nick moskovitz lowell observatory nick moskovitz lowell observatory workshop on potentially...

Nick MoskovitzLowell Observatory

Workshop on Potentially Hazardous Asteroids: Characterization, Atmospheric Entry and Risk Assessment

Telescopic Insight into the Physical Properties

of Earth-Impacting Asteroids

7 July 2015 NASA Ames Research Center

Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids

• Techniques and data products

• Current state of knowledge

• Ongoing characterization efforts

Outline


Discovery SurveysCurrent major players: - Catalina Sky Survey - PanSTARRS

CSS - 1.5m, 0.7m, (1.0m)

PS - Two 1.8m


Discovery > 100 NEOs / month


• Optical astrometry

• Visible photometry

• Thermal-IR photometry

• Visible and near-IR spectroscopy

• 3-μm spectroscopy

Characterization Techniques


Optical Astrometry Orbital Properties: a, e, i, Ω, ω

⟶ Δv, MOID, v∞

⟶ Impact geometry Non-gravitational forces:

⟶ Yarkovsky ⟶ Relativity


Visible Photometry

Rotation periods Axis ratios Convex shape model Pole orientation Absolute magnitude

⟶ Diameter Internal structure

constraints


Thermal-IR Photometry Albedo Diameter Thermal properties: η, , 𝛤 k

(Trilling et al. 2010)

(Mommert et al. 2014)


Visible & Near-IR (0.5-2.5 μm) Spectroscopy

Taxonomy Composition

⟶ Meteorite Analogs

Mineralogy Taxonomic albedo


3-μm Spectroscopy

Composition ⟶ Hydrated

minerals ⟶ Water ice ⟶ Organics Thermal properties

(Takir & Emery 2012)

(Rivkin & Emery 2010)

H2OOrganics


Characterization Products

Absolute magnitude ⟶ Diameter Rotation periods Axis ratios Convex shape model Pole orientation Internal structure

constraints

Taxonomy Composition

⟶ Meteorite Analogs Mineralogy Taxonomic albedo

Composition ⟶ Hydrated

minerals ⟶ Water ice ⟶ Organics Thermal properties

Orbital Properties: a, e, i, Ω, ω

⟶ Δv, MOID, v∞

⟶ Impact geometry Non-gravitational forces:

⟶ Yarkovsky ⟶ Relativity

Albedo Diameter Thermal properties: η, , 𝛤 k

Ast

rom

etr

yV

isib

le P

hoto

metr

yV

isible

+ N

IRS

pectro

scop

y3

-μm

Sp

ectro

scop

yTherm

al-IR

Photo

metry


Impact Frequency (yr)106 104 10


• Characterization demands urgency

• Large aperture facilities (>2 meters) necessary• Ground-based characterization is essential precursor to mission planning/mitigation

Time Magnitude Event

t = 0 V~20Catalina or PanSTARRs

discovery

t ~ 2-3 days V~20Object designated

(MPEC’d)

t ~ 1-2 weeks V<21 Spectroscopy

t ~ 1 month V < 22 Photometry

t ~ 1-2 months

V < 24 Astrometry

t ~ several years

V<23 Next observing window

Characterization Timeline

The Mission Accessible Near-Earth Object Survey

Katheryn Neugent

(Lowell)

Michael Person (MIT)

David Polishook (MIT)

Henry Roe (Lowell)

Rob Schottland (Kelis

Innov.)

Hosea Siu (MIT)

Audrey Thirouin

(Lowell)

Cristina Thomas

(GSFC)

David Trilling (NAU)

Larry Wasserman

(Lowell)

Mark Willman (IfA)

Nick Moskovitz (PI,

Lowell)

Paul Abell (NASA/JSC)

Dan Avner (Lowell)

Richard Binzel (MIT)

Brian Burt (Lowell, MIT)

Eric Christensen (UA)

Francesca DeMeo (CfA)

Tom Endicott (UMass

Boston)

Will Grundy (Lowell)

Mary Hinkle (NAU)

Michael Mommert (NAU)


GoalsCatalog physical properties of several hundred mission accessible sub-km NEOsMethods

Rapid follow-up with large aperture (>4m)

facilities → Astrometry + Photometry + Spectroscopy = comprehensive characterization Target selection

10 targets / month: Mission accessible →

Δv < 7 km

Size < 1 km

M A N S


Impact Frequency (yr)106 104 10


2014 RC


Mary Hinkle (NAU) — Master’s Thesis

C-types

S-type

s

Composition• S-types = Ordinary chondrites; C-types = Carbonaceous chondrites

• OC ~80% of meteorites; S-types ~30% of km-scale NEOs• Average S-type asteroid composition ≠ Average OC

(see Stuart & Binzel 2004; Vernazza et al. 2008; Thomas et al. 2011)


(Binzel et al. 2010)


(Siu, Moskovitz & Binzel 2015, in revision)

Ro

tatio

n F

req

ue

ncy

Dis

pe

rsio

n

Earth Encounter Distance (Lunar distances)

Rotational Properties


Rotational Propertiesa/

b A

xis

Rat

io


http://manosobs.wordpress.com

http://manosobs.wordpress.com/


Object Astrometry Light Curve Shape Model Vis Spec NIR Spec

http://manosobs.wordpress.com

http://manosobs.wordpress.com/


Summary• Discovery rates at historic highs

• Representative data sets provide probabilistic assessment of physical properties

• Composition: km-scale NEOs ≠ small NEOs ≠ meteorites

C-types

S-types

• Earth encounters alter physical properties

Rot

atio

n F

req

uen

cy D

isp

ers

ion

Earth Encounter Distance (Lunar distances)

M A N SAcknowledgment: NASA NEOO Grant NNX14AN82G + NSF AAPF

Thank you!

Nick [email protected]

nick moskovitz lowell observatory nick moskovitz lowell observatory workshop on potentially...

Documents

physical properties

earthimpacting asteroids3

impacting asteroids7

hazardous asteroids

ir spectroscopy3

atmospheric entry

essential precursor

object designated mpecdt