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Transcript of 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
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Discovery SurveysCurrent major players: - Catalina Sky Survey - PanSTARRS
CSS - 1.5m, 0.7m, (1.0m)
PS - Two 1.8m
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Discovery > 100 NEOs / month
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
• Optical astrometry
• Visible photometry
• Thermal-IR photometry
• Visible and near-IR spectroscopy
• 3-μm spectroscopy
Characterization Techniques
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Optical Astrometry Orbital Properties: a, e, i, Ω, ω
⟶ Δv, MOID, v∞
⟶ Impact geometry Non-gravitational forces:
⟶ Yarkovsky ⟶ Relativity
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Visible Photometry
Rotation periods Axis ratios Convex shape model Pole orientation Absolute magnitude
⟶ Diameter Internal structure
constraints
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Thermal-IR Photometry Albedo Diameter Thermal properties: η, , 𝛤 k
(Trilling et al. 2010)
(Mommert et al. 2014)
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Visible & Near-IR (0.5-2.5 μm) Spectroscopy
Taxonomy Composition
⟶ Meteorite Analogs
Mineralogy Taxonomic albedo
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
3-μm Spectroscopy
Composition ⟶ Hydrated
minerals ⟶ Water ice ⟶ Organics Thermal properties
(Takir & Emery 2012)
(Rivkin & Emery 2010)
H2OOrganics
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
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
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Impact Frequency (yr)106 104 10
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
• 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)
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
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
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Impact Frequency (yr)106 104 10
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Impact Frequency (yr)106 104 10
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
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)
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
(Siu, Moskovitz & Binzel 2015, in revision)
Ro
tatio
n F
req
ue
ncy
Dis
pe
rsio
n
Earth Encounter Distance (Lunar distances)
Rotational Properties
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Rotational Propertiesa/
b A
xis
Rat
io
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
http://manosobs.wordpress.com
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
Object Astrometry Light Curve Shape Model Vis Spec NIR Spec
http://manosobs.wordpress.com
Nick Moskovitz | Physical Properties of Potentially Earth-Impacting Asteroids
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)