1. LYRA Tests and Calibration
the Lyman-alpha Radiometer onboard PROBA-2
LYRA Tests and Calibration
LYRA Meeting Davos 05/06 Oct 2006

2. Contents I. From Model to Configuration II. BESSY Campaigns
a. Flux Linearity
b. Stability, Drift
c. LEDs, Dark Current
d. Spectral Responsivity
e. Homogeneity, Flatfield
f. Cadence, Response Time
III. Summary
IV. Additional Topics

3. I. From Model to Configuration
Choice of filters: Zirconium (150 nm, 300 nm), Aluminium, Lyman-alpha (N, XN, VN, and combinations thereof), Herzberg, …
Choice of detectors: MSMxx (diamond), PINxx (diamond), AXUVxx (silicon), …
Tested separately to find transmittance and responsivity
Simulated with TIMED-SEE solar spectra to find expected response values and purities
cf.
Example: “high” flux + “Herzberg” filter + “PIN” detector

5. Selected configurations:
filter detector nominal FWHM measured
1-1 Ly XN + MSM /- nm nm
1-2 Herzberg + PIN nm nm
1-3 Aluminium + MSM nm (1)-2.4, nm
1-4 Zr (300nm) + AXUV20D 1-20 nm (1)-1.3, 6-15 nm
2-1 Ly XN + MSM /- nm nm
2-2 Herzberg + PIN nm nm
2-3 Aluminium + MSM nm (1)-1.4, nm
2-4 Zr (150nm) + MSM nm (1)-1.3, 6-12 nm
3-1 Ly N+XN + AXUV20A /- nm nm
3-2 Herzberg + PIN nm nm
3-3 Aluminium + AXUV20B nm (1)-2.4, nm
3-4 Zr (300nm) + AXUV20C 1-20 nm (1)-1.3, 6-15 nm

6. Consequence: All channels individual No simple redundancy
Combined responsivities
New estimates for response and purity (cf. II d.)

7. II. BESSY Campaigns NI beamline (40 – 240 nm, 60 C) July 2005
Doc. RP-ROB-LYR-0132-NI-July2005
GI beamline (1 – 30 nm, 60 C) July 2005
Doc. RP-ROB-LYR-0132-GI-July2005
(Final) NI beamline (40 – 240 nm, 37 C) March 2006
Doc. RP-ROB-LYR-0132-NI-March2006
(Final) GI beamline (1 – 30 nm, 37 C) March 2006
Doc. RP-ROB-LYR-0132-GI-March2006

8. a. Flux Linearity Using different aperture stops, or
Varying exit slit of monochromator
Relation fitted (2006) with a function I=[c+]a*P^b
Results: almost linear, slightly sub/superlinear, sub/superlinear (qualitatively)
or: b~1, c~0 (quantitatively)

9. Results in detail: NI 2006 GI 2005 NI 2006 GI 2006
(121.6 nm, 200 nm) (20 nm, 10 nm) (121.6 nm, 210 nm, 50 nm) (18 nm, 10 nm)
1-1 MSM slightly sublin
1-2 PIN slightly superlin
1-3 MSM , but c>0
1-4 AXUV
2-1 MSM slightly sublin
2-2 PIN slightly superlin
2-3 MSM superlinear
2-4 MSM slightly superlin
3-1 AXUV almost linear
3-2 PIN almost linear
3-3 AXUV sublinear
3-4 AXUV almost linear

10. b. Stability, Drift
Shutter was opened and closed every 60 s, then every 600 s
Some additional longer tests were executed
BESSY 2005 campaigns (60 C) still to be analyzed in detail
LED values, dark current values and 44 C, 50 C temperature effects: see below
Example:
Channel 2-1 (Ly XN + MSM21) at BESSY NI 2006

