Recovery of NEAR's mission to Eros

On December 20, 1998, the main bipropellant thruster on the Near Earth Aste roid Rendezvous (NEAR) spacecraft was commanded to start a 15-minute burn. It was the first and largest of four planned maneuvers that would cancel NE AR's velocity relative to (433) Eros to allow capture into orbit about the asteroid in January 1999. But the burn aborted and the spacecraft tumbled, causing loss of communication. The spacecraft corrected the problem, but us ed 29 kg of fuel in the process. A day later, NEAR was reacquired with just enough time to upload a sequence of commands to image Eros extensively as the spacecraft hurtled past the asteroid on December 23. The NEAR team desi gned a large bipropellant maneuver that successfully cancelled most of NEAR 's velocity relative to Eros on January 3, 1999. But then NEAR was almost I million kilometers from Eros, so a long "U-turn" journey was begun to retu rn to the asteroid on February 14, 2000. The spacecraft remains healthy and enough fuel remains to enter orbit about Eros to complete all of the missi on goals. This will be the first time that an interplanetary spacecraft has failed an orbital capture burn and returned to accomplish its objectives. This is possible because NEAR had a generous fuel supply and a robust conti ngency plan. (C) 2000 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved.