EUCLID Thales Alenia Space system concept · 2012-06-04 · EUCLID TAS study: introduction...

All rights reserved, 2008, Thales Alenia Space

EUCLID Thales Alenia Space system concept

Alberto Anselmi (1) and Eric Thomas (2)

(1)Thales Alenia Space, Torino, Italy (2)Thales Alenia Space, Cannes, France

Euclid Mission Conference 2012 The Black Diamond, The Royal Library, Copenhagen, May 15-16, 2012


EUCLID TAS study: introduction

High-precision survey mission to map the geometry o f the Dark Universe, optimized for two complementary cosmologi cal probes� 15,000 deg² extragalactic sky survey with 1.2m telescope at L2� High precision imaging at visible wavelengths

� Photometry/Imaging in the near-infrared

� Near Infrared Spectroscopy

Experienced TAS team comprising TAS-I (Prime) and T AS-F (PLM) � 2 industrial design studies performed for ESA in 2008-2009 (Assessment)

and 2010-2012 (Definition – Phase A/B1)� support by Deimos Space and Kayser-Threde in Phase A


Mission phases

� LEOP: launch to completion of perigee velocity and launcher dispersion correction manoeuvres (L+2, L+5, L+20)

� 3-month initial check-out phase including 1-month P erformance Verification at L2

� Science operations for 6 years � 2 ground stations (Cebreros & New Norcia) taking tur ns

Arrival at L2

Cebreros New Norcia

Commissioning (1 mo.)Performance Verif. (1 mo.)

Operational orbit

Cebreros orNew Norcia

End of Mission

Transfer orbit Operational orbit (free-insertion, large-amplitude orbit around L2)

deep survey

Nominal Science Operations Phase (6 years)

Kourou

Cebreros

New Norcia

Transfer (1 mo.)

wide extragalactic survey

S/C separationlaunch

Pre-Launch LEOPCommissioning


Sky survey

� Coverage: 15,000 deg² at galactic latitude b >|30º|

� Limited to parts of the sky compatible with -5°< αsun<5°, 89°< βsun <121°

� Covered by contiguous 0.5deg² tiles (fields)

� 4 dithers per field, each dither including simultaneous VIS imaging and spectroscopy, followed by photometry in 3 bands� < 4500s per field (including field-to-field

slew)

� Deep Survey: enhanced coverage of ecliptic pole areas by monthly revisits

� Extensive calibration

βsun


System requirements

Driving performance requirements:� 15,000 deg² Wide Extragalactic Survey completed in 6 years

� Ellipticity of the telescope system PSF < 14% at any point of the FOV

� Ellipticity variation δe < 5*10-3 over 8 consecutive exposures of two adjacent fields

� Relative pointing error < 19 milli-arcsec @ 585s, 68% CL

� Low-temperature focal planes (100K, 150K)� 850 Gbit/day science data volume

→→→→ State of the art mirror technology, high stability telescope structure, large radiator area, high accuracy & fas t AOCS, K-band telemetry


Satellite configuration

Telescope

Sunshield

PLM

SVM housing warm PLM

electronics

Telescope Baffle

Optical bench

Instrument radiators

Star tracker cluster

Thruster pods

High gain antenna

Photovoltaic assembly


Euclid Telescope & instruments

� Telescope:■ 3 mirrors off-axis Korsch design

■ 1.2 m diameter primary mirror, f=24.5 m

■ ~110 mm dichroïc in output pupil separates VIS and NISP beams

� VIS instrument■ FPA + shutter + calibration

■ Optical interface: telescope focus

� NISP instrument

■ Optical interface: telescope output pupil (dichroic)

FPA + FEE Shutter Unit Calibration Unit

Opto-mechanical assembly +

Detection System

Euclid optical layout proposed by ESA


Euclid Telescope Overview

M2 Frame

Ultra Stable M1M2 truss

Optical Bench

M1

M2 and Focalisation

system

Highly recurrent design

- Mature technologies already flight proven or in implementation phase- Mastered development aspects

240 K telescope temperature- Limited excursion between integration and operational temperature- Limited impact on WFE

Instrument Cavity


System Performance drivers

Vis :- requirement for high quality optics: wfe is a major contributor to ellipticity - high sensitivity to defocus- Impact of pointing on ellipticity is found nearly negligible

