ATMOS Modèle numérique d`atmosphère

ATMOS Modèle numérique d'atmosphère
Jihane Moultaka
LATT
Observatoire Midi­Pyrénées
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Goal : Simulate the effect of Atmosphere on the ideal (simulated) data cube
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Use : Produce the most realistic data in order to
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➔ Prepare the instrument
➔ Determine the needs in terms of software
➔ Validate MUSE softwares (DRS and DAST, see other talks)
➔ Optimally exploit the instrument characteristics
➔ Prepare the strategy of observations especially in the case of the GT
➔ Limit learning time on sky
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Data observed with MUSE
Simulated data cube
ATMOS
Instrument Numerical Model
(INM)
Talk A. Jarno
Data Reduction Software
(DRS)
Talk R. Bacon
Quick SIMulation of the instrument (QSIM)
Atelier MUSE – Lyon – Novembre 2007
Reduced data cube
Data Analysis Software Tool
(DAST)
Talk E. Emsellem
ATMOS Modèle numérique d'atmosphère
Goal : Simulate the effect of Atmosphere on the ideal (simulated) data cube
This includes : 1­ An additive component (Moon + sky emission)
2­ A multiplicative component (atmospheric extinction) 3­ The atmospheric differential refraction
4­ The atmospheric distortion (PSF with or without AO)
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
1­ Additive component : Effect of the Moon
Moon spectrum from UVES archive (Echelle spectrograph): ➔ Resolution of about 85000­100000
➔ No correction for telluric lines ➔ Gaps and problems in some wavelength ranges
➔ Bad flux calibration in some intervals
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The final spectrum is absolute flux calibrated (model from Krisciunas 1991) given: ✔ the Moon phase ✔ the separation angle between the Moon and the FOV, ✔ the zenith distance of the Moon
✔ and zenith distance of the FOV ● The final spectrum is smoothed to a spectral resolution of 9000 (3 times the resolution of MUSE). ● The final spectrum is added to the simulated spectra of the data cube
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Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
2­ Additive component (sky emission)
Sky spectrum obtained with UVES (Hanuschik 2003):
➔ Resolution of about 45000 ➔ Free from extinction
➔ Flux calibrated
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The emission lines vary with time: ●
➔ A random variation of the lines is applied conserving the total flux (variation of the V band sky brightness at Paranal between 20.99 to 22.10 mag arcsec­2 , Patat 2003)
The final spectrum is smoothed to a spectral resolution of 9000 (3 times the
resolution of MUSE). ● The final spectrum is added to the simulated spectra of the data cube
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Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
3­ Multiplicative component (Atmospheric extinction)
The continuum extinction:
Due to 3 components (Hayes & Latham 1975, Tug 1980) dependent on the airmass (A ∝airmass):
1­ Rayleigh scattering by air molecules Aray(,h)
2­ Ozone molecule Aoz() (only a mean value)
2'­Water vapor (~0.01 mag (airmass)­1 @ 
 > 7000 A) Impossible to calculate
3­ Aerosol scattering Aaer(,h)
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The telluric lines (list from HIRES spectrograph with residual intensities):
Dependence on airmass (A ∝airmass­1/2) (Wade & Horne 1988, Merci à E. Pecontal et C. Buton)
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The simulated object's spectrum is multiplied by the final extinction spectrum.
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Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Total magnitude
Rayleigh
Ozone
Aerosol
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
4­ Atmospheric differential refraction
The apparent position of an object at a given wavelength  is displaced along the direction of the parallactic angle  by a distance R() (in '') (Filippenko 1982).
