Introducing JWST’s NIRISS : The N ear I nfra R ed I mager & S litless S pectrograph

Introducing JWST’s NIRISS:The Near InfraRed Imager & Slitless Spectrograph

TIPS/JIM2011 September 15

Alex FullertonSTScI / HIA


The Tunable Filter Imager (TFI)

TIPS / JIM Presenter Title

2004 May 20 Nelan JWST FGS SRR (April 7, 2004)

2005 March 17 Fullerton Overview of Calibration Activities for the JWST FGS-TFI

2005 May 19 Fullerton FGS Tunable Filter Imager: Updates from PDR

2006 June 15 Fullerton “Phase C” Design of the JWST/FGS Tunable Filter Imager

2008 Sept. 18 Fullerton The Tunable Filter Imager Passes its CDR[s]

2010 Sept. 16 Sivaramakrishnan The Non-Redundant Mask on JWST

2010 Nov. 18 Sivaramakrishnan Non-Redundant Tilts (NRT): A Fallback Coarse Phasing Method for JWST Using TFI

2011 March 17 Chayer JWST FGS & TFI Cryovac Risk Mitigation Tests


TFI Lessons Learned

#1: Cryogenic etalons are tricky.

July 20, 2011:

Wave good-bye to TFI.

Say hello to NIRISS.

Near InfraRed Imager & Slitless Spectrograph


Design Considerations for NIRISS

Maintain capability to address core TFI Science• “First Light”• Exoplanets

Minimize technical risk • Schedule is a (big) issue• Cost is a (big) issue

Simplify operations

Emphasis of nascent GTO Programs

“Scope” is the only adjustable parameter available to CSA Program Management.

Helps the S&OC (i.e., us) a bit.


Observing Modes

TFI NIRISSNarrow-Band Imaging

R~100; tunable 1.5 – 2.6 & 3.0 – 5.0 micronsWide-Field Slitless Spectroscopy

R~ 150; 1.0 – 2.5 microns

Coronagraphic ImagingR~100; tunable 3.0 – 5.0 microns XXXXXXXXXXXXXXXXX

Sparse-Aperture Interferometric ImagingR~100; tunable 3.0 – 5.0 microns

Sparse-Aperture Interferometric ImagingFixed medium-band filters

Single-Object Slitless SpectroscopyR~700; 0.7 – 3.0 microns

Broad-Band ImagingFixed filters; 1 – 5 microns


Optical Layout of the TFI

20482048 HgCdTe5.2 micron cut-off18 micron pixels


Optical Layout of NIRISS

20482048 HgCdTe5.2 micron cut-off18 micron pixels


Elements in the NIRISS Dual Wheel


Wide-Field Slitless Spectroscopy

Slitless Spectroscopy with Two Orthogonal Grisms

• A spectrum for every source in the field of view.

NIRISS is Competitive With NIRSpec

Bad

Good


Sparse-Aperture Interferometric Imaging

Sparse-aperture interferometry with NIRISS pushes the angular resolution of JWST to its limit

goal

Beichman et al 2010

Bright planets

Faint planets

Filter Set (3) for Use With MASKNR Optimized for constraining temperature and mass.


Single-Object Slitless Spectroscopy

G700XD design

R 700 dispersion with grism along V2∼ Low dispersion with prism along V3, to separate orders Weak cylindrical lens on front side of prism to induce a

defocus along V3

weak cylindrical

surface

m=0

m=1

m=2

m=3

Slitless cross-dispersed 0.6-3.0 μm spectroscopy

17

Schematic of Transit and Eclipse Science

Measure size of planet 10-2

See starlight transmittedthrough planet atmosphere 10-4

Eclipse

Planet thermalemission appearsand disappears 10-3

Learn about atmosphericcirculation from thermalphase curves

Transit

Seager & Deming (2010, ARAA, 48, 631)

Transit Spectrum of Habitable “Ocean Planet”

NIRISS G700XD perfectly suited for such challenging programs. The water vapor features below have a depth of 50 parts per million.

0.6 μm 2.5 μm

NIRISS wavelength range


Broad-Band Imaging - Blue


Broad-Band Imaging - Red

NIRISS Sensitivity vs NIRCam

Good

In general , NIRISS is more sensitive than NIRCam.

NIRISS with spare NIRCam filter filter


Summary

NIRISS is coming!

Capable instrumentComplements & Extends near-IR capability of JWSTStraightforward to operate*

* Grisms / aperture mask introduce complexity on the “back end”.

First Light: Lyman alpha emitters (10< z<13) ; photometric redshifts

High-resolution imaging: exoplanet imaging and characterization

Spectroscopy of transiting exoplanet atmospheres (including H2O, CO2 features…)

Introducing JWST’s NIRISS : The N ear I nfra R ed I mager & S litless S pectrograph

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