STATUS REPORT OF FPC

SPICA Task Force MeetingMarch 29, 2010

MATSUMOTO, Toshio (SNU)

Concept of FPC

FPC consists of two instrumentsFPC-G: Focal plane guiding cameraFPC-S: Near infrared camera for scientific observation

FPC-S has a back up function of FPC-G

FPC-G and S must have a same FOV and pixel scale with same detector.1K x 1K InSb array (25mm pixel)

ROIC developed for MIRI/JWST by Raytheon5 arc-minutes FOV for 1 frame0.3 arc-second FOV for 1 pixel (~diffraction limit at

5mm)

Detector proposed by Raytheon

• Format: 1024 x 1024 active (plus two columns of reference pixels)

• Pixel Pitch: 25 μm • Input Circuit: SFD (source follower per detector) • Active Fill Factor: > 98% • Spectral Response: 0.4-5.3 μm • Average Quantum Efficiency: > 90% (1 - 5 μm) • Typical Response Uniformity: ≤ 5% (1σ) • Average Dark Current: ≤ 0.02 e-/sec at 30 K • Read Noise: 25 ~ 30 e- for single CDS (~20 e- for 0.4 Hz

eadout)• Power Dissipation: 0.5 mW (0.4 Hz readout), 1.2 mW ( 1Hz

readout) • Well Capacity: 2x105 e- • Outputs: 4 • Reset Modes Global Reset or reset by Row pair • Operating temperature >10 K

Optical design of FPC-G

Optical axes of lens group are shifted to improve off axis image

7 lenses with 4 aspherical surfaces

Lens materials are ordinary used ones

Spot size ( I and z band) is typically 10 mm. Maximum size is ~35 mm at a far end from the telescope axis

Distortion effect can be corrected by interpolation formula.

Structure of FPC-G

Cross sectional view of FPC-G

Weight ~ 4kg (Support structure and FPA are not included)

Performance of FPC-GRequired accuracy of the determination of centroid: 0.05 arcsec

Wavelength band: I band (0.8 mm)Detection limit: 18.6 mag (1Hz read out, 25s)Number of stars in 1 frame: ~12 stars (GSCII Catalog)FPC-G can achieve required accuracy

Power dissipation1.2 mW (1 Hz readout), 0.5 mW (0.4 Hz readout)

Optical design of FPC-SFPC-S covers wavelength range from 0.5 mm to 5 mmone more optical element

a little longer than previous design (520 mm)

Spot diagram for white light (0.8-5 mm)

Typical spot size 24 mm Max spot size 31 mm

For monochromatic light2-5mm max spot size ~34 mm0.8-2mm max spot size ~42 mm

Distortion effect can be corrected by interpolation formula. Error of centroid for 4’x4’ field is

average:0.03”, Max 0.06”Error of centroid for 5’x5’ field is

average:0.07”, Max 0.37”

Structure of FPC-S

Weight ~ 6kg (Support structure and FPA are not included)Filter wheel 10 positions (blank, diffuser, 8 filters)

New mode: LVF Spectroscopy

• Three LVFs (Linear Variable Filter) are installed on the filter wheel

cf. 0.8-1.6, 1.4-2.8, 2.5-5• LVF has transmission depending on the

physical position (scanning direction).Wavelength coverage is factor 2

Wavelength resolution is ~ 50.http://www.lwecorp.com/product-literature/lvf_ds_co_ae_042506.pdf

• Slit less spectroscopy at the wavelength range from 0.8 to 5 mm

• Combined with slow scan, surface spectroscopy can be done efficiently for diffuse extended source

Scan direction

↓

← 5 arc-minute → LVF

0.8 mm

1.6 mm

Expected performance of FPC-S

• Assumed parametersTelescope 3-m aperture (7m2)Efficiency 0.5 (Optical + quantum efficiency)Read out noise 20 e- image size 4 pixels

• 3 s detection limit for point sources (100 sec integration, R~5) 26.3mag(AB) for all bandsVega magnitude

J(1.25mm) H(1.6mm) K(2.2mm) L(3.5mm)M(5.0mm)

25.5 24.8 24.423.4 23.0

Photon noise becomes dominant for integration time lon ger than 100 sec3s detection limit for surface brightness (100sec integration, R~5)

81 nW.m-2.sr-1

• 3 s detection limit fro LVF mode, R~50, integration time ~tPoint sources, Fl 3.4x10-16.l-2.t-1 W.m-2.mm-1

Extended source, l.Fl 8.1x104.l-1.t-1 nW.m-2.sr-1

Line intensity for point source 6.84x10-18.l-1.t-1 W.m-2

Line intensity for extended source 1.62x103.l-1.t-1 nW.m-2.sr-1

Comparison with JWST

• Larger field of viewJWST 2.2x4.4 arcminFPC-SPICA 5x5 arcmin

• Much larger throughputx 20 of JWST

• Capability of surface spectroscopy

• New science that can not be done with JWST will be possible