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Tutorial on Process of Finding Small NEAs
Target NEO 2
Open Community Workshop
Timothy SpahrDirector, Minor Planet Center
Smithsonian Astrophysical Observatory9 July 2013
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Discovery of Small NEOs
--Nearly all “small NEOs” found by NASA-fundedsurveys
--Found when close to the Earth (<< 0.1 AU)
--Move very rapidly at discovery (several degreesper day)
--Streaked/trailed images (hard to detect); nonlinearmotion
--First discoveries of small objects from Spacewatch team, visual detection in CCD images. Eg, 1991 BA
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NASA’s NEO Observation Program(Current Systems)
LINEAR
MIT/LL Soccoro, NM
Catalina SkySurvey
UofAZArizona & Australia
Minor Planet Center (MPC)• IAU sanctioned• Int’l observation database• Initial orbit determinationwww.cfa.harvard.edu/iau/mpc.html NEO Program Office @ JPL• Program coordination • Precision orbit determination • Automated SENTRY http://neo.jpl.nasa.gov/ Pan-STARRS
Uof HIHaleakula, Maui
NEO-WISE
JPLSun-synch LEO
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End ofOperationsFeb 2011,AnalysisOf Data
Continues
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Discovery of NEOs—MPC!
--All observations of all minor planets and comets made worldwide sent to the Minor Planet Center or MPC
--Round-the-clock, year-round operation
--Automatic software attempts to identify candidateNEOs and posts on public web page observations,orbit, ephemeris, and uncertainty area
--Other observers worldwide attempt to confirm the object
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What is a small NEO?
A small NEA for us is defined as smaller than ~ 20 meters in diameter (H < 25-26 ish)
--Only a few hundred discoveries
--Total population of objects < 20 metersin diameter is > 1,000,000
--Very difficult to discover using groundbasedoptical telescopes (short discovery window)
Space-based IR great, but scope must beclose to Earth!! (Venus is right out)
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2011 MD
Nick Howes/Ernesto Guido/Giovanni Sostero/Faulkes Telescope
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Ecliptic Latitude & Elongation
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Discovery Magnitudes
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How to Increase Discovery Rate??
--More sky coverage at fainter magnitudes (this increases volumeof space sampled)
--note even modest phase angleshamper discovery; GO FAINTER!
--Refresh rate is a few days, so repeated coverage essential (6-8 Xa month
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Discovery Improvement Details
--Very important—fainter discovery magnitude = more time we have for physical studies and orbit evaluation!! (see Beeson, Galache & Elvis 2013)
--Longer arcs essential for orbit quality
--Rotation periods can only be determined by radar or photometry; possible when close to Earth
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Small NEO discoveries by team
Prepared by CSS
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Small NEO discoveries by team
Prepared by CSS
Prepared by CSS
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Monthly Sky Coverage
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Sky Coverage Fraction
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Conclusions
--Dominant player in discovery of small NEOs is the CSS team; get new cameras online quickly for best bang-for-buck and hopefully a good small target!
--Wider sky coverage to much fainter magnitudes essential to find more small NEOs; perhaps software improvements
--While space-based IR would help, we need meter class instruments and in space NOW to contribute to target search