Cospar Capacity Building WorkshopOn

Planetary Science

N e a r E a r t h A s t e r o i d R e n d e z v o u s

Dr. Lucy McFadden

July 30, 2007

NEAR-Shoemaker Missionto 433 Eros

NEAR-Shoemaker Missionto 433 Eros

Scientific ObjectivesScientific Objectives

• Determine physical and chemical properties of 433 Eros

• Address major questions: – formation of the Solar

System

Eros’ Orbital PropertiesEros’ Orbital Properties

• Mars-crossing• i=10.8°• Orbital period= 1.76 y• Rotation period=5.27hr

Journey to ErosBei dem WaldgottJourney to Eros

Bei dem Waldgott

Launched Feb. 17, 1996Launched Feb. 17, 1996

• Delta 7925 launch vehicle

• Cape Canaveral

QuickTime™ and aVideo decompressor

are needed to see this picture.

SpacecraftSpacecraft

• Fixed solar panels• 1.5 m high-gain

antenna• 6 instruments

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are needed to see this picture.

253 Mathilde253 Mathilde

• June 27,1997• 1212 km flyby • C-type asteroid• 66 x 48 x 44 km• Albedo = 0.047• =1.340± 200 kg/m3

Earth SwingbyEarth Swingby

• Jan. 23, 1998• 106.300 - 306.600 km• Trajectory maneuver

– Match inclination

– i=10

• Test and calibrate instruments

Psyche in der untweltPsyche in der untwelt

Engine burn abort/Eros flyby

Engine burn abort/Eros flyby

• December 20, 1998– Aborted maneuver

– +27 hrs regained contact

• December 23, 1998– 3827 km flyby

• January 3, 1999– Bipropellant burn

– Feb. 2000 rendezvous

Psyche for VenusPsyche for Venus

Fundamental PropertiesFundamental Properties

• Mass=6.687 ± 1015 kg• Volume=2550 km3

• kg/m3

• Size=32x8x8 km• Rotation pole

– RA 11.4°– Dec 17.3°±0.1

Eros : Major QuestionsEros : Major Questions

• Is Eros a fragment or agglomerate?

• Is Eros’ composition primitive or differentiated?

• Does it have a magnetic field?

• Are there satellites?

ShapeShape

Near-IR SpectroscopyNear-IR Spectroscopy

• Low phase flyby 0-50°• >5600 spectra • 800-2500 nm• 12 -2.5 km/spectrum

– 0.76 x 0.38° slit

• 1st spatially resolved spectra

Mineral Structure

The pyroxene group is composed of minerals of the general formula XYSi2O6, where X and Y are two divalent cations and occupy twoStructurally different sites. If X and Y are the same small-radius divalent cation like Fe or Mg the resultant structure is commonly orthorhombic, giving us the orthopyroxene group.

Orthopyroxene

Olivine

The olivine group is composed of minerals of the general formula X2SiO4 where X = Mg ,Fe2+, or Ca; Y = Al, Cr, or Fe3+; and Z = Si. The X-site is 8 coordinated, the Y -site is 6-coordinated (octahedral) and the Z-site is 4-coordianted

Clinopyroxene

Low Phase Flybyfor SpectroscopyLow Phase Flybyfor Spectroscopy

Spatially Resolved Spectroscopy

Spatially Resolved Spectroscopy

• Variations in band depth and spectral slope– Range 1-4%

– Includes phase angle corrections

– Homogeneous to 4%

– At 3 km resolution

Map of 1-µm Band DepthMap of 1-µm Band Depth

Laser Rangefinder-lidarLaser Rangefinder-lidar

• Nd:YAG laser rangefinder

• First detections from Eros at 290 km

• Measures distance to surface along line of sight

MagnetometerMagnetometer

• Three-axis fluxgate magnetometer

• No magnetic field detected

• Sensitivity of 1 nT

• Upper limit at 200 km orbit is B=30,000 nt (earth-like)

Global Rotation 2 Days after

going into orbit around Eros

Global Rotation 2 Days after

going into orbit around Eros

200 km orbit200 km orbit

100 Km orbit100 Km orbit

Psyche CraterPsyche Crater

Psyche is the same size as Barringer Crater Arizona,

US

Psyche is the same size as Barringer Crater Arizona,

US

Low Altitude Flyover Oct. 26

Low Altitude Flyover Oct. 26

X-ray Gamma-Ray Spectrometer

X-ray Gamma-Ray Spectrometer

• First detections – class X solar flare

• Mg, Fe, Ca– Verified calibrations

• Interplanetary Gamma Ray Burst Network– Earth orbiting satellites

and Ulysses s/c– Location of optical and

radio counterparts

X-ray and -ray spectroscopy

• Data acquired during 5 solar flares and during two extended “quiet Sun” periods.

• Large systematic uncertainties, but relative ratios are reliable.

• Primitive, undifferentiated ratios of– Mg/Si, Al/Si, Ca/Si and Fe/Si

• global differentiation is ruled out.• S/Si is below chondritic values• Nittler et al. 2001 MAPS, 36, 1673-1695

End of MissionEnd of Mission

http://near.jhuapl.eduhttp://near.jhuapl.edu

Science Team LeadersScience Team Leaders

• Tom Coughlin• Andy Cheng• Joe Veverka

• Jacob Trombka• Bill Boynton• Mario Acuna• Maria Zuber

Science Team MembersScience Team Members

• J.P. Barriot• James F. Bell• Mark Robinson• Scott Murchie• Michael Malin• Clark Chapman• Lucy McFadden

• William Boynton• Christopher Russell• Alexander Konopliv• Steven Squyres• Peter C. Thomas• Johannes Brueckner