Inside NASA's Asteroid Redirect Mission - what,when and why

NASA's Asteroid Redirect Mission (ARM) has two mission segments,according to NASA's Formulation Assessment and Support Team (FAST),a group of government and academic solar system exploration experts advising NASA on mission requirements.The Asteroid Redirect Robotic Mission (ARRM),slated for an end of year 2020 launch,will be the first mission ever to visit a large Near Earth Object,land on it,collect and return the asteroid material to a stable orbit around the Moon.The second mission segment is the Asteroid Redirect Crew Mission (ARCM),planned for a late 2025 launch of the Orion spacecraft on the new Space Launch System rocket,in which astronauts will explore the boulder and return to Earth with samples.*
A principal objective of the ARM is the development of a high-power Solar Electric Propulsion vehicle for the ARRM and the demonstration that it can operate for many years in interplanetary space.A second prime objective is to conduct a human spaceflight mission including in-space interaction with a natural object,to provide the systems and operational experience required for eventual human exploration of Mars,including the Martian moons Phobos and Deimos.The ARRM will test how Orion can dock and operate with a SEP-powered spacecraft.This new technology will help send the large amount of cargo,habitats and propellant to Mars in advance of a human mission.*
ARCM provides a compelling focus for the Orion program before the infrastructure for more ambitious flights will be available.The ARCM will provide the opportunity for human explorers to work in space with asteroid material,testing the activities that would be performed and tools that would be needed for later exploration of primitive body surfaces in deep space,close to our home planet and making it a significantly more affordable approach to obtaining this experience.*
According to the FAST draft report for public comment dated 23 November 2015,NASA has identified the NEA 2008 EV5 (the 5 is formally rendered as a subscript numeral) as the reference target for the ARRM.Final target selection will be made approximately a year before launch.2OO8 EV5 provides a valid target that can be used to help with formulation and development efforts.It is about 400m in diameter and has a reflectance spectrum consistent with carbonaceous chondrite meteorites (meteorites are small pieces of asteroids or comets that entered the atmosphere and survived to reach the surface of Earth).It is possible to identify 6 distinct candidate 10-m scale boulders on 2008 EV5's surface by visual inspection of radar images.One of the candidate boulders is located near the asteroid's South Pole;the others cannot be located with certainty at this time.
As for regoliths,or unconsolidated rocky material,there are likely millions of 10-cm scale cobbles on this NEA;and 3000 1-5m boulders would be expected on its surface.In terms of vehicle safety,steep cratered topography is not prevalent on asteroids less than 1 km in diameter,which are of interest to the ARRM.*
Initial dynamic modeling indicates 2008 EV5 began its existence as part of a much larger body in the Asteroid Belt (likely diameter 100 km) and migrated inward across the inner main belt over many millions of years until it reached a planetary gravitational resonance that drove it into the NEA population.Besides material collection,2008 EV5 will also be used for an enhanced gravity tractor asteroid deflection demonstration.This is one of the prospective defence techniques to deflect dangerous asteroids and protect Earth if needed in the future.