[meteorite-list] Number of Known Accessible Near-Earth Asteroids Doubles Since 2010

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 6 Feb 2015 16:27:46 -0800 (PST)
Message-ID: <201502070027.t170Rkfu025579_at_zagami.jpl.nasa.gov>

http://neo.jpl.nasa.gov/news/news189.html

Number of Known Accessible Near-Earth Asteroids Doubles Since 2010
NASA/JPL Near-Earth Object Program Office
February 6, 2015

NASA performed the first Near-Earth Object Human Space Flight Accessible
Targets Study (NHATS) in September/October of 2010, and 666 of the known
near-Earth asteroids (NEAs) were identified as meeting the NHATS
criteria for mission accessibility (classifying those NEAs as
"NHATS-compliant"). These are asteroids in near-Earth orbits that are
more dynamically accessible (requiring less time and energy to visit)
than round-trip spacecraft missions to Mars.

At that time, just over 7,000 NEAs had been discovered, while today we
know of over 12,000 NEAs, an increase of 70%. The percentage increase in
the number of accessible asteroids in the catalog has been even greater:
On January 18, 2015 - a little over four years since the NHATS
assessments began - the 1332nd NHATS-compliant asteroid was identified,
doubling the number of known accessible NEAs. The sizes of these
asteroids range from as small as a few meters to as large as a few
kilometers. While all these asteroids are more dynamically accessible
than a round-trip mission to Mars, many of them (hundreds) require less
energy to visit (round-trip) than does the lunar surface, and dozens of
them require less energy to visit than does a low orbit around the Moon.
NASA uses the automated NHATS system (http://neo.jpl.nasa.gov/nhats/) to
monitor the NEA population for mission accessibility. This monitoring
assists the identification of attractive destinations for future robotic
and crewed missions.

[Graphic]
The figure above shows the number of accessible (NHATS-compliant)
NEAs discovered each year since the first one (Anteros) was discovered
in 1973. Until the NHATS system was established in 2010, we did not have
a good measure of just how accessible some NEAs could be. The
discoveries tabulated in black in this figure represent those NEAs that
were recognized as accessible when the system started up in 2010. The
discoveries shown in blue are of the NEAs that were recognized as
accessible as soon as they were discovered, due to the automated NHATS
monitoring.

------------------------------------------------------------------------

Brent Barbee (GSFC) developed the process that automatically downloads
orbital information on newly discovered NEAs from the JPL Small Bodies
Database (SBDB) on a daily basis. He then performs trajectory
calculations using the method of patched conics for the spacecraft and
with full precision ephemerides for the Earth and NEOs obtained from
JPL's Horizons system to determine which among them may meet the NHATS
accessibility constraints. The results of this daily analysis are then
immediately uploaded to the NHATS 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. Working closely with Brent Barbee and
Paul Chodas, Alan Chamberlin (JPL) was largely responsible for creating
this Accessible NEAs website.
Received on Fri 06 Feb 2015 07:27:46 PM PST