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Recent Changes and Current Issues in Red Focal Plane Design for Plato Telescope

This meeting discusses the recent changes, current issues, and the thermomechanical design of the red focal plane for the Plato telescope, including the location in relation to the telescope, CCD characteristics, and CCD procurement.

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Recent Changes and Current Issues in Red Focal Plane Design for Plato Telescope

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  1. Plato meeting Estec Fri 27/Feb/09 Focal Plane Dave Walton UCL/MSSL Miguel Mas INTA/CAB + LIDAX (mechanical + thermal) Recent changes, current issues etc. in red

  2. FPA: location in relation to telescope

  3. PLATO FPA Thermomechanical Design Current Design from LIDAX following discussions with telescope group SHIM MASK CCDs + CCD SUPPORT PLATE FPA HOUSING FEE + FEE SUPPORT PLATE THERMAL STRAP COVER

  4. PLATO FPA Thermomechanical Design Mass Budget • Mass Budget (per FPA, including FEE & CCDs)

  5. CCD: Using Gaia for prototyping • Plato CCD characteristics • Flight: 42 telescopes, 4 CCDs per telescope -> 168 flight CCDs. • Each CCD 3584x3584 18µm pixels. • Full-frame (except for 2 bright-source telescopesusing same chip butframe transfer). • Red-enhanced AR coating. • Thin oxide and doping to increase full-well to ~1Me-. Gaia CCD at MSSL

  6. Normal telescope electrical architecture • 8 output ports multiplexed into 2 ADCs

  7. Normal telescope: Time-multiplexing of CCDs • In order to remain close to FEE power budget, may be necessary to unpower CCD output nodes when not active

  8. Fast telescope electrical architecture • Due to high duty cycle, 1 ADC per port required. • Similarly, unpowering of CCD output stages not possible • Therefore, power consumption significantly higher than normal telescope, so just as well there are only two.

  9. CCD Procurement: Delivery rate • Potentially 42 telescopes, -> 168 flight CCDs.e2v say this is feasible in a 3-phase programme:Phase 1: Development activities – 18 monthsPhase 2: Evaluation activities and FM preparation – 18 monthsPhase 3: FM manufacturing – 2 years • ESA have queried delivery rate, based on Gaia rate. • Initial response from e2v:* Agree the device is somewhat larger. However, from Gaia experience, more than half of yield loss was not area-related (e.g. mechanical packaging).* Plato delivery rate higher than Gaia, but not by a huge margin (~10 per month). Can be accommodated: more an issue of planning the resources rather than e2v’s capacity.* Cyril Vetel (Astrium) very pleased with progress of Gaia CCD procurement.

  10. CCD Procurement: Thin oxide • In Dave Morris’s note, he assumed a lower yield for thin oxide devices, and was satisfied that the delivery rate could be achieved. Recent tests by e2v of small area devices showed a similar yield to normal devices.

  11. CCD Temperature • PDD assumed TCCD ~-100 C. • Design/implementation simpler if TCCD ~-70 C. • Issues: • Dark current: Not a problem at these temperatures (much lower than other noise sources) • CTE effects from irradiation-induced traps: the principal reason for -100C in PDD. Being addressed by simulation, comparison with Corot, Integral data.

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