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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