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Answer …  Readout mode: BRIGHT1, 1 integration of 10 groups takes 203.99 seconds, two integrations take 418.73 seconds. The clock time of two integrations is more thantwice one integration, because there is a reset in between. Thiswouldnot be the case for MIRI because aread-reset (rather than a reset) is executed between integrations, adding no extra time.

Done.

Homework 3, ETC

Exercise 1 exploration:

o What do you think the “out-of-date” field in the workbook list means?

Probably workbooks made with an older version of the ETC.

o Try to find out how you can share a workbook with a collaborator. Experiment

with read and write permissions.

Highlite the workbook on the available workbooks page, that enables a set of options at the bottom under “User Access permissions”.

Exercise 2: Explore an ETC workbook

https://youtube.com/watch?v=2IpSHsPda2A

1. Workbooks open in the “Calculations” tab. You will see three other tabs are also

available: “Scenes and Sources,” “Upload Spectra,” and “Caveats and Limitations.”

1. A workbook always includes three boxes at the top of the page.
2. One contains a unique workbook ID, which cannot be edited.
3. The second is a box for the title of the workbook. Name your workbook.
4. The third is a box for you to provide additional information on what is contained

in the workbook. Add a description.

1. Move to the “Available Workbooks” browser page. You will see that the title and

description have automatically updated for this workbook.

1. Now, return to the workbook. Take note of the “Help” dropdown menu at the top right.

Click on each of the options in the dropdown to see what they link to.

1. Scroll to the bottom of the page and view the “Notes” section. Typing in this section will

automatically save notes you leave for yourself or your collaborators. Type something in

the Notes.

• Exercise 2 exploration:

o Find the known issues under the help menu. Which one, if any, do you think

could most affect your favorite science case?

The ability to deal with a large load of users could be a problem.

Exercise 3: Using the Calculations Tab

1. Create a NIRCam SW Imaging calculation. Remember the first step in the “Quick Start”

walkthrough.

Done.

1. Highlight the calculation by clicking on it. This populates the “Calculation Editor” pane in

the top right with additional options for customizing the calculation.

Done.

1. A new calculation always begins with the “Instrument Setup” tab selected. For NIRCam

SW Imaging, you will see a dropdown providing a list of all available short-wavelength

filters. Change the filter.

OK, F200W

1. Now move to the “Detector Setup” tab. Change the “Readout pattern” from DEEP2 to

RAPID. Click calculate.

Done, SNR dropped from 97 to 31.

Note: The ability to change other parameters is not available while the calculation is running.

1. Locate the “Expand” dropdown menu in the top bar. This dropdown lets you easily copy

calculations with one parameter altered. Select the “Expand Groups” option.

In the dialog box, fill in 11 for the “Start Value,” 1 for the “Step Size,” and 10 for the

“Iterations.” Click “Submit” to create 10 new NIRCam SW Imaging calculations covering

the range from 11 to 20 groups. Observe that the exposure time increases with the

number of groups.

Done,  gradually goes up to SNR=55 in 215 seconds.

1. Highlight the original calculation and repeat the process for the “Expand Integrations”

option (Start Value=2, Step Size=1, Iterations=10).

Done,  gradually goes up to SNR=100 in 1288 seconds seconds.

1. You can view the results of all the calculations at once in the “Plots” pane by clicking on

the checkmark icon above the rows of calculations and selecting “All.” Then scroll down

to view the “Plots” pane.

Done.

1. Since all of these calculations were made using the same filter, the default “SNR” tab is

not particularly illuminating. Switch to the “SNR (time)” tab.

SNR increases with time very rapidly with more groups, relative to more integrations.

• Exercise 3 exploration:

o Note the two different slopes in the signal-to-noise ratio (SNR) for increasing the

number of groups and increasing the number of integrations. What do you think

causes this behavior?

The additional integrations lead to the addition of more readout time and more bias noise.

o Experiment with other readout patterns (under the Detector Setup tab) to find

the highest SNR for a total exposure time of about 1000 seconds. What is it?

I’m assuming DEEP8, which reaches SNR=125 in 944 seconds.