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R() depends on ➔ the zenith angle z of the object
➔ the Pressure P, Temperature T and water vapor pressure f
 depends on ➔ the zenith angle z, hour angle HA and declination  of the object
➔ the latitude of the telescope
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ssuming that the position of the object (or FOV) is the position at =5000 A, we calculate R()=R()­R(5000A) (in '') 
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
R ('')
4­ Atmospheric differential refraction
sec(z)=1.5
sec(z)=1
sec(z)=4.5
Atelier MUSE – Lyon – Novembre 2007
 (Angstroem)
ATMOS Modèle numérique d'atmosphère
4­ Atmospheric differential refraction
=30°
=0
Atelier MUSE – Lyon – Novembre 2007
=­25°
=­70°
°)
Parallactic angle (
1
Hour Angle west of meridian (hours)
ATMOS Modèle numérique d'atmosphère
4­ Atmospheric differential refraction
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
5­ The AO and non­AO PSFs
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AO and non­AO PSF simulations provided by the Leiden observatory ➔ Available wavelengths : 465,550,650,750,850,930 & 2200 nm ➔ Available zenith angles : 0°
➔ Available dimm­seeings : 0.6”, 0.8” and 1.0”.
The PSFs are fitted with up to 5 gaussians with 3 parameters ➔Interpolation or analytic model
● We consider no variation of the PSF for a given object
● But variation in the FOV
● The images at each wavelength of the data cube are convolved with the PSF for a
given zenith angle and seeing. ●
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
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Output: Fits files • Format: INM compact format (3 spatial and 3 spectral objects)
Code: Python ●
Libraries: PyFits, SciPy, numpy
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Status: Test phase of 1rst version and final development
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Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
Atelier MUSE – Lyon – Novembre 2007
ATMOS Modèle numérique d'atmosphère
4­ Atmospheric differential refraction
 127°
Old XPOS=0''
• Old YPOS=0''
•
New XPOS & YPOS ('')
 127°
 55°
 55°
 (Angstroem)
Atelier MUSE – Lyon – Novembre 2007
ATMOS Work Package
The output of ATMOS
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The primary header of the FITS files will contain the following ATMOS keywords:
ATM_MOONPHASE (in\%)
ATM_MOONANGLE (in degrees)
ATM_RESOL
ATM_PARAL (in '')
ATM_FITGAU0
ATM_FITGAU1
ATM_FITGAU2
ATM_FITGAU3
ATM_FITGAU4
ATM_AO (Y or N)
ATM_DIMM (in '')
ATM_FIELD (N or W)
DAST Kick­Off meeting – Toulouse – 5 & 6th of June 2007
The output of ATMOS
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The FITS files:
1­ SkyAbsorption.fits : Describes the spectrum of the atmospheric extinction
It has 2 extensions each is a binary table:
1­ ABSCONT describes the continuum spectrum of the
atmospheric extinction.
2­ ABSLINE describes the telluric absorption lines.
2­ SkyEmission.fits : Describes the spectrum of the Moon and the Sky
It has 3 extensions of binary tables:
1­ EMICONT describes the continuum spectrum of the atmospheric emission added to the continuum of the Moon.
2­ EMILINE describes the sky emission lines.
3­ ABSLINE describes the absorption lines of the moon.
DAST Kick­Off meeting – Toulouse – 5 & 6th of June 2007
The output of ATMOS
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The FITS files:
3­ Refraction.fits : Describes the R displacement as a function of wavelength
It has 1 extension (a binary table):
1­ DRCONT describes the continuum of the
 R ) distribution
4­ RefractionXPos.fits : Describes the new X position as a function of wavelength
It has 1 extension (a binary table):
1­ XCONT describes the variation of the Xpos() 5­ RefractionYPos.fits : Describes the new Y position as a function of wavelength
It has 1 extension (a binary table):
1­ YCONT describes the variation of the Ypos()
➔ The format and keywords of the binary tables are the same as the ones of the
Point Source compact format.
DAST Kick­Off meeting – Toulouse – 5 & 6th of June 2007
The output of ATMOS
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The FITS files:
6­ PSF.fits : Describes the PSF (!!! To be discussed !!!)
7­ ATM_name.fits : The transformed data cube if the input is a data cube (the output format is the same as the input one)
8­ ATM_objectname.fits : The transformed object (Point source, Extended source or Background) if the input is an object given in a compact format (the output format is the same as the input one)
DAST Kick­Off meeting – Toulouse – 5 & 6th of June 2007