An Introduction to the FGS-TFI:The Tunable Filter Imager

STScI Training for Data Analysts2008 January 15

Alex Fullerton

STScI / HIA

STScI Training for Data Analysts 2008 January 15

Optical Layout of the FGS-TFI

20482048 HgCdTe5.2 micron cut-off18 micron pixels

STScI Training for Data Analysts 2008 January 15

FGS Optical Assembly – TFI Side

TFI POM on Coarse Focus Mechanism

TFI Collimator TMA

TFI Camera

TMA

TFI Detector Assembly (1 FPA)

TFI SIDECar ASIC

TFI ICP -1

Dual Wheel Assembly

Etalon Assembly

KinematicMounts (3)

Optical Alignment Cubes (2)

TFI POM on Coarse Focus Mechanism

TFI Collimator TMA

TFI Camera

TMA

TFI Detector Assembly (1 FPA)

TFI SIDECar ASIC

TFI ICP -1

Dual Wheel Assembly

Etalon Assembly

KinematicMounts (3)

Optical Alignment Cubes (2)

STScI Training for Data Analysts 2008 January 15

Fabry-Perot Etalons

Optical path difference = 2µl cos

Phase difference = (2/) 2µl cos + r

µ=index of refraction

m = 2µl cos + r /2

Tuning: For fixed m, on-axis (=0) l

Detuning: For fixed m, l, off-axis () cos 1 2/2

STScI Training for Data Analysts 2008 January 15

Etalon Coating Design (17 Layers)

65

70

75

80

85

90

95

100

105

110

115

120

1500 2000 2500 3000 3500 4000 4500 5000 2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

Gap (nm)

Wavelength (nm)

Resolution Gap

Non-Functional Waveband

Resolution

m = 3 m = 1

SHORT1500 to 2600 nm~55 filters

LONG3000 to 5000 nm~51 filters

STScI Training for Data Analysts 2008 January 15

Pupil and Filter Wheels

FLAT Lamp

LINE Lamp

Blocking Filters

CLEAR

STScI Training for Data Analysts 2008 January 15

Key Performance Requirements

Parent* TFI Requirement Description Requirement Value Current Design Value

FGS-308 TFI Channel FOV > 4.7 sq. arcmin 4.88 sq. arcmin

FGS-638 TFI Pixel Size 65 mas 64.3 to 65.5 mas

FGS-306 TFI Wavelength Range 1.6 – 2.5 m 3.2 – 4.9 m

1.5 – 2.6 m 3.0 – 5.0 m

FGS-311 TFI Spectral Resolution > 70 & < 150 90 to 115

FGS-315 Wavelength Shift in FOV < 1.0% (50% of FOV) < 0.3% (complete FOV)

FGS-317 TFI Sensitivity at 3.5 m 126 nJy 105 nJy

FGS-355 Coronagraphic Capability 2 Pupil masks 2 Lyot occulters

4 Pupil masks 4 Lyot occulters

NIRCam bandpass TFI

bandpass

- Wavelength Selection Flexibility - Good Sensitivity for Emission Line Objects

- Emission Line Diagnostic Imaging - Coronagraphy: Extrasolar Planets, Brown Dwarfs