wfGSETC is the Web-based interface to the Roman Space Telescope Telescope Galaxy Survey Exposure Time Calculator (DEPC) by Chris Hirata, Neil Gehrels, Jean-Paul Kneib, Jeffrey Kruk, Jason Rhodes, Yun Wang, and Julien Zoubian.

For detailed information, please see the Reference Manual.

wfGSETC is a Web-based GUI for running the calculator for you on our server. The results are presented to you via your browser.

Please be patient. Some queries may take several minutes to run. How long a query takes depends on several factors. Performance may also be affected by other activity on our server.

The results you see will not be stored permanently on our server. When you see results you want to keep, remember to save them onto your local disk. We will try to provide a grace period of a week during which you may save your results.

Below you will find sections on:

• Input
  • Mode Specfic Input
  • Telescope and Detector Input
  • Action Buttons
• Output
  • The Result Page
  • How to Save Your Results
  • Email Calculation Results

   

 

To learn more about the available input fields, please click on the links below. For each input field, we show the name as it appears on the query form. More information on the parameters and options may be found in the Reference Manual.

 

• WL Specific Input
• BAO Specific Input
• SPCONT Specific Input
• PZCAL Specific Input
• Telescope Configuration
• Observing Strategy and Detector Characteristics

The parameters and options which need to be supplied depend on the calculation mode selected. When a mode is selected, input fields for the other modes are disabled. The Telescope configuration and Observing Strategy and Detector Characteristics input elements may be used in any mode.

 

The WL sensitivity-only mode, SPCONT mode, and PZCal mode run very quickly (several seconds), whereas full WL mode and BAO mode will take several minutes to run.

 

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In Sensitivity-only Mode, all input fields will be disabled.

Minimum Resolution Factor

The minimum value for the resolution factor, R, for galaxies to be used in the calculation. R is defined on a scale of 0 (galaxy small compared to the PSF) to 1 (galaxy large compared to the PSF); see the User Manual for a full discussion. Galaxies with R<<1 usually have unreliable shapes. In the SDSS lensing analyses the standard cut on R was 1/3; the recent Roman Space Telescope forecasts have used 0.4.

Maximum Ellipticity Error

The maximum value of the elliptical error of the galaxies to be measured. Ellipticity error is defined as an rms per component. The computation of the ellipticity uncertainty assumes an exponential profile galaxy and does a full integration over scales as described in the methodology section of the User Manual. It does not yet account for undersampling considerations.

Galaxy Catalog File

The input galaxy catalog is an ASCII file describing the redshift, size (r_eff), and spectral energy distribution of the galaxies to be used as the basis of the weak lensing simulations. The format is specified in the User Manual. The CANDELS GOODS catalog file that was used as input to the 2015 WFIRST SDT Final Report has the following references if you use it: Guo et al. (2013), ApJS, 207, 24 for the source catalog and Hsu et al. (2014) ApJ, 796, 60 for the photometric redshifts. The CMC1.cat file was the COSMOS Mock Catalog (Jouvel et al 2009), 435W-606W-775W-850LP-110-160-Ks. The CMC2.cat file was the COSMOS Mock Catalog - Update August 15, 2011.

 

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Emission Line Selection

Including four options: 0.Hα only; 1.Hα and [N II]; 2.Use [O II] instead of Hα; 3.Use [O III] instead of Hα.

Significance Cut

The minimum signal-to-noise ratio (SNR) for an Hα detection.

Galaxy Population Model

A population model that is a non-negative integer of the form 10i+j, where i indicates the choice of the Hα Luminosity Function and the single-digit j indicates the choice of a conditional size probability distribution. At present there is only one supported choice for the size distribution, so j = 0. The most conservative choice for i, over most redshift ranges, is i=1. See the User Manual for a full discussion.
Selection of the Galaxy population Model should match with the choice of Emission Line Selection. e.g., Galaxy Population Model from (42) to (00) are good for Emission Line Selection of (Hα only) or (Hα and [N II]); Galaxy Population Mode (2002) is only good for Emission Line Selection of (Use [O II] instead of Hα); Galaxy Population Mode (1002) to (1992) are good for Emission Line Selection of (Use [O III] instead of Hα).

