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KMOS Exposure Time Calculator

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Infrared Mode Version 5.0.2
Description.
F.A.Q
 
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Target Input Flux Distribution

Uniform (constant with wavelength) Target Magnitude and Mag.System:   
= Vega
AB
Blackbody: Temperature: K
Template Spectrum: Spectral Type: Redshift
z =
Upload Spectrum:
Supported formats: FITS images and two-column ASCII, with
wavelength unit
nm and a flux unit proportional to erg/cm2/s/A
Single Line:
Lambda: nm
Flux: 10-16 ergs/s/cm2 (per arcsec2 for extended sources)
FWHM: nm
Spatial Distribution: Point Source
Extended Source (per pixel)
Extended Source, area Ω: arcsec2
The magnitude (or flux) is given per arcsec2 for extended sources.

Sky Conditions

Moon phase: days from new Moon
PWV: mm   Precipitable Water Vapor.
Airmass: ( ≥ 1)
Seeing: arcsec (FWHM in V-band at zenith). The seeing is irrelevant for extended sources.
For point sources, the resulting Image Quality FWHM is modeled by the ETC considering the transfer functions of the atmosphere, telescope and instrument. For details see the helpfile.
Choose Sky model (experimental)
Old ETC sky model
The new Cerro Paranal advanced sky model

In this experimental version of the ETC, the parameters for the background contributions can be configured (only with the new sky model). An option to adjust the width of a gaussian instrumental Line Spread Function (LSF) is provided as well (irrelevant for imagers).

The default values in this experimental section are used in the normal ETC.

The total background is modeled as a sum of contributions:

Btotal = Bsky + Btherm + Aobj(obj) + Asky(sky) + A?ext + A?int

Bsky Background from the night sky as such. This is given by the new sky model with the normal parameters given in the Sky Conditions section above.
Btherm Thermal contributions of different temperatures (T ≥ 0) and emissivities (0 ≤ ϵ < 1), modeled as if the sources were outside the telescope. See section 6.2.4 in the document Cerro Paranal advanced sky model.
Element1 (e.g. Telescope) T1 = K    ϵ1 =
Element2 (e.g. Instrument) T2 = K    ϵ2 =
Element3 (e.g. Cryostat) T3 = K    ϵ3 =
Aobj Additional background that is outside the telescope and with a signal proportional with the astronomical target.
Aobj = kobj · Fobj     , with kobj=
Asky Additional background that is outside the telescope and with a signal proportional with the sky background.
Asky = ksky · Bsky     , with ksky=
The ETC model can support further contributions of unknown origin to the additional background. This experimental version supports the following two additional contributions, each of which can be given as a constant, or a profile read from a file on the server. You can contact Jakob (jvinther@eso.org) to discuss how to enable the latter option.
Additional background that is outside the telescope :
Constant: ph/s/cm2/A/arcsec2
Use the file on the ETC server Contact Jakob (jvinther@eso.org) to discuss how to enable this option.
Additional background in unit electrons/s :
Constant: e-/s
Use the file on the ETC server Contact Jakob (jvinther@eso.org) to discuss how to enable this option.

For spectrographs the resulting total background spectrum is normally convolved by a flat kernel with width=slitwidth (Exceptions SINFONI and KMOS). Here you can configure the FWHM of an additional convolution by a gaussian kernel, representing the instrumental Line Spread Function (LSF):

LSF FWHM= spectral pixels (use 0 to suppress this gaussian LSF convolution). The LSF is not relevant for imagers.

Instrument Setup

Grating: Range to plot: - nm
Reference wavelength: nm
    The numeric results will refer to the Reference wavelength.
To revert the three fields to the default values, press here: .

Results

S/N ratio: S/N = DIT = sec
Exposure Time: NDIT =

The total exposure time is the product of DIT (Detector Integration Time) by NDIT (number of DITs). This exposure time does not take into account instrument and telescope overheads.


Plots: Toggle All / No Plots

Resultant spectrum including background
Object spectrum only
Background emission spectrum
Sky radiance spectrum in physical units (ph/s/m2/micron/arcsec2)
Sky transmission spectrum
S/N as a function of wavelength
Total efficiency and wavelength range
Input spectrum in physical units
Details of Image Quality Calculations (only for pointsources)

Detailed S/N info
   

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