TRANSIT OF VENUS 2012, Observation with PICARD/SODISM during transit

Transcription

1 TRANSIT OF VENUS 2012, Observation with PICARD/SODISM during transit SODISM (Solar Diameter Imager and Surface Mapper): An instrument of the PICARD payload, is a high resolution imaging telescope. SODISM allows us to measure the solar diameter and shape. M. Meftah, A. Hauchecorne, And the PICARD Team CNRS/LATMOS (France) 3 rd Europlanet strategic workshop 4 th PHC/Sakura meeting

2 PICARD PICARD is a Satellite dedicated to the study of the Sun.

3 Presentation outline Ø Fundamental Solar inputs Ø Scientific objectives of the PICARD mission Ø The space instrument SODISM of the PICARD mission Ø Transit of Venus 2012 Ø Conclusion PICARD / SODISM 393 nm ( )

4 1 Fundamental Solar inputs (1/3) SODISM images the solar atmosphere at a temperature of 5800 Kelvin. These images reveal the photosphere of the solar atmosphere. Structure of the Sun: Interior Corona Convective zone HINODE JAXA, NAOJ, PPARC and NASA. Radiative zone Chromosphere Core Photosphere (From H. Haubold and A. M.Mathai, 4 Atmosphere

5 1 Fundamental Solar inputs (2/3) Measuring the Sun s radius remains complex. It is usually measured by determining the inflection point of solar limbs. CLV (Center to Limb Variation Pecker and Schatzman, 1959) contains information about solar photosphere that can not be derived from observations of the disk center: - At the limb, the optical depth of the solar atmosphere steeply decreases and becomes optically tin resulting in a drop of emerged intensity over the entire solar spectrum, - The CLV is an important characteristic to constrain/test models. Solar limb shape:

6 1 Fundamental Solar inputs (3/3) The variability of the solar diameter is more complicated to measure from the ground. There is great diversity in results. Solar radius variability Solar cycle change (a) and secular change (b) 1 mas: one milliarcseconds (0.725 km) Negative values indicate fluctuations that are anti correlated with solar activity and positive values indicate radius changes that are in phase.

7 PICARD is a French space scientific mission. Its objectives are: 2 Scientific objectives of the PICARD mission (1/1) The study of the origin of the solar variability - To measure the solar diameter and shape with an accuracy of few milliarcseconds (few km) - Oblateness measurement of the Sun The study of the relations between the Sun and the Earth's climate Helio seismology - Detection of sun oscillations: mode between 1 µhz to 10 mhz, forecast by theory - Knowledge of the dynamics of the radiative zone and thermonuclear core, and in particular study of the role of the magnetic fields - Requires very long integration times (several months) requiring permanent visibility of the sun during these periods Detection of sun spots à contribution to forecast solar storms

8 3 The space instrument SODISM of the PICARD mission (1/4) SODISM (SOlar Diameter Imager and Surface Mapper), is an 11-cm Ritchey-Chretien imaging telescope developed at CNRS by LATMOS (ex. Service d Aéronomie) associated with a 2Kx2K Charge-Coupled Device (CCD), taking solar images at five wavelengths. CNRS has designed, manufactured and tested a very high dimensional stability telescope. PICARD was launched on June 15, 2010 on a Dnepr-1 launcher. SODISM main characteristics: - Telescope type: Ritchey Chretien - Focal length: 2626 mm - Dimensions: 300x308x370 mm 3 - Mass: 27.7 kg - Power (SODISM and PGCU): 43.5 W - Data flow: 2.2 Gbits per day Orbit: - Sun Synchronous Orbit - Ascending node: 06h00 - Altitude: 735 km - Inclination: Eccentricity: 1.04x Argument of periapsis: 90

9 3 The space instrument SODISM of the PICARD mission (2/4) SODISM optical path and interferential filters characteristics Field of view: - 35 arcminutes Angular resolution: arcseconds Measurement precision: - Few mas per image Wavelength λ in nm Bandwidth Δλ in nm Function Sun activity, O3, measurement, diameter Active regions observation Diameter, oscillations (helioseismology) Diameter Diameter

10 3 The space instrument SODISM of the PICARD mission (3/4) Solar images are recorded every minute with SODISM and processed on-board. They are compressed before being transmitted. PICARD / SODISM 215 nm PICARD / SODISM 393 nm

11 3 The space instrument SODISM of the PICARD mission (4/4) The PICARD/SODISM images the solar atmosphere and reveal the solar atmosphere. PICARD / SODISM 535 nm PICARD / SODISM 607 nm

12 4 Transit of Venus 2012 (1/2) The next transit of Venus will occur on June 5-June 6 in 2012, succeeding the previous transit on June 8, The "Venus transit» is a rare celestial event. Visible Venus Real color Venus image UV Venus False color UV Venus image Transit of Venus Animation Credits: R. Nunes/NASA Credits: R. Nunes/NASA Source NASA: SEC/Gen_SEC/IP/Transit.mpg Transit of Venus NASA's Sun-observing TRACE spacecraft Source NASA: venus_transit/uv1600_eastlimb.mov

13 4 Transit of Venus 2012 (2/2) The apparent crossing of Venus in front of the Sun will be observed with PICARD/ SODISM at different wavelength (215 nm, 393 nm, 535 nm, 607 nm and 782 nm). VENUS TRANSIT CONTACT VENUS TRANSIT CONTACT June 5, 2012 from 10:00 p.m. to 10:40 p.m. (UTC): - We will take an image per minute - Wavelength: 607 nm - 41 images June 6, 2012 from 04:20 a.m. to 05:00 a.m. (UTC): - We will take an image per minute - Wavelength: 607 nm - 41 images VENUS TRANSIT June 5, 2012 from June 6, 2012 : - Wavelength: 215 nm 2 images - Wavelength: 393 nm 20 images - Wavelength: 535 nm 20 images - Wavelength: 607 nm 21 images - Wavelength: 782 nm 20 images

14 5 Conclusion (1/1) - Interest 1: Technique in exoplanet search (Intensity variation) Measurement of the characteristics of the decrease in brightness of the Sun obscured by Venus (techniques implemented in exoplanet search). These test methods help to detect exoplanet and their atmosphere (refraction and absorption). - Interest 2: Atmosphere and refraction effect Venus is surrounded by an atmosphere. We want to make observation of horizontal refraction of the atmosphere of Venus. SODISM observations in several wavelengths (215 nm, 393 nm, 535 nm, 607 nm, 782 nm). - Interest 3: Solar Diameter, shape and limb darkening function by the transit method This is to make a determination of the solar diameter, shape and limb darkening function (Center to Limb Variation) by the transit method (adjusting the light curve in the area around Venus by a theoretical curve taking into account limb darkening function). - Interest 4: SODISM Point Spread Function (PSF) and scale factor of the telescope Determination of SODISM PSF depending on the position of Venus on the solar disk: we look at how the flow varies in the pixels near the disk of Venus. - Open to suggestions