Rotational Poles and Dimensions of Ceres and Vesta

and three STEAs

Jack DrummondStarfire Optical Range

Air Force Research Lab

Rotating 3x2x1 Asteroid

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Fits are Made in the Fourier Plane

Image = E ּס L

₣ (Image) = K0 2J1(x)/x

Juno Fit DiagnosticsShane 3 m at 2.1μmImage

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Davida Fit Diagnostics Keck 10 m at 2.1μm

Ceres(λ=5550) December 2003 HST

Ceres Oblate Spheroid Observations

Ceres’ Pole

Ceres Dimensions

This work Thomas et ala=b=α= 480±1 km 487.3±1.5 km

c=[β2-a2 sin(θ)2]½ / cos(θ)= 448±1 km 454.7±1.5 km

Vesta October 1997 HST

VestaTriaxial Results

Vesta: AO on Lick 3 m

Vesta Resolved

HST Lightcurves

SI AO

Weighted Mean Vesta

This Work (n=4) Thomas et ala = 562±2 km 578±10 kmb = 543±2 km 560±10 kmc = 458±4 km 458±10 km

RA = 325° 301°Dec= +55° +41°Error radius = 6.7° 5°

511 Davida with AO at Keck

511 Davida with AO at Keck

511 Davida with AO at Keck

Davida Edge Features

52 Europa with AO at Keck

52 Europa with AO at Keck

52 Europa with AO at Keck

2 Pallas with AO at Keck

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Rotational Phase

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July 18, 2006 UT

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Pallas Pole on Ecliptic Globe

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STEAs(Standard Triaxial Ellipsoid Asteroids)

a Al Conrad, Bill Merline, Christophe Dumas, Drummond et al. 2007, Icarus in press:‘Direct measurement of the size, shape, and pole of 511 Davida with Keck AO in a single night’

b Merline et al. 2007, In prep: ‘Direct measurement of the size, shape, and pole of 52 Europa with Keck AO in a single night’

c Drummond and Julian Christou 2007, Icarus submitted:‘Triaxial Ellipsoid Dimensions and Rotational Poles of Seven Asteroids from Lick Observatory

Adaptive Optics Images, and of Ceres’