1. Synergies between solar UV radiometry and imaging
Matthieu Kretzschmar °
Jean-François Hochedez °
Véronique Delouille °
Vincent Barra *
Thierry Dudok de Witte ‘
° Royal Observatory of Belgium, Brussels
* ISIMA, Clermont-Ferrand, France
‘ LPCE, Orléans, France
J.-F. Hochedez, COSPAR ’06, Beijing

2. A metaphor about multi-dimensionality
A curtain !
Dr Elephant
A snake !
A wall !
J.-F. Hochedez, COSPAR ’06, Beijing

3. Dimensions of (solar UV) observations
Effective area, calibration
& signal to noise
Cadence
Exposure time
Field of View
Spatial resolution
Temporal coverage
(Long-term and duty cycle)
Spectral range & resolution +
polarimetric diagnostics
J.-F. Hochedez, COSPAR ’06, Beijing

4. Imagers vs. spectro-radiometers
TIMED-SEE, PROBA2-LYRA…
No spatial resolution
Spectral resolution!
Inflight re-calibrated
Full Sun
More or less spectral resolution
Avoid time gaps
Good cadence & SNR
EUV Imagers
SOHO-EIT, PROBA2-SWAP…
Imaging
Optical design or rastering
Flatfield issues
Partial FOV
Multilayer passbands
Usually not 100% duty cycle
Possible polarimetry
Photon limited
J.-F. Hochedez, COSPAR ’06, Beijing

5. « the High-cadence solar mission »
Launch end 2007 (2-year mission)
60 cm x 70 cm x 85 cm, 120 kg
LEO dawn-dusk orbit
Demonstrate new space technologies
SWAP & LYRA
« the High-cadence solar mission »
J.-F. Hochedez, COSPAR ’06, Beijing
Image courtesy: Verhaert

6. The solar payload of PROBA2
LYRA
VUV, EUV & XUV radiometer
PI: JF Hochedez
LYRA.oma.be
SWAP
EUV imager
PIs: D Berghmans JM Defise
SWAP.oma.be
Sun
J.-F. Hochedez, COSPAR ’06, Beijing

7. LYRA highlights 4 channels covering a wide temperature range
nm Herzberg continuum range
Lyman-alpha (121.6 nm)
Aluminium filter channel (17-70 nm) incl. He II at 30.4 nm
Zirconium filter XUV channel (1-20 nm) (rejects strongly He II)
Traceable to radiometric standards
Calibration campaigns at PTB Bessy synchrotron
In-flight stability
Rad-hard, not-cooled, oxide-less diamond UV sensors
2 different LEDs per detector
Redundancy (3 units)
High cadence (up to 100Hz)
Quasi-continuous acquisition during mission lifetime
J.-F. Hochedez, COSPAR ’06, Beijing

8. Dec 2005 tbc
J.-F. Hochedez, COSPAR ’06, Beijing
April 2006 tbc

9. One of the 3 LYRA units
J.-F. Hochedez, COSPAR ’06, Beijing

10. SWAP highlights 1 channel at 17.4 nm, 1kx1k CMOS-APS detector
Detector and global instrument calibrated at PTB
Good cadence
1 min consistent with spatial resolution
Quasi-continuous acquisition during mission lifetime
Duty cycle limited by telemetry only
J.-F. Hochedez, COSPAR ’06, Beijing

11. PROBA2 SWAP
J.-F. Hochedez, COSPAR ’06, Beijing

12. SWAP TARGETS Dimmings EIT wave Post-eruption arcade
Target 1 min image cadence will really resolve in time events like EIT waves.
1 min is what is needed for events propagating at sonic speeds
Loop openings Plasmoid lifting
Flares
Erupting prominences
J.-F. Hochedez, COSPAR ’06, Beijing

13. How can SWAP and LYRA work together?
3,11’’
1 mn
～10s
17.5 nm
1nm FWHM
LYRA
None
～50 ms
10 ms
[0,20]nm
[17,70]nm
121.6 nm
[ ]nm
Spatial resolution:
Temporal resolution:
- Nominal:
- Optimal/max:
… x 1200
Time
0 mn
1 mn
Spectral resolution:
Wavelength

14. Spectral information 1 20 121 200 220 17 70 Wavelength (nm)
Can we use the fact that the spectral overlap between the Al & Zr LYRA channels corresponds roughly to the SWAP pass band ?
No TBC
Can we use the 4 (wide ) LYRA pass bands to model 17.5nm?
DEM-like, statistical and/or empirical methods
2 pass bands are optically thick 

15. Plasma temperatures seen by SWAP and LYRA
Zirconium
Aluminium
SWAP
Corona (cold 1MK, and ‘hot’ 10MK)
Transition region + Corona.
Corona mainly cold
LYRA & SWAP spectral coverage are very different
 useful to think in term of T°
Contribution functions
(assuming thermal equilibrium)
104
105
108
106
107
J.-F. Hochedez, COSPAR ’06, Beijing

16. Preliminary conclusions on combining spectral information
Hard to “spectrally” combine LYRA and SWAP
But, LYRA Al and Zr include SWAP
LYRA-Zr and SWAP observe ~same plasma
J.-F. Hochedez, COSPAR ’06, Beijing

