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.

• 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

EUV-E FOV-E

MDP

EUV

Baffle

Dec. 2012

Jan. 2013

Feb. 2013

Feb. 2013 (@ISAS)

3

EXCEED optical layout

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

4

EXCEED/Entrance mirror

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

5

EXCEED/Entrance mirror

• The reflectivity of the entrance mirror has been evaluated successfully. • The shape (optical performance) has been evaluated.

The reflectance of FM mirror

60 80 100 120 1400

0.2

0.4

0.6

Wavelength [nm]

Refl

ecti

vit

y

Measured (FM) Theoretical

6

Photo of the entrance mirror with alignment mirror (FM)

EXCEED/Slit with filters

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

7

60 80 100 120 14010-2

10-1

100

Wavelength [nm]

Tra

nsm

itta

nce

Indium CaF2

• Three types of slit shape. – 10”

– 60”

– dumbbell

• Two types of filters and blank (without filter). – Blank (w.o. filter),

– Indium t=100nm,

– CaF2 t=3mm

• 3×3 = 9 types of slits.

Transmittance of FM filters

Photo of Slits plate (reflective surface) 8

EXCEED/Slit with filters

Io torus observation by dumbbell slit.

EXCEED/FOV guiding camera

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

9

EXCEED/FOV guiding camera

Slit images taken by FOV camera. The focus is OK.

10

EXCEED/Grating

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

11

EXCEED/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.

The reflectance of FM grating

60 80 100 120 1400

0.1

0.2

0.3

Wavelength [nm]

Dif

fracti

on e

ffic

ien

cy

Measured (FM) Theoretical

12

EXCEED/Light trap

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

13

EXCEED/Light trap

0th order

Lyman-α(-1st )

• Light trap is set in order to capture the 0th order light and -1st order Lyman alpha (121.6nm) which may cause serious stray light problem. 14

The photo of the light trap (FM) The photo of the spectrometer (FM)

EXCEED/MCP+RAE

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

15

60 80 100 120 1400.1

0.5

1

5

10

50

100

FM MCP Lab MCP

Quan

tum

det

ecti

on e

ffic

iency

[%

]

Wavelength [nm]

• 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.

EXCEED/MCP+RAE

16

The absolute efficiency of the detector (FM) (see the next presentation)

EXCEED/MDP

• Entrance mirror • An off-axis parabolic,

CVD-SiC coated

• Slit • Three types of shape,

and three types of filters

• Grating

• Laminar type, toroidal, CVD-SiC coated

• Photon detector

• Microchannel plate and Resistive anode

The optical layout of EXCEED

Baffle

Entrance mirror

Slit-1

Target

FOV Grating

MCP+RAE

MDP

Slit-2 Slit-9

Light trap

17

Total sensitivity (with/without filters)

The sensitivity of EXCEED. (The integration time is assumed as 50 minutes. The field of view is assumed 10”×10”)

60 80 100 120 14010-4

10-3

10-2

10-1

Wavelength [nm]

Co

unts

per

ph

oto

n

Direct Indium CaF2

60 80 100 120 14010-2

10-1

100

101

Wavelength [nm]C

oun

ts p

er

Ray

leig

h (

10"x

10",

50

min

.) Direct Indium CaF2

The total sensitivity (Photon to count conversion factor) as a function of wavelength. The version with Indium filter (red) and CaF2 filter (blue)

18

Optical performances ~Entrance mirror slit~

• The FWHM of the spot diagrams are smaller than 10 arc-seconds.

Tsukuba, 2013/01/20 19

Optical performances ~Slit MCP~

0 200 400 600 800 1000

1000

2000 Argon Neon Oxygen HeliumO

I 1304Å

(M)

ArI

1067Å

ArI

1048Å

ArI

I 932Å

ArI

I 930Å

OII

834Å

NeI

744Å

NeI

736Å

HeI

584Å

X-axis [10bits]

OI

1026Å

(M)

OI

989Å

(M)

NeI

630Å

OI

1356Å

OII

1154Å

(M)

OII

1132Å

(M)

ArI

I 1463Å

OI

949Å

Spectra from pinhole slit (after VT) 2012.01.10

20

Optical performances (spatial and spectral resolutions)

60 80 100 120 1400

5

10

15

Wavelength [nm]

Spati

al

reso

luti

on f

or

poin

t so

urc

e[a

rc-s

ec.]

