The EChO payload instrument – an overview

Eccleston, Paul; Swinyard, B.; Tessenyi, Marcel; Tinetti, Giovanna; Waldmann, I. P.; Ferlet, Marc; Irshad, Ranah; Lim, T.; Middleton, Kevin; Bradshaw, T.; Crook, M.; Hunt, Tom; Winter, B.; Bryson, Ian; Bezawada, Naidu; Taylor, W. D.; Bowles, Neil E.; Pascale, Enzo; Morgante, G.; Pace, E.; Adriani, A.; Réess, Jean-Michel; Ollivier, M.; Ottensamer, R.; Rataj, M.; Zapata, Gonzalo Ramos; Schrader, Jan-Rutger; Selig, A.; Isaak, K. G.; Linder, M.; Puig, L.

doi:10.1007/s10686-014-9428-8

Cited by 25 publications

(12 citation statements)

References 17 publications

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“…The frequency band over which the requirement applies is between 2.8×10 −5 Hz and 3.7 mHz, or~5 min to 10 h [60,122,127,187]. This implies having the capability to remove any residual systematics and to co-add the elementary observations from many repeat visits to a given target.…”

Section: Echo Performance Requirementsmentioning

confidence: 99%

The EChO science case

et al. 2015

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The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune-all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10 −4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4 to 16 μm. Only modest spectral resolving power is needed, with R~300 for wavelengths less than 5 μm and R~30 for wavelengths greater than this. spectroscopy technique means that no spatial resolution is required. A telescope collecting area of about 1 m 2 is sufficiently large to achieve the necessary spectro-photometric precision: for the Phase A study a 1.13 m 2 telescope, diffraction limited at 3 μm has been adopted. Placing the satellite at L2 provides a cold and stable thermal environment as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. EChO has been conceived to achieve a single goal: exoplanet spectroscopy. The spectral coverage and signal-to-noise to be achieved by EChO, thanks to its high stability and dedicated design, would be a game changer by allowing atmospheric composition to be measured with unparalleled exactness: at least a factor 10 more precise and a factor 10 to 1000 more accurate tha...

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Section: Echo Performance Requirementsmentioning

confidence: 99%

The EChO science case

et al. 2015

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“…In the EChO instrument all the opto/mechanical systems are attached to a single, monolithic optical bench that is passively cooled to~45 K [3]. To maximise the efficiency of the thermal interface to the 45 K optical bench (Figs.…”

Section: The Lwir Module As Part Of the Echo Instrument Common Opticsmentioning

confidence: 99%

“…To maximise the efficiency of the thermal interface to the 45 K optical bench (Figs. 1 and 2, [3]), the LWIR module is attached via four M6 screws (Figs. 2 and 3).…”

Section: The Lwir Module As Part Of the Echo Instrument Common Opticsmentioning

confidence: 99%

“…This paper describes the optical and mechanical design of the Long Wave Infrared (LWIR) channel for the proposed EChO mission payload instrument [3,13]. The EChO payload is a multi-module spectrometer that allows simultaneous wavelength coverage from 0.5 to 11.5 μm with a goal to extend the spectral range to 16 μm.…”

Section: Introductionmentioning

confidence: 99%

“…To provide some initial signal-tonoise estimates, typical stellar photon fluxes were defined based on 'bright' and 'faint' cases as well as an empirical model of the zodiacal light [10,3]. During this study several designs were considered, including classical dispersive spectrometers based on prisms and gratings, as well as a static, spatially modulated Fourier transform interferometer [11] One of the main concerns for measurements at wavelengths greater than 11 μm was managing the signal contributions at the detector due to broadband thermal emission from the telescope, instrument enclosure and final focusing optics of the spectrograph.…”

Section: Introductionmentioning

confidence: 99%

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The Long wave (11–16 μm) spectrograph for the EChO M3 Mission Candidate study

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The results for the design study of the Long Wave Infrared Module (LWIR), a goal spectroscopic channel for the EChO ESA medium class candidate mission, are presented. The requirements for the LWIR module were to provide coverage of the 11-16 μm spectral range at a moderate resolving power of at least R=30, whilst minimising noise contributions above photon due to the thermal background of the EChO instrument and telescope, and astrophysical sources such as the zodiacal light. The study output module design is a KRS-6 prism spectrograph with aluminium mirror beam expander and coated germanium lenses for the final focusing elements. Thermal background considerations led to enclosing the beam in a baffle cooled to approximately 25-29 K. To minimise diffuse astrophysical background contributions due to the zodiacal light, anamorphic designs were considered in addition to the elliptical input beam provided by the EChO telescope. Given the requirement that measurements in this waveband place on the performance of the infrared detector array, an additional study on the likely scientific return with lower resolving power (R<30) is included. If specific high priority molecules on moderately warm giant planets (e.g. CO 2 , H 2 O) are targeted, the LWIR channel can still provide improvements in determining the atmospheric temperature structure and molecular abundances. Thus, the inclusion of even a coarse-resolution (R≈10) LWIR module would still make an important contribution to measurements of exoplanet atmospheres made by EChO.

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