This will count as one of your downloads.
You will have access to both the presentation and article (if available).
The payload is based on a 1-m class telescope ahead of a suite of instruments: two spectrometric channels covering the band 1.95 to 7.80 μm and four photometric channels working in the range 0.5 to 1.9 μm.
The production of the primary mirror (M1) is one of the main technical challenges of the mission. A trade-off on the material to be used for manufacturing the 1-m diameter M1 was carried out, and aluminium alloys have been selected as the baseline materials both for the telescope mirrors and structure. Aluminium alloys have demonstrated excellent performances both for IR small size mirrors and structural components, but the manufacturing and thermo-mechanical stability of large metallic optics still have to be demonstrated especially at cryogenic temperatures.
The ARIEL telescope will be realized on-ground (1 g and room temperature), but it shall operate in space at about 50 K. For this reason a detailed tolerance analysis was performed to assess the telescope expected performance.
M1 is an off-axis section of a paraboloidal mirror and will be machined from a single blank as a stand-alone part. To prove the feasibility of such a large aluminium mirror, a pathfinder mirror program has been started. The prototype has been realized and tested, so far at room temperature, by Media Lario S.r.l.. Cryogenic testing of the prototype will be performed during Phase B1.
Leonardo Avionics & Space System Division is the prime contractor for the FLORIS Instrument for which Media Lario is manufacturing the QM unit of the spherical mirror included in the High-Resolution Spectrometer (HRSPE), hereafter called HRM mirror.
The High-Resolution Mirror is a 250-mm diameter spherical mirror with a radius of curvature of approximately 440 mm. For the mirror substrate, Leonardo has selected the Aluminium alloy AlSi40, a special alloy with 40% Silicon content, coated with a hard polishing layer of Nickel Phosphorus (NiP), deposited by electroless chemical process. The Silicon content allows this special Aluminium alloy to have the same coefficient of thermal expansion (CTE) of the NiP layer, therefore preventing thermal deformations deriving from the bimetallic effect. The mirror structure is light-weighted to approximately 2.8 kg. The required wave-front error of the mirror is better than 0.5 fringes PV, while the surface microroughness has been specified at 0.5 nm RMS due to stringent straylight requirements of the FLORIS instrument.
Media Lario has been selected for the mirror development phase because of their experience in the design and manufacturing of AlSi/NiP mirrors demonstrated in the development of the Earth Observation optical payload for small satellites (called STREEGO), based on an AlSi40 TMA telescope. The manufacturing process includes precision diamond turning, optical figuring and super-polishing. The optical coating will be done by Leonardo at their thin-films facility of Carsoli, Italy. Since the recipe prescribes to pre-heat the mirror surface at 100° C, Media Lario will qualify the mirror substrate with -25/+110°C thermal cycles to ensure adequate thermal stability for the coating process.
ARIEL has been selected by the European Space Agency (ESA) as the next medium-class science mission (M4) to be launched in 2028. The aim of the ARIEL mission is to study the atmospheres of a selected sample of exoplanets.
The payload is based on a 1-m class telescope ahead of a suite of instruments: two spectrometric channels covering the band 1.95 to 7.80 μm without gaps, three photometric channels working in the range 0.5 to 1.2 μm, and a low-resolution spectrometer in the range 1.25 to 1.95 μm.
The telescope layout is conceived as an eccentric pupil two-mirror classic Cassegrain configuration coupled to a tertiary off-axis paraboloidal mirror. The telescope will be realized on-ground, i.e. subjected to gravity and at room temperature, but it shall operate in space, at 0 g, and at a temperature of about 50 K. For this reason, the telescope expected “as-built” in-flight performance has to be determined via a detailed thermo-elastic analysis.
A trade-off on the material to be used for manufacturing the 1-m diameter primary mirror (M1) was carried out, and aluminum alloys have been selected as the baseline materials for both the telescope mirrors and structure.
The use of metals, like aluminum alloys, is nowadays frequently considered for the fabrication of space telescopes observing in the infrared wavelength range. Small-size aluminum parts have been proved to be popular both for IR mirrors and structural components, but the manufacturing and stability of large metallic optics still have to be demonstrated. The production of a large aluminum mirror such as that of ARIEL is a challenge, and to prove its feasibility a dedicated study and development program has been started. A prototype, with the same size of the M1 flight model but a simpler surface profile, has been realized and tested.
View contact details
No SPIE Account? Create one
