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James Webb Space Telescope:

A steroids & Near-Earth Objects

J W S T will enable a s ter oid obser vations at key inf r ared waveleng ths that are impos sible to acces s f r om the gr ound, and with a combination of sensitivit y and waveleng th cover age va s tly superior to previous space ba sed obser vatories and complement ar y to SOF I A and f uture ground-ba sed obser vatories. J W S T also f ills a unique niche in N A S A Planet ar y S cience Division a s set s by obt aining critical suppor ting dat a for N A S A mis sion t arget s a s well a s af for ding the oppor tunit y to make obser vations of member s of the a s ter oid population for which spacecr af t visit s are pr ohibitively dif f icult .

· Surface composition Spectroscopy and numerous filters spanning 0.6 ­ 28 µm will enable characterization of absorption and emission features (including the critical 3 µm spectral region) on even small asteroids. · Imaging Near-IR spatial resolution rivaling that of HST at V-band will enable unprecedented study of surface compositional heterogeneity and support continued study of asteroid shapes, dust, outgassing, and multiplicity.
Near-Ear th object (433) Eros. ( N ASA /JPL /JHUA PL)

· Thermal Proper ties Imaging and spectroscopy from 5 ­ 28.5 µm will enable detailed study of albedos, sizes, surface roughness, and thermal inertia.

Image produced by GSFC Visualization Lab


Asteroids
A. S. Rivkin (A PL), F. Marchis (SE TI ), D. Takir ( USGS), C. A. Thomas (GSFC/ USR A / PSI ) J WST will have spatial resolution compa r a b l e to Hubble and the IF U spectrometers provide spectral information at each pixel in order to decipher compositional va r iat i o n (e.g. cr ater s denoted by black circle). HST image of Pallas from S chmidt et al. (2 0 0 9, Science, 326, 275).

JWST will provide the opportunity for ground-breaking observations of asteroids in three major ways:
High Spatial Resolution in the near-IR · JWST can resolve asteroids as small as 80 km at 2.8 AU. Broad Wavelength Coverage · Broad wavelength coverage will improve our understanding of how space weathering affects asteroid spectra. · Measurements of hydroxyl and organic fundamental absorptions in the near-IR and thermal emission in the mid-IR. · Obser vations in wavelength regions that are challenging or impossible from the ground, and with only limited asteroidal data from spacecraft. Exceptional Sensitivit y · Thermal wavelength photometr y will enable derivation of albedos and diameters for smaller objects than previously obser vable. · NIRSpec can obser ve nearly ever y object from the main belt through the Trojan clouds with S/ N > 10 in 1000 s across the entire 0.6 ­ 5 m range.

Composition

Surface Features

Size/Brightness Limits

Asteroids Expanded wavelength coverage Dozens of main-belt asteroids MIRI saturates on many asteroids, will further our understanding of large enough to be compositionally depending on fraction of pixel filled asteroid compositions for all asteroid mapped by NIRCam and/or NIRSpec. and temperature. populations. NEOs Comparisons between NEOs and their Main Belt source regions will enable study of how the near-Earth environment impacts volatile content of NEOs. NEOs will not be resolved, but the high sensitivity of the instruments will enable studies of rotational variation. Saturation possible for the brightest objects. Photometry is possible for objects down to diameters of a few meters

The relative proximity of Near-Earth Objects (NEOs) to JWST and the unprecedented sensitivit y of the instruments will enable scientific investigations of objects as small as a few meters in diameter.

Near-Earth Objects
C.A Thomas (GSFC/ USR A / PSI ), P. Abell (JSC), J. Castillo-Rogez (JPL), N. Moskovitz ( Lowell), M. Mueller (SRON ), V. Reddy ( PSI ), A.S. Rivkin (A PL), E. Ryan ( UMD/GSFC)

JWST observations of NEOs will further our understanding of: · The size frequency distribution of the smallest NEOs. · Enable precise investigations of individual objects such as spacecraft targets. · Enable spectral characterization of the majorit y of known NEOs. · Permit spectral comparisons of NEOs to their Main Belt source regions.

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Images cour tesy of N ASA