1. Alex Fullerton NIRISS Team Lead RE207 / x1341 / fullerton@stsci.edu
JWST FGS
Almost All About JWST / NIRISS: Near Infrared Imager and Slitless Spectrograph
Alex Fullerton
NIRISS Team Lead
RE207 / x1341 /
INS Training
2016 July 13

2. OTE + ISIM + OTIS

4. JWST: Four Science Instruments
NIRCam
Near Infrared Camera
NIRSpec
Near Infrared Spectrograph
MIRI
Mid-Infrared Instrument
GR150R
GR150C
NIRISS

5. JWST Focal Plane
GR150R
GR150C

6. The Elevator Pitch: FGS & NIRISS
Fine Guidance Sensor (FGS)
The camera to acquire targets and guide
on them during observations. Used for
purely functional purposes.
Supplied by CSA
Prime Contractor: COM DEV International
GR150R
Optical Bench
GR150C
NIRISS
A near-infrared science instrument for imaging
and slitless (grism) spectroscopy.
Supplied by CSA
Prime Contractor: COM DEV International
Principal Investigator:
René Doyon, Université de Montréal

7. Optical Layout of NIRISS
NIRISS has a very simple,
all-reflective design

8. Detector Parameter Value Array Size 2048 × 2048 (2040 x 2040 active)
Pixel size
18 μm × 18 μm
Dark rate
< 0.02 e−/s
Noise
23 e− (correlated double sample)
Gain
1.6 e− / ADU
Field of View
2.2´ × 2.2´
Plate scale in x
arcsec/pixel
Plate scale in y
arcsec/pixel
Detector:
HAWAII 2RG HgCdTe
5.2 μm cutoff

9. epoxy void features occulting spots detector defects cross-hatching
Flight Detector
F200W External Flat
epoxy void features
detector defects
occulting spots
cross-hatching
POM spot

10. What Can NIRISS Do?
Pupil Wheel
Filter Wheel

11. NIRISS Has 4 Observing Modes
Name
Acronym
What It’s Good For
1) Imaging
Imaging
Imaging with filters matched to NIRCam
2) Wide-Field Slitless Spectroscopy
WFSS
Getting spectra of everything in the field of view
3) Single Object Slitless Spectroscopy
SOSS
Getting very precise spectra of bright objects. Especially transiting exoplanets
4) Aperture Masking Interferometry
AMI
High-contrast imaging with very high spatial resolution

12. 1) Imaging

13. Filter Transmission & Sensitivity
nJy
m(Vega)
F090W
11.28
28.28
F115W
11.22
28.06
F140M
14.80
27.43
F150W
9.19
27.83
F158M
12.88
27.39
F200W
7.81
27.54
F277W
6.63
27.09
F356W
6.89
26.56
F380M
18.74
24.34
F430M
28.32
24.65
F444W
12.29
25.49
F480M
36.85
24.14
S/N = 10 in
10 ks

14. 2) Wide-Field Slitless Spectroscopy

15. Seeking Rare Objects in the High-z Universe
MACS J
HST Image: Composite of ACS and WFC3 exposures.
Credit: NASA, ESA, M. Postman, D. Coe (STScI), and the CLASH Team.
Simulation of the CLASH field through the NIRISS F200W filter by
Chris Willott (NRC) and Van Dixon (STScI).

