LYRA Radiometric Model
Latest document on Radiometric Model: RadiometricModel_R1V4.doc (report 1, version 1.2)
Photons from the sun with an energy distribution E(λ) (Watts per square meter as a function of wavelength) enter the LYRA instrument through a circular aperture of 3mm diameter, resulting in an aperture size of A = 7.06858e-08 square meter, pass one of a set of filters of a certain transmissivity F(λ) (throughput as a function of wavelength), and are converted to an electric current by a detector with a certain spectral responsivity D(λ) (Ampere per Watt as a function of wavelength).
Based on simulations with filter transmissivities F(λ) and detector responsivities D(λ)
measured in the laboratory,
the 12 heads in the 3 channels have been equipped with detectors as summarized in the table below
(to do the simulations, click here for an interactive table).
The table lists resulting signals i and purities from measurements of the assembled channels
( = filters+detectors together, whereas the data in the
interactive table are individually measured filter transmissivities and detector responses).
The used solar irradiances E(λ) are based on two TIMED-SEE measurements.
The resulting current i at the detector (Amperes,
integrated over all wavelengths) is calculated according to
The purity is defined as the ratio of the flux in the interesting wavelength range to the total signal (ideally close to 100%).
Table: expected output signals and purities in all LYRA channels for solar minimum and solar maximum. Each signal and purity entry is a link to a graphical representation of the result.
signal and purity
@ solar minimum
signal and purity
@ solar maximum
|1||1 - Lyα 122XN||MSM12||240.497 pA||24.4%||266.917 pA||30.2%|
|2 - Herzberg||PiN10||12.565 nA||83.3%||12.587 nA||83.2%|
|3 - Aluminium||MSM11||85.880 pA||58.3%||4.945 nA||2.5%|
|4 - Zirkonium||AXUV20 D #||699.189 pA||99.8%||19.091 nA||100.0%|
|2||1 - Lyα 122 XN||MSM21||103.870 pA||21.1%||113.883 pA||26.4%|
|2 - Herzberg||PiN11||13.745 nA||83.6%||13.761 nA||83.6%|
|3 - Aluminium||MSM15||74.020 pA||59.3%||3.837 nA||2.7%|
|4 - Zirkonium||MSM19||94.822 pA||99.6%||2.772 nA||100.0%|
|3||1 - Lyα 122XN + Lyα 122N||AXUV20 A #56||112.539 pA||80.6%||147.553 pA||84.3%|
|2 - Herzberg||PiN12||10.145 nA||83.3%||10.156 nA||83.2%|
|3 - Aluminium||AXUV20 B #59||1.090 nA||71.6%||36.827 nA||5.3%|
|4 - Zirkonium||AXUV20 C #44||709.525 pA||99.8%||19.311 nA||100.0%|
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last update: 25/05/2005