NIRCam: A 40 Megapixel Camera for JWST Marcia Rieke NIRCam P.I.

A Competitor 39 million pixels The H2D-39 uses a 39 megapixel sensor that is more than twice the physical size of today’s 35mm sensor…. You only need to spend $33K to get nearly as many pixels as NIRCam So what do you get for your extra $100M for a NIRCam? -- a camera that works from 0.6 to 5 microns, not just from 0.36 microns to 0.8 microns and which can survive the space environment

NIRCam Partners Science Team from Arizona, JPL, Rochester Institute of Technology, Canada, Hawaii, Switzerland, Spitzer Science Center, NASA Ames Lockheed-Martin in Palo Alto, CA, is responsible for design and construction of the most of the instrument Arizona is procuring detectors from Teledyne Imaging Systems in Camarillo, CA, and will deliver them to L-M after characterization and assembly into mosaics Space Telescope Science Institute will operate NIRCam after launch: Current NIRCam Team includes Jay Anderson, Massimo Robberto, and Kailash Sahu

Full Science Team Science Theme Leads Chas Beichman (Debris Disks &Planet.Systems) JPL Daniel Eisenstein (Extragalactic) University of Arizona Michael Meyer (Star Formation) University of Arizona Team Members Stefi Baum Roch. Institue of Tech Simon Lilly ETH Laura Ferrarese HIA/DAO Peter Martin University of Toronto René Doyon Université de Montréal Don McCarthy (EPO Lead) U of Arizona Alan Dressler Carnegie George Rieke University of Arizona Tom Greene NASA Ames Tom Roellig NASA Ames Don Hall University of Hawaii John Stauffer Spitzer Science Center Klaus Hodapp University of Hawaii John Trauger JPL Scott Horner Lockheed Martin ATCr Erick Young University of Arizona Doug Johnstone HIA/DAO Associated scientists: Doug Kelly, John Stansberry, Christopher Willmer, Karl Misselt, Chad Engelbracht (Az), John Krist (JPL)

NIRCam Design Features NIRCam images the 0.6 to 5mm (1.7 - 5mm prime) range Dichroic used to split range into short (0.6-2.3mm) and long (2.4-5mm) sections Nyquist sampling at 2 and 4mm 2.2 arc min x 4.4 arc min total field of view seen in two colors (40 MPixels) Coronagraphic capability for both short and long wavelengths NIRCam is the wavefront sensor Must be fully redundant Dual filter/pupil wheels to accommodate WFS hardware Pupil imaging lens to check optical alignment

Dichroic Provides Two Channels Per Module Short wavelength channel Long wavelength channel Each module has two spectral wave bands SW:0.6mm - 2.3mm LW: 2.4 mm to 5 mm The majority of NIRCam exposure time will be used for deep survey observations over the 7 wide band filters Survey efficiency is increased by taking observations of the same fields in long wave and short wave bands simultaneously Module A Module B

NIRCam’s Role in JWST’s Science Themes The First Light in the Universe: Discovering the first galaxies, Reionization NIRCam executes deep surveys to find and categorize objects. Period of Galaxy Assembly: Establishing the Hubble sequence, Growth of galaxy clusters NIRCam provides details on shapes and colors of galaxies, identifies young clusters NIRCAM_X000 Inflation Forming Atomic Nuclei Recombination First Galaxies Reionoization Clusters & Morphology Modern Universe NIRCam Quark Soup Stars and Stellar Systems: Physics of the IMF, Structure of pre-stellar cores, Emerging from the dust cocoon NIRCam measures colors and numbers of stars in clusters, measure extinction profiles in dense clouds Planetary Systems and the Conditions for Life: Disks from birth to maturity, Survey of KBOs, Planets around nearby stars NIRCam and its coronagraph image and characterize disks and planets, classifies surface properties of KBOs young solar system Kuiper Belt Planets

NIRCam Science Requirements 5-s 50,000 secs Detection of first light objects, studying the epoch of reionization requires: Highest possible sensitivity – few nJy sensitivity is required. Fields of view (~10 square arc minute) adequate for detecting rare first light sources in deep multi-color surveys. A filter set capable of yielding ~4% rms photometric redshifts for >98% of the galaxies in a deep multi-color survey. Observing the period of galaxy assembly requires in addition to above: High spatial resolution for distinguishing shapes of galaxies at the sub-kpc scale (at the diffraction limit of a 6.5m telescope at 2µm). Point source sensitivities for 50,000 sec exposures and 5:1 signal-to-noise ratio. The z=10 galaxy has M=4x108M and the z=5 galaxy has M=4x109M. Number of Filters 6 5 4 Performance of adopted filter set 7 8 0.00 0.05 0.10 0.15 0.20 |Zin-Zout|/(1+Zin) 1<Z<2 2<Z<5 5<Z<10