16. WFSS Simulations: F200W + GR150R
GR150R Disperses Along Rows

17. WFSS Simulations: F200W + GR150C
GR150C Disperses Along Columnss

18. Orthogonal Dispersion of GR150R and GR150C
89.99 ± 0.04 degrees
0th order

19. Geometry of Orders: GR150R + blocking filters-1 +1 +2 +3 +4 +5
F090W
F115W
F150W
F200W +1 +2

20. First-Order Sensitivity: Emission Lines

21. NIRISS Can Detect the Oesch et al. z=11.09 Source in ~20 hours

22. 3) Single-Object Slitless Spectroscopy

23. Transiting Exoplanet Science
Seager & Deming (2010, ARAA, 48, 631)
Precision needed: 1 part in 1,000
This is a schematic illustration (not to scale!) of how transits and eclipses of planets around other stars provide information about the planet.
In general, we see the combined light from the star + planet; but the planet’s contribution is extremely small. Periodically – if the orientation is correct – the planet passes in front of the star (“transits”) and blocks out a bit of starlight, so the combined signal drops. When the planet moves behind the star, it is eclipsed; but since its contribution to the total is small, the reduction in the total signal is also small. Looking for periodic reductions in light is how NASA’s Kepler satellite has successfully detected many planetary systems around other stars (more than 700 announced last week!). The duration of the eclipse provides information about the size of the planet.
By disentangling spectra of (star + planet) and (star alone during secondary eclipse), we can obtain the spectrum of the planet alone – AMAZING! The spectrum tells us about the physical conditions in the atmosphere of the planet. The trick is that we need to be able to do this with extraordinary precision. During a transit we can also use spectroscopy to probe the light that’s transmitted by the planet’s atmosphere, but that requires even greater precision.
Transit
Learn about atmospheric
circulation from thermal
phase curves
Measure size of planet. Precision needed: 1 part in 100
See starlight transmitted
through planet atmosphere. Precision needed: 1 part in 10,000

24. cylindrical surface (lens)
GR700XD Grism
weak
cylindrical surface (lens)
Weird Stuff!
Prism: ZnS (Zinc Sulfide)
Grism: ZnSe (Zinc Selenide)
Weak Lens + Prism Side
Grism Side
Unruled Perimeter

25. GR700XD Trace & Orientation
0.6 – 2.8 μm
Rλ 500 – 1600

26. GR700XD Monochromatic PSF
Spatial
CV3 monochromatic PSF
FWHM
Dispersion
Trace Width (Defocus)
Point spread function of the monochromatic source at μm seen through the GR700XD element. The intensity is displayed in a logarithmic scale. The width of the PSF is due to the GR700XD weak lens and the height of the PSF depends on the quality of the optics, since the width of the monochromatic the source spectrum is much smaller than 1 pixel.

27. SOSS Expected Performance
2nd order
1st order

28. SOSS Saturation Limits

29. NIRISS Can Access Most Targets That Will Be Detected by TESS

30. 4) Aperture Masking Interferometry

31. Non-Redundant Mask (NRM)
7 undersized apertures: ~15% throughput
Arranged so that the 21 distances between pairs of apertures (“baselines”) are unique (“non-redundant”)
Science Coffee
2013 May 23

32. Signal is Not the Problem Throw away light but get the science!
Rayleigh
Criterion
 = /D
Michelson
Criterion
 = 0.5 /D
Huge blob Airy
Price on redundancy of short baselines
If you know you’re looking for a binary the tight core of fringe is great!
Coro obscures out to several Airy rings, not just central core

33. V = V(u,v) exp{if(u,v} Works like Magic But It’s Really Science
Subapertures in pupil
Image on detector
Each pixel points to different part of sky,
acts like a different t in correlator
Pixel records square of electric field
Fourier transform image data
V = Abs(V ) displayed here
f array has same areas of data
f is still a FRINGE PHASE
V = V(u,v) exp{if(u,v}
Science Coffee
2013 May 23

34. ONE VOLTAGE per antenna
E1(t)
E2(t)
Correlator t
One fringe per antenna pair
Visibility (amplitude) & phase
V12 = V12 exp{if12}
visibility t

35. Interferogram Produced by the NIRISS NRM
“The Snowflake”

36. AMI in [Simulated] Action

37. A Niche for AMI
70 mas
400 mas
NIRCam soft occulting spot inner working angle
(IWA; 50% transmission point)

38. Predicted Performance of AMI

39. The NIRISS@STScI Team (5/26/16)
Key:
NIRISS Expertise
NIRISS Responsibility
NIRISS Liaison
Cross-SI WG Lead
Alex Fullerton
PhD Astronomy
Toronto (1990)
Van Dixon
PhD Astronomy
JHU (1995)
Team Lead
WFSS
Pipeline WG
Team Deputy
Paul Goudfrooij
PhD Astronomy
Amsterdam (1994)
Nikole Lewis
PhD Planetary Sci
Arizona (2012)
André Martel
PhD Astronomy
UC Santa Cruz (1996)
Swara Ravindranath
PhD Astronomy
IIA Bangalore (2000)
SOSS
Ops
Cross-SI Ops
SOSS
TrExo WG
I&T
Commissioning
WFSS
ETC
JDox
Anand
Sivaramarkrishnan
PhD Astronomy
UT Austin (1983)
Deepashri Thatte
MSc Physics
South Carolina (2004)
Kevin Volk
PhD Astronomy
Calgary (1986)
Michael Wolfe
MSc Applied Physics
Washington (2007)
AMI
AMI
Calibration
Imaging
Reference Files
SOSS

40. Reinforcements are on their Way!
Gabe Brammer
Joe Filippazzo
Katie Gossmeyer
Julia Roman-Duval
Johannes Sahlmann

41. FGS / NIRISS