A novel slow push asteroid deflection strategy has been recently proposed in which an Earth threatening asteroid can be deflected by exploiting the momentum transmitted by a collimated beam of quasi-neutral plasma impinging against the asteroid surface. The beam can be generated with state-of-the art ion engines from a hovering spacecraft with no need for physical attachment or gravitational interaction with the celestial body. The spacecraft, placed at a distance of a few asteroid diameters, would need an ion thruster pointed at the asteroid surface as well as a second propulsion system to compensate for the ion engine reaction and keep the distance between the asteroid and the shepherd satellite constant throughout the deflection phase. A comparison in terms of required spacecraft mass per total imparted deflection impulse shows that the method outperforms the gravity tractor concept by more than one order of magnitude for asteroids up to about 200 m diameter. The two methods would yield comparable performance for asteroids larger than about 2 k

Twelve years ago the Catalina Sky Survey discovered Earth's first known natural geocentric object other than the Moon, a few-meter diameter asteroid designated 2006 RH₁₂₀. Despite significant improvements in ground-based telescope and detector technology in the past decade the asteroid surveys have not discovered another temporarily-captured orbiter (TCO; colloquially known as minimoons) but the all-sky fireball system operated in the Czech Republic as part of the European Fireball Network detected a bright natural meteor that was almost certainly in a geocentric orbit before it struck Earth's atmosphere. Within a few years the Large Synoptic Survey Telescope (LSST) will either begin to regularly detect TCOs or force a re-analysis of the creation and dynamical evolution of small asteroids in the inner solar system. The first studies of the provenance, properties, and dynamics of Earth's minimoons suggested that there should be a steady state population with about one 1- to 2-m diameter captured objects at any time, with the number of captured meteoroids increasing exponentially for smaller sizes. That model was then improved and extended to include the population of temporarily-captured flybys (TCFs), objects that fail to make an entire revolution around Earth while energetically bound to the Earth-Moon system. Several different techniques for discovering TCOs have been considered but their small diameters, proximity, and rapid motion make them challenging targets for existing ground-based optical, meteor, and radar surveys. However, the LSST's tremendous light gathering power and short exposure times could allow it to detect and discover many minimoons. We expect that if the TCO population is confirmed, and new objects are frequently discovered, they can provide new opportunities for (1) studying the dynamics of the Earth-Moon system, (2) testing models of the production and dynamical evolution of small asteroids from the asteroid belt, (3) rapid and frequent low delta-v missions to multiple minimoons, and (4) evaluating in-situ resource utilization techniques on asteroidal material. Here we review the past decade of minimoon studies in preparation for capitalizing on the scientific and commercial opportunities of TCOs in the first decade of LSST operations.

The population of “temporarily captured asteroids” offers attractive candidates for asteroid retrieval missions. Once naturally captured, these asteroids have lifetimes ranging from a few months up to several years in the vicinity of the Earth. One could potentially extend the duration of such temporary capture phases by acting upon the asteroid with slow deflection techniques that conveniently modify their trajectories, allowing for an affordable access and in situ study. In this paper, a case study on asteroid 2006 ${\mathrm{RH}}_{120}$ is presented, which was temporarily captured during 2006–2007 and is the single known member of this category to date. Simulations estimate that deflecting the asteroid with 0.27 N for less than six months and a change of velocity, $\mathrm{\Delta }V$ of barely $32\mathrm{m}/\mathrm{s}$ would have sufficed to extend the capture for over five additional years. The study is extended to another nine virtual asteroids, showing that low-$\mathrm{\Delta }V$ (less than $15\mathrm{m}/\mathrm{s}$) and low-thrust (less than 1 N) deflections initiated a few years in advance may extend their capture phase for several years, and even decades.