The Solar Oblateness Measured On Board
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The Solar Oblateness Measured On Board The PICARD Spacecraft, and The Solar Disk Sextant Instrument. Gérard Thuillier 1 , Alain1 Hauchecorne 1 , Sabatino Sofia 2 , Terry Girard 2 , Jean-François Hochedez 1 , Abdenour Irbah 1 , Jean-Pierre Marcovici 1 ,

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The Solar Oblateness Measured On Board

The PICARD Spacecraft,

and The Solar Disk Sextant Instrument

Gérard Thuillier1, Alain1 Hauchecorne1, Sabatino Sofia2, Terry Girard2,

Jean-François Hochedez1, Abdenour Irbah1, Jean-Pierre Marcovici1,

Mireille Meissonnier1, Mustapha Meftah1, Ulysses Sofia1, and the PICARD team

1 LATMOS-CNRS (F), 2 Yale University (US), 3 American University (US)

.

OUTLINE

(1) Title

(2) PICARD Mission

(3) and (4) SODISM instrument

(5) Why and how to measure the solar oblateness?

(6) Method

(7) Results

(8) SDS instrument

(9) SDS results

(10) The Yale Convective Zone model

(11) Comparison and discussion

(12) Conclusion


THE PICARD mission

LATMOS (F)

IRMB (B)

PMOD (Ch)

OCA

Meudon Obs.

Nice University

IAS

LMD

DAPNIA-CEA

Yale University

GSFC

JPL

NRL

CSA / EC

ILWS

PICARD was launched on 15 June 2010 in a sun synchronous orbit. It consists of a microsatellite carrying four instruments: two radiometers (PREMOS and SOVAP), a bolometric sensor and an imaging telescope (SODISM).

Two other presentations will be given on PICARD: to complete with the reference


SODISM INSTRUMENT (2)

SODISM instrument is an imaging telescope observing in four wavelength domains equipped with a 2 K x 2 K CCD detector. The payload is actively pointed on the Sun with 0.2 arcsecond accuracy

The wavelenghts are chosen in the solar photospheric continuum and in the Ca II line at 393 nm to monitor the occurrence of active regions.


Image at the guiding focus

Sun

4 guiding

detectors

Interference filters

Image on the CCD

Image after the

annular mirror

Image generated by the telescope

Image after the

primary mirror

4 prisms

Entrance

window

SODISM OPTICAL SCHEMATICS


Why and how to measure the solar oblateness?

Why: The solar oblateness is the result of the internal rotation of the Sun. As a

consequence, it can test the rotation properties determined from helioseismology.

In addition, it determines the quadrupole moment of the Sun, responsible for

producing the advance of Mercury’s perihelion. Since this phenomenon is due

to general relativistic effects, the measurementis also important for basic

physics.

How:The oblateness measurements are obtained during special operations in which

the spacecraft turns around the Sun direction. The rotation, made by 30° angular

increments, allows us to determine the instrument optical distortion and

the solar oblateness.




SODISM Oblateness Results (preliminary)

90°

135°

45°

MDO 535 DL: 2011-07-04

Ang Oblateness

0 4.7 ± 1.2 x10-6

45 2.6 ± 1.2

90 2.2 ± 1.1

135 6.7 ± 1.2

MDO 535 RS: 2011-07-15

Ang Oblateness

0 6.9 ± 1.9 x10-6

45 2.7 ± 1.7

90 -0.2 ± 1.4

135 5.0 ± 1.6

MDO 782DL: 2011-05-14

Ang Oblateness

0 5.3± 1.2 x10-6

45 7.3± 1.0

90 3.9± 1.0

135 6.8±0.9




THE YALE MODEL OF THE SOLAR INTERIOR

TWO-DIMENSIONAL STRUCTURE AND EVOLUTION

EMPHASIS ON CONVECTION ZONE

INCLUDES MAGNETIC FIELDS, DIFFUSION, ROTATION, AND TURBULENCE

HIGH PRECISION TO BE ABLE TO HANDLE WITH SMALL CHANGE

MOST ACCURATE MICRO-PHYSICS CURRENTLY AVAILABLE

OBJECTIVES

TO DETERMINE THE PHYSICAL MECHANISM FOR SOLAR VARIABILITY

WITH CLIMATE CONSEQUENCES, BY MEASURING W=dlnR/dlnL, and

DETERMINING THE INTERNAL SOLAR CONFIGURATIONS THAT LEAD TO IT.

USE W AND OLD VALUES OF R (MEASURED e.g. FROM SOLAR ECLIPSES, TO DETERMINE PAST VALUES OF THE SOLAR LUMINOSITY.



CONCLUSION

References:


Not fpr use in the presentation (part of the submitted abstract)

SODISM, an imaging telescope with a 2K x 2K CCD detector, is dedicated to the measurement of the solar diameter and the limb shape. Although the data processing is still in a validation phase, we already present some preliminary results concerning the solar oblateness.

These measurements are obtained during a special operation in which the spacecraft turns around the Sun direction. The rotation, made by 300 angular increments, allows us to determine the instrument optical distortion and the solar oblateness. The method used to extract this information will be described. We shall present the preliminary results as a function of wavelength, and compare them with measurements obtained with the SDS instrument, and with the predictions from theoretical modeling


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