PLATO Main Electronics Units (MEU)based on inputs from P. Plasson and the system team

J. Miguel Mas-Hesse

Centro de Astrobiología (CSIC-INTA)

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On-board data processing: Introduction

Stellar field PLATO image

• DPS goal: automatically process and extract accurate stellar light curves from the raw, messy CCD images.

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On-board data processing: baseline concept

• The normal-telescopes onboard data processing system will be formed by:

– 4 CCD + 1 FEE per focal plane (telescope)• 32 telescopes

– 1 Data Processing Unit (DPU) per 2 focal planes• 16 DPU boards

– 4 DPUs per 1 Main Electronics Unit (MEU)• 4 MEU boxes

– 1 Instrument Control Unit (ICU) per 4 MEUs• 1 ICU (+ 1 fully redundant ICU)

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On-board data processing: architecture

1 N-DPU for 2 N-cameras

F-cameras

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On-board data processing: architecture

Present MEU baseline concept:

+ 1 DPU per 2 focal planes+ 1 single DPU PSU box, external to the MEU’s

To ICU-M To ICU-R

SpW

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PLATO MEU: FEE – DPU SpW link

• FEE – DPU link baseline:– 2 SpaceWire links per FEE (100 Mbps)

• Alternative:– 1 SpaceWire link per FEE (200 Mbps)

• Feasibility has to be demonstrated.

SpW 100 Mbps

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On-board data processing: architecture

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On-board data processing: architecture

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PLATO MEU: operation

Window Extraction

up to 330.000 stars / 25 sec

FullimageAcquisition x 82 images / 6.25 sec

Data correction and LC extraction

Masks & window positions

updating

6.25 sec

6.25 sec

6.25 sec

5400sec

• Target count for 2 x 4 CCD per DPU (to be processed every 25 sec.):

Nominal sample 2x(110.000 stars/telescope) = 220.000 stars/DPU Extended sample (+50% margin) = 330.000

stars/DPU Background win. 2 x 400 Imagettes up to 2 x 2.000 Offset windows 2 x 2 x 4 half-row (2.255 pixels) Smearing rows 2 x 4 x 10 overscan rows

• Total memory requirement, including 50% margin on star count: 250 Mbytes per DPU

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PLATO MEU: CPU load

• The CPU load has been estimated for various processors, based on current baseline for number of stars + extraction algorithms. At this phase the %CPU load should be ≤ 50%.

• The present concept seems feasible, but:– with 1 DPU/2 telescopes, no margin on star counts acceptable.

– with 1 DPU/telescope an extended sample with +50% margin in star counts could be considered, if required. .

Weighted mask photometry assumed

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PLATO MEU: open points

SpaceWire

Router(M)

SpaceWire

Router(R)

Power Supply(M + R)

N-DPU #1

N-DPU #2

N-DPU #3

N-DPU #4

SpW

MEU

SpW

To redundant ICU

To main ICU

235 kbps

235 kbps

235 kbps

235 kbps

<1 Mbps

Test I/F - SpW

180 Mbps(2 x 64 x 1.4)

4 Mpx/s

SpWI/F

ADC

ADC

FEE #14510 px

4510

px

SpWI/F

ADC

ADC

FEE #24510 px

4510

px

SpWI/F

ADC

ADC

FEE #34510 px

4510

px

SpWI/F

ADC

ADC

FEE #44510 px

4510

px

Power Distribution

HK

Cmd

28 V, Cmd from S/CM + R

Backup concept:

+ 1 DPU board per telescope+ 4 DPUs per MEU+ 8 MEU More powerful, but too heavy

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PLATO MEU: open points

Baseline Alternative

Number of telescopes per DPU

2 1

MEU-PSU 1 MEU-PSU box for 4 MEU boxes

4 MEU-PSU inside each MEU box

FEE / DPU number of SpaceWire links

2 SpaceWire links per FEE (100 Mbps)

1 SpaceWire links per FEE (200 Mbps)

FEE DPU image transfer mechanism and protocol

RMAP DMA transfer tables

DPU Boot mechanism Boot Software in PROM Pure RMAP hardware boot

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PLATO: next steps

• The industrial MEU definition study is starting now.

• Goals: – Definition and dimensioning of the N-DPUs

• Global architecture, choice of processors, number of SpaceWire data links, location of PSUs, mass, power comsumption,…

• Trade off on algorithms potential increase of complexity

– Development of simulators/breadboards for critical interfaces

• Spacewire link FEE – DPU

Final design within mass and power budgets, but compliant with scientific requirements!