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MONITOR OF SOLAR EUV/XUV IRRADIATION PHOKA

MONITOR OF SOLAR EUV/XUV IRRADIATION PHOKA. A. Kochemasov. Astrophysics institute at Moscow engineering-physics institute. Instrument Phoka. Instrument Phoka is being designed at Astrophysics Institute at MEPhI. Phoka will operate onboard Russian space observatory “CORONAS-PHOTON”.

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MONITOR OF SOLAR EUV/XUV IRRADIATION PHOKA

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  1. MONITOR OF SOLAR EUV/XUV IRRADIATIONPHOKA A. Kochemasov Astrophysics institute at Moscow engineering-physics institute

  2. Instrument Phoka Instrument Phoka is being designed at Astrophysics Institute at MEPhI. Phoka will operate onboard Russian space observatory “CORONAS-PHOTON”. Phoka is the photometer of solar EUV/XUV irradiation with temporal resolution up to 0,1s. During entering the Earth shadow and leaving it instrument will measure solar irradiation passed throw the Earth atmosphere (make occultation measurements). • Scientific data received with Phoka instrument will be used for: • studying of development of solar flares and variation of solar irradiation. • Studying of the Earth upper atmosphere layers

  3. Solar spectrum Typical solar spectrum

  4. PHOKA channels

  5. Signal at Ti/Pd channel Useful signal at Ti/Pd channel calculated for solar spectrum on 23.02.2004: 210pA Useful signal purity for range0,1-10nm: 99,8%

  6. Signal at Al/Cr channel Useful signal at Al/Cr channel calculated for solar spectrum on 23.02.2004 : 340 pA Useful signal purity: for range 0,1-7nm68,5%for range 27-35nm29%

  7. Signal at Ly-α channel Ly-α channel (measuring solar irradiation at wavelength 121,6 nm): Bare photodiodeAXUV + 2 filtersActon 122-XN-.5D collimator interference filters Useful signal110-190 pA Signal purity ~80% photodiode

  8. AXUV photodiodes Silicon photodiodes IRD AXUV are used in PHOKA. AXUV have one hundred percent internal carrier collection efficiency in EUV/XUV region. Some of photodiodes have directly deposited metal filters Ti/Pd and Cr/Al). Such photodiodes were successfully used in many European and American space instruments.

  9. Phoka calibration • Photodiodes will be absolutely calibrated at VNIIOFI (Russia) and PTB (Germany). • Expected absolute calibration accuracy <10%

  10. PHOKA block-diagram

  11. Block of detectorsPhoka-DM Phoka-DM onboard“CORONAS-PHOTON” with closed cover

  12. Block of detectorsPhoka-DM

  13. Visible light background Transmittance of fused silicaKS-4V. Sample 10мм thick, rejections are included. For measuring visible light background signal Phoka has fused silica filters. 1. photodiode deposited filter 1. Measuring without filter. EUV/XUV + Visible light photocurrent = I tot silicafilter 2. Measuring with silica filter. Visible light photocurrent = I vl 2. - Visible light - EUV/XUV 3. EUV/XUV photocurrent: I uv = Itot-I vl

  14. Silica filter wheel Enter mask Closed aperture Silica filter Open aperture Stepper motor Optocoupler Fused silica filters are placed in filter wheel. Different wheel positions corresponds to different Phoka operation regimes. Photodiodesplate Collimators Visible light channel collimator

  15. Phoka operation regimes

  16. Conclusion At present Phoka has successfully passed almost all preflight tests. Flight model is under making now. Phoka Web-page: http://iaf.mephi.ru/coronas-photon_phoka_e.htm

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