The Near-Earth Object Human Space Flight Accessible Targets Study (NHATS) began in September 2010 under the auspices of NASA Headquarters Planetary Science Division of the Science Mission Directorate in cooperation with the Advanced Exploration Systems Division of the Human Exploration and Operations Mission Directorate. Its purpose was to identify any known NEOs, particularly Near-Earth Asteroids (NEAs) that might be accessible by future human space flight missions. The Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL) independently performed the first phase of the NHATS study in parallel to validate the results.
NEAs are discovered almost daily, and often the time just after discovery is also the optimal time to provide follow-up observations to secure their orbits and characterize their physical nature. These follow-up observations are particularly important for those NEAs that could become potential future mission targets. Hence, it is prudent to monitor these NEA discoveries daily and run an analysis to determine if any among them warrant additional study as they might become attractive mission targets.
Brent Barbee (GSFC) developed the original software that performs NHATS round-trip trajectory calculations for NEAs from the JPL Small Body Database (SBDB). This software uses the method of patched conics for the spacecraft, with full precision JPL ephemerides for the Earth and NEAs, to determine which NEAs may meet the NHATS accessibility criteria (see this page for subscription options). This software is currently implemented at JPL/CNEOS, where it automatically processes new NEAs and those with updated orbit solutions. The results of this daily analysis are made available via the NHATS data table.
A process generated by Paul Chodas (JPL) then provides, for each NHATS-compliant NEA, the details of future observation opportunities that might allow the NEA orbit to be improved with follow-up optical astrometric data. Some of these observing opportunities would also allow the NEA’s physical nature to be characterized using photometric and spectroscopic observations. In cases where there are future close Earth approaches, radar astrometric and physical characterization observations may be possible; these opportunities are listed as well.