visual and infrared mapping spectrometer cassini-huygens...

Cassini-Huygens

September 13, 2011ASTR 5835

Visual and Infrared Mapping Spectrometeron the Cassini Spacecraft

Emily PilinskiUniversity of Colorado at Boulder

Credit: NASA / JPL

Cassini-Huygens


Topics to Cover

Introduction to the Instrument

Instrument Requirements and Design

Science Motivation

Science Results

Recommended Reading

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September 13, 2011ASTR 5835 3

VIMS Characteristics Mass (current best estimate) = 37.14 kg Peak Operating Power (current best estimate) = 27.20 W Average Operating Power (current best estimate) = 21.83 W Peak Data Rate (current best estimate) = 182.784 kilobits/sec Dimensions (approximate) = 78 cm x 76 cm x 55 cm 2-in-1 Instrument: VIMS-Visible, VIMS-Infrared

http://www.ifsi-roma.inaf.it/cassini/?page_id=8 http://saturn.jpl.nasa.gov/spacecraft/cassiniorbiterinstruments/instrumentscassinivims/instcassinivimsdetails/

Cassini-Huygens


VIMS-Infrared, VIMS-IR

VIMS – Infrared Mapper Built at JPL using heritage from

Near Infrared MappingSpectrometer (NIMS) that flewon Galileo to Jupiter

Spectral Range 0.85– 5.1microns

256 Channels, Field of View: 32x 32 mrad

1-D InSb (Indium Antimonide)Detector captures spectrum ofone point and time

Whiskbroom scanningtechnique

Thermally isolated from S/C

Solar calibration port, LEDcalibration

[Brown, et al. 2004] & [Miller, et. al]

Cassini-Huygens


VIMS-Visible (VIMS-V) VIMS-Visible

Built by Italian Collaborators

Spectral Range 0.30 – 1.05 microns

96 Channels, Field of View: 32 x 32 mrad

Optical Head consists of scanning telescope and diffraction grating spectrometer

Scanning telescope uses push-broom technique in down-track direction to generatea 3-d “image cube” with information as a function of wavelength, position, time

[Miller, et al.]

Cassini-Huygens


Operating in Tandem

[Miller, et al.]

“Mapping” because mirror can be adjusted to acquire different areas of target

Data from both optical systems combined before transmitting to Earth to maximizeinformation content

Not only VIMS-V and VIMS-IR that operate together, but also used with RADAR, ISS,and more.

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Cassini-Huygens


Condensed Science Objectives Flyby of Venus/Jupiter…

Titan

Surface and atmospheric composition and interactions

Identify volcanism, surface geology, geomorphology

Winds and upper atmosphere dynamics from clouds

Saturn

Distribution and profiles of clouds, aerosols, variable gases

Rings

Map particle distribution and dynamics

Characterize particle size and surface properties

Icy Satellites

Mineralogical compositions at surface

Relate material to other icy satellites of other planets (Iapetus, Hyperion and Phoebe)


Cassini-Huygens


Traceability Matrix: Titan-specific ExampleScience Goal Science Objective Instrument/Obs.

Requirements

Composition anddistribution ofaerosols

Studies of methane, ethane, and acetylene, and more atmicrobar and millibar levels using stellar occultationmeasurements.

A1, A2, A4

Characterizeatmosphericcirculation andphysics

Determination of equipotential surfaces near the 1 mbarlevel. Determination of the 3-d solar flux deposition andconstrain the surface solar energy flux over latitude,longitude and time.Determination of wind fields as revealed by movementsof clouds and hazes

A1, A2, A4

Determine verticaloptical extinctionprofile of atmos.

Determination of vertical aerosol distributions andassociated microphysicaland optical properties, over latitude/longitude and time.Studies of stratospheric aerosol distributions from stellaroccultation measurements.

A1-A4

CharacterizeSurface geologyandgeomorphology

Composition determination at thewavelengths of near-infrared atmospheric windows inTitan’s atmosphere (e.g. 0.95, 1.1, 1.3, 1.6, 2.0, 2.7 μm).Map composition as a function of longitude and latitude

S1-S4

Identify Volcanismand Lightning

Searches for signs of active volcanism and tectonism S1-S4, A5

Atm

osph

eric

Sur

face


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Atmospheric Measurements Types

ObservationType

SpectralResolution

SpatialResolution

Distance Result

A1 High High Within 25object radii

Used during closestapproach combined forFeature Tracks. Both V& IR.