12. Results (2006) in detail: start drift stop 1-1 MSM slow upward tail
(“slow” ~min, “almost immediate” ~s) (“tail” ~min, “almost immediate” ~s)
1-1 MSM slow upward tail
1-2 PIN almost immediate (almost) no almost immediate
1-3 MSM almost immediate, slow upward tail, almost immediate
1-4 AXUV immediate no immediate
2-1 MSM slow upward tail
2-2 PIN almost immediate (almost) no immediate
2-3 MSM slow upward almost immediate
2-4 MSM slow upward almost immediate
3-1AXUV (almost) immediate (almost) no almost immediate
3-2 PIN almost immediate no immediate
3-3 AXUV (almost) immediate (almost) no (almost) immediate
3-4 AXUV immediate no almost immediate

13. c. LEDs, Dark Current visLED uvLED offset @37 C 44 C 50 C
1-1 MSM (0.005) (0.024)
1-2 PIN
1-3 MSM (0.100) ,
1-4 AXUV
2-1 MSM (0.012) (0.023)
2-2 PIN
2-3 MSM (( )) ,
2-4 MSM
3-1 AXUV 0.000?
3-2 PIN
3-3 AXUV (1.059) ,
3-4 AXUV
All values in nA
(x) = varying around x, ((x-y)) = unstable from y to x, “negative” current values due to conversion

14. d. Spectral Responsivity
Filters and detectors measured together (“channels” as configurated)
Relevant spectral range is tested, with special attention to range borders
V changed to A using appropriate gain resistor
Corrections for ring current applied
Example: “high” solar flux simulated with measurements of channel 1-1 (Ly XN + MSM12) at BESSY NI 2006
How to estimate “correction factors”?
Consequences for data levels?

16. Expected Signal and Purity
theorectical: “min” “high” measured: “min” “high”
1-1 MSM nA (37%) nA (44%) nA (24%) nA (30%)
1-2 PIN nA (86%) nA (86%) nA (83%) nA (83%)
1-3 MSM nA (61%) nA ( 3%) nA (58%) nA ( 3%)
1-4 AXUV nA (99%) nA (88%) nA (100%) nA (100%)
2-1 MSM nA (39%) nA (46%) nA (21%) nA (26%)
2-2 PIN nA (83%) nA (83%) nA (84%) nA (84%)
2-3 MSM nA (73%) nA ( 6%) nA (59%) nA ( 3%)
2-4 MSM nA (99%) nA (100%) nA (100%) nA (100%)
3-1 AXUV nA (46%) nA (54%) nA (81%) nA (84%)
3-2 PIN nA (85%) nA (85%) nA (83%) nA (83%)
3-3 AXUV nA (75%) nA ( 6%) nA (72%) nA ( 5%)
3-4 AXUV nA (99%) nA (88%) nA (100%) nA (100%)

17. Calibration Factor, Data Levels
How to estimate the solar signal from the LYRA signal?
LYRA signal * purity / area / responsivity = solar signal
[A] [%] [m2] [A W-1] [W m-2]
\___________________/
calibration factor
Example: “max”, “high”, “min” flux + Channels 1-1, 1-2, 1-3, 1-4
Use constant factor, linear dependency on signal, knowledge about solar flux?
Change public data each time when calibration factor gets more realistic? Use different data levels?

19. e. Homogeneity, Flatfield
Example: Channel 2-3 (detector diameter 4.2 mm)
What consequences will an off-pointing have?

21. f. Cadence, Response Time
Example: Signal vs. integration time
Channel 2-3 (Aluminium + MSM15) at BESSY GI 2006

22. III. Summary Linearity Stability LEDs Signal, Purity 1-1 MSM + -- + -
1-2 PIN
1-3 MSM ?
1-4 AXUV ??
2-1 MSM
2-2 PIN
2-3 MSM ?
2-4 MSM ??
3-1 AXUV
3-2 PIN ?
3-3 AXUV ?
3-4 AXUV ??

23. IV. Additional Topics Cross-calibration
Degradation of filters, detectors, LEDs
Tests to be performed
Normal cadence (acquisition rate)
Nominal units
Rate of calibration with LEDs