STSAT-3

UN BSSW, June 2008 KASI

Compact Wide-Field Survey IR Space Telescope Design

Wonyong Han

Korea Astronomy & Space Science Institute (KASI)

Park J. H., Lee S., Nam U.-W., Yuk I.-S., Jin H., Park Y. S., Park S. J.,

Jeong W. S., Lee C. H., Lee H. M., Ree S. W., Matsumoto T.

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OutlineOutline - - Introduction Introduction

- Science Goals- Science Goals

- System Design- System Design

- Opto-Mechanics- Opto-Mechanics

- Detector & - Detector &

ElectronicsElectronics

- Thermal analysis- Thermal analysis

- Mission Operation- Mission Operation

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- Korea Sci & Tech Satellite (STSAT) began 1999- Korea Sci & Tech Satellite (STSAT) began 1999

- FIMS : KASI developed- FIMS : KASI developed FIMS,FIMS, Main Payload of Main Payload of

STSAT-1,STSAT-1,

in collaboration with KAIST & UC Berkeleyin collaboration with KAIST & UC Berkeley

- STSAT-1 (FIMS) Launched in 2003- STSAT-1 (FIMS) Launched in 2003

- FIMS Science Results were Published on ApJL in - FIMS Science Results were Published on ApJL in

20062006

- STSAT-3 Program started in 2007 - STSAT-3 Program started in 2007

- KASI Proposal, MIRIS was Chosen as Main Payload- KASI Proposal, MIRIS was Chosen as Main Payload

- MIRIS is small wide-field IR Space Telescope - MIRIS is small wide-field IR Space Telescope

[ [ MMulti-purpose ulti-purpose IInfra-nfra-RRed ed IImaging maging SSystem ]ystem ]

IntroductionIntroduction

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FIMS Heritage

• ApJL, 2006, Vol 644, Special Issue

- First results from the FIMS Mission

- 9 papers published including Instruments & System Performances

Total diffuse intensity map of the sky for the SPEAR/FIMS L-band (1360-1730 A) observations. Evident features include the Galactic plane, the Sco-Cen association, and the LMC.

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MIRIS : Scientific Goal (1/3)• Galactic Plane Survey (1/2)

Origin of the Warm Ionized Medium (WIM)– Challenge to the current paradigm of the Ionization theory– Test the effect of Dust scattering for the WIM observation

Observation : Pa survey – Pa (MIRIS) vs. H (Ground-based) : Scattering difference

Hαmap from a ground-based survey

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Scientific Goal (2/3)• Galactic Plane Survey (2/2)

Physical Properties of Turbulence in the Galaxy– Survey the physical parameters of turbulence in the Galaxy– Derive Magnetic field strength from the structure characteristics of

turbulence

Observation : Pa survey – Pa (MIRIS) vs. H (Ground-based) : Extinction difference

Measurement of the turbulence structure

Turbulence model

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Scientific Goal (3/3)

• Cosmic Infrared Background (CIB) Observation

Origin of the Near-IR CIB– Test the hypothesis of the Pop III origin– Confirm the degree-scale fluctuation suggested by IRTS & AKARI and reveal its

nature Observation : I & H-band – I-band (no Pop III) vs. H-band (Pop III expected)

Matsumoto et al. 2005

Spectral bump suspected to be redshifted from the Pop III Ly-cutoff

Degree-scale fluctuation in the power spectrum from IRTS

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MIRIS System Design

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STSAT-3 Layout

Space Observation Camera

Earth Observation Camera

Secondary Payload, COMIS

Sun Avoidance = ±90 degree

Earth Avoidance = ±30 degree

Sun Avoidance = ±30 degree

Star Tracker

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Space Observation Camera (SOC)

MIRIS Layout

Controller box

Nadir

Flightdirection

X(Roll)

Z(Yaw)

Y(Pitch)

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MIRIS Specifications

Space Obs. Camera (SOC)Earth Obs. Camera

(EOC)

Wavelength 0.9 – 2 um 3 – 5 um

Aperture 80 mm 100 mm

Focal ratio f/2 f/5

Pixel FOV 51.6 arcsec

Detector FOV 3.67o x 3.67o

Ground pixel size 42 m @700km

Swath width 13.4 km @700km

Sensor Teledyne PICNIC i3 system

Filter Filter Wheel (6 filters) Band pass filter

Telescope Temp180-200 K (passive

cooling)300 K

Sensor Temp 77 K 77 K

Performance MTF > 60% MTF > 20%

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MIRIS Operation Concept

Mode Test (3 months) 1st Year 2nd Year

Bus Test 10 orbits/day(1 month)

(if needed) (if needed)

Space Observation -Galactic Plane -Cosmic Background -Calibration

(1 month)4 orbits/day4 orbits/day2 orbits/day

6 orbits/day2 orbits/day2 orbits/day

User time(if needed)

Earth Observation(1 month)2 orbits/day

Regular Test & Emergency Observation

6 orbits/day

Ground Contact 4 orbits/day 4 orbits/day 4 orbits/day

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SOC LayoutCooler

Lens

Detector

Baffle

Radiator

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SOC Optics

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SOC Filter System

Purpose ID CWL (um) FWHM (um)

Cosmic Infrared Background

I 1.05 0.3

H 1.6 0.8

Galactic Plane Survey

Pa alpha 1.876 0.0188

Pa alpha cont 1 1.84 0.0184

Pa alpha cont 2 1.92 0.0192

Dark & Shutter Blank

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Performance of SOC Optics

Field(degree)

RMS spot size (um)

0.000 12.4

0.895 10.8

1.790 12.0

2.612 24.0

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SOC Structure (1/2)

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SOC Structure (2/2)

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Passive Cooling for SOC (1/2)

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Passive Cooling for SOC (1/2)Temperature profile during one orbit

(1) The telescope can be cooled below the goal temperature of 200K(2) The detector can be cooled below the goal temperature of 80K

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MIRIS Eelectronics

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MIRIS Electronics Box

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SOC Electronics

Q1 Q2

Q3 Q4 AMP ADC

PATTERNGENERATOR

4 channel VIDEO SiganalProcessing

IMAGEDATA

DECODER

AMP ADC

AMP ADC

AMP ADC

FPGA

MEMEORYIMAGE

BUFFER

CONTROLCOMMAND

MMS

GSE

DSP UNIT

PICNIC256256ARRAY

BIAS

CLOCK

FIFO FIFO

SOC READOUT UNIT

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SOC Detector

- HgCdTe Astronomical Wide Area Infrared Imager (PICNIC)- 256256 IR FPA HgCdTe/Al2O3 (MBE)

Parameter Specification Goal

Format 256 256 256 256

Pixel Pitch (μm) 40 40

Fill Factor 90 90

Quantum Efficiency(77K) @2.3 μm 55% 75%

Long wavelength cutoff (μm) 2.5 2.5

Short wavelength cut on (μm) .9 .9

Read noise: multiple sample (e- @ 77K) < 40 < 20

Dark current (e-/s @ 77K) < 2 < 0.2

Well capacity(e-, Vb = 0.5V) 150,000 200,000

Yield(working pixels) > 95% > 99%

Temperature 77K 77K

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MIRIS Operation

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Plan for Galactic Plan Survey

6°

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Plan for Galactic Plan Survey

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Plan for the CIB Observation

• 10ox10o deep field @ NEP

• 50%(1.84o) overlap mosaic for uniform sensitivity

• Best in October & November

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Thank you

whan@kasi.re.kr