NIRCam Science Requirements cont’d Stars and Stellar Systems: High sensitivity especially at l>3mm Fields of view matched to sizes of star clusters ( > 2 arc minutes) High dynamic range to match range of brightnesses in star clusters Intermediate and narrow band filters for dereddening, disk diagnostics, and jet studies High spatial resolution for testing jet morphologies Planetary systems and conditions for life requires: Coronagraph coupled to both broad band and intermediate band filters Broad band and intermediate band filters for diagnosing disk compositions and planetary surfaces

Derived Requirements nJy (10-35 W/m2/Hz) sensitivity Detectors with read noise < 9 e-, Idk<0.01 e/sec QE>80% Focal plane electronics with noise < 2.5e- so detector performance is not degraded High throughput instrument: 70% for optics, 85% for filters At least 7 broadband filters for redshift estimates Large Field of View Dichroics to double effective FOV Large format detector arrays Large well-depth on detectors High spatial resolution Nyquist sampling at 2mm and 4mm

Derived Requirements cont’d Selection of intermediate and narrowband filters 8 R~10 filters needed to classify ices, cool stars At least 4 R~100 filters for key jet emission lines (want higher spatial resolution than Canadian tunable filters) Coronagraph required in all modules Coronagraph most important at long wavelengths Coronagraphic field must not reduce survey FOV Need fluxes calibrated to 2% Requires gain stability on week time scales Requires on-orbit calibration plan using on stars

Field of View Layout

NIRCam as Wavefront Sensor: Initial Capture and Alignment Telescope focus sweep Segment ID and Search Global alignment Image stacking Coarse phasing Fine phasing Multi-field fine phasing. First Light After segment capture Coarse phasing w/DHS NIRCam provides the imaging data needed for wavefront sensing. Two grisms have been added to the long wavelength channel to extend the segment capture range during coarse phasing and to provide an alternative to the Dispersed Hartmann Sensor (DHS) Entire wavefront sensing and control process demonstrated using prototypes on the Keck telescope and on the Ball Testbed Telescope. Spectra recorded by NIRCam DHS at pupil Fine phasing After coarse phasing Fully aligned

Coarse Phasing with the Dispersed Hartmann Sensor DHS is collection of grisms and wedges that are placed in the NIRCam pupil wheel. Every segment pair is covered by one grism so coarse phasing consists of measuring spectra to determine the offset in the focus direction between segments. Process is robust even if a segment is missing. After correction Max piston error=0.66 m Rms=0.18 microns Initial errors Max piston error=19 m Rms=5 microns A prototype DHS was tested on Keck.

NIRCam Optical Train Today V1 1 Pick-off Mirror assembly ** 2 Coronagraph 3 First Fold Mirror 4 Collimator lens group 5 Dichroic Beamsplitter 6 Longwave Filter Wheel Assembly 7 Longwave Camera lens group 8 Longwave Focal Plane 9 Shortwave Filter Wheel Assembly 10 Shortwave Camera lens group 11 Shortwave Fold Mirror 12 Pupil Imaging Lens ** 13 Shortwave Focal Plane 1 10 9 8 7 6 5 4 3 2 11 12 13 V3 V2 ** These items + bench design changed from original proposal ETU will have Only one Module (B) No LW Channel No Coronagraphic capability

Coronagraph Concept Pupil Wheel Collimator Optics Camera NIRCam Pickoff Mirror Telescope Focal Surface Coronagraph Image Masks Coronagraph Wedge JWST Telescope Not to scale NIRCam Optics Field-of-View FPA Coronagraph Image Masks Without Coronagraph Wedge With Coronagraph Wedge Filter Calibration Source Collimator Optics Camera Wedge

Planet Observations Simulation by John Krist

100 Myr-Old, 2 MJup Planet

Shortwave Optical Path SW FPA Flat SW FPA SW Camera Triplet SW Fold Flat Dichroic Beamsplitter Filter(s) FFM Collimator Triplet POM Lenses fabricated from either LiF, BaF2 or ZnSe.

Longwave Optical Path LW FPA Flat LW FPA LW Camera Triplet Filter(s) Dichroic Beamsplitter FFM Collimator Triplet POM

WFE Performance

Transmission

Pathfinder - COL and SW Cam Singlets ZnSe Singlet Singlet with Vibe Fixture LiF Singlet

Pathfinder DBS – Thermal Test to 105 K White Chamber Pathfinder DBS Thermal Strap Interface Plate Cold Table

SW Camera Assy – Thermal Vac Testing White Chamber Pathfinder DBS SW Cam Assy Thermal Straps Interface Plate Cold Table

Pupil Imaging Lens (“The PIL”) A pupil imaging lens was added to NIRCam to assist with aligning NIRCam to the telescope and to provide pupil data to the wavefront sensing algorithm. Qual unit pupil imaging lens

FAM Role in NIRCam The NIRCam Focus and Alignment Mechanism (FAM) contains the Pick-Off Mirror (POM), the first element in the NIRCam optical train. It has the capability to position the POM in 3 degrees of freedom; focus, tip, and tilt. POM Assembly Linear Actuators Sensor & Target Assy

