Payload & Data Rate
for Option-A
H. Hara（NAOJ)
JAXA SOLAR-C WG
2010 Mar 9

Requirements for S/C System Design• Sojourn time >40 days (TBD) for a solar latitude of >30 deg (TBD)– Target of max. latitude : ~40 deg (higher is better, of course)– Need to define these numbers clearly from evaluation through helioseismic
model calculations• Distance to the Sun in the final orbit: 1.0 AU– Minimum distance to the sun is 0.7 AU from the thermal-design point of view
– Maximum distance to the sun is not defined because of a possibility ofballistic orbits by Jupiter swing-by• Use 7 deg tilt angle of the solar rotation axis to the ecliptic plane• Duration of cruise phase to the final orbit: ~5 years– Need 40-days (TBD) observations near perihelion/aphelion points
in the cruise phase• Payload weight: 130 kg• Data recording rate: >100 kbps ave.
• Mission life:
cruise phase N0~5 yr + N1 yr + extended duration N2 yr (total ~N3 yr)

Visible-light Magnetic-field andDoppler imager• Full-disk imager like SOHO MDI or SDO HMI~1” spatial resolution [ MDI: 55 kg, HMI: ~70 kg ]• Will require multiple wavebands for the first mapping ofpolar regions• Need on-board processing to reduce the amount of data
SDO HMI• Vector magnetic fields
mandatory?
[ probably yes, but uncertain ]• Lighter option possible?

X-ray / EUV Telescope• G.I. X-Ray Telescope：– Difficult to achieve a high-spatial resolution bya limited instrument mass.
– Hinode XRT 46 kg, Yohkoh SXT: 24 kg– Worthwhile for a low-resolution imaging? Probably no.

• EUV telescope:– STEREO EUVI: 7.7 kg excluding electronics– Scanning-spectrograph may become a substitute fordynamic events in a small FOV?

STEREO EUVIEUV Imaging Spectrograph• Possible to make an imaging spectrograph of a similar
performance by half-scale size of EIS• Optics is similar to that of the UV/EUV spectrograph inOption-B (Plan-B)• A better sensitivity (by a factor of 4-10) than EIS/SUMER
will be possible with a similar spatial resolution. This is quitea new instrument.
• Similar spectrograph is proposed as SPICE in Solar Orbiter.
• Become a substitute for a small-FOV imager: partially Yes• Shimizu san will report its optics in the next presentation.

TSI monitor• Space Heritage (not in Japan)

ACRIM/SMM

VIRGO/SOHOTIM/SORCE• Require multiple cavities for self-calibration• mass ~10 kg (ACRIM, TIM);
Need light-weight solution• Data recording rate << 1kbps (negligible)

Heliospheric Imager• STEREO-HI: sufficient sensitivity
Parker-spiral structures in solar wind may be detected asdensity inhomogeneity• Zodiacal light distribution
will be obtained when looking
at opposite side to the ecliptic plane• Data size becomes small by
on-board integration.
STEREO-HI: ~1kbps

STEREO-HI 13.4 kg
Visible-light range

in-situ measurements?
• Have not discussed with heliophysics group• Wind velocity, magnetic field, cosmic rays
– B-field measurement will not be possible inSEP-option orbit (by use of permanent magnet)• Gain/advantage from Ulysses?
– ans. Periodic fast scan in the 11-yr activity cycle
SOLAR-C Option-A S/Cin-situ measurements

Magnetic Filed Line

Remote-sensingimaging/spectroscopic
observations

Magnetometer: ~ 2 kg
Need a boom of exclusive use?
SunEarthOption-A model payload
mass crude allocation
including electronics package• Doppler/Magnetic field imager like HMI: 70 kg( MDI: 55 kg )• Imaging Spectrometer like SPICE: 30 kg• X-ray/EUV imager: 15 kg• TSI monitor: 5 kg• Electronics like Hinode MDP?
: α120 + α kg
Options• Heliospheric imager• In-situ instruments and others: 10 kg: 10 kg

Contamination monitor may be required near the aperture of telescopes
for the use of ion engine systems.

Requirement
for average data recording rate
• Data Recording Rate: ~100 kbps (Total)• Estimation for a model case (very preliminary)– Helioseismology/B-field observations ~ 50kbps- Study on compression not enough– 256×256(pixels) ×16(bit/pixel) - Higher compression used in Hinode×0.4(comp.)/60(s)/1024(kbps/bps) = 6.8 kbps ave.
– without on-board processing: 6.8 × number of λ positions• Global helioseismology• Local helioseismology– 1024 ×1024 ×16 ×0.4 /60(s)/1024 = 109 kbps ave.

• Magnetic (B) field– 1024 ×1024 ×16 ×0.4 /3600(s)/1024 ×4(pol.state) = 7.3 kbps
– 512 ×512 ×16 ×0.4 /60(s)/1024 ×2(pol.state) = 54 kbps

– EUV imaging spectroscopy ~20 kbps ave.
– EUV/X-ray imaging ~20 kbps ave.
– TSI monitor: <1 kbps, negligible– Heliospheric imager ~ 1kbps by on-board summing– Others: probably negligible