Monitor PHOKA for solar XUV/EUV irradiation measurement onboard Coronas-Photon mission
Abstract
PHOKA is one of the scientific instruments onboard solar satellite Coronas-Photon. The instrument registries fluxes of solar disks radiation in two EUV bands (1-11nm and 27-37nm) and in Ly-αband (121.6nm). Minimum accumulating time of the fluxes is 0.1sec. The silicon Absolute XUV photodiodes AXUV-50(have been fabricated by IRD) are used in PHOKA. AXUV have one hundred percent internal carrier collection efficiency in EUV/XUV region. For blocking of light that is out of the measured EUV band the photodiodes have directly deposited metal filters: Ni-Pd for 1-11nm band and Cr/al for 27-37nm. The Cr/Al devices have at least 7 orders of magnitude visual light blocking. For the Ti/Pd filters the visual light blocking of six order magnitude is achieved. For measuring of visible light background signal the fused silica filters are used. Fused silica filters are placed in filter wheel. Different wheel positions correspond to different PHOKA operation regimes. In Ly-α channel (measuring solar irradiation at 121.6nm) the bare photodiode AXUV and two external filters Acron 122-XN-).5D are used. To ensure the flux measurements with good absolute accuracy the filtered photodiodes are calibrating at synchrotron radiation devices in VNIIOFI (Moscow) and PRB (Germany). The satellite will be launch in autumn season this year to 550km circular orbit with inclination 82.5 degrees. PHOKA instrument Data will be used for studying of development of solar flares and variation of solar irradiation over a long period. During entering and leaving the Earth shadow the instrument will measure solar irradiation passed throw the upper Earth atmosphere (for making occultation measurements to study of the Earth upper atmosphere layers). Detailed description of the instrument, used operation regimes, results of calibration and estimated values of signal/background will be presented and discussed in the report.
- Publication:
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37th COSPAR Scientific Assembly
- Pub Date:
- 2008
- Bibcode:
- 2008cosp...37.1595K