The Comet Interceptor mission was selected by ESA in June 2019 as ESA's new fast-class mission in its Cosmic Vision Programme. Comprising three spacecraft, it will be the first to visit a Long Period Comet (LPC) or even an interstellar object that is only just starting its journey into the inner Solar System. The RMA, under CSL responsibility, is a mechanism rotating a mirror which ensures that the comet is kept within the FoV of the CoCa instrument during the closest part of the approach. The RMA is composed of the Scanning Mirror Assembly (SMA), including a protection baffle, and the associated electronics (SME). The technical role of CSL is to design, develop, build and verify the SMA to be finally delivered to ESA as part of the RMA. This paper introduces the current activities on the RMA development with a deeper insight on the design steps and the preliminary results of the performed breadboard tests (mechanism actuation and coating impact tests). Additional presentation content can be accessed on the supplemental content page.
CHEOPS (Characterizing Exoplanets Satellite) is an ESA scientific mission devoted to the characterization of known exoplanets orbiting bright stars, achieved through the precise measurement of exoplanet radii using the technique of transit photometry. CHEOPS was selected in October 2012 as the first Small-class mission (S) within the Agency’s Scientific Programme, with an implementation cycle drastically shorter than for Medium-class (M) and Large-class (L) missions and strict cost-cap to ESA. Following the phase A/B1 study, CHEOPS was adopted for implementation in February 2014 as a partnership between the ESA Science Programme and Switzerland, with a number of other Member States delivering significant contributions to the instrument development and to operations. The CHEOPS payload is a high precision photometer, with an optical Ritchey-Chrétien telescope with 300 mm effective aperture and a large external baffle to minimize straylight. The CHEOPS spacecraft (280 kg mass, 1.5 m size) is based on a flight-proven platform and is now operating in a dawn-dusk Sun Synchronous Orbit at 700 km altitude. CHEOPS completed the Preliminary Design Review at the end of September 2014, passed the Critical Design Review in May 2016 and the Qualification and Acceptance review in February 2019. CHEOPS was launched on a shared Soyuz flight from the European Space Centre of Kourou on 18 December 2019 (VS23), completing the In-Orbit Commissioning in March 2020. The paper describes the CHEOPS launch campaign, the early operations phase and the In-Orbit Commissioning results, including instrument and spacecraft performance.
CHEOPS (Characterizing Exoplanets Satellite) is devoted to the characterization of known exoplanets orbiting bright stars, achieved through the precise measurement of exoplanet radii using the technique of transit photometry. CHEOPS was selected in October 2012 as the first Small-class mission (S1) within the Agency’s Scientific Programme, with the following programmatic requirements: science driven mission selected through an open Call; an implementation cycle, from the Call to launch, drastically shorter than for Medium-class (M) and Large-class (L) missions; a strict cost-cap to ESA, with possibly higher Member States involvement than for M or L missions. Following a phase A/B1 study, CHEOPS was adopted for implementation in February 2014 as a partnership between the ESA Science Programme and Switzerland, with a number of other Member States delivering significant contributions to the instrument development and to operations. The CHEOPS payload is a high precision photometer, with an optical Ritchey-Chrétien telescope with 300 mm effective aperture and a large external baffle to minimize straylight. The CHEOPS spacecraft (280 kg mass, 1.5 m size) is based on a flight-proven platform and will orbit the Earth in a dawn-dusk Sun Synchronous Orbit at 700 km altitude. CHEOPS completed the Preliminary Design Review at the end of September 2014, and passed the Critical Design Review in May 2016. In 2017, flight platform and payload have been separately integrated and tested, while satellite activities were completed by end 2018, allowing to reach flight readiness. CHEOPS is scheduled for launch on a shared Soyuz flight by the end of 2019.
CHEOPS (CHaracterizing ExOPlanets Satellite) is an ESA Small Mission, planned to be launched in early 2019 and whose main goal is the photometric precise characterization of the radii of exoplanets orbiting bright stars (V<12) already known to host planets. The telescope is composed by two optical systems: a compact on-axis F/5 Ritchey-Chrétien, with an aperture of 320 mm and a Back-End Optics, reshaping a defocused PSF on the detector. In this paper we describe how alignment and integration, as well as ground support equipment, realized on a demonstrator model at INAF Padova, evolved and were successfully applied during the AIV phase of the flight model telescope subsystem at LEONARDO, the Italian industrial prime contractor premises.
CHEOPS is the first small class mission adopted by ESA in the framework of the Cosmic Vision 2015-2025. Its launch is foreseen in early 2019. CHEOPS aims to get transits follow-up measurements of already known exo-planets, hosted by near bright stars (V<12). Thanks to its ultra-high precision photometry, CHEOPS science goal is accurately measure the radii of planets in the super-Earth to Neptune mass range (1<Mplanet/MEarth<20). The knowledge of the radius by transit measurements, combined with the determination of planet mass through radial velocity techniques, will allow the determination/refinement of the bulk density for a large number of small planets during the scheduled 3.5 years life mission. The instrument is mainly composed of a 320 mm aperture diameter Ritchey-Chretien telescope and a Back End Optics, delivering a de-focused star image onto the focal plane. In this paper we describe the opto-thermo-mechanical model of the instrument and the measurements obtained during the opto-mechanical integration and alignment phase at Leonardo company premises, highlighting the level of congruence between the predictions and measurements.