Vis :- requirement for high quality optics: wfe is a major contributor to ellipticity - high sensitivity to defocus- Impact of pointing on ellipticity is found nearly negligible

NISP:- Compatible with telescope optics temperature of 24 0 K

NISP:- Compatible with telescope optics temperature of 24 0 K

Thermal shields and radiators provided to instruments cold units accommodated in PLM

Thermal shields and radiators provided to instruments cold units accommodated in PLM

PLM instrument cavity architecture and instrument accommodation authorizes a modular instrument integration sequence

PLM instrument cavity architecture and instrument accommodation authorizes a modular instrument integration sequence

PLM design optimized to limit contribution to syste m mass budget

PLM design optimized to limit contribution to syste m mass budget

Proposed PLM architecture based on mature solutions and no need of specific developments- High Resolution / stable architecture telescope he ritage

Proposed PLM architecture based on mature solutions and no need of specific developments- High Resolution / stable architecture telescope he ritage


Euclid IQ Performance

� Image Quality Performance analysis:■ VIS IQ performance calculation including

� Mirrors WFE• Based on experience

� AIT performance� Misalignments

• Ground to orbit effects• Cool down• Thermo-elastic• Hygro-elastic

� Compensation by M2� AOCS contribution

■ Sensitivity analyses to simulation parameters, comparison with ESA approach� Pupil/PSF sampling effects on results stability, FWHM calculation method

■ Complete telescope system performance calculated including optics+ structure + AOCS

Telescope PSF Line of Sight movement

Ellipticity distribution

FWHMdistribution

R² variation Ellipticity variation

R² variation

0.00E+00

2.00E-04

4.00E-04

6.00E-04

8.00E-04

1.00E-03

1.20E-03

1.40E-03

1.60E-03

1.80E-03

2.00E-03

1 2 3 4 5 6 7 8 9

Field position

Ellipticity variation

0.0E+00

5.0E-04

1.0E-031.5E-03

2.0E-03

2.5E-03

3.0E-03

3.5E-034.0E-03

4.5E-03

5.0E-03

1 2 3 4 5 6 7 8 9

Field Position


Euclid IQ performance

� Complete analyses performed for all requirements

■ Absolute and variations of IQ for VIS, Encircled energy for NISP■ Optics + line of sight effects included for absolute performances

� Ellipticity and R² performance driven by mirrors wfe

� Ellipticity and R² Variation requirements achieved through fine regulation of telescope cavity

� 240 K telescope temperature ensures■ Limited excursion between integration and operational temperature

■ Stable design

■ Limited contribution to straylight

� PLM proposed concept based on high heritage in High Resolution Telescopes validated by analyses


AOCS performance

� AOCS image quality (585s)(VIS):■ FWHMmax: < 25 mas (see figure 1)■ Ellipticity: < 30% (99.3%, see figure 2)

� Relative Pointing Error (NISP) (68% c.l.) : ■ < 12mas (X,Y),< 100 mas (Z)

� Absolute Pointing Error (68% c.l.) : ■ < 2.5 arcsec (X,Y), < 5.5 arcsec (Z)

� Dither-to-dither a-posteriori measurement accuracy (68% c.l.) :

■ <0.015 mas (X,Y)� Maneuver time

■ Slew (0.7deg) : 150s■ Dither : 80s

� Fine pointing: Fine Guidance Sensor + gyroscope + cold-gas thrusters

� Slew/dithers: Star trackers + gyroscope + small reaction wheels

Fig. 1: PSF AOCS - FWHMmax distribution

Fig. 2: PSF AOCS - Ellipticity distribution


Conclusions

EUCLID is technically feasible with available and d emonstrated technologies� System requirements are met� Instrument interfaces can be accommodated

� Design extensively validated by modelling and simulation

An effective and robust development plan has been d eveloped� 6-yr plan, compliant with 6-month system margin, launch at the end of 2019� Telescope performance verification at PLM level with selected checks

repeated at integrated system level

EUCLID Thales Alenia Space system concept · 2012-06-04 · EUCLID TAS study: introduction...

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