A2 High Moderate Outside of 25object radii

Provides globalmosaics. Uses both V& IR.

A3 Not specified. Not specified. Not specified. Nightime thermalmeasurements ofSaturn’s atmosphericthermal profile. IR only

A4 Not specified. Not specified. Not specified. Observations of weakemissions and hightaltitudes. Obs.Integrated from IR only.

A5 Full spectrum Not specified. Less than 10Saturn radii.

High-speed detection oflightening to determinealtitude and totalenergy.


Cassini-Huygens


Surface Measurements Types

ObservationType

SpectralResolution

SpatialResolution

Distance Result

S1 High Low Far Away Baseline for futuretargets, performedshortly after SOI

S2 High Modest (10-20 km) Approach Provides bestcoverage

S3 High High Approach (Goodcoverage)

Product of tradeoffsbetween S1/S2

S4 High High ClosestApproach(Limitedcoverage)

Ride alongmeasurementswhen otherinstrument is prime,ex. ISS.

Other measurement types not included in this summary are the modes forstellar occultations and ring observations.


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Selection of Spectral and Spatial Resolution

Designed a robust instrument toadapt to many possible outcomesand discoveries

Variation of targets size anddistance:

Rings, Icy Satellites, Titan,Saturn, Enceladus

Atmospheric, ring dynamics on thescale of ~100 km

Surface composition on the scaleof ~10 km

Variation of distance from the target,see orbital progression to the right

Unknown constituents, designed tobe robust to what they would find

Credit: NASA / JPL

Cassini-Huygens


Spectrum Selection

Example spectrum from Titan withmethane atmospheric transmissionbands highlighted in grey.

Titan’s atmospheric windows at 2.0, 2.7and 5.0 mm are useful for surfacecomposition studies

[McCord, et al. 2008]

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Cassini Wide Angle Camerahttp://photojournal.jpl.nasa.gov/catalog/PIA06230

Cassini VIMS-IRhttp://photojournal.jpl.nasa.gov/catalog/PIA09034

Science Motivation: Titan Example

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Spectrum Usage Example

14[Brown, et al. 2008]

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Science Highlights: Titan’s Lakes

VIMs/RADAR have helped to peer through the haze to characterize thehydrocarbon lakes of Titan.

Observations:

Lakes appear to change with the season

Smooth surfaces indicate no waves despite windy surface

Composed of primarily methane and ethane and …

Contain sediments which could be helpful in reconstructing history of Titan

Credit: NASA/JPL/University ofArizona/DLR

Cassini-Huygens


Science Highlights: Rings

http://photojournal.jpl.nasa.gov/jpegMod/PIA06443_modest.jpg

VIMs confirmed the sources of the E-ring were the ice plumes from Enceladus

Cryon Volcanism on Titan fromRADAR/VIMS observations.

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Recommended Reading

Global-scale surface spectral variations on Titan seen fromCassini/VIMS [Barnes, et. al 2007]

The identification of liquid ethane in Titan’s Ontario Lacus [Brown, etal. Nature 2008]

The Visual and Infrared mapping spectrometer for Cassini [Miller, etal. unknown]

Recommend websites if interested in more information on VIMsand Cassini:

http://vimeo.com/9489624

http://www.youtube.com/watch?v=Ioiy43pxyH0

Cassini-Huygens


Flyby Example

http://www.youtube.com/watch?v=9Pfz1n6tMUg

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References

Barnes, et. al. Global-scale surface spectral variationson Titan seen from Cassini/VIMS, Icarus 186, 242–258,2007.

Brown, et al. The Cassini Visual and Infrared MappingSpectrometer (VIMS) Investigation, Space ScienceReviews, 111-168, 2004.

Brown, et al. The identification of liquid ethane in Titan’sOntario Lacus, Nature, Vol. 454, 607-610, 2008.

Miller, et al. The Visual and Infrared MappingSpectrometer for Cassini, www.ifsi-roma.inaf.it/cassini/downloads/VIMS-paper.pdf .

visual and infrared mapping spectrometer cassini-huygens...

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