THE PICARD mission
Gérard Thuillier1, Steven Dewitte2, Werner Schmutz3,
and the PICARD team4
1 LATMOS-CNRS, France
2 Royal Meteorological Institute of Belgium
3 Physikalisch-Meteorologisches Observatorium Davos, Switzerland
4 CEA, CSA, IAS, Obs. Meudon, OCA, Yale
Outline
Fundamental measurements for Solar Physics
PICARD scientific objectives
PICARD measurements
PICARD Solar and Climate modeling
PICARD launch date
ESA, Bruxelles, May 2010
FUNDAMENTAL SOLAR INPUTS
Parameters that are key constraints for validating the physics of solar interior
models:
- Solar diameter, limb shape, asphericity in the photosphere
- Total solar irradiance (TSI)
- Oscillation modes
- Temperature
- Solar spectrum
and their variability
SUN GLOBAL PARAMETERS
Total Solar Irradiance
Solar
luminosity
UARS, SoHO, SORCE, SOLAR,
…
PSPT
Solar oscillations
Asphericity, dif. rotation
Internal
structure
SoHO, and ground network, SDO
Solar spectrum
Solar limb
Composition
Temperature
ATLAS, UARS, SORCE, SOLAR
Solar diameter
Internal
structure
SDS, ground-based
instruments
Photosphere temperature
Variability of these quantities is a key input for the study of the internal Dynamics,
In particular for the convective zone.
SITUATION OF THE SOLAR DATA
Among the previous quantities, the solar diameter is the least reliable.
Several reasons may explain the discrepancies and lack of reliability:
- Measurements on the ground, which introduces the effect of the Earth’s
atmosphere.
- Instrumental effects (sampling, psf, wavelength domain…)
- Absence of angular reference inside the instruments
- Data processing
PICARD MISSION MAIN SCIENTIFIC OBJECTIVES
(1) Modelling of the solar machine
using simultaneous measurements of several fundamental solar
properties and their variability.
Role of the magnetic field, on surface or deeper in the convective
zone. Origin of the solar activity?
This is an essential objective. Results are applicable to all planetary
atmospheres.
(2) Contribution to solar luminosity reconstruction
(3) Long term trend using the solar diameter refered to stars angular
distances
(4) Understanding of the ground based measurements
(5) Contribution to Space Weather
A strong synergy with several other solar missions is anticipated.
THE PICARD MEASUREMENTS
To achieve the PICARD objectives, the following measurements will be made:
- TSI by two independent radiometers,
- Bolometric measurements (unscaled TSI),
- Solar oscillations (Helioseismology),
- Diameter, asphericity and limb shape measured in the solar photospheric continuum
using an imaging telescope incorporating an angular reference,
The absolute diameter will be referred to a set of angular distances of
9 couples of stars for future use.
- Spectral irradiance at several wavelengths using photometers with redundancy,
- Observations from ground and stratospheric balloon.
INSTRUMENTS FOR THE PICARD MISSION
In orbit:
Two radiometers of different type allow to discriminate between variations of
instrumental origin and of solar origin. PICARD uses the same configuration
as SoHO with the DIARAD instrument (IRMB) and the PMO6 instrument
(PMOD-WRC).
- BOS: high precision bolometric measurements, OR(B)
- PREMOS: radiometer and 3 sunphotometers, PMOD(CH)
- SODISM: metrological imaging telescope, LATMOS(F)
- SOVAP: radiometric measurements, IRM(B)
Instruments take into account the heritage of the instruments previously
designed for these measurements.
.
ACCURACY AND PRECISION OF THE MEASUREMENTS
Diameter and asphericity: using an image in the
continumm and a 2Kx2K CCD, numerical
simulation shows that 3 mas precision are
achievable per image.
PSPT image at 607 nm
TSI: The two type of radiometers ensure continuity with SohO.
Stability: 0.04W/m2; accuracy: 0.8W/m2.
Spectral irradiance: stability 0.2 %, accuracy 5%
ASSOCIATED MEASUREMENTS WITH PICARD
On the ground:
At an observatory (Calern or OHP), SODISM II measures the solar diameter, and limb
shape. MISOLFA measures the local turbulence, and a set of instrument characterizes
the atmosphere (minor constituent, aerosols liquid and solid).
A collaboration with PSPT network and Observatoire de Meudon is foreseen
providing images at 607 and 393 nm.
