Instrumentation forhelioseismology
T.AppourchauxInstitut d’Astrophysique Spatiale, Orsay, FranceContent• The novelty with Plan-A• Helioseismic instrumentation• What can be done for Plan-A ?
• Conclusion

Nishikawa et al (1986)

The novelty: stereoscopy• Idea originates back from the 80’s for avoiding spatial
gaps (full hemisphere instead of half hemisphere)• Best way to probe the core (besides g-mode detection)• What is the best instrumentation?
– Resolution, observable, angle separation (TBD)• At least another instrument required (SDO, Solar orbiter)

Helioseismic instrumentation• Ground based:– Global Oscillation Network Group (GONG)– Taiwan Oscillation Network (TON)– Magneto-Optical filters (LOWL, ECHO)• Space based:– Luminosity Oscillations Imager (LOI / SOHO)– Michelson Doppler Imager (MDI / SOHO)– Solar Optical Telescope (SOT / Hinode)– Helioseismic and Magnetic Imager (HMI / SDO)
– Polarimetric and Heliseismic Imager (SO / PHI)

Instruments

Array

Pixel(in arcsec)

Pupil(in cm)

Wavelength(in nm)

TechniqueGONG

1k x 1k2.5

2.8

676.9 (Ni I)

Velocity(tachometer)TON

1k x 1k

1.89K line

Intensity

ECHO

0.7k x 0.1k25

1770 (K)

Velocity (MOF)

LOI

16 (total)

480

5500

Intensity

MDI

1k x 1k212.5

676.9 (Ni I)

Velocity(tachometer like)

SOT / BFI

4k x 2k

0.05

50

Ca II, R, G, B

Intensity

SOT / NFI

4k x 2k0.08

50

Mg IIb, Fe I

Velocity(Lyot)

HMI

4k x 4k0.5

14617.3 (Fe I)

Velocity(tachometer like)

PHI / HRT

2k x 2k0.5

14617.3 (Fe I)

Velocity(Fabry-Perot)

PHI / FDT

2k x 2k3-6

1617.3 (Fe I)

Velocity(Fabry-Perot)

Instrument

Mass(kg)

Telemetry(kbps)

Power(Watt)

Dimensions
(cm3)

Built

LOI

2.5

0.01

2.530 x 9 x 9

ESA / SSD

MDI

56.5

5 - 160

3878 x 40 x 24(OP)Stanford /Lockheed

SOT

46 (OP)

1400--

Japan / USA

HMI

455000060

118 x 53 x 24(OP)Stanford /Lockheed

PHI

30.5

203575 x 40 x 29(OP)MPS / INTA /IASWhat can be done for Plan-A ?
••Solar radial velocity:– Better signal-to-noise ratio (300)– Low-frequency modes– Polarimetry as a « by-product »– Wavelength stability demanding– Large space experience– Require a lot of glass (mass)
Intensity:– Lower signal-to-noise ratio (30)– High-frequency modes– No polarimetry– Photometry not very demanding– Space experience– Light

Solar Radial Velocity for Plan-A ?
••

•

•

LYOT / Michelsons:– Well space proven but heavy (>30 kg, <20kg ?)LYOT only– Space proven (besides the bubbles) but heavy?
– Several wavelength (if UBF like)
Magneto-Optical Filters– Not space provenbut Na cell aboard SOHO (GOLF)– Various gases: Na, K, Ca, He– Require magnets (2 of them, heavy?)– No moving partsFabry-Perot– Space proven (but not for solar physics)– Light if Lithium Niobate is used (solid etalon)– Several wavelengths

Intensity for Plan-A ?
•Various wavelength and various passbands– All space proven– Light– Use of CCDs, photodiode or APS

What can be done for Plan-A ?
••••A strawman design:– Entrance pupil of 10 cm dia (1 arcsec resolution)– Detector: at least 4k x 4k (10 µm pitch)– Full disk
Observables:– Velocity: various wavelengths– Intensity: wide passbands
Several instruments:– 2 different wavelengths / heights for velocity– 1 wavelength for intensity
Mass / ressources:– Total 25 kg for 1 instrument or 3 instruments?
– If 3 instruments: 10 kg for each wavelength (realistic?),
2 kg for intensity (well feasible)

Conclusion•••••

Ressources will drive the design (not new),especially mass
Solar radial velocity preferred…but intensity easier
Do we want to do a better-than instrument?
Stereoscopy:– What is the best instrumentation?
– At least another required (SDO, Solar orbiter)

Comments on mission profile•> 45 deg: 70 deg after 10 years of Scenario A_Ballistic
1: THANK YOU !

•Observation during cruise phase : YES !

•Circular orbit: BETTER !

Plan A vs Plan B• Competition with an other mission in Japan?
– If no, Solar-C could also be appealing tosolar physicists outside Japan– If yes, Solar-C must be appealing to nonsolar physicists in Japan