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

• 3s detection limit for point sources (100 sec integration, R~5) 26.3mag(AB) for all bandsVega magnitudeJ(1.25mm) H(1.6mm) K(2.2mm) L(3.5mm) M(5.0mm)25.5 24.8 24.4 23.4 23.0Photon 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

• 3s 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