60 80 100 120 1400

0.5

1

Wavelength [nm]

Spec

tral

res

olu

tion

(F

WH

M)

[nm

]

Point source 10" slit 60" slitSpatial resolution (FWHM) as a function of wavelength.

Spectral resolution (FWHM) as a function of wavelength for various slits.

Spatial resolution: 6~10 arc-seconds Spectral resolution: 0.3nm ~ 1nm.

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O+ 83nm resonant scattering （escaping plasma）

charge exchange （solar wind）

H 121nm resonant scattering O 130nm resonant scattering (exospheric neutral particle)

O+ 83nm resonant scattering (ionosphere)

(2) Spectral analysis for aurora and gas torus.

Jupiter and Saturn

(1) Simultaneous observation of exosphere, ionosphere, and escaping plasma down the tail.

Venus, Mars, and Mercury

FUV/EUV aurora H2 Lyman & Werner bands

Allowed transition lines of S,O ions (satellite origin)

Io plasma torus : Cassini/UVIS. Jupiter’s UV aurora : HST/WFPC2

Two primary science targets

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Escaping atmosphere from terrestrial planets

O+ 83nm resonant scattering （escaping plasma）

charge exchange （solar wind）

H 121nm resonant scattering O 130nm resonant scattering (exospheric neutral particle)

slit

EXCEED will measure outflow rate of the atmosphere (O+. C+, N+) depending on solar (wind) conditions (short-term) from Mars and Venus

O+ 83nm resonant scattering (ionosphere)

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.

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Can EXCEED detects the faint targets?

0 10 20 3010-2

10-1

100

101

102

Accumulation time [Days]

Bri

ghtn

ess

[R

] (A

vera

ged f

or

FO

V)

Worst caseSeff = 1cm2

Nominal caseSeff = 3cm2

FOV = 10"x10"Spectral resolution = 0.3nm (FWHM)Lower limits to be SNR=1

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Can EXCEED detects the faint targets?

0 10 20 3010-2

10-1

100

101

102

Accumulation time [Days]

Bri

gh

tness

[R

] (A

vera

ged

fo

r F

OV

)

Worst caseSeff = 1cm2

Nominal caseSeff = 3cm2

FOV = 10"x60"Spectral resolution = 0.9nm (FWHM)Lower limits to be SNR=1

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.

Hot electrons

The extra energy source

Frank and Paterson, 1999 mod.

Ions : S+, S++, S3+, S4+, O+, O++, Na+, Cl+

electrons:

(~5 eV, ~2000 ele./cc)

Pick up energy

EUV radiation ~ 2 TW

Fast neutral

Transport

Can we detect hot electrons through remote observation? 26

The approach for Io plasma torus ~spectral diagnosis~

EUV-FUV spectrum taken by Cassini/UVIS (Steffl et al. 2004b)

• 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.

1 10 100 1000

10-9

10-8

10-7

10-6

Electron temperature [eV]

Em

issiv

ity [

eV

cm

3/s]

S++ Emissivity through the electron impact excitation. The calculation use the CHIANTI database.

Visible (631nm)

EUV (120nm)

EUV (68nm)

27

EUV is the best band for spectral diagnosis

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).

Ground based obs. Space based obs.

28

EUV observation of Io tours from EXCEED

60 80 100 120 1400

100

200

Wavelength [nm]

Counts

/pix

FOV = 10" x 10"Integration time = 50 minutes

60 80 100 120 1400

100

200

Wavelength [nm]

Counts

/pix

FOV = 10" x 10"Integration time = 50 minutes

• EXCEED can distinguish the spectra with and without hot component by the 1 orbit (50min.) observation..

Model spectra with hot electron 4.2% Model spectra with hot electron 0%

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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.

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