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Disk-Integrated Polarization of the Moon in the Ultraviolet from SOLSTICE. M. Snow, G. Holsclaw, W. McClintock, T. Woods University of Colorado/LASP [email protected] Outline. SOLSTICE Instrument Lunar observing campaign Observing geometry Polarization observations.

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Disk integrated polarization of the moon in the ultraviolet from solstice

Disk-Integrated Polarization of the Moon in the Ultraviolet from SOLSTICE

M. Snow, G. Holsclaw,

W. McClintock, T. Woods

University of Colorado/LASP

[email protected]


Outline
Outline from SOLSTICE

  • SOLSTICE Instrument

  • Lunar observing campaign

  • Observing geometry

  • Polarization observations


Solar stellar irradiance comparison experiment solstice
SOLar from SOLSTICESTellar Irradiance Comparison Experiment (SOLSTICE)

  • Measures irradiance in ultraviolet

    • 115-180 nm Far Ultraviolet (FUV)

    • 180-300 nm Middle Ultraviolet (MUV)

  • Measures stellar irradiance for tracking long term degradation.

  • On board SORCE:

    • Low Earth Orbit

SOLSTICE Lunar Irradiance


Solar stellar ratio
Solar-Stellar Ratio from SOLSTICE

Need a large dynamic

range to measure both sun and stars with same optics and detectors

SOLSTICE Lunar Irradiance


Solstice layout
SOLSTICE Layout from SOLSTICE

  • Change entrance aperture 2x10^4

  • Widen exit slit 10 or 20

  • Lengthen integration 10^3

SOLSTICE Lunar Irradiance


Lunar observing campaign
Lunar Observing Campaign from SOLSTICE

  • June 2006 to December 2010

  • Added the Moon to the schedule of eclipse calibration activities

  • On average, we observed one disk-integrated spectrum per day in each channel

  • NASA Grant: LASP Lunar Albedo Measurement and Analysis from SOLSTICE (LLAMAS)

SOLSTICE Lunar Irradiance


Overview of observations

(MESSENGER) from SOLSTICE

SSBUV

ROLO

GOME

SOLSTICE

(Galileo)

(SNOE)

(Cassini)

(HUT)

(Apollo 17)

(Mariner 10)

NOZOMI

Overview of Observations


Lunar irradiance spectra
Lunar Irradiance Spectra from SOLSTICE

Phase angle 2 degrees


Phase angle
Phase Angle from SOLSTICE

SOLSTICE Lunar Irradiance


Phase curve 282 nm
Phase Curve (282 nm) from SOLSTICE


Uv disk integrated albedo
UV Disk-integrated Albedo from SOLSTICE

Phase angle 10 degrees


Instrument sensitivity to polarization
Instrument Sensitivity to Polarization from SOLSTICE

Measured at SURF before launch for both channels.

Very little sensitivity to polarization in FUV channel.


Instrument roll angle
Instrument Roll Angle from SOLSTICE


Calculating polarization fraction
Calculating Polarization Fraction from SOLSTICE

Using Mueller Matrices, we can express the measured signal in terms of the spacecraft roll angle, θ

= A + B cos 2

The polarization of the lunar irradiance is then given by:


Extracting p m
Extracting P from SOLSTICEm

For each wavelength and phase angle, we can find A and B using least-squares fitting algorithm.


Polarization vs phase
Polarization from SOLSTICEvs Phase


Polarization vs wavelength
Polarization from SOLSTICEvs Wavelength


Summary
Summary from SOLSTICE

  • SOLSTICE has observed the disk integrated albedo of the Moon from

    • -170 to 170 degrees phase

    • 130-300 nm

  • Instrument is sensitive to polarization above 250 nm

  • Reasonable signal-to-noise measurement of polarization from -90 to 90 degrees phase

  • Consistent with WUPPE measurements and trends from visible region of the spectrum

  • Analysis of systematic errors in data processing continues!


Acknowledgements references
Acknowledgements & from SOLSTICEReferences

This work was supported by NASA grant NNX09AQ60G (LLAMAS) and NASA contract NAS5-97045 (SORCE) at the University of Colorado.

Snow, M., Holsclaw, G., McClintock, W. E., and Woods T. N. (2012) Absolute ultraviolet irradiance of the Moon from the LASP Lunar Albedo Measurement and Analysis from SOLSTICE (LLAMAS) project. In: Cross-calibration of Past and Present Far UV Spectra of Solar System Objects and the Heliosphere, E. Quemerais, M. Snow, and R. M. Bonnet (eds), ISSI Scientific Report No. 12 (in press)

Snow, M., Holsclaw, G., McClintock W. E., and Woods, T. N. (2007) Absolute ultraviolet irradiance of the Moon from SORCE SOLSTICE. Proc. SPIE 6677:66770D


Questions
Questions? from SOLSTICE


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