Linear Spectral Dispersion

The linear spectral dispersion d(θ)/d(λ) = D_θ/d(λ) (roughly constant for a grism) is also required, as this is needed in the calculation of the splitting of [N II] and Hα features in pixel units. The units of linear spectral dispersion are arcsec/μm.

Completeness

Completeness is defined as the as fraction of the number of emission lines theoretically detected above a certain number of sigmas. Completeness is generally < 1 due to e.g. collisions with star traces or image defects.

SNR Computation

Specifying the "Use Expected SNR" switches the BAO SNR computations from a cut on observed SNR to a cut on expected SNR. See the manual for a more detailed discussion on the differences on these two SNRs.

Sampling Mode

The options including default sample-up-the-ramp for NIR detectors and Fowler- m sampling (m=4 or 8). Roman Space Telescope will have selectable (table-controlled) on-board processing of the individual reads; for long, background-limited exposures, Fowler-m will be the preferred choice.

 

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Spectral Dispersion

The spectral continuum mode is intended to estimate the SNR of the continuum of a dispersed source. It therefore requires additional knowledge of the spectral dispersion D_θ. The spectral dispersion is defined by D_θ = P*λ*d(X)/d(λ), where P is the pixel scale (in arcsec) and X(θ₁,θ₂,λ) is the astrometric solution of the dispersed image as a function of field position (θ₁,θ₂) and wavelength λ. [Here (X,Y) is the position on the focal plane in pixels, the along-dispersion direction is X, and the cross-dispersion direction is Y.]

Source Effective Radius

The effective radius of a galaxy with an exponential profile to be convolved with the PSF, in arcseconds. A value of zero means the object is unresolved.

 

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There are no inputs unique to the PZCAL mode. In general the inputs are identical to the BAO mode, except that the galaxy population model is not required.

Significance Cut

The minimum signal-to-noise ratio (SNR) for an Halpha detection.

Linear Spectral Dispersion

The linear spectral dispersion d(θ)/d(λ) = D_θ/d(λ) (roughly constant for a grism) is also required, as this is needed in the calculation of the splitting of [N II] and Hα features in pixel units. The units of linear spectral dispersion are arcsec/μm.

 

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RMS Wavefront Error

The rms wavefront error is measured in waves at the geometric central wavelength (SQRT(λ_min λ_max)). The value specified on the form will be overridden if there's a '!WAVEFRONT' directive in the telescope configuration file and the input field will be disabled.

Select Telescope Configuration File

The telescope configuration file is a text file that contains basic properties such as the aperture and pixel scale, as well as a table of throughput as a function of wavelength. It is also possible to incorporate thermal properties of the telescope in the configuration file that override the default settings of the ETC. Configuration files are always limited to lines of no more than 254 characters. The configuration files that are used in the calculator currently are all related to the most recent (as of Oct. 2015) version of the Roman Space Telescope telescope.
 

The following configuration file options are available currently:

• The WL imaging mode (including sensitivity only), has separate files, imaging in H & bluer imBlue.dat and F184 + F213 ImRed.dat.
• The BAO mode has two files: grism.dat or prism.dat.
• The SPCONT mode uses prism.dat.
• The PZCAL mode uses grism.dat.

 

 

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Detector Type

The following detector types are available for selection (see User Manual for specs): H2RG 32 channels [0], e2v CCD [1], H4RG 32 channels [2], H4RG 64 channels [3], IFC-grade H1RG 16 channels [4] and H1RG 16 channels 2x2 bin in software [5].

Pointing Jitter

The overall PSF is taken to be the convolution of the diffraction pattern from the annulus, aberrations if non-zero, wave front error if specified, the detector response (pixel tophat plus charge diffusion), and the pointing jitter.

