Werner Schmutz PMOD/WRC, Switzerland TOSCA Workshop Berlin, May 14, 2012 Measurements of TSI and...
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![Page 1: Werner Schmutz PMOD/WRC, Switzerland TOSCA Workshop Berlin, May 14, 2012 Measurements of TSI and SSI.](https://reader036.fdocuments.us/reader036/viewer/2022081513/5517e307550346cb568b45cc/html5/thumbnails/1.jpg)
Werner SchmutzPMOD/WRC, Switzerland
TOSCA WorkshopBerlin, May 14, 2012
Measurements of TSI and SSI
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Werner Schmutz 2
Overview
14. May 2012
• Total Solar Irradiance
• Absolute calibration (first light PREMOS)
• Composites (relative calibration)
• Spectral Solar Irradiance (SSI)
• SIM/SORCE
• VIRGO/SOHO
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PICARD
PREMOS – SOVAP – SODISM
Werner Schmutz 314. May 2012Total Solar Irradiance
Filter Radiometers
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Werner Schmutz 4
TSI calibration
14. May 2012
PREMOS A is the first and only radiometer in space with a SI-traceable irradiance calibration in vacuum
Traceable to the irradiance calibration facility at LASP in Boulder (TRF)
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Werner Schmutz 5
Traceability of PREMOS-TSI
14. May 2012
PREMOS B
Comparison to cryogenic rad.
(power in vacuum)
NPL
Comparison to cryogenic rad.
(power and irradiance in
vacuum)TRF @ LASPPREMOS A3
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Werner Schmutz 6
Uncertainty of the calibration
14. May 2012
+ absolute uncertainty of TRF facility (70 ppm)
= uncertainty of TRF comparison (220 ppm)
PREMOS APREMOS A
TRF radiometerTRF radiometer
![Page 7: Werner Schmutz PMOD/WRC, Switzerland TOSCA Workshop Berlin, May 14, 2012 Measurements of TSI and SSI.](https://reader036.fdocuments.us/reader036/viewer/2022081513/5517e307550346cb568b45cc/html5/thumbnails/7.jpg)
Werner Schmutz 7
Calibration uncertainty budget
14. May 2012
Traceable via TRF, LASP, Boulder to NIST
• Irradiance in vacuum PREMOS A uncertainty: ± 280 ppm
(± 0.4 W/m2)
Table compiled by Greg Kopp for an ISSI workshop March 2012
Flight-spare recalibrations
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Werner Schmutz 814. May 2012
Comparison PREMOS – TIM
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Werner Schmutz 9
Status of PREMOS-TSI
14. May 2012
„PREMOS is in excellent health“
o PREMOS-TSI is the most accurate absolute measurement;
±0.4 W/m2 or ±290 ppm
o After 2 years, PREMOS-TSI has at most 50 ppm relative deviation to TIM/SORCE.
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The Future of TSI observations:Are relative observations sufficient?
Werner Schmutz 1014. May 2012
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Werner Schmutz 11
There are three TSI composites
20.12.2011
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TSI-composites normalized
Werner Schmutz 1220.12.2011
!normalized 2004-2005
DIARAD
PMOD, ACRIM
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Composite 1996-2010
Werner Schmutz 1314. May 2012
!0.2 W/m2
± 0.2 W/m2 / 10-years
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Werner Schmutz 14
Is there a long-term trend?
14. May 2012
Fröhlich 2009, A&AL 501, L27-L30
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Werner Schmutz 15
Could we detect a long-term trend with a composite?
14. May 2012
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Werner Schmutz 16
Requirements for a TSI monitoring
14. May 2012
„Any plan to rely on an unbroken chain of measurements is broken“
o Not only because of a potential gap;o But mainly because of the uncertainty
is continuously increasing with time !
Accurate absolute measurements are required !
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Werner Schmutz 17
Requirements for a TSI monitoring
14. May 2012
Accurate absolute measurements are required: Nowadays possible !
But we certainly also want to assess the variations of TSI and therefore, we still need to aim for continues and overlapping data !
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Werner Schmutz
TSI monitoring today …
1814. May 2012
Presently, 4 operational space experiments observing TSI:
- VIRGO (launched 1995)- ACRIM III (launched 2000)- TIM (launched 2003)- PREMOS (launched 2010)
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Part II:Spectral Solar Irradiance
Werner Schmutz 1914. May 2012
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Werner Schmutz 2014. May 2012
The open question !
Is the SIM observation really correct?
Or is it rather a degradation problem?
The bands 410-470 and 480-730 nm are anti-correlated to TSI variations
Compensated by larger (than TSI) UV variations
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Werner Schmutz 2114. May 2012
Anti-correlation in models
Contrast between active and quite Sun (SSN 150 vs SSN 0)
Black: Bright+DarkRed: bright componentsBlue: dark components
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Werner Schmutz 2214. May 2012
VIRGO and PREMOS bands
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Werner Schmutz
215 nm PREMOS vs SOLSTICE
2314.05.2012
Independant correction of PREMOS
Strong correlation of13.5 and 27 days modulation
PREMOS sampling is faster Rotational modulation more accurate
PREMOS
SOLSTICE
PREMOS
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NIST SSI workshop, February 2012
VIRGO SSI time series 1996 - now
Christoph Wehrli & VIRGO TeamPMOD/WRC Davos
An attempt to assess instrument degradation in a self consistent way by:
• referring operational measurements to occasional backup operations
• correcting the backup channel by initial ageing of operational channel
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NIST SSI workshop, February 2012
VIRGO Sun Photometers
• Interference filter radiometer with 3 channels centered at 862nm, 500nm and 402nm (R,G,B); FWHM bandwidths 5nm; silicon PD detectors; rad-hard windows.
