CHEOPS under polishing
The CHaracterising Exoplanets Satellite (CHEOPS) mission, the first satellite entirely dedicated to the characterization of small planets, has been jointly developed by the European Space Agency (ESA) with the contribution of other ESA Member States including Italy, and by Switzerland, with the main scientific objective to study the structure of extrasolar planets orbiting stars close to us that have a size and mass similar to that of the Earth and are no larger than Neptune.
The space telescope with which CHEOPS is equipped will measure with high precision the brightness of a number of stars already known to host planets, recording the variation due to the transit of the planet in front of the parent star, allowing the accurate calculation of the size of the planet, a parameter that, together with the mass measured using ground-based telescopes, will allow astronomers to determine the internal structure of the planet providing important information to understand the formation of planets and, more generally, the composition of planetary systems outside our own.
Thanks to the Italian Space Agency’s (ASI) support, the CHEOPS telescope was designed by National Institute for Astrophysics (INAF) researchers of Padua and Catania and is being built by Avionics Systems Division Space of Finmeccanica in Campi Bisenzio near Florence.
In anticipation of the satellite launch, scheduled for the end of 2017, the surface finishing and the polishing of CHEOPS flight primary mirror have begun, carried out by Media Lario SRL, a SME based in Bosisio Parini, near Lecco. The mirror, built in ZERODUR®, a glass-ceramic material, was previously worked so as to remove unwanted mass, maintaining the robustness to allow the flight into space.
“CHEOPS is the first satellite entirely dedicated to the characterization of small size planets”, said Isabella Pagano, INAF Catania and scientific coordinator of the project in Italy. “Most of the planets under study will be those whose mass has already been measured using high-precision instruments available at large ground-based telescopes (eg. the HARPSN planet hunter at Telescopio Nazionale Galileo). CHEOPS will try to determine the size which, combined with the mass, informs us about the structure, whether rocky or gaseous, of the planet”.
“The construction of the CHEOPS telescope is a recognition of the Italian leadership in the field of optics achieved in recent years by the scientific community and industry of our country. ASI considers that the CHEOPS mission, in addition to the important scientific aspects of the study of extrasolar planets, is of strategic importance for its technological aspects, also in view of the construction of the 34 telescopes that will be provided by Italy for the PLATO mission”, added Barbara Negri, responsible for ASI’s Universe Exploration and Observation Unit and advisor of ESA’s Science Programme Board which selected the mission.
“A piece of Italian excellence will be on board CHEOPS”, said Roberto Regazzoni, INAF researcher responsible for the satellite’s optical system. “This optical system is the result of the work of a team of astronomers and engineers from Astronomical Observatories, Universities and the Italian industry. It ensures a particularly stable focusing of starlight even in the extreme environment of circumterrestrial space”.
The telescope optical design was driven by the need to produce stable and high precision photometry. Besides the optical design of mirrors and the focal plane optics, the researchers involved in the project have also taken care of the analysis of the diffused light.