Plato meeting MSSL Wed+Thur 15+16/Oct/08

UK interests/activities

Alan Smith and Dave Walton UCL/MSSL

Agenda

Wednesday• Organisation of project, System Group• Organisation of ‘focal plane’ WP (UK+Spain)• CCD characteristics and procurement• CCD optimal operating temperature• Characterisation, CCD, FPA, ...

Thursday• Tour of lab• Front end electronics• FPA interface definitions• AOB

UK groups with hardware interests

• MSSL• Leicester University• RAL• Astrium

Proposal submitted to STFC:

• Awaiting bridging grant• Proposal presentation/decision meeting with STFC

24/Sep/08• Final outcome expected in November

Plato proposal to STFC identifies 9 workpackages for UK

1. Preparation: UK exoplanet community

2. Preparation: UK asteroseismology community

3. CCD specification and characterisation

4. Impact of L2 environment

5. Front end electronics

6. AIV for focal planes

7. Calibration

8. End-to-end simulation

9. Data processing

Baseline

Flexible to the needsof the consortium

Themes

WP Calibration Engineering Data Centre

CCD specification & characterisation

Characterisation Specification

Radiation Damage Characterisation Shielding

Front End Electronics

Design

Thermo-mechanical design

Design

AIV focal planes Verification Assembly and Integration

CalibrationEnd-to-end simulation

Calibration Data processing

Data Centre Calibration Post launch data processing and archive

WP3. CCD Specification and characterisationUK lead: MSSL

Review PDD CCD spec wrt:

• science performance• Manufacturability• Cost• Schedule• packaging

Gaia CCD at MSSL

CCD Specs: see e.g. Payload Definition Doc (PDD)• Flight: 28 telescopes, 4 CCDs per telescope• Each CCD 3584x3584 18µm pixels• Full-frame (except for 2 bright-source telescopes

using same chip but frame transfer)

~150 CCDs

CCD specs (continued)

• 4-phase IФ• Back-illuminated, AR coated, wavelength range

TBC, ~400-1000nm• 2 readout ports, ~4Mpix/s, <20e- rms• SiC package (TBC) with flexi• 2- or 3-side buttable, metallisation of bus lines

CCD open issues

• Integration of JFET (or even controller and/or readout electronics) into CCD package

• Operating temperature: baseline 170K, higher T easier to implement but need to assess effect on trap/release

CCD characterisation• Prototype

– Design verification– In depth charaterisation– Sub-pixel characterisation– Calibration process trials– General optimisation including FEE

• CCD (E2V)– Acceptance testing

• CCD (MSSL)– Delta acceptance (tbc)– Characterisation– Optimisation

• Focal Plane– Noise, alignment– Function

• Telescope– PSF– Function

• Spacecraft– Co-alignment– Function

• In-flight

• Characterisation• Linearity (including Full-

Well domain)• Full-Well• Noise• CTE• Responsivity• Gain• Flat field

• Vs• Temperature• Drive voltages• Wavelength

WP7. CalibrationUK lead: MSSL

• Develop overall scheme to integrate calibration at all levels and be complementary to in-flight calibration practicalities

WP6. AIV for focal planesUK lead: MSSL

• Study verification (Test) strategy at Payload level, to be consistent with calibration strategy (see WP7)

WP8. End-to-end simulationUK lead: MSSL

• Co-ordination with Denmark• Definition of CCD performance model• Definition of focal plane performance model• Consideration of model requirements wrt post-

launch analysis.

WP4. Impact of L2 environment on CCD performanceUK lead: Leicester University

• CCD Requirements study• L2 environment study: radiation and dust• Impact of environment on CCD, shielding• Review of previous and current studies/missions• Scientific impact of above assessments

• Dose: Ionising ~8 Krad(Si)Non-ionising ~5e9 p cm-2

WP5: Front end electronicsUK lead: MSSL

• Analysis and decomposition of Science Requirements and PDD

• Generation and assessment of FEE design options

• Analysis of compatibility of optimum design wrt Science Requirements and payload constraints

• Support to Spain’s thermo-mechanical design work

PEM, developed for ESA Gaiacontract with RAL, Astrium

Front end electronics

• Integrated in CCD package?• 16-bit, 4Mpix/s, 2 ports per CCD. Described in

PDD as “modest extension” to existing components, but suitable rad-hard ADC may be a challenge

• Integral non-linearity important for photometry• Differential non-linearity important for small deltas

(asteroseismology and transits). GATTI scaling may be required.