Q. After the NEAR spacecraft passed Mathilde, on some occasion's rocket propellant was expelled to adjust the spacecraft's momentum in order to follow a path that would approach the asteroid Eros, final destination for the mission. After getting close to Eros, further small adjustments made the momentum just right to give a circular orbit of radius 45 km (45 × 103 m) around asteroid. So much propellant had been used that the final mass of the spacecraft while in circular orbit around Eros was only 515 kg. The spacecraft took 1.04 days to make one complete circular orbit around Eros. Determine what the mass of Eros should be.