As of March 30, 2011, 7922 Near-Earth objects have been discovered. Some 824 of these NEOs are asteroids with a diameter of approximately 1 kilometer or larger. Also, 1214 of these NEOs have been classified as Potentially Hazardous Asteroids (PHAs). The next phase of discovery (over ten years) is expected to find over 50,000 NEOs.
NEO Next Gen Search (2010 – 2021) will be at 100 times the current discovery rate
– First month of PanSTARRS-4 and LSST operation is estimated to discover more asteroids than are currently known
– ~500,000 new asteroids
– ~50,000 near-Earth objects (Diameter greater than 140meters)
– ~10,000 PHOs (Potentially hazardous object )140 meters and larger by 2021
Many PHOs could be possible candidates for Crewed NEO Missions.
The Large Synoptic Survey Telescope is a revolutionary facility which will produce an unprecedented wide-field astronomical survey of our universe using an 8.4-meter ground-based telescope. It is in design phase and would begin operating 4 years after construction starts.
* High resolution optical camera system
– Surface identification, navigation, characterization, and optical mapping
– Topographical mapping, gravitational field survey, and shape modeling
* Visible and near-IR spectrometer
– General compositional investigation
* Small lander package
– APXS, micrometeorite counter, dust collector, solar wind/particle collector, imager, radiometer, etc.
The velocity requirements can be far lower for NEO missions versus lunar missions. It can be two to four times easier to go to a near earth asteroid than to the moon.
In general, mission ΔV can be reduced by
– Longer mission duration
– Shorter stay times (second order)
– Lunar gravity assist (second order)
• NEO Launch Windows
– Two ~equal launch opportunities to NEOs – each several days long
• A NEO must be in the right place in its orbit at the right time to have a really close approach to Earth, thus allowing a low-ΔV fast mission
• Can we do it? Yes. And – more NEOs are being discovered all the time.
Potential Hazardous Asteroids
Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid’s potential to make threatening close approaches to the Earth. Specifically, all asteroids with a minimum orbit intersection distance (MOID) of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less are considered PHAs. In other words, asteroids that can’t get any closer to the Earth (i.e. MOID) than 0.05 AU (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 150 m (500 ft) in diameter (i.e. H = 22.0 with assumed albedo of 13%) are not considered PHAs.
This “potential” to make close Earth approaches does not mean a PHA will impact the Earth. It only means there is a possibility for such a threat. By monitoring these PHAs and updating their orbits as new observations become available, we can better predict the close-approach statistics and thus their Earth-impact threat.