NIRCam Filter Wheels Filter/pupil wheels include extra cal features. Both the long and the short wave channels have dual-filter wheel assemblies The first wheel is located at the NIRCam pupil and is referred to as the pupil wheel The second wheel is referred to as the filter wheel Longwave FWA Dichroic Beam Splitter Filter/pupil wheels include extra cal features. Shortwave FWA Longwave Camera Shortwave Camera

NIRCam Filters P

Pupil Wheel Calibration Source & Projectors Pupil Alignment Pinhole Projector Flat Field Projector Calibration Light Source

Grism 1: Horizontal Dispersion Grism 2: Vertical Dispersion Grism Motivation Primary technique for JWST coarse segment phasing uses 2 Dispersed Hartmann Sensors (prism arrays); reduces phase offsets from ~100 m to < 1m (PSF is sensitive to even larger errors) Each prism covers 2 segments; fringes produced when segment offsets cause pos / neg interference as function of wavelength Has been successfully demonstrated on Keck 2 identical grisms (rotated 90 deg) are being added as a backup for coarse phasing technique, but they will also enable science Dispersed Fringe Sensing: tilt of dispersed fringe yields segment piston Also validated on Keck (90-142 nm RMS error) Each grism covers all segments Grisms in series with a LW filter High dispersion @ long wavelengths gives large capture range Grism 1: Horizontal Dispersion Grism 2: Vertical Dispersion

Spectra Positions on FPA of a Point Source at the Center of the Field 36.7 mm 4950 nm 4700 nm 3950 nm 3700 nm 3200 nm 2950 nm LW FPA size 36.7 X 36.7 mm Center Field Dispersion by Grism Grism: Design Spectra Positions on FPA of a Point Source at the Center of the Field 65 gv/mm design meets WFS requirements Maximum piston listed is from the red-spectral DFS algorithm with short wavelength end starts from center of spectral range Minimum piston listed comes from fringe tilt detected by using differential centroid of the cross-section profile between long and short wavelength ends Centroiding accuracy determines the minimum piston detection. (s = 1/20 pixel is used) Grism Wavelength Range NIRCam Filters Maximum Piston Minimum Piston Grism Thickness 65.0 gv/mm 3.30 – 5.0 mm F322W (partial), F356W, F444W ±291 mm ±0.12 mm Min = 3.3 mm, Max = 8.5 mm 75.0 gv/mm F322W (partial), F356W (partial), F444W ±344 mm Min = 3.5 mm, Max = 9.8 mm

Near IR Detectors Three instruments (NIRCam, NIRSpec, FGS/TFI) use the same detectors. NIRCam uses two flavors of HgCdTe, 2.5mm and 5.2mm cut-off material. Basic format is 2040x2040 with 4 reference pixels around the periphery Performance is great – dark current at 37K is ~.005 e/sec, QE is > 80% over the full 0.6 - 5mm range Three development detectors in test dewar. Read Noise: median is 7.5 electrons in 1000 sec. Well depth is nearly 2x the required 60,000 electrons.

Other Properties Excellent, too! 2mm flat fields. Flats show little wavelength dependence. .025% of full well Dark current floor Differential Cumulative HgCdTe material is now produced by molecular beam epitaxy rather than liquid phase epitaxy which produces much more uniform and high quality material. 0.5 1.0

Detector Result: Using Reference Pixels Reference pixels act like detector pixels electrically. They can be used to Correct for drifts in the readout electronics (upper panel) Correct for drifts due to temperature changes (lower panel)

Interpixel Capacitative Coupling “Popcorn” Noise Not Quite Perfect! Time  Interpixel Capacitative Coupling

Producing Mosaics After SCAs (sensor chip assemblies) are produced at Teledyne, they will be mounted with minimal gaps to produce a 4Kx4K mosaic for NIRCam’s short wavelength arm. Location of SCAs within the mosaic will be verified by using a precise measuring microscope which can measure the location of a surface to better than 10 microns in all three coordinates. Mosaicing done at Steward. Four arrays () are mounted to create a 4Kx4K mosaic ().

FPA Mock-up Assembled FPA less SCAs and the mask. All parts can be machined in Tucson, most on campus. Mask to cover gaps and bond wires. Ti flexure.

FPA Assembly Verification Insert Plates Black Epoxy Visible Through Plastic FPA Baseplate

FPA Heater Assembly Verification Mosaic Baseplate Temperature Sensors Titanium Struts Heater

ETU Bench is finished!

Why Being PI Isn’t Fun!

NIRCam is on its way! Much of the NIRCam Engineering Test Unit hardware has been delivered to Palo Alto with the ETU to be delivered to Goddard early next year. Collection of detector calibration data in progress. Some flight hardware is also already in hand. The flight unit is to be delivered in the spring of 2010.