• Active (SPM-A) and Backup (SPM-B) instruments– SPM-A: exposed continuously for helioseismology
application– SPM-B: exposed rarely for solar spectral irradiance
measurements• Calibrated by EG&G FEL lamps, NBS 1973
traceable
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NIST SSI workshop, February 2012
VIRGO SPM: Level1 data
1996 1998 2000 2002 2004 2006 2008 2010 20120
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
spec
tral
irra
dia
nce
[W
m-2
nm
-1]
VIRGO SPM-A
70%
20%
5%
Sen
sitivity after 5825 days
1996 1998 2000 2002 2004 2006 2008 2010 20120
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
spec
tral
irra
dia
nce
[W
m-2
nm
-1]
VIRGO SPM-B
Number of Backups 178Total exposure time 2.6 days
SPM-B:Number of backups 178Total exposure time 2.6 days
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NIST SSI workshop, February 2012
1996 1998 2000 2002 2004 2006 2008 2010 20120.990
0.992
0.994
0.996
0.998
1.000
1.002
1.004
1.006
1.008
1.010
rel.
Var
iati
on
(T
SI*
5)
VIRGO SPM-B and TSI
Raw variations of SPM-B
VIRGO-SPM-B changes are about 5 times larger than the (real) solar variations in TSI.
Solar cycle 24 SSI variation is not obvious (smaller), hidden in instrumental ageing.
5*(TSI/<TSI>) - 4
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NIST SSI workshop, February 2012
Initial ageing of SPM-A
Steep degradation during first hours!
17.Jan 18.Jan 19.Jan 20.Jan0.990
0.995
1.000
1.005
1.010
1.015
1.020
1.025
1.030
1.035
Date 1996
rel.
Var
iatio
n
VIRGO SPM-A First Light
Linear degradation during first month
{Commissioning activities until 29.03.1996}
28.Jan 04.Feb 11.Feb 18.Feb 25.Feb 03.Mar0.990
0.995
1.000
1.005
1.010
1.015
Date 1996
rel.
Var
iatio
n [T
SI*
100]
VIRGO SPM-A Operational
∂TSI (*100)
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NIST SSI workshop, February 2012
Ageing of SPM-A and SPM-B versus exposure time
0 0.5 1 1.5 2 2.50.985
0.990
0.995
1.000
1.005
1.010
1.015
exposure time [d]
rel.
Var
iatio
n
VIRGO SPM A & B
polynomial fit SPM-A
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NIST SSI workshop, February 2012
SPM-B corrected by operational degradation of SPM-
A
Instrumental effects dominating over solar cycle
1995 1997 2000 2002 2005 2007 2010
0.992
0.994
0.996
0.998
1.000
1.002
1.004
1.006
1.008
rel.
Var
iatio
n
VIRGO SPM-B corrected for SPM-A operational degradation
1%
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NIST SSI workshop, February 2012
Empirical Approach
• SSI timeseries represent a mixture of Solar Cycle and instrumental effects
• Active & Backup SPM degrade differently in time or exposure time
• Linear correction accounts for probable decline of SSI, i.e. first order estimation of instrumental effect.
• Exponential correction eliminates most of solar cycle variation as well
2000 2002 2004 2006 2008 2010 20121.815
1.820
1.825
1.830
SP
M-B
500
[Wm
-2n
m-1
]
VIRGO SSI
0.5%
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NIST SSI workshop, February 2012
Linear vs. Exponential Detrending: what does it to
TSI ?
1000 2000 3000 4000 5000 6000
1363.0
1364.0
1365.0
1366.0
1367.0
1368.0
MissionDay
TS
I
1000 2000 3000 4000 5000 6000
-3.0
-2.0
-1.0
+0.0
+1.0
+2.0
MissionDay
TS
I (re
sid
ual
s)
1363 1364 1365 1366 1367 1368-2.5
-2.0
-1.5
-1.0
-0.5
+0.0
+0.5
+1.0
+1.5
TSI
TS
I (re
sid
ual
s)
Lslope 0.54 [ 0.47 0.62]Eslope 0.32 [ 0.27 0.36]
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NIST SSI workshop, February 2012
Linear Detrending 2000-2012
1000 2000 3000 4000 5000 60001362
1364
1366
1368
MissionDay
TS
I
1000 2000 3000 4000 5000 6000-5
0
5
MissionDay
SS
I500
(res
)
1363 1364 1365 1366 1367 1368-5
-4
-3
-2
-1
0
1
2
3
TSI
SS
I500
(res
idu
als)
slope 1.20 [ 1.02 1.38] [1/µm]
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NIST SSI workshop, February 2012
Summary
Normalization of SPM-A by SPM-B:– Larger than expected variations of Backup channel
“instrumental effects”• Rapid initial degradation in Active channelversus• ‘Early increase’ of Backup (not observed in operational
channel)
Empirical correction of SPM-B: fitting degradation in time with:
– Linear or exponential detrending yields positive correlation with solar cycle (TSI) in
all 3 visible channels !!!
None of VIRGOS’s wavelength bands 862 nm, 500 nm, 402 nm
isanti-correlated to TSI variations
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Thank you for your attention
Werner Schmutz 3514. May 2012
PREMOS PICARD
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NIST SSI workshop, February 2012
Alternative analysis including proxies
(C. Fröhlich, EGU 2011)
Empiric correction versus Time (double exponential), Temperature (linear + Boltzmann), TSI and Mg-II Index.
SORCE