On board a stratospheric balloon: The Solar Disk Sextant (SDS)
This instrument flew four times on board stratospheric balloon. It showed the
anticorrelation between the diameter and solar activity variation (Egidi et al. 2005,
Djafer et al, 2007).
A first flight was achieved on 17 October 2009. It constitutes a reference for diameter,
asphericity and limb shape obtained at low solar activity given the launch PICARD
scheduled for 15 June 2010.
Regular SDS flights would bring validation of space measurements and would allow to
extent the observation after the PICARD mission completion.
PICARD MISSION updates (2/3)
Djafer, Thuillier, Sofia, 2007.
A new processing of the SDS data show similar variation with time. However, the
diameter is larger as an effect of the FFTD filtering processing (choice of the
parameter a).
PICARD MISSION AND MODELING
Solar Modeling
The 2D convective zone modeling is working at Yale as well as at CEA.
The dependence of the diameter with solar activity may be predicted
(Sofia et al. 2005).
Limb modeling
Climate modeling
Models: LMDz (F), CMAN (Ca), FASTOC (Ca), SOCOL (Ch)
in which the solar variability is introduced and stratosphere-troposphere
coupling.
SOLAR ATMOSPHERE MODELS
VALC (Vernazza, 1981), SH09 (Short and Hauschild, 2010), FCH09
(Fontenla et al, 2010), COSI (Shapiro et al., 2010) models for quiet sun conditions.
Electrons density, left panel; temperature, right panel
-5
2
x 10
1.8
Intensity(cm-2s -1Hz -1sr-1)
1.6
800 nm
1.4
1.2
1
600 nm
0.8
0.6
0.4
0.2
0
-500
400 nm
0
500
Distance (mas)
1000
Limb shapes for three wavelengths predicted by four current solar atmosphere models
SH09 (red), FCH09 (black), VAL-C (blue), and COSI (green)
PICARD AND CLIMATE: LUMINOSITY RECONSTRUCTION
Two possibilities are:
1) If PICARD determines the diameter (R)/luminosity (L) relationship, the best
historical diameter determination as provided by eclipses, will be used. Eclipse
of 1715 presents an important opportunity.
W = ∆ log R/ ∆ log L
2) Solar modeling by use of the fundamental solar parameters measured by
PICARD
Convection (oscillations modes)
Development of the magnetic field constrained by the diameter and
asphericity
Role of turbulence also constrained by diameter and asphericity
In this approach the solar model will be coupled with a model of the solar
atmosphere constrained by the solar limb shape and TSI measurements.
PICARD MISSION LAST UPDATES
Instruments: The three instruments are at CNES Toulouse integrated phase on the
spacecraft. The whole is ready for shipping.
Characterisation measurements are taken as much as possible.
Start of the launch campaign: 19 May 2010.
Launch date: 15 June
Operation during the commissionning phase are defined.
The data processing center is ready for operation. Several rehearsal were made.
Orbit: sunsynchroneous at 725 km altitude. Accuracy of injection: better than 0.03
arcdegree in order to minimize the eclipses occurrence.
MAIN IMAGE - AUXILIAIRY IMAGES
Prism dispersion
1
calibration distance
2
4
1
3
2
PUPILLE
MAIN
FAISCEAU
PRINCIPAL
BEAM
4
3
PUPIL PLANE
CCD PLANE
Sun
Image at the
guiding focus
4
prisms
4 guiding
detectors
Entrance
Interference filters
window
Image
on the
CCD
Image generated
by the telescope
Image after the
primary mirror
Image after the
annular mirror
SOLAR ACTIVITY
SoHO MDI continuum 676.7 nm
10 May 2010
SoHO MDI magnetogram
10 May 2010
PICARD and the solar activity
An investigation dedicated to search about the solar activity origin, needs data gathered
when the Sun activity is changing during the period of measurements. Based on the
following prediction and the launch date, PICARD mission is appropriatelly scheduled.
160
140
120
100
Série1
80
Série2
Série3
60
40
20
0
2008
2010
2012
2014
2016
2018
2020
2022
Solar activity prediction by Ken Schatten (24 March 2010). The blue prediction is the
one having the highest probability. Up to now, Ken’s predictions were exact.
PREMOS
SOVAP
SODISM
Launch:
February
2010
SDS
Ground –based instruments
Institutes providing instruments: CNRS, RMIB, PMOD-WRC, OCA
http://smsc.cnes.fr/PICARD/Fr/