MIRHES (Mid-IR high-resolution echelle spectrometer)

MIRHES team

Outline

MIRHES is a high dispersion spectrometer based on immersion grating. It has two channels for short wavelength region and long wavelength region. These two channels are completely independent from each other.

Scientific Objectives/Targets& Required Specifications

Scientific Targets

Consistency with MRD

2.3 Life Cycle of Interstellar Dust Objective #2: Dust and Molecular Shells around Low- and Intermediate-mass

Stars examine the properties of molecules in MOLsphere of redgiant

Objective #3: Dust formation and grain growth in Dense Molecular Clouds examine the properties of molecules in dense molecular clouds and their chemical

evolution including the formation of icy mantles onto the dust grains

2.4 Studies of Exoplanets and Solar Systems Objective #2: Dissipation of Gas from Proto-planetary Disks

Explore the gas at intermediate radii from the star (i.e., 1-30 AU), the key zone for understanding planet evolution

MIRHES would be sensitive to the profiles of various emission lines, leading to the determination of physical/chemical conditions as a function of radius. To facilitate this, its spectral coverage is designed to observe a variety of emission lines (CO, H2O, HCN, CO2, C2H2 etc.) at 4-8 and 12-18 m. This would allow us to observe how the structure of gas disks evolve due to planet formation.

Specification of Instrument

Short(S)-mode Long(L)-mode

Wavelength coverage 4 – 8m 12 – 18m

Spectral resolution (R=/

30,000 20,000 – 30,000

Slit width 0.72” 1.20”

Slit length 3.5” 6.0”

Dispersion element

ZeSe immersion grating

KRS5 immersion

grating

Cross disperser Reflective reflective

Concept StudyCurrent Status

Optics & Volume (S)

S-modeThe light from the slit enters to the immersion grating through the collimator lenses. The dispersed light goes through the collimator lenses again, then collimated by the relay optics. This relay optics makes a pupil image on the cross-disperser, resulting in the small size of the entire optical system. S-mode requires two cross-dispersers to cover the entire 4-8m range. The cross-dispersed light enters to the detector through the camera optics. The size of the entire optical system is about 200mm(L)X200mm(WW)X100mm(H).

Optics & Volume (L)

L-modeSimilar optical layout as for S-mode (Fig.2). Only one cross-disperser is required to cover the entire wavelength range (12 -18 m). The size of the entire optical system is about 350mm(L)X350mm(W)X200mm(H).

Optical Elements

Achieved Spec for SPICA ZnSe grating

< 0.2λ< 0.4λSurface @633nm

< 0.2μm< 1μmEdge

3.6nm (rms)< 10nm (rms)Groove Random errors

1.8nm< 10nmGroove Periodic errors

5nm (rms)< 15nm (rms)Surface roughness

Achieved Target

Grating Efficiency > 70-80% ⇒ Technical goal achieved for ZnSe

Detectors

Si:As 2kx2k (Raytheon)Each arm has own detector, total 2 chips2048 x 2048 pixel fomatPixel pitch; 25um/pixDark current; 0.1e/sec (TBM)Full well; 1.0x106 (electron/pix)Thermal output; 1mWQuantum Efficiency; N/A

Thermal Design

Expected Performance

Resource Requirements

Field-of-View Requirement

MIHES share the fore-optics of MIRACLE

FOV is 0.72 x 3.5 arcsec for S-arm and 1.20 x 6.0 arcsec for L-arm

FOV should be allocated besides MIRACLE FOV.

Thermal & Cryogenic Requirement

Pointing / Attitude control Requirement

Structural Requirement

Data Generation Rate & Data Handling Requirement

Warm Electronics

Operation & Observing Mode

Development and Test Plan

Key Technical Issues & TRL

Development Plan

Test & Verification Plan

Development Cost

Observing Program

Observation Plan to perform Science Targets

Outline of Ground Data Processing

Organization & Structure for Development

Summary