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Transcript
ACRIM and ATLAS-1
FAUST and ATLAS-1
Mike Lampton
Space Science Lab
UC Berkeley
September 2012
Understanding the Sun
http://acrim.com/Educational%20Material.htm
• All life on Earth depends on sunlight
• The sun is a slightly variable star! (Why?!)
– Sunspot cycles; Maunder minimum; Little Ice Age...
– What are all the other short and long term cycles?
• Variations in the sun’s spectrum
– Controls what altitudes on Earth sunlight is delivered
– Crucial separate drivers to climate & climate change
– SOLSPEC (aboard ATLAS; EURECA; ISS-Columbus); SORCE/SIM...
• Variations in the sun’s total irradiance
– ACRIM; SOLCON; SOHO/VIRGO; SORCE/TIM;
– “Absolute”: need electrical & mechanical calibration but not thermal
M. Lampton UCB SSL 2012
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What is going on?
Solar drivers:
sunspot cycles & TSI
variations in spectrum
Earth orbit (Milankovich) drivers
Precession cycle 26000 years
Elliptical orbit rotation 21000 year
Obliquity period 41000 years
Worldwide climate:
Radiative
a nonlinear chaotic system cooling
complex radiation budget
Tectonic drivers:
continental plate motions
ocean - land latitude coverage
volcanism: SO2, sulfates, ash...
Anthropogenic influences
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Thermal Balance Method: can achieve absolute error <0.01%
Solar heating power = TSI ∙ Area
Electrical heating power = V∙I
At null, TSI = Δ V∙I/Area
Mechanical standard: aperture A
Electrical standards: V and I
solar
heat
moveable
shutter
aperture
area = A
meter
cone 1
data out
cone 2
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•
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•
•
bias power supply
meter
data out
power amplifier
ΔT
null signal
isothermal enclosure
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Also: short-term missions: cross calibration
Spacelab 1 (1983)
ATLAS 1 (1992)
ATLAS 2 (1993): comparison SARR2
Spacelab ACRIM
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Solar Irradiance and Spectra are studied worldwide....
from “Measurement And Uncertainty Of The Long Term Total Solar Irradiance Trend,” Steven Dewitte, Dominique
Crommelynck, Sabri Mekaoui and Alexandre Jouko, Royal Meteorological Institute of Belgium, (2004)
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Transit of Venus
5 June 2012
This “transit method” for discovering planets has been in
continuous use since 2009 with the KEPLER mission: so
far 2200 planet detections made, and 77 confirmations.
HINODE image of sun JAXA/NASA
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Historical Proxies for TSI
• Total Solar Irradiance goes back ~ 30 years
• Sunspots: go back ~ 400 years
• Rates of growth of tree rings ~ 1000 years
• 14C and 10Be content of organic matter: yet further back
http://en.wikipedia.org/wiki/Maunder_Minimum
Great Frost of
1709
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Ultraviolet Astronomy and FAUST
• Astronomy at visible wavelengths...
– easily done at night through Earth’s atmosphere
– shows stars & galaxies under usual “main sequence”
evolutionary circumstances
• Astronomy at ultraviolet wavelengths...
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reveals fluxes & spectra of very hot (short-lived) stars
reveals properties of interstellar gas and dust
starbirth: massive, very hot short-lived stars; OB’s
star death: fuel exhaustion; WDs;
variable galaxies; AGNs, BL-Lacs, LINERS, QSOs....
but of course requires spaceborne platforms.
Frequent access to space speeds technology.
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UV Space Astronomy
excluding solar
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What was FAUST?
• Created by L.A.M. as a rocket-borne UV camera for studies of
nearby galaxies and especially star formation
– used a UV intensifier and a photographic film recording canister
• Adapted by L.A.M. and UCB for Spacelab 1 (1983)
– same UV intensifier and a photographic film recording canister
– unfortunately SL1 β-angle did not permit dark nights
• Remanifested on ATLAS-1 (1992) for an enlarged program
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Motive: star formation in our Galaxy and in other galaxies
total scientific success; 21 papers and all objectives met
allowed us at UCB to develop a new kind of photon counting imager
Spacelab HRM permitted high rate digital photon downlink
legacy for future UV missions: photon counting imager technology
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FAUST ATLAS-1 Mission Highlights
•
Overall: 4.4% of the night sky was covered
– 19 deep fields, 4698 objects measured; fluxes &
locations for all targets
– 2239 of them are stars; others are galaxies,
nebulae, or unidentified
– Ten times more sensitive than previous UV
catalogs
– Bowyer, S., et al., ApJS v.96, 461 (1995)
– eleven other papers on sources, maps,
identifications
•
Observations of the diffuse UV sky
– Cohen, M., et al., ApJ v.427 848 (1994)
•
Observations of terrestrial UV nightglow
– Chakrabarti, S., et al., GRL v.20 535 (1993)
•
Observations of the STS UV environment
– Lampton, M., et al., GRL v.20, 539 (1993)
•
FAUST sensor technology development
– Lampton, M., et al., Proc SPIE 627, 383 (1986)
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Andromeda galaxy at visible wavelengths
... and in the ultraviolet using GALEX
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Hubble Space Telescope and its Upgrades
Launch SM1
SM2
SM3a
SM3b
STS31 STS61
STS82
STS103
STS109
Apr1990 Dec1993 Feb1997 Dec1999 Mar2002
SM4
STS125
May2009
Photon counting
Photon counting
Photon counting
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Photon-counting image sensor concept -- now flying on many missions
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Future of Ultraviolet Astronomy
• Astonishing developments in Cosmology
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1929: Hubble and the expanding universe
1933: Zwicky and missing mass. (Now: not even baryonic mass!)
1963: Penzias & Wilson: cosmic microwave background & hot Big Bang
1990: COBE satellite and gradients in the CMB; seeds for growth
1998: Perlmutter; Riess; accelerating universe. Dark energy!
Picture emerges: denser regions collapsed first, then outer regions followed
Star formation peaked at redshift ~ 2, and continues to this day. UV traces it.
• Cosmology is now pressing hard on reconciling gravity, space, time....
• Beyond that: stars, planets, nebulae, SNe, ISM, IGM....
• Future UV space observatories?
– ASTROSAT (India)
– World Space Observatory WSO (Russia; ESA; Spain)
– Space Ultraviolet Observatory SUVO (NASA)
– ATLAST (NASA + ESA)
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