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

2. Instrument Phoka. Satellite «CORONAS-PHOTON» 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. Instrument Phoka. Satellite «CORONAS-PHOTON» Solar spectrum Typical solar spectrum

4. Instrument Phoka. Satellite «CORONAS-PHOTON» PHOKA channels Channel No. Filter coating Filter thickness, nm Bandpass, nmComment Primary channels 1None-<1100Optic channel 2Ti/Pd200/1001- 11Deposited filter 3Cr/Al100/20027- 37Deposited filter 4 2 external filters 116- 125Ly-α channel Calibration (redundant) channels 5Ti/Pd200/1001- 11Deposited filter 6Cr/Al100/20027- 37Deposited filter 7 2 external filters 116- 125Ly-α channel

5. Instrument Phoka. Satellite «CORONAS-PHOTON» Signal at Ti/Pd channel Useful signal at Ti/Pd channel calculated for solar spectrum on 23.02.2004: 210 pA Useful signal purity for range 0,1-10nm: 99,8%

6. Instrument Phoka. Satellite «CORONAS-PHOTON» 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 0,1-7nm 68,5% for range 27-35nm 29%

7. Instrument Phoka. Satellite «CORONAS-PHOTON» Signal at Ly-α channel collimator interference filters photodiode Ly-α channel (measuring solar irradiation at wavelength 121,6 nm): Bare photodiode AXUV + 2 filters Acton 122-XN-.5D Useful signal 110-190 pA Signal purity ~80%

8. Instrument Phoka. Satellite «CORONAS-PHOTON» 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. Instrument Phoka. Satellite «CORONAS-PHOTON» Phoka calibration Photodiodes will be absolutely calibrated at VNIIOFI (Russia) and PTB (Germany). Expected absolute calibration accuracy <10%

10. Instrument Phoka. Satellite «CORONAS-PHOTON» PHOKA block-diagram

11. Instrument Phoka. Satellite «CORONAS-PHOTON» Block of detectors Phoka-DM Phoka-DM onboard “CORONAS-PHOTON” with closed cover

12. Instrument Phoka. Satellite «CORONAS-PHOTON» Block of detectors Phoka-DM

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

14. Instrument Phoka. Satellite «CORONAS-PHOTON» Fused silica filters are placed in filter wheel. Different wheel positions corresponds to different Phoka operation regimes. Silica filter wheel Enter mask Closed aperture Silica filter Open aperture Stepper motor Optocoupler Photodiodes plate Collimators Visible light channel collimator

15. Instrument Phoka. Satellite «CORONAS-PHOTON» Phoka operation regimes Filter wheel position Primary channels status Redundant channels status Phoka operation regimes A OpenClosedRegular measurements B With silica filter With silica filter Visible light background measuring C Open In-flight calibration D Closed Measuring of dark currents

16. Instrument Phoka. Satellite «CORONAS-PHOTON» 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