Analyse statistique et physique d'images hyperspectrales

planétaires: objectifs, objets et méthodes

Icy and mineral surfaces of the Solar SystemIcy and mineral surfaces of the Solar System

scientific interestscientific interest

The surfaces of evolved planets and satellites are « boundary layers »

Their physical, chemical and structural properties

characterize the nature and the evolution of these processes

marked by numerous internal or external geophysical processes

dark materials produced by irradiation of SO2 ice by magnetospheric particles lava flows resulting from

the upwelling of asthenospheric magmavolatile deposits condensed

from the atmosphere after eruption and transport of volcanic gases

Remote sensing of planetary surfaces by NIR imaging spectroscopyRemote sensing of planetary surfaces by NIR imaging spectroscopy

conceptsconcepts

Specifications OMEGA visiblerange

OMEGA infrared range

Spectral range 0.50 - 1.05 m 1.0 - 2.77 m 2.65 - 5.14Spectralresolution

6 nm 14 nm 19 nm

Spatial resolution 0.4 x 0.8 mrad 1.2 x 1.2 mradSpatial field 154 mrad 154 mradSignal to noiseratio

100 100

Type of detector Si InSb

Principal characteristics of the imaging spectrometer OMEGA (Mars Express)

The imaging spectrometers measure the spectrum of the solar light or of the thermal radiation respectively reflected or emitted by a planetary surface for an array of discretized pixels distributed throughout the scene

Remote sensing of planetary surfaces by NIR imaging spectroscopy Remote sensing of planetary surfaces by NIR imaging spectroscopy

The bidirectional reflectanceThe bidirectional reflectance

The bidirectional reflectance of a medium is defined as the radiance emerging in a given direction from the surface illuminated by a collimated irradiance per unit incident irradiance.

x

y

z

O

Flux F

e

i

e

I (0, e, e)incidence angle

emission angle

azimuth

Remote sensing of planetary surfaces by NIR imaging spectroscopyRemote sensing of planetary surfaces by NIR imaging spectroscopy

nature of retrieved scientific informationnature of retrieved scientific information

An imaging spectrometer samples the bidirectional reflectance (BRDF) of the observed surface both in the :

Absorption bands Surface properties

position identification of presentcompounds

relative shifts of position temperature, phase

width to depth ratio phase, stratification,granularity

shape phase, stratification,granularity

depth granularity,relatives abundances,stratification

Geometry Probed surfaceproperties

small phase angles Coherent backscatteringÊ:grain size, density, opticalproperties

Shadow hidingÊ: roughness(slope distribution at allscale)

any phase angles roughness, grain shape,stratification

mirror grain shape, superficialdistribution of facetorientations

Spatial complexity at all Spatial complexity at all scalesscales

1 cm

Remote sensing of planetary surfaces by NIR imaging spectroscopy Remote sensing of planetary surfaces by NIR imaging spectroscopy

physics of spectral signal formationphysics of spectral signal formation

specular reflection coherent effects

multiple scattering between particles

absorption

Shadow hiding effets

diffuse multiplescatteringatmospheric

absorption

atmospheric scattering and diffuse illumination

The analysis of hyperspectral dataThe analysis of hyperspectral data

a possible methodological schemea possible methodological scheme

Segmenting the scene into spatial units

Mapping of their physical, chemical and structural properties

Détection automatique composants - classification spectroscopique

CO2 glace

H2O glaceCO2+H2O

minéraux

« wavanglet »

Réduction de dimensionnalité et classification statistique

« MNF+PPI »

Modélisation -caractérisation physique

« spectribase + SYSPIMS »

OMEGA : instrument is still operating well with almost no aging

OMEGA/Mars Express

3200 séquences d’observation contenant des volatiles (40% des images)

Collection du LPG (images prétraitées et calibrées) :

• 25 hour-orbit: the spacecraft is circling the planet roughly once per martian sol (day)• Periapsis altitude of the orbit : 106 kilometers • Periapsis is near 75 degrees south latitude in the South Pole region of Mars.

This summer, the CRISM team will continue planning for the next round of spacecraft checkouts and instrument calibrations which begin when the aerobraking phase ends in September and refining the software it will use to operate the instrument and collect data. The mission primary science phase, set to last two years, starts in early November.

CRISM/MRO