MAVIS will be part of the next generation of VLT instrumentation and it will include a visible imager and a spectrograph, both fed by a common Adaptive Optics Module. The AOM consists in a MCAO system, whose challenge is to provide a 30” AO-corrected FoV in the visible domain, with good performance in a 50% sky coverage at the Galactic Pole. To reach the required performance, the current AOM scheme includes the use of up to 11 reference sources at the same time (8 LGSs + 3 NGSs) to drive more than 5000 actuators, divided into 3 deformable mirrors (one of them being UT4 secondary mirror). The system also includes some auxiliary loops, that are meant to compensate for internal instabilities (including WFSs focus signal, LGS tip-tilt signal and pupil position) so to push the stability of the main AO loop and the overall performance. Here we present the Preliminary Design of the AOM, which evolved, since the previous phase, as the result of further trade-offs and optimizations. We also introduce the main calibration strategy for the loops and sub-systems, including NCPA calibration approach. Finally, we present a summary of the main results of the performance and stability analyses performed for the current design phase, in order to show compliance to the performance requirements.
MAVIS is a Multi-Conjugate Adaptive Optics for the UT4 of VLT designed to deliver a corrected FoV to a spectrograph, an imager, and a visiting instrument. An optical bench is used to support the post focal relay optics, which include the ADC, a K-mirror, the DM, and the selector. Said bench also rigidly supports the calibration, the LGS module, the NGS module and the imager providing the maximum stability and repeatability during maintenance operations. The Adaptive Optics Module structure (AOMS) was rigidly connected to the Nasmyth platform structure via the Overall Mechanical Structure (OMS). The OMS also provides structural integrity for the Spectrograph sub-system while isolating it from the main enclosure. At this level the AOMS and the OMS have been merged in a single structure; the decision about keeping them together or separated will be taken in the future depending on mechanical and integration considerations. The preliminary design choices adopted while designing these subsystems are presented considering the actual mechanical and thermal requirements. Particular attention is given to the derotation system design (K-mirror) and the analyses done to choose the materials and the adhesives.
The Research School of Astronomy and Astrophysics at the Australian National University is currently building the Dynamic REd All-sky Monitoring Survey (DREAMS). DREAMS is a 0.5m wide-field near-infrared survey telescope that will be located at Siding Spring Observatory, Australia. DREAMS will utilise Indium Gallium Arsenide (InGaAs) detectors and a 3.71 sq. degree field-of-view to survey the visible sky to MAB=17.8 in the J-band every 4-7 days. Due to the noise properties of the InGaAs detectors, DREAMS is required to convert a F/6 telescope beam to an F/2 detector beam. Combining this with the wide-field nature of the telescope, DREAMS requires a large number of additional optical and mechanical elements with relatively tight tolerances to meet the performance requirements. This paper discusses the current status of the assembly and alignment of DREAMS, along with the on-going alignment procedures, techniques, and methods used to meet these survey requirements.
The Mount Stromlo LGS facility includes two laser systems: a fiber-based sum-frequency laser designed and built by EOS Space Systems in Australia, and a Semiconductor Guidestar Laser designed and built by Aret´e Associates in the USA under contract with the Australian National University. The Beam Transfer Optics (BTO) enable either simultaneous or separate propagation of the two lasers to create a single LGS on the sky. This paper provides an overview of the Mount Stromlo LGS facility design, integration and testing of the two sodium guidestar lasers in the laboratory and on the EOS 1.8m telescope.
The DREAMS telescope is currently under construction at the Siding Spring Observatory. Once completed, the 0.5m telescope will be the fastest infrared surveyor in the southern hemisphere and one of the best tool available for transient astronomy. The Opto-mechnical design is fully custom and consists of two distinct sections: The telescope tube assembly and the instrument optical relay that feeds the light into six InGaAs cameras. We present here, the details of the mechanical design of the telescope.
There have been a dramatic increase in the number of optical and radio transient surveys due to astronomical transients such as gravitational waves and gamma ray bursts, however, there have been a limited number of wide-field infrared surveys due to narrow field-of-view and high cost of infrared cameras, we present two new wide-field near-infrared fully automated surveyors; Palomar Gattini-IR and the Dynamic REd All-sky Monitoring Survey (DREAMS). Palomar Gattini-IR, a 25 square degree J-band imager that begun science operations at Palomar Observatory, USA in October 2018; we report on survey strategy as well as telescope and observatory operations and will also providing initial science results. DREAMS is a 3.75 square degree wide-field imager that is planned for Siding Spring Observatory, Australia; we report on the current optical and mechanical design and plans to achieve on-sky results in 2020. DREAMS is on-track to be one of the first astronomical telescopes to use an Indium Galium Arsenide (InGaAs) detector and we report initial on-sky testing results for the selected detector package. DREAMS is also well placed to take advantage and provide near-infrared follow-up of the LSST.
As space debris in lower Earth orbits are accumulating, techniques to lower the risk of space debris collisions must be developed. Within the context of the Space Environment Research Centre (SERC), the Australian National University (ANU) is developing an adaptive optics system for tracking and pushing space debris. The strategy is to pre-condition a laser launched from a 1.8 m telescope operated by Electro Optics Systems (EOS) on Mount Stromlo, Canberra and direct it at an object to perturb its orbit. Current progress towards implementing this experiment, which will ensure automated operation between the telescope and the adaptive optics system, will be presented.
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