Instrument Phoka. Satellite

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Instrument Phoka. Satellite
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 “CORONASPHOTON”.
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
Instrument Phoka. Satellite «CORONAS-PHOTON»
Solar spectrum
Typical solar spectrum
Instrument Phoka. Satellite «CORONAS-PHOTON»
PHOKA channels
Channel
No.
Filter
coating
Filter
Bandpass, nm Comment
thickness, nm
Primary channels
1
None
-
<1100
Optic channel
2
Ti/Pd
200/100
1- 11
Deposited filter
3
Cr/Al
100/200
27- 37
Deposited filter
4
2 external filters
116- 125
Ly-α channel
Calibration (redundant) channels
5
Ti/Pd
200/100
1- 11
Deposited filter
6
Cr/Al
100/200
27- 37
Deposited filter
7
2 external filters
116- 125
Ly-α channel
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%
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%
Instrument Phoka. Satellite «CORONAS-PHOTON»
Signal at Ly-α channel
Ly-α channel (measuring solar irradiation
at wavelength 121,6 nm):
Bare photodiode AXUV + 2 filters Acton 122-XN-.5D
collimator
interference filters
Useful signal
Signal purity
photodiode
Instrument Phoka. Satellite «CORONAS-PHOTON»
110-190 pA
~80%
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.
Instrument Phoka. Satellite «CORONAS-PHOTON»
Phoka calibration
•Photodiodes will be absolutely calibrated at VNIIOFI
(Russia) and PTB (Germany).
•Expected absolute calibration accuracy <10%
Instrument Phoka. Satellite «CORONAS-PHOTON»
PHOKA block-diagram
Instrument Phoka. Satellite «CORONAS-PHOTON»
Block of detectors Phoka-DM
Phoka-DM onboard
“CORONAS-PHOTON”
with closed cover
Instrument Phoka. Satellite «CORONAS-PHOTON»
Block of detectors Phoka-DM
Instrument Phoka. Satellite «CORONAS-PHOTON»
Visible light background
Transmittance of fused silica KS-4V.
Sample 10мм thick, rejections are included.
For measuring visible light
background signal Phoka has fused
silica filters.
1.
deposited filter
photodiode
silica filter
1. Measuring without filter. EUV/XUV + Visible light
photocurrent = I tot
2. Measuring with silica filter. Visible light
photocurrent = I vl
2.
- Visible light
- EUV/XUV
Instrument Phoka. Satellite «CORONAS-PHOTON»
3. EUV/XUV photocurrent: I uv = Itot - I vl
Silica filter wheel
Enter mask
Closed aperture
Silica filter
Open aperture
Stepper motor
Optocoupler
Fused silica filters are placed in
filter wheel.
Photodiodes
plate
Different wheel positions
corresponds to different Phoka
operation regimes.
Collimators
Instrument Phoka. Satellite «CORONAS-PHOTON»
Visible light
channel collimator
Phoka operation regimes
Filter wheel
position
Primary
channels
status
Redundant
channels
status
Phoka
operation regimes
Open
Closed
Regular
measurements
With
silica filter
With
silica filter
Visible light
background
measuring
Open
Open
In-flight calibration
Closed
Closed
Measuring of
dark currents
A
B
C
D
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
Instrument Phoka. Satellite «CORONAS-PHOTON»

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