Post conjunction detection of β\beta Pictoris b with VLT/SPHERE

With an orbital distance comparable to that of Saturn in the solar system, \bpic b is the closest (semi-major axis $\simeq$\,9\,au) exoplanet that has been imaged to orbit a star. Thus it offers unique opportunities for detailed studies of its orbital, physical, and atmospheric properties, and of disk-planet interactions. With the exception of the discovery observations in 2003 with NaCo at the Very Large Telescope (VLT), all following astrometric measurements relative to \bpic have been obtained in the southwestern part of the orbit, which severely limits the determination of the planet's orbital parameters. We aimed at further constraining \bpic b orbital properties using more data, and, in particular, data taken in the northeastern part of the orbit. We used SPHERE at the VLT to precisely monitor the orbital motion of beta \bpic b since first light of the instrument in 2014. We were able to monitor the planet until November 2016, when its angular separation became too small (125 mas, i.e., 1.6\,au) and prevented further detection. We redetected \bpic b on the northeast side of the disk at a separation of 139\,mas and a PA of 30$^{\circ}$ in September 2018. The planetary orbit is now well constrained. With a semi-major axis (sma) of $a = 9.0 \pm 0.5$ au (1 $\sigma$), it definitely excludes previously reported possible long orbital periods, and excludes \bpic b as the origin of photometric variations that took place in 1981. We also refine the eccentricity and inclination of the planet. From an instrumental point of view, these data demonstrate that it is possible to detect, if they exist, young massive Jupiters that orbit at less than 2 au from a star that is 20 pc away.Comment: accepted by A&

HARPS3 for a Roboticized Isaac Newton Telescope

We present a description of a new instrument development, HARPS3, planned to be installed on an upgraded and roboticized Isaac Newton Telescope by end-2018. HARPS3 will be a high resolution (R = 115,000) echelle spectrograph with a wavelength range from 380-690 nm. It is being built as part of the Terra Hunting Experiment - a future 10 year radial velocity measurement programme to discover Earth-like exoplanets. The instrument design is based on the successful HARPS spectrograph on the 3.6m ESO telescope and HARPS-N on the TNG telescope. The main changes to the design in HARPS3 will be: a customised fibre adapter at the Cassegrain focus providing a stabilised beam feed and on-sky fibre diameter ~ 1.4 arcsec, the implementation of a new continuous flow cryostat to keep the CCD temperature very stable, detailed characterisation of the HARPS3 CCD to map the effective pixel positions and thus provide an improved accuracy wavelength solution, an optimised integrated polarimeter and the instrument integrated into a robotic operation. The robotic operation will optimise our programme which requires our target stars to be measured on a nightly basis. We present an overview of the entire project, including a description of our anticipated robotic operation.Comment: 13 pages, 8 figures, SPIE conference proceeding

Design and development of a freeform active mirror for an astronomy application

The advent of extremely large telescopes will bring unprecedented light-collecting power and spatial resolution, but it will also lead to a significant increase in the size and complexity of focal-plane instruments. The use of freeform mirrors could drastically reduce the number of components in optical systems. Currently, manufacturing issues limit the common use of freeform mirrors at short wavelengths. This article outlines the use of freeform mirrors in astronomical instruments with a description of two efficient freeform optical systems. A new manufacturing method is presented which seeks to overcome the manufacturing issues through hydroforming of thin polished substrates. A specific design of an active array is detailed, which will compensate for residual manufacturing errors, thermoelastic deformation, and gravity-induced errors during observations. The combined hydroformed mirror and the active array comprise the Freeform Active Mirror Experiment, which will produce an accurate, compact, and stable freeform optics dedicated to visible and near-infrared observations.Comment: 11 pages, 12 figure

Cryogenic characterisation of a permanent magnet stepper motor and its impact on the MICADO atmospheric dispersion corrector

The MICADO atmospheric dispersion corrector (ADC) will be the first ADC built for an astronomical instrument that has to operate in a cryogenic environment (T = 77 K). A detailed understanding of the system behaviour is necessary to maximise the operational lifetime of the planned design concept and to design a suitable controller. The MICADO ADC design features a friction drive concept that is powered by a commercially available permanent magnet stepper motor (PMSM). Here, we report on an extensive characterisation of this PMSM. By matching the experimental results to an analytical description of PMSMs, we obtain a solid foundation to build a complete dynamical model of the ADC system. A prototype of the ADC design concept had already been built and tested at its operational temperature. The results from these tests allowed us to compare the measured and modelled response and discuss the implications. With respect to the motor characterisation, we find no significant performance difference of the tested stepper motor when operated at room temperature, compared to at 77 K. However, we do find that static friction plays a large role in the precise response of the ADC mechanism

Cryogenic characterisation of a permanent magnet stepper motor and its impact on the MICADO atmospheric dispersion corrector

The MICADO atmospheric dispersion corrector (ADC) will be the first ADC built for an astronomical instrument that has to operate in a cryogenic environment (T = 77 K). A detailed understanding of the system behaviour is necessary to maximise the operational lifetime of the planned design concept and to design a suitable controller. The MICADO ADC design features a friction drive concept that is powered by a commercially available permanent magnet stepper motor (PMSM). Here, we report on an extensive characterisation of this PMSM. By matching the experimental results to an analytical description of PMSMs, we obtain a solid foundation to build a complete dynamical model of the ADC system. A prototype of the ADC design concept had already been built and tested at its operational temperature. The results from these tests allowed us to compare the measured and modelled response and discuss the implications. With respect to the motor characterisation, we find no significant performance difference of the tested stepper motor when operated at room temperature, compared to at 77 K. However, we do find that static friction plays a large role in the precise response of the ADC mechanism