17. Using SWAP to identify the regions that make the irradiance vary
Mid-term variation
Using SWAP to identify the regions that make the irradiance vary
EUV irradiance model
track AR, QS, CH
Cf. NRLEUV (Warren et al 2001), Kretzschmar et al 2004
If success, whole spectral irradiance variability is modeled
hence LYRA time series (at SWAP cadence only)
J.-F. Hochedez, COSPAR ’06, Beijing

18. Using SWAP to identify the regions that make the LYRA irradiances vary
Small-term variations
Using SWAP to identify the regions that make the LYRA irradiances vary
A prospectful new field
4 LYRA pass bands  chronology of solar events in different parts of the solar atmosphere
Can we observe irradiance counterparts
brightenings, dimmings, others?
SEM:0-50 nm
J.-F. Hochedez, COSPAR ’06, Beijing

19. Temporal evolution (1/3) Using radiometers to re-calibrate imagers
If roughly the same plasma, one expects similar normalized variations for integrated count rates
Cross-calibrations mutually improve long-term stability
J.-F. Hochedez, COSPAR ’06, Beijing

20. Temporal evolution (2/3) Contribution of solar regions to irradiance variations
SEM [0.5-50nm]
EIT 19.5 nm (integrated)
Comparing instruments with different aim(s) and pass bands…
e.g. SEM Flares not visible in the integrated EIT flux at 19.5

21. Temporal evolution (2/3) Contribution of solar regions to irradiance variations
Method:
Segment regions by hand on 1st image
Rotate images so that regions of interest appear always at the same position.
Not the best method but fast and quite easy
The rotation induces some unwanted effects
 Results are indicative & illustrative
Data:
1st of April 1997; Several flares and EIT waves
EIT image at 19.5 nm every 12 min
Irradiance data from SEM
nm and 26-34nm, cadence 5 min

22. last Last image First image Last, and rotated Last image (rotated)
SEM [0.5-50nm]
EIT 19.5 nm (integrated)
Last image
(rotated)

23. last First image Last, and rotated Last image (rotated)
ACTIVE REGION 1 (AR1)
Last, and rotated
SEM [0.5-50nm]
EIT 19.5 nm (integrated)
Last image
(rotated)

24. last First image Last, and rotated Last image (rotated)
ACTIVE REGION 2 (AR2)
Last, and rotated
SEM [0.5-50nm]
EIT 19.5 nm (integrated)
Last image
(rotated)

25. last First image Last, and rotated Last image (rotated)
QUIET SUN 1 (QS1)
Last, and rotated
SEM [0.5-50nm]
EIT 19.5 nm (integrated)
Last image
(rotated)

26. last First image Last, and rotated Last image (rotated)
QUIET SUN 2 (QS2)
Last, and rotated
SEM [0.5-50nm]
EIT 19.5 nm (integrated)
Last image
(rotated)

27. Most of the activity associated to AR1 AR2 anti-correlated?
SEM nm
SEM 30.4 nm
AR1
Most of the activity associated to AR1
AR2 anti-correlated?
Some SEM flares not seen in EIT
Finer details!
AR2
QS1
QS2
(around AR)
Instrumental pb

28. EIT difference images SEM 0.1-50 nm SEM 30.4 nm AR1 AR2 QS1 QS2
(around AR)
EIT difference images

29. Bright front of EIT wave
SEM nm
SEM 30.4 nm
Flare
AR 1
AR 2
Bright front of EIT wave
QS 1
QS2
.. And dimming

30. Temporal evolution (3/3)
Imagers can potentially compute irradiance for other heliospheric directions
i.e. other planets
c.f. Auchère et al 2005
Use hi-cadence radiometer time series to decrease temporal aliasing in image sequences…
Having assessed expected variability = f(x,y)
J.-F. Hochedez, COSPAR ’06, Beijing

31. Using LYRA for aeronomy studies
Apparent Sun diameter: 25 km
PROBA2 has eclipse periods. During occultation, it will see the Sun thru the Earth’s atmosphere
This allows LYRA to measure the attenuation of the solar flux from which one can derive atmospheric properties
LYRA measurements
J.-F. Hochedez, COSPAR ’06, Beijing

32. Using SWAP for aeronomy studies
Independent SWAP occultation observations
Cadence limited 
Only 17.4nm 
Imaging sequence 
No need to deconvolve for Sun area
No need to assume disc homogeneity
SWAP measurements
J.-F. Hochedez, COSPAR ’06, Beijing

33. Conclusion
Design new full Sun instruments meant to optimize the spectro-spatio-temporal balance!
Spectro-heliograph (such as on CORONAS-F)?
Array of >9 “low” spatial resolution multilayer telescopes paving the accessible UV spectrum
Smart camera schemes autonomously compromising between cadence and SNR
J.-F. Hochedez, COSPAR ’06, Beijing

34. J.-F. Hochedez, COSPAR ’06, Beijing

35. Quit complaining about your job!
J.-F. Hochedez, COSPAR ’06, Beijing