The Performance of the EUV Spectroscope (EXCEED) Onboard the SPRINT-A Mission K. Yoshioka, G. Murakami, A. Yamazaki, K. Uemizu, T. Kimura (ISAS/JAXA), I. Yoshikawa, K. Uji (Univ. Tokyo) F. Tsuchiya, and M. Kagitani (Tohoku Univ.)
EXCEED The observing module contains Entrance mirror Spectrometer Slit with filters Grating EUV detector Light trap Target finding camera Total weight : 99kg ( ) The inner part of the EUV spectrometer ( ) The schematics of the EXCEED instrument (without bus system) 2
EXCEED current status The assembly of the spectrometer part is completed in last January. Jan. 2013 The main body has been constructed. Environmental tests have been done. EXCEED is integrated on the bus module! SPRINT-A SPRINT-A is under final environmental test at ISAS Baffle Feb. 2013 (@ISAS) EUV EUV-E FOV-E Dec. 2012 MDP Feb. 2013 3
EXCEED optical layout Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 4
EXCEED/Entrance mirror Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 5
Reflectivity EXCEED/Entrance mirror 0.6 Measured (FM) Theoretical 0.4 0.2 0 60 80 100 120 140 Wavelength [nm] Photo of the entrance mirror with alignment mirror (FM) The reflectance of FM mirror The reflectivity of the entrance mirror has been evaluated successfully. The shape (optical performance) has been evaluated. 6
EXCEED/Slit with filters Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 7
Transmittance EXCEED/Slit with filters Three types of slit shape. 10 60 dumbbell Two types of filters and blank (without filter). Blank (w.o. filter), Indium t=100nm, CaF 2 t=3mm 3 3 = 9 types of slits. 100 10-1 10-2 Indium CaF 2 60 80 100 120 140 Wavelength [nm] Transmittance of FM filters Io torus observation by dumbbell slit. Photo of Slits plate (reflective surface) 8
EXCEED/FOV guiding camera Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 9
EXCEED/FOV guiding camera Slit images taken by FOV camera. The focus is OK. 10
EXCEED/Grating Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 11
Diffraction efficiency EXCEED/Grating 0.3 Measured (FM) Theoretical 0.2 0.1 0 60 80 100 120 140 Wavelength [nm] The reflectance of FM grating The diffraction efficiency of FM Grating has been evaluated successfully. The difference between theoretical and measured values are possibly due to the surface roughness. But not critical. 12
EXCEED/Light trap Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 13
EXCEED/Light trap 0 th order Lyman-α(-1 st ) The photo of the light trap (FM) The photo of the spectrometer (FM) Light trap is set in order to capture the 0 th order light and -1 st order Lyman alpha (121.6nm) which may cause serious stray light problem. 14
EXCEED/MCP+RAE Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 15
Quantum detection efficiency [%] EXCEED/MCP+RAE 100 50 10 5 1 0.5 FM MCP Lab MCP CsI photocathode is deposited on the MCP surface The detection efficiency increase x1.5~x100 The MCP should be kept under vacuum until the launch. 0.1 60 80 100 120 140 Wavelength [nm] The absolute efficiency of the detector (FM) (see the next presentation) 16
EXCEED/MDP Entrance mirror An off-axis parabolic, Target Baffle Slit Three types of shape, and three types of filters Slit-1 Entrance mirror Slit-2 Slit-9 Grating Laminar type, toroidal, FOV Grating Photon detector Microchannel plate and Resistive anode Light trap MCP+RAE MDP The optical layout of EXCEED 17
Counts per photon Counts per Rayleigh (10"x10", 50min.) Total sensitivity (with/without filters) 10-1 Direct Indium CaF 2 10 1 Direct Indium CaF 2 10-2 10 0 10-3 10-1 10-4 60 80 100 120 140 Wavelength [nm] 10-2 60 80 100 120 140 Wavelength [nm] The total sensitivity (Photon to count conversion factor) as a function of wavelength. The version with Indium filter (red) and CaF2 filter (blue) The sensitivity of EXCEED. (The integration time is assumed as 50 minutes. The field of view is assumed 10 10 ) 18
Optical performances ~Entrance mirror slit~ The FWHM of the spot diagrams are smaller than 10 arc-seconds. Tsukuba, 2013/01/20 19
NeI 744Å NeI 736Å NeI 630Å HeI 584Å ArII 1463Å OI 1356Å OI 1304Å(M) OII 1154Å(M) OII 1132Å(M) ArI 1067Å ArI 1048Å OI 1026Å(M) OI 989Å(M) OI 949Å ArII 932Å ArII 930Å OII 834Å Optical performances ~Slit MCP~ Spectra from pinhole slit (after VT) 2012.01.10 2000 Argon Neon Oxygen Helium 1000 0 200 400 600 800 1000 X-axis [10bits] 20
