Page tree

Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.


Content Block
overflowauto
meta-propertiestrue
nameSummary
id277319516
classpdf-full

The imaging mode of JWST's Near Infrared Imager and Slitless Spectrograph (NIRISS) images its entire 2.2' × 2.2' FOV at ~0.065"/pixel using 12 filters covering 0.8–5.0 μm.  This mode is only available in parallel or for calibrations.


Content Block
overflowauto
nameContent
id277805920
classpdf-full

Introduction

Parent page: NIRISS Observing Modes
See also: NIRISS Imaging APT Template, NIRISS Imaging Recommended Strategies, JWST Parallel ObservationsNIRISS Wide Field Slitless Spectroscopy

The NIRISS imaging mode enables standard multi-wavelength imaging over the NIRISS detector's 2.2' × 2.2' field of view with an image scale of 0.065"/pixel, using a suite of 12 filters to cover the wavelength range 0.8–5.0 μm.  

Imaging is a fundamental component of the wide field slitless spectroscopy mode of NIRISS. However, the imaging mode will only be used as a "prime" capability to collect data for instrumental calibrations.

Although most JWST imaging science programs will use NIRCam at near-IR wavelengths, NIRISS science imaging can be used effectively for parallel observations with other instruments. Currently, NIRISS imaging is only supported to be used in parallel when NIRCam imaging is used as the prime science mode. Parallel observations with NIRCam are particularly interesting because all the NIRISS filters (except for F158M) have essentially identical counterparts in NIRCam. Consequently, NIRISS effectively becomes a third channel of NIRCam when the two instruments are used in parallel.

Other prime+parallel combinations involving NIRISS imaging in parallel will be considered for implementation in cycle 2.

 


Imaging exposures

Main article: NIRISS Pupil and Filter Wheel
See also: NIRISS Filters, NIRISS Wide Field Slitless Spectroscopy

Target acquisition is not needed for the imaging mode.

Exposures with short wavelength filters in the pupil wheel (PW) are implemented in combination with the CLEAR aperture in the filter wheel (FW). For imaging with any of the long wavelength filters located in the FW, the CLEARP aperture is used in the PW. 

Figure container


Figure title

Figure 1. Elements in the NIRISS pupil and filter wheel used for short wavelength imaging

Elements in the NIRISS pupil and filter wheel used for short-wavelength imaging

Figure caption

Optical elements available for short wavelength imaging by NIRISS are indicated by green dashed circles. "Blue" filters in the PW are used in combination with the CLEAR element in the FW.



Figure container


Figure title

Figure 2.  Elements in the NIRISS pupil and filter wheel used for long wavelength imaging

Elements in the NIRISS pupil and filter wheel used for long-wavelength imaging

Figure caption

Optical elements available for long wavelength imaging by NIRISS are indicated by green dashed circles. "Red" filters in the FW are used in combination with the CLEARP aperture in the PW. The pupil alignment reference (PAR) and its support spiders reduce the throughput of the CLEARP element by ~16%.




Imaging filters

Main article: NIRISS Filters

NIRISS has 12 filters in the pupil (PW) and filter wheels (FW) that collectively cover the wavelength range between 0.8 and 5.0 μm.

The PW carries four wideband (F090W, F115W, F150W, F200W) and two medium-band (F158M, F140M) filters, all of which are centered at wavelengths shorter than 2.3 μm.

The FW has three wideband (F277W, F444W, F356W) and three medium-band (F430M, F380M, F480M) long wavelength filters.

Figure container


Figure title

Figure 3. Transmission profiles for the NIRISS filters

 Transmission profiles for the NIRISS filters

 



Imaging subarrays

Main article: NIRISS Detector Subarrays

The NIRISS imaging mode will use the entire detector array to obtain direct images for the wide field slitless spectroscopy (WFSS) mode and parallel science observations. Calibration data will be taken using subarrays; details are available in the NIRISS subarrays page.

 


Imaging dither patterns

Main article: NIRISS Dithers

Dithering is important for direct imaging observations with NIRISS, in particular at wavelengths ≤3 μm where the PSF is signficantly undersampled. Details of available patterns for different modes are available in the NIRISS Dithers article.

 


 


Content Block
overflowauto
nameReferences
id281944791
classpdf-full

References

Fullerton, A., 2016, ESAC JWST "On Your Mark" Workshop,
NIRISS: Imaging and Interferometry

JWST technical documents


Content Block
overflowauto
nameIcon
id278719485
classpdf-hide

Multiexcerpt include
MultiExcerptNameNIRISS icon and name
PageWithExcerptMR:NIRISS icon and name


Content Block
nameUpdates
id1074221578
classpdf-hide


HTML Wrap
padding0
margin0
idupdatesbox


HTML Wrap
tagspan
classupdatesbox-heading

Last updated

Published December 30, 2016


 

Comment

The format for 'Last updated' is shown below. Enter updates above this internal"Comment" box. Only enter major updates (not typos or formatting changes).


Updated April 05, 2017

  • Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aliquam fermentum vestibulum est. Cras rhoncus. 
  • Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Sed quis tortor. 

Published March 02, 2017