Sensitivity Estimate for SPICA/SMI/MRS
-array size; 1K×1K Si:Sb BIB detector
-dark current; 0.8 electron/pix
-read noise; 25.0 electrons per readout
-saturation full well; 1.0E+5 (electrons)
-pixel pitch; 18 (µm/pix)
-exposure time; 600 (sec)
-shortest exposure time; 2 (sec)
-detector qunatum efficiency; "DETQE_SISB.DAT" (electron/photon)
【optics】
-diameter of the primary mirror; 2.5m
-secondary mirror shielding rate; 0.2
-plate scale; 0.725 (arcsec/pix)
-slit width; 3.7 (arcsec)
-energy fraction within 1st null radius; 0.9
-system efficiency (incl. mirror ref., short cut filter trans., etc); 0.3
-peak efficiency for echelle grating and cross disperser; 0.8
-relative grating efficiency (echelle grating and cross disperser); "SMI-MRS_GEFF.DAT"
Data Format:
1st column; Echelle order
2nd column; wavelength (µm)
3rd column; relative grating efficiency; ηechelle(λ) x ηcross disperser(λ)
【others】
-high background case;
・zodiacal light emission at ecliptic plane (β=0.0deg and ε=60deg)
・black body of T=268.5 K normalizzed to 80 MJy/sr at 25µm
-low background case;
・zodiacal light emission at ecliptic pole (β=90.0deg)
・black body of T=274.0 K normalizzed to 15 MJy/sr at 25µm
(Reach et al. 2003; Ootsubo et al. 2000)
- safety factor; 0.8
- number of pixels used to extract spectrum along cross dispersion direction;
first null diameter of the airy disk
Data Format:
1st column; Echelle Order
2nd column; wavelength (µm)
3rd column; X (pix)
4th column; Y (pix)
5th column; PSF FWHM size on detector plate along X direction (µm)
6th column; PSF FWHM size on detector plate along Y direction (µm)
note: pixel pitch is 18 (µm/pix)
X [pix] =α [pix/µm2] λ2+β [pix/µm]λ+γ [pix]
(calculated for the adopted spectral resolution of R=λ/Δλairy)
ASKII Data:
"1H5S_SENSITIVITY_MRS_uJy_R.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma continuum sensitivity for a point source (µJy) [low background case]
3rd column; 1-hour 5-sigma continuum sensitivity for a point source (µJy) [high background case]
ASKII Data:
"1H5S_LINE_SENSITIVITY_MRS_Wm-2.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma line sensitivity for a point source (W/m2) [low background case]
3rd column; 1-hour 5-sigma line sensitivity for a point source (W/m2) [high background case]
(calculated for the adopted spectral resolution of R=λ/Δλslit)
ASKII Data:
"1H5S_SENSITIVITY_MRS_MJY-SR_R.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma continuum sensitivity for extended sources (MJy/sr) [low background case]
3rd column; 1-hour 5-sigma continuum sensitivity for extended sources (MJy/sr) [high background case]
ASKII Data:
"1H5S_LINE_SENSITIVITY_MRS_Wm-2-SR.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma line sensitivity for extended sources (W/m2/sr) [low background case]
3rd column; 1-hour 5-sigma line sensitivity for extended sources (W/m2/sr) [high background case]
ASKII Data:
"SATURATION_MRS_JY.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; saturation limit for a point source (Jy) [low background case]
3rd column; saturation limit for a point source (Jy) [high background case]
version 2015.12.05 (Itsuki Sakon) [contact: isakon@astron.s.u-tokyo.ac.jp]
1. Assumptions
【detectors】-array size; 1K×1K Si:Sb BIB detector
-dark current; 0.8 electron/pix
-read noise; 25.0 electrons per readout
-saturation full well; 1.0E+5 (electrons)
-pixel pitch; 18 (µm/pix)
-exposure time; 600 (sec)
-shortest exposure time; 2 (sec)
-detector qunatum efficiency; "DETQE_SISB.DAT" (electron/photon)
【optics】
-diameter of the primary mirror; 2.5m
-secondary mirror shielding rate; 0.2
-plate scale; 0.725 (arcsec/pix)