The CHaracterising ExOPlanet Satellite (CHEOPS) is a joint ESA-Switzerland space mission dedicated to search for exoplanet transits by means of ultra-high precision photometry whose launch readiness is expected end 2017. The CHEOPS instrument will be the first space telescope dedicated to search for transits on bright stars already known to host planets. By being able to point at nearly any location on the sky, it will provide the unique capability of determining accurate radii for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys. CHEOPS will also provide precision radii for new planets discovered by the next generation ground-based transits surveys (Neptune-size and smaller). The main science goals of the CHEOPS mission will be to study the structure of exoplanets with radii typically ranging from 1 to 6 Earth radii orbiting bright stars. With an accurate knowledge of masses and radii for an unprecedented sample of planets, CHEOPS will set new constraints on the structure and hence on the formation and evolution of planets in this mass range. To reach its goals CHEOPS will measure photometric signals with a precision of 20 ppm in 6 hours of integration time for a 9th magnitude star. This corresponds to a signal to noise of 5 for a transit of an Earth-sized planet orbiting a solar-sized star (0.9 solar radii). This precision will be achieved by using a single frame-transfer backside illuminated CCD detector cool down at 233K and stabilized within ~10 mK . The CHEOPS optical design is based on a Ritchey-Chretien style telescope with 300 mm effective aperture diameter, which provides a defocussed image of the target star while minimizing straylight using a dedicated field stop and baffle system. As CHEOPS will be in a LEO orbit, straylight suppression is a key point to allow the observation of faint stars. The telescope will be the only payload on a spacecraft platform providing pointing stability of < 8 arcsec rms, power of 60W for instrument operations and downlink transmission of at least 1.2GBit/day. Both CHEOPS paylaod and platform will rely mainly on components with flight heritage. The baseline CHEOPS mission fits within the technical readiness requirements, short development time and the cost envelope defined by ESA in its first call for S-missions. It represents a breakthrough opportunity in furthering our understanding of the formation and evolution of planetary systems.
CHEOPS (CHaracterising ExOPlanet Satellite) is the first ESA Small Mission as part of the ESA Cosmic Vision program 2015-2025 and it is planned launch readiness end of 2017.
The mission lead is performed in a partnership between Switzerland, led by the University of Bern, and the European Space Agency with important contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom.
The CHEOPS mission will be the first space telescope dedicated to search for exoplanetary transits on bright stars already known to host planets by performing ultrahigh precision photometry on bright starts whose mass has been already estimated through spectroscopic surveys on ground based observations.
The number of exoplanets in the mass range 1-30 MEarth for which both mass and radius are known with a good precision is extremely limited also considering the last two decades of high-precision radial velocity measurement campaigns and the highly successful space missions dedicated to exoplanets transit searches (CoRoT and Kepler).
KEYWORDS: Space telescopes, Planets, Telescopes, Charge-coupled devices, Stars, Space operations, Sensors, Scanning electron microscopy, Point spread functions, Electronics
CHEOPS (CHaracterizing ExOPlanets Satellite) is the first ESA Small Mission as part of the ESA Cosmic Vision program 2015-2025. The mission was formally adopted in early February 2014 with a planned launch readiness end of 2017. The mission lead is performed in a partnership between Switzerland, led by the University of Bern, and the European Space Agency with important contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The mission is dedicated to searching for exoplanetary transits by performing ultrahigh precision photometry on bright starts already known to host planets whose mass has been already estimated through ground based observations. The instrument is an optical Ritchey-Chretien telescope of 30 cm clear aperture using a single CCD detector. The optical system is designed to image a de-focused PSF onto the focal plane with very stringent stability and straylight rejection requirements providing a FoV of 0.32 degrees full cone. The system design is adapted to meet the top-level science requirements, which ask for a photometric precision of 20ppm, in 6 hours integration time, on transit measurements of G5 dwarf stars with V-band magnitudes in the range 6≤V≤9 mag. Additionally they ask for a photometric precision of 85 ppm in 3 hours integration time of Neptune-size planets transiting K-type dwarf stars with V-band magnitudes as faint as V=12 mag. Given the demanding schedule and cost constrains, the mission relies mostly on components with flight heritage for the platform as well as for the payload components. Nevertheless, several new developments are integrated into the design as for example the telescope structure and the very low noise, high stability CCD front end electronics. The instrument and mission have gone through critical design review in fall 2015 / spring 2016. This paper describes the current instrument and mission design with a focus on the instrument. It outlines the technical challenges and selected design implementation. Based on the current status, the instrument noise budget is presented including the current best estimate for instrument performance. The current instrument design meets the science requirements and mass and power margins are adequate for the current development status.
CHEOPS (CHaracterizing ExOPlanets Satellite) is an ESA Small Mission, planned to be launched in mid-2018 and
whose main goal is the photometric precise characterization of radii of exoplanets orbiting bright stars (V<12) already
known to host planets.