Spectral resolution (FWHM) [nm] Spatial resolution for point source [arc-sec.] Optical performances (spatial and spectral resolutions) 15 10 5 0 60 80 100 120 140 Wavelength [nm] Spatial resolution (FWHM) as a function of wavelength. Spatial resolution: 6~10 arc-seconds Spectral resolution: 0.3nm ~ 1nm. 1 Spectral resolution (FWHM) as a function of wavelength for various slits. Point source 10" slit 60" slit 0.5 0 60 80 100 120 140 21 Wavelength [nm]
Two primary science targets (1) Simultaneous observation of exosphere, ionosphere, and escaping plasma down the tail. Venus, Mars, and Mercury charge exchange (solar wind) H 121nm resonant scattering O 130nm resonant scattering (exospheric neutral particle) O + 83nm resonant scattering (ionosphere) O + 83nm resonant scattering (escaping plasma) (2) Spectral analysis for aurora and gas torus. Jupiter and Saturn Allowed transition lines of S,O ions (satellite origin) FUV/EUV aurora H 2 Lyman & Werner bands Io plasma torus : Cassini/UVIS. Jupiter s UV aurora : HST/WFPC2 22
Escaping atmosphere from terrestrial planets charge exchange (solar wind) H 121nm resonant scattering O 130nm resonant scattering (exospheric neutral particle) O + 83nm resonant scattering (ionosphere) O + 83nm resonant scattering (escaping plasma) slit EXCEED will measure outflow rate of the atmosphere (O+. C+, N+) depending on solar (wind) conditions (short-term) from Mars and Venus Through the simultaneous observation of exosphere, ionosphere, and escaping plasma down the tail, EXCEED will reveal * The total amounts of escaping atmosphere * Its dependency on Solar wind activity The targets are Venus, Mars, and Mercury. 23
Brightness [R] (Averaged for FOV) Can EXCEED detects the faint targets? 102 FOV = 10"x10" Spectral resolution = 0.3nm (FWHM) Lower limits to be SNR=1 101 100 Worst case S eff = 1cm 2 10-1 Nominal case S eff = 3cm 2 10-2 0 10 20 30 Accumulation time [Days] 24
Brightness [R] (Averaged for FOV) Can EXCEED detects the faint targets? 102 FOV = 10"x60" Spectral resolution = 0.9nm (FWHM) Lower limits to be SNR=1 101 100 Worst case S eff = 1cm 2 10-1 Nominal case S eff = 3cm 2 10-2 0 10 20 30 Accumulation time [Days] 25
The energy flow around the Io plasma tours There must be an extra energy source. A small amount of hot electron is the candidate. The hot electron component has been detected through in situ observation by Galileo space craft. Frank and Paterson, 1999 mod. Pick up energy The extra energy source Ions : S +, S ++, S 3+, S 4+, O +, O ++, Na +, Cl + electrons: (~5 ev, ~2000 ele./cc) Hot electrons EUV radiation ~ 2 TW Fast neutral Transport Can we detect hot electrons through remote observation? 26
Emissivity [ev cm3/s] The approach for Io plasma torus ~spectral diagnosis~ EXCEED will take spatially resolved spectra Emission line intensities from the Io torus depend on the ambient electron temperature. The EUV spectra tell us not only the ion composition but also the electron temperature. 10-6 10-7 Visible (631nm) EUV (120nm) EUV (68nm) 10-8 10-9 1 10 100 1000 Electron temperature [ev] EUV-FUV spectrum taken by Cassini/UVIS (Steffl et al. 2004b) S ++ Emissivity through the electron impact excitation. The calculation use the CHIANTI database. 27
EUV is the best band for spectral diagnosis Space based obs. Ground based obs. More than 80% of the lines are in the EUV region. The distribution of Sulfur ion emissions. These emissivities are calculated with same plasma conditions (Yoshioka et al. 2012). 28
Counts/pix Counts/pix EUV observation of Io tours from EXCEED Model spectra with hot electron 0% Model spectra with hot electron 4.2% 200 200 FOV = 10" x 10" Integration time = 50 minutes FOV = 10" x 10" Integration time = 50 minutes 100 100 0 60 80 100 120 140 Wavelength [nm] 0 60 80 100 120 140 Wavelength [nm] EXCEED can distinguish the spectra with and without hot component by the 1 orbit (50min.) observation.. 29
Summary and next steps Flight model of the whole EXCEED instruments have been evaluated. (good!) Entrance mirror, slit, filter, detector The EXCEED structure has been installed and the optical performances have been evaluated. (good!) EXCEED will be launched in next August from Uchinoura Space center. 30