was not interested in an asteroid mission . Instead , ESA set up a technological study of a spacecraft with an ion drive . Other missions to the asteroid belt was proposed in the 1980s by France , Germany , Italy , and the United States , but none was approved . Exploration of Ceres by fly @-@ by and impacting penetrator was the second main target of the second plan of the multiaimed Soviet Vesta mission , developed in cooperation with European countries for realisation in 1991 – 1994 but canceled due to the Soviet Union disbanding .