UV/EUV Spectroscopy
Science requirements, strawman
instrument design and its
feasibility	
Toshifumi Shimizu (ISAS/JAXA)
high throughput UV/EUV spectroscopy
sub-WG
10 March 2010

SCSDM-2

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High throughput UV/EUV
spectroscopy s-WG	
Task:• Establish science cases for the UV/EUV range in terms of the Plan B mission
purpose and develop plans for a model payload for high-resolution, highthroughput, and high-cadence spectroscopy.
• Science cases and instrument for the plan A mission may be included in thescope of the working group.

Members:• s-WG was organized with scientists and instrument experts from various institutes overthe world.
Luca Teriaca, Udo Schuehle (MPS)Louise Harra (MSSL)
George Doschek (co-chair for this sub WG) , Clarence Korendyke (NRL)
Joe Davila (NASA/GSFC)
Ted Tarbell (LMSAL)
Hiroaki Isobe (Kyoto University)
Shinsuke Imada (ISAS/JAXA)
Tetsuya Watanabe, Hirohisa Hara (NAOJ)
Toshifumi Shimizu (ISAS/JAXA, Chair for this sub WG)

10 March 2010

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Top-level Science Goals
1. Trace energy flow at natural dynamic solar time scales over alarge dynamic range from the photosphere into the corona
through small spatial-scale elementary solar structures anddetermine the resulting large-scale structures
2. Understand physical processes such as magnetic dissipation
and reconnection in astrophysical plasmas, under a wide
variety of physical conditions
3. Understand and spatially resolve elementary atmosphericstructures over each temperature domain of the atmosphereand determine how they are created and evolve
4. Understand how small-scale physical processes initiate large
scale dynamic phenomena that affect the environment aroundthe Earth (space weather)
5. Understand how physical processes alter coronal properties
such as variations in its composition
6. How are energetic particles accelerated during magnetic
reconnection?
10 March 2010

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Top-level Science Goals
1. Trace energy flow at natural dynamic solar time scales over alarge dynamic range from the photosphere into the corona
through small spatial-scale elementary solar structures anddetermine the resulting large-scale structures [Harra]
2. Understand physical processes such as magnetic dissipation
and reconnection in astrophysical plasmas, under a wide
variety of physical conditions [Imada]
3. Understand and spatially resolve elementary atmosphericstructures over each temperature domain of the atmosphereand determine how they are created and evolve [Doschek]
4. Understand how small-scale physical processes initiate large
scale dynamic phenomena that affect the environment aroundthe Earth (space weather) [Teriaca]
5. Understand how physical processes alter coronal properties
such as variations in its composition [Doschek]
6. How are energetic particles accelerated during magnetic
reconnection? [Watanabe]
10 March 2010

SCSDM-24

Plan BHigh throughput UV/EUV spectrometer• Science requirements for the spectrometer	
1.

High temporal resolution (cadence) For quantitatively understanding the physics of dynamical
phenomena.
 High throughput, one order of magnitude or more higher thanthe existing spectrometers (EIS and SUMER). 	

2.

With spectral lines from a broad temperature range, covering all
relevant temperatures
 The chromosphere, the transition region, low corona and flare
temperatures, in order to track the flow of energy from thechromosphere into the corona.
 With adequate plasma diagnostics

10 March 2010

SCSDM-25

Plan BHigh throughput UV/EUV spectrometer• Science requirements for the spectrometer	3.

High spatial resolution
 To resolve structures with 0.5” or better (hopefully 0.2-0.3”)
 Roughly equivalent to the chromospheric spicules observedwith SOT	

4.

A field of view as large as possible
 The best resolution may be restricted to ~5x5 arcmin (amedium size AR) Lower resolution should cover a larger FOV, in order to link
dynamics to space weather topics	

10 March 2010

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Plan BHigh throughput UV/EUV spectrometer• Science requirements for the spectrometer	5.

Observations with low-scattering optics
 Diagnostics of Low EM areas.
 Faint reconnection outflow region, coronal holes, off-limb
observations (solar wind acceleration, shock formation)	

6.

Precise co-alignment
 Spatial alignment of the spectrometer data with the data fromother onboard telescopes.	

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High throughput UV/EUV spectrometerTo archive higher throughput	

Strawman
instrument schematic
Schematic view of strawman
spectrometer	solarradiation

Primary Mirror
30~40cm
Focal Plane Detectors(Solar-blind intensified
APS or CCD)
Entrance Slit

Grating(TVLS)•Two element optical layout: off-axis primary and grating
minimizing the number of optical elements, same as EIS.

•The diameter of the primary mirror is 30-40cm, which gives a 4 times orlarger area, compared with EIS.