Wavelength Minimum

The minimum wavelength response of the system (filter, detector, etc.).

Wavelength Maximum

The maximum wavelength response of the system (filter, detector, etc.).

Single Exposure Time

The time in seconds for each exposure.

Read Noise Floor

The read noise is in effective electrons rms per exposure. In principle, this is determined by the readout mode. At present, this and the dark current are allowed to be user inputs.

Dark Current

The dark current in electrons per pixel per second.

Ecliptic Latitude

The position of the observation on the sky required in order to calculate the zodiacal foreground radiation.

Ecliptic Longitude Relative to the Sun

The position (longitude relative to the Sun) of the observation on the sky required in order to calculate the zodiacal foreground radiation.

Galactic Reddening

The Galactic dust column is specified by the color excess E(B-V). All output sensitivities are quoted in terms of extinction-corrected (rather than observed) fluxes and magnitudes. If observed flux limits are desired (e.g. for Galactic objects that may be in front of some or all of the dust column, or for consistency with other surveys that usually quote sensitivities in observed fluxes), then one should input E(B-V) = 0.

Number of Exposures

The number of exposures to be used for the particular observing strategy.

 

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Submit

Submit the calculation to run in the background. You will be forwarded to the result page which will auto-refresh itself until results are displayed.

Set Defaults

Reset numeric fields to their default values; enable all controls which are enabled by default.

Save Form

Clicking this button redisplays the current form with all form values saved in the URL. Bookmarking the new page allows you to reproduce the same form settings so you may edit them for use in further calculations.

 

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Because runs can take several minutes, processing is done in the background, and the output of your calculation will be presented via your browser on the result page and by email if requested.

 

 

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Each run has its own unique page to display the results of the calculation. For long runs, this page will auto-refresh until results are ready. This can take several minutes, or longer if the job has to wait in the queue. There is a button to halt the auto-refresh if you find it annoying; it can be restarted by reloading the page. Another button cancels the calculation in case you realize it was not what was intended.

The result page also offers a link to a tar file containing the same information as that displayed on the result page plus other files associated with your run.

The result page displays this content:

Run Information

This section displays the time the run was submitted for processing, the run mode (WL, BAO, etc.), and the unique ID assigned to the run.

Run Parameters

This section displays the parameters specified on the web form, as described above.

Run Output

When the run has completed, this section shows the textual output from the run, including all the results of the performance calculations. For long runs, a status message will be displayed until results are ready.

 

Note that WL mode, when run using the Im140805b.282.dat configuration file (see above), will display these warning messages:

 

Warning: PM/SM emissivity 1.05860E-01 is unusual.
Warning: post-filter thermal background 7.70000E-02 e-/pix/s is unusual.

 

These messages are no longer relevant for the most recent baseline mission definition and can be ignored.

 

These links are available:

Start a New Calculation

Return to the wfGSETC form with default values filled in.

Modify This Calculation

Return to the form with the values used in this calculation filled in.

Download Full Results

Open a file download dialog to download a tar file containing your results (see below).

 

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We provide a grace period of up to one week during which you may save your results; this grace period is not guaranteed.

 

You can save your results by selecting the [Save Full Results] link on the result page. A uniquely named tar file is created that contains these files:

• Results.html: the result web page.
• Out.txt: the run output.
• RunParameters.txt: the run parameters.
• RunInfo.txt: the run information.
• Telescope configuration file: The telescope configuration file you selected.
• Galaxy catalog: The galaxy catalog used in WL mode.

Save the tar file to your local disk and extract the files. The files will be created in a subdirectory named with your run's unique ID. You can view your html result page in a web browser. Other pages are plain text.

 

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When processing is finished, a notification and run output can be sent by email to a given address. The notification includes:

 

• the run's input;
• the textual output;
• a link to the result page.

To get an email notification, click on the check box and fill in a valid email address.