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Venue: UCI Beall Applied Innovations - Venture Cove B

Location: 5141 5270 California Avenue Suite 100, Irvine, CA 92697 (Free parking in the lot)

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Contact: Hooshang Nayyeri (hnayyeri@uci.edu) and Vivian U (vivianu@uci.edu)

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HW2 HW3 - 

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ETC

Exercise 1

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exploration:

o What do you think the “out-of-date” field in the workbook list means?

• version control 

o Try to find out how you can share a workbook with a collaborator. Experiment with read and write permissions.

• Add user by email, permission checkboxes

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?

• For IFU calculations, which allow the user to choose between two strategies, changing the strategy for a selected calculation will revert to the default settings to the newly selected strategy. All previous user inputs in the strategy tab will be lost. (#1072)
• The extinction calculation assumes a simple relationship between the magnitude and the column density. It is correct for a source with a smoothly varying or reasonably flat input flux density.  It will be inaccurate for sources with extremely steep gradients.(#1884)
• NIRSpec noise is underestimated in some readout patterns.(#2429)
• The ETC allows detector parameters that may lead to large exposure times. Users are advised to check with APT and choose detector parameters accordingly. (#2099)
• For near-infrared detectors, APT allows 1 group per integration, but the ETC does not because the magnitude of systematic errors will not be known until measurements are made in orbit. (#246)

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?

• integration takes longer because it includes readout time in between

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?

• medium8

Exercise 4 exploration

o A scene can contain multiple sources. Using the “Offset” parameter in the scene, determine the minimum unblended separation of a binary star for your chosen

NIRCam imaging filter.

• ??

Exercise 5 exploration

o What is the faintest point source that will yield a “SOSS or AMI faint” target acquisition without a warning for NIRISS?

• 14 mJy at 1.3 microns

Exercise 6 exploration

o What if you knew that the surface brightness of Pluto at 3 micron is 1000 MJy/sterad. How would you renormalize the spectrum to this value?

• "Source Editor" → "Renorm", and "Shape" → "Surface Brightness"

Exercise 7 exploration

o How can the “Groups Before Saturation” image help you quickly determine the optimal number of groups?

• It displays the min. number of groups before saturation - usually at source center where the surface brightness peaks.

o How much exposure time is needed to observe Pluto with the NIRSpec IFU in high resolution at 2.7-5.2 micron with a minimum SNR of 20?

• about 300 seconds

Exercise 8 and 9 exploration

o Create a new workbook and share it with a colleague. Now delete your version of the workbook. What happens with your colleagues’ version?

• done

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HW2 - 

Understanding JWST detectors questionnaire

1. What is the difference between the JWST NIR and MIR detectors?

• Different types of electronics driven by wavelength range over which photons can be Different types of electronics driven by wavelength range over which photons can be efficiently detected: H2RG detectors for NIR and Si:As detectors for MIRI

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5. What’s the meaning of “group gap” or “dropframes” in the JWST NIR detectors?

6. What is a reset?

detectors?

• these are frames between groups that are sampled but not included in the group average

6. What is a reset?

• stops the pixels from accumulating charge and resets them to the bias level

7. What is an integration?

• a set of groups starting with the first group after a reset and ending with either the last group before a reset (NIR) or the last read-reset group (MIRI)

87. What is an integration?8. What is an exposure?exposure?

• a set of identical integrations that are separated by only a constant number of resets (nominally 1)

9. Suppose you have data from a CCD and from a JWST detector. They both reach the saturation level in one-half of the total integration time. Can you describe what the main difference is? Can you recover information in the saturated pixels?

• You can recover info in saturated pixel in JW detector but not from CCD because the charge/signal as a function of time is recorded in JW detector.

10. What will be the impact of a cosmic ray in a JWST integration? Can information be recovered?

• impact is a jump in signal as function of time; yes info can be recovered.

11. a) What is the practical difference between a MIRI SLOW mode exposure and a NIR exposure with NFRAMES=8? b) Which has a higher data rate: a single MIRI Si:As

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