10 March 2010

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High throughput UV/EUV spectrometer
Some key technologies available•••

The strawman design removes the metal prefilters, to achieve higher
throughput, low scatter and broad wavelength coverage.
The opaque photocathode ensures that the detector is solar blind.
Intensified CCD or APS (CMOS active pixel sensor)
Example: MPS APS detector	
Sensor	  sec)on	  of	  EUNIS	  rocket	  with	  intensiﬁed	  APS	

10 March2010
SCSDM-2
A photocathode separated by a small gap on the input side of a micro-channel plate (MCP) electron
multiplier and a phosphorescent output screen on the reverse side of the MCP.	

9High throughput UV/EUV spectrometer
Some key technologies available•A single coating on the mirror available for covering a broad EUV-UV range.
Reflectivity: 500-1200A	

••150-400A	

TVLS (Toroidal Varied Line-Space) grating with
optical magnification, providing the optical layout
for realizing sub-arcsec resolution.
The grating divided into segments for 2-4
bandpasses.

10 March 2010

SCSDM-2Hassler	

10High throughput UV/EUV spectrograph
Performance much improved from previous instruments
Effective area of the strawman instrument (solid lines).
Previous comparable effective areas for EIS, CDS and SUMER areplotted for comparison. 	

•10 March 2010

The calculated effective area is afactor of 10 or more, compared withprevious instruments.

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Expected count rates of spectral lines
as a function of ionization temperature for a spatial sampling of 0.33”
Velocity diagnostics possible with >100 photons	

Typical quiet Sun	With SUMER	

Typical AR	

With EIS	

Flare plasma	•Temporal resolution can be more improved with observing bright lines,
10 March 2010
SCSDM-2
which are available in wide temperature
range in 104-107 K.

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Plan B: High throughput UV/EUV spectrometer
Strawman design: scientific characteristics

10 March 2010

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Plan B: High throughput UV/EUV spectrometer
Strawman design: scientific characteristics• > 10 improvement in effective area••This means > 10 improvements on temporal resolution ifobserved with the same sampling scale (~1”).
This means• > 18 improvement in spatially resolved area on thesolar disk•

Roughly equivalent to the chromospheric spicules observedwith SOT.

• Spectral lines provides complete temperature
coverage in 104-107 K, although the bands need to be furtheroptimized.
10 March 2010

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Substan(al	  jumps	  from	  IRIS?	  
• IRIS	  (Interface	  Region	  Imaging	  Spectrograph)	  is	  approved	  for	  launch	  in	  2012.	  	  – Spectral	  lines	  in	  120-­‐280nm	  with	  0.3”	  and	  1-­‐5s	  cadence	  to	  discover	  how	  an	  outer	  stellar	  atmosphere	  is	  energized.	  	  – The	  spectral	  lines	  observed	  with	  IRIS	  are	  suitable	  to	  explore	  the	  interface	  between	  upper	  chromosphere	  and	  lower	  transi)on	  region.	  

• S)ll	  substan)al	  jumps	  from	  IRIS,	  because	  the	  S-­‐C	  plan-­‐B	  can	  provide	  unique	  observa)ons	  which	  have	  never	  been	  realized:	  – Quan)ta)ve	  measurements	  of	  magne)c	  ﬁelds	  in	  the	  chromosphere	  – EUV/UV	  spectral	  lines	  used	  in	  Solar-­‐C	  spectrometer	  will	  seamlessly	  cover	  from	  chromospheric	  temperature	  through	  the	  coronal	  temperature	  with	  0.1-­‐0.5”	  and	  1-­‐5	  s	  cadence.	  
– Energy	  spectral	  (thermal	  and	  non-­‐thermal)	  diagnos)cs	  in	  106-­‐107	  K	  plasma	  for	  ﬂares	  and	  ac)ve	  region	  dynamics.	  

10	  March	  2010	  SCSDM-­‐2	  15	  10	  March	  2010	  SCSDM-­‐2	  16	  High	  Throughput	  UV/EUV	  Spectrometer	• The	  common	  desire	  that	  all	  the	  s-­‐WG	  members	  have	  is	  to	  realize	  a	  large-­‐scale	  EUV/UV	  spectrograph	  with	  high	  throughput	  performance	  as	  soon	  as	  possible,	  which	  requires	  plan	  B.	  
• A	  desired	  spectrometer	  can	  be	  designed	  with	  key	  technologies	  available,	  as	  demonstrated	  as	  the	  strawman	  design.	  
• Substan)al	  improvements	  from	  IRIS	  is	  possible,	  although	  needs	  clearer	  explana)ons.	  
10	  March	  2010	  SCSDM-­‐2	  17