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