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

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

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. http://lyra.oma.be/radiometric_model/radiometric_model.php Example: “high” flux + “Herzberg” filter + “PIN” detector

Selected configurations: filter detector nominal FWHM measured 1-1 Ly XN + MSM12 121.5 +/- nm 116-126 nm 1-2 Herzberg + PIN10 200-220 nm 197-218 nm 1-3 Aluminium + MSM11 17-80 nm (1)-2.4, 17-35 nm 1-4 Zr (300nm) + AXUV20D 1-20 nm (1)-1.3, 6-15 nm 2-1 Ly XN + MSM21 121.5 +/- nm 116-126 nm 2-2 Herzberg + PIN11 200-220 nm 199-219 nm 2-3 Aluminium + MSM15 17-80 nm (1)-1.4, 17-27 nm 2-4 Zr (150nm) + MSM19 1-20 nm (1)-1.3, 6-12 nm 3-1 Ly N+XN + AXUV20A 121.5 +/- nm 116-126 nm 3-2 Herzberg + PIN12 200-220 nm 198-219 nm 3-3 Aluminium + AXUV20B 17-80 nm (1)-2.4, 17-35 nm 3-4 Zr (300nm) + AXUV20C 1-20 nm (1)-1.3, 6-15 nm

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

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

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)

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. 0.99572 1-2 PIN slightly superlin. 1.00656 1-3 MSM 0.98565 1.1719, but c>0 1-4 AXUV 1.00155 2-1 MSM slightly sublin. 1.03661 2-2 PIN slightly superlin. 0.99483 2-3 MSM superlinear 1.02234 0.97894 2-4 MSM slightly superlin. 1.04009 3-1 AXUV almost linear 1.02434 3-2 PIN almost linear 0.99529 3-3 AXUV sublinear 0.00230 0.99253 3-4 AXUV almost linear 1.00064

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

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

c. LEDs, Dark Current visLED uvLED offset @37 C 44 C 50 C 1-1 MSM (0.005) (0.024) 0.001 0.010 1-2 PIN 0.004 0.014 0.000 -0.002 1-3 MSM (0.100) 0.000, -0.007 0.003 0.010 1-4 AXUV -0.004 2-1 MSM (0.012) (0.023) 0.001 0.009 2-2 PIN 0.015 -0.001 -0.002 -0.005 2-3 MSM ((0.016-0.136)) 0.000, -0.008 0.002 0.007 2-4 MSM -0.001 3-1 AXUV 0.000? 0.000 0.002 0.008 3-2 PIN 0.006 -0.003 -0.005 3-3 AXUV (1.059) -0.001, -0.011 -0.003 -0.005 3-4 AXUV -0.014 All values in nA (x) = varying around x, ((x-y)) = unstable from y to x, “negative” current values due to conversion

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?

Expected Signal and Purity theorectical: “min” “high” measured: “min” “high” 1-1 MSM 0.139 nA (37%) 0.161 nA (44%) 0.240 nA (24%) 0.267 nA (30%) 1-2 PIN 12.75 nA (86%) 12.77nA (86%) 12.57 nA (83%) 12.59 nA (83%) 1-3 MSM 0.120 nA (61%) 5.264 nA ( 3%) 0.086 nA (58%) 4.945 nA ( 3%) 1-4 AXUV 0.530 nA (99%) 15.37 nA (88%) 0.699 nA (100%) 19.09 nA (100%) 2-1 MSM 0.115 nA (39%) 0.135 nA (46%) 0.104 nA (21%) 0.114 nA (26%) 2-2 PIN 13.80 nA (83%) 13.82 nA (83%) 13.75 nA (84%) 13.76 nA (84%) 2-3 MSM 0.127 nA (73%) 3.821 nA ( 6%) 0.074 nA (59%) 3.837 nA ( 3%) 2-4 MSM 0.111 nA (99%) 2.878 nA (100%) 0.094 nA (100%) 2.772 nA (100%) 3-1 AXUV 0.132 nA (46%) 0.156 nA (54%) 0.113 nA (81%) 0.148 nA (84%) 3-2 PIN 10.20 nA (85%) 10.22 nA (85%) 10.15 nA (83%) 10.16 nA (83%) 3-3 AXUV 1.072 nA (75%) 34.95 nA ( 6%) 1.090 nA (72%) 36.83 nA ( 5%) 3-4 AXUV 0.530 nA (99%) 15.37 nA (88%) 0.710 nA (100%) 19.31 nA (100%)

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?

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

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

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 + + ?? +++

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