content 26-September-2018 16:12:14

Mission concept

The measurement principle of PLATO is to carry out high precision, long (months to years), uninterrupted photometric monitoring in the visible band of very large samples of bright (mV ≤ 11–13) stars. The resulting light curves will be used for the detection of planetary transits, from which the planetary radii will be determined, and for the asteroseismology analysis to derive accurate stellar parameters and ages. Since the PLATO targets are bright, the masses of the detected planets can be determined from radial velocity observations at ground-based observatories.

The key scientific requirement to detect and characterise a large number of terrestrial planets around bright stars determined the design of the payload module. The module provides a wide field-of-view (FoV) to maximise the number of the sparsely distributed bright stars in the sky with one pointing, and allows the satellite to cover a large part of the sky. In addition, it provides the required photometric accuracy to detect Earth-sized planets and a high photometric dynamic range, allowing astronomers to observe bright stars (mV < 11) as well as fainter stars down to V-magnitude of 16. This performance is achieved by a multi-telescope instrument concept, which is novel for a space telescope.

Schematic figure of one of the cameras of the PLATO spacecraft. Credit: PLATO Mission Consortium

The payload consists of 24 'normal' cameras with CCD-based focal planes, operating in white light. They will be read out with a cadence of 25 s and will monitor stars with mV > 8. Two additional 'fast' cameras with high read-out cadence (2.5 s) will be used for stars with mV ~4–8.  The 'normal' cameras are arranged in four groups of six. Each group has the same field-of-view but is offset by a 9.2° angle from the payload module +Z axis, allowing astronomers to survey a total field of about 2250 deg2 per pointing, but with different sensitivities over the field.

The ensemble of instruments is mounted on an optical bench. The cameras are based on a fully dioptric design with 6 lenses. Each camera has an 1100 deg2 field-of-view and a pupil diameter of 120 mm and is equipped with a focal plane array of 4 CCDs each with 4510×4510 pixels of 18 μm size, working in full frame mode for the 'normal' camera and in frame transfer mode for the 'fast' cameras.

The PLATO satellite will be built and verified for an in-orbit lifetime of 6.5 years, accomodating consumables for 8 years, which offers the possibility of mission operation extensions.

ESA provides the spacecraft, the CCDs, the mission operations, and parts of the science operations. The PLATO Mission Consortium, funded by national Funding Agencies, provides the payload and contributions to the science operations.

Payload Consortium contributions

Principal Investigator DLR, Germany
PMC management
System engineering
Performance monitoring & assessment
Data Processing System
Fast Electronics Unit including Fine Guidance System
Telescope Optical Units thermal hardware
Front-end Electronics of the fast telescopes
DLR, Germany
Telescope Optical Units
Instrument Control Unit
ASI, Italy
Focal Plane Assemblies
Main Electronic Unit
Contribution to camera integration, testing and calibration
Software data processing for the normal telescopes
Contribution to Fast Front-End Electronics
Contribution to camera integration, testing and calibration
CNES, France
Optical Ground Support Equipment FCT, Portugal
Ancillary Electronic Units
Multilayer Insulation
MNDH, Hungary
Front-End Electronics of the normal telescopes UK Space Agency
Contribution to camera integration, testing and calibration SRON, The Netherlands
Contribution to the Broadband Filtering Coating of the fast telescopes SNSB, Sweden
Router and Data Compression Unit in the Instrument Control Unit
On-board data compression algorithms
AASA/FFG, Austria
Camera integration, testing and calibration Belgian Federal Science Policy Office
Telescope Optical Units mechanical structure Swiss Space Office

Last Update: 05 September 2018

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