Given the fast-track nature of this mission, we developed a non-flying Demonstration Model, whose optics are flight
representative and whose mechanics provides the same interfaces of the flight model, but is not thermally representative.
In this paper, we describe CHEOPS Demonstration Model handling, integration, tests, alignment and characterization,
emphasizing the verification of the uncertainties in the optical quality measurements introduced by the starlight simulator
and the way the alignment and optical surfaces are measured.
The CHEOPS (CHaracterising ExOPlanet Satellite), which is an ESA mission developed in cooperation with Switzerland and a number of other member-states, is the first one dedicated to search for transits by means of ultrahigh precision photometry on bright stars already known to host planets. The optical design is based on a Ritchey-Chretien style telescope to provide a de-focussed image of the target stars.
The telescope’s mirrors M1, M2 as well as the focal plane detector are supported by a thermally controlled CFRP structure suspended on isostatic mounts. The dimensional stability of the structural system supporting the optics is a key requirement as it directly impacts the instrument’s accuracy. The M1 and M2 mirrors are supported by a tubular CFRP telescope design which has been optimized by analyses down to carbon fibre layer level with the support of extensive sample test results for model correlation and accurate dimensional stability predictions. This sample characterization test campaign has been conducted on samples with different carbon fibre layups (orientation and stack sequence) to measure accurately the Coefficient of Thermal Expansion (CTE) over a wide temperature range extending from -80°C to +80°C. Using the correlated Finite Element Model, the fibre orientation layup that minimized the relative displacement between the M1 and M2 mirrors, including the consideration of the thermo-elastic contributions of the isostatic mounts on the overall stability of this optical system, has been identified and selected for the baseline design of the CHEOPS Structure.
A dedicated Structural and Thermal Model (STM2), which was then refurbished to a PFM, was manufactured and tested with an ad hoc setup to verify the overall structural stability of the optical train assembly [2]. The relative distance between M1 and M2 was measured under thermal vacuum conditions using laser interferometer techniques. Thermal cycling tests were initially conducted to eliminate and characterize settling effects. Then, the structure’s stability was measured at three stabilised operational temperatures: -5, -10 and -15°C. The thermally induced M1-M2 misalignment on the optical axis was measured to be between -0.156 and -0.168 micron/°C. Relative mirror tilt and lateral centre shifts were also measured. The obtained focal distance, tilt and centre shift stability between mirrors M1 and M2 were all compliant with the system level requirements such that both an STM and PFM model of the CHEOPS CFRP Structure were successfully qualified and delivered in due time for integration on the spacecraft.
The CHaracterizing ExOPlanet Satellite (CHEOPS) is an ESA Small Mission whose launch is planned for the end of 2017. It is a Ritchey-Chretien telescope with a 320 mm aperture providing a FoV of 0.32 degrees, which will target nearby bright stars already known to host planets, and measure, through ultrahigh precision photometry, the radius of exo-planets, allowing to determine their composition. This paper will present the details of the AIV plan for a demonstration model of the CHEOPS Telescope with equivalent structure but different CTEs. Alignment procedures, needed GSEs and devised verification tests will be described and a path for the AIV of the flight model, which will take place at industries premises, will be sketched.
The CHaracterising ExOPlanet Satellite (CHEOPS) is a joint ESA-Switzerland space mission (expected to launch in 2017) dedicated to search for exoplanet transits by means of ultra-high precision photometry. CHEOPS will provide accurate radii for planets down to Earth size. Targets will mainly come from radial velocity surveys. The CHEOPS instrument is an optical space telescope of 30 cm clear aperture with a single focal plane CCD detector. The tube assembly is passively cooled and thermally controlled to support high precision, low noise photometry. The telescope feeds a re-imaging optic, which supports the straylight suppression concept to achieve the required Signal to Noise.
Spreading the PSF over a quite large amount of pixels is an increasingly used observing technique in order to reach
extremely precise photometry, such as in the case of exoplanets searching and characterization via transits observations.
A PSF top-hat profile helps to minimize the errors contribution due to the uncertainty on the knowledge of the detector
flat field. This work has been carried out during the recent design study in the framework of the ESA small mission
CHEOPS. Because of lack of perfect flat-fielding information, in the CHEOPS optics it is required to spread the light of
a source into a well defined angular area, in a manner as uniform as possible. Furthermore this should be accomplished
still retaining the features of a true focal plane onto the detector. In this way, for instance, the angular displacement on
the focal plane is fully retained and in case of several stars in a field these look as separated as their distance is larger
than the spreading size. An obvious way is to apply a defocus, while the presence of an intermediate pupil plane in the
Back End Optics makes attractive to introduce here an optical device that is able to spread the light in a well defined
manner, still retaining the direction of the chief ray hitting it. This can be accomplished through an holographic diffuser
or through a lenslet array. Both techniques implement the concept of segmenting the pupil into several sub-zones where
light is spread to a well defined angle. We present experimental results on how to deliver such PSF profile by mean of
holographic diffuser and lenslet array. Both the devices are located in an intermediate pupil plane of a properly scaled
laboratory setup mimicking the CHEOPS optical design configuration.
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