-slit width; 3.7 (arcsec)
-energy fraction within 1st null radius; 0.9
-system efficiency (incl. mirror ref., short cut filter trans., etc); 0.3
-peak efficiency for echelle grating and cross disperser; 0.8
-relative grating efficiency (echelle grating and cross disperser); "SMI-MRS_GEFF.DAT"
Data Format:
1st column; Echelle order
2nd column; wavelength (µm)
3rd column; relative grating efficiency; ηechelle(λ) x ηcross disperser(λ)
【others】
-high background case;
・zodiacal light emission at ecliptic plane (β=0.0deg and ε=60deg)
・black body of T=268.5 K normalizzed to 80 MJy/sr at 25µm
-low background case;
・zodiacal light emission at ecliptic pole (β=90.0deg)
・black body of T=274.0 K normalizzed to 15 MJy/sr at 25µm
(Reach et al. 2003; Ootsubo et al. 2000)
- safety factor; 0.8
- number of pixels used to extract spectrum along cross dispersion direction;
first null diameter of the airy disk
2. Properties of MRS Spectra
2.1. Spectral Format
2.2. Point Spread Function
PSF FWHM size on detector plate; "SMI-MRS_PSF.DAT"Data Format:
1st column; Echelle Order
2nd column; wavelength (µm)
3rd column; X (pix)
4th column; Y (pix)
5th column; PSF FWHM size on detector plate along X direction (µm)
6th column; PSF FWHM size on detector plate along Y direction (µm)
note: pixel pitch is 18 (µm/pix)
2.3. Pixel-to-Wavelength Relation
Assumption for the pixel-to-wavelength relation;X [pix] =α [pix/µm2] λ2+β [pix/µm]λ+γ [pix]
| Echelle Order | λmin [µm] | λmax [µm] | α [pix/µm2] | β [pix/µm] | γ [pix] |
| 11 | 18.000 | 19.714 | 0.6011E+01 | 0.1133E+03 | -0.3758E+04 |
| 10 | 19.714 | 21.789 | 0.5338E+01 | 0.8839E+02 | -0.3613E+04 |
| 9 | 21.789 | 24.353 | 0.4837E+01 | 0.5739E+02 | -0.3373E+04 |
| 8 | 24.353 | 27.600 | 0.4545E+01 | 0.1609E+02 | -0.2952E+04 |
| 7 | 27.600 | 31.277 | 0.4526E+01 | -0.4336E+02 | -0.2167E+04 |
| 6 | 31.277 | 36.000 | 0.8231E+01 | -0.3718E+03 | 0.3533E+04 |
3. Estimated Sensitivity
3.1. 1-hour 5-sigma continuum sensitivity for a point source
(calculated for the adopted spectral resolution of R=λ/Δλairy)
ASKII Data:
"1H5S_SENSITIVITY_MRS_uJy_R.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma continuum sensitivity for a point source (µJy) [low background case]
3rd column; 1-hour 5-sigma continuum sensitivity for a point source (µJy) [high background case]
3.2. 1-hour 5-sigma line sensitivity for a point source
ASKII Data:
"1H5S_LINE_SENSITIVITY_MRS_Wm-2.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma line sensitivity for a point source (W/m2) [low background case]
3rd column; 1-hour 5-sigma line sensitivity for a point source (W/m2) [high background case]
3.3. 1-hour 5-sigma continuum sensitivity for extended sources
(calculated for the adopted spectral resolution of R=λ/Δλslit)
ASKII Data:
"1H5S_SENSITIVITY_MRS_MJY-SR_R.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma continuum sensitivity for extended sources (MJy/sr) [low background case]
3rd column; 1-hour 5-sigma continuum sensitivity for extended sources (MJy/sr) [high background case]
3.4. 1-hour 5-sigma line sensitivity for extended sources
ASKII Data:
"1H5S_LINE_SENSITIVITY_MRS_Wm-2-SR.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; 1-hour 5-sigma line sensitivity for extended sources (W/m2/sr) [low background case]
3rd column; 1-hour 5-sigma line sensitivity for extended sources (W/m2/sr) [high background case]
3.5. Saturation limit for a point source
ASKII Data:
"SATURATION_MRS_JY.DAT"
Data Format:
1st column; wavelength (µm)
2nd column; saturation limit for a point source (Jy) [low background case]
3rd column; saturation limit for a point source (Jy) [high background case]