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FEATURE S
DRIVES, CONTROLS & MOTORS
upernovae – exploding stars at the end of their lives – and the black-hole-powered enormous explosions of gamma ray bursts,
are occurring in galaxies all around us. However, even when these phenomena are identified by powerful telescopes, they might only be visible for a matter of minutes, meaning opportunities to study them are rare. This ephemeral display will be the target of a New Robotic Telescope (NRT). Not only with the NRT be able to move to a
target in just 30 seconds, making it ten times faster than its predecessor, but it will be four times more sensitive too. These capabilities will give scientists the opportunity to make new discoveries about the universe, capturing the very first seconds of evolution after an explosion. The project to develop the new telescope is
a consortium led by Liverpool John Moores University (LJMU) in partnership with the Institute of Astrophysics of the Canary Islands (IAC) and the University of Oviedo in Spain. It will be based on La Palma in the Canary Islands, where it will benefit from high altitude, stable atmospheric conditions, and low light pollution. The increased sensitivity of the NRT will
be a result of its much larger size, with a primary mirror diameter twice as large as its predecessor, increasing up to 4m. Being fully automated, the robotic telescope can remain unstaffed. However, the crucial benefit of automation is achieving the 30-seconds time to target. The NRT will receive early warning signals about the presence of astronomical phenomena from telescopes, including those located in space, and automated control will then quickly react to find its target.
PROVES KEY FOR NEW ROBOTIC TELESCOPE
A motion solution has been provided
by maxon for a new robotic telescope designed to shed light on supernovae
the third mirror in the optical path. This mirror is angled at 45 degrees and rotates to reflect the light towards the required instrument. The instrument array, positioned around the focal station, includes spectrographs that can identify aspects such as the target object’s chemical composition, as well as its temperature, mass, luminosity, and even its relative motion – all by measuring a spectrum of the light. The focal station also includes a polarimeter that can identify the angle of the approaching wave of light to identify phenomena like magnetic fields. Arguably the most desirable
location for an instrument is the straight-through port. This is positioned directly below the primary mirror and directly receives the incoming beam of light with no interaction with the science fold mirror. Usually, the straight-through port hosts the instrument that requires the largest field of view of the sky. This is often an imaging camera that carries out photometry, used to explore brightness, that can help indicate the nature of supernovae and gamma-ray bursts. The NRT’s straight- through port will either host a camera like this, or a polarimeter, as a straight-
The NRT features a clamshell enclosure, which will help it achieve fast deployment with 360-degree viewing. To reach the 30-second to target mark, the ability to quickly position the telescope is also crucial. With such a short time window to observe the phenomena, this must be combined with rapid engagement of the telescope’s instrumentation. The instrumentation will measure different
properties of the light coming from space, and it will be installed in an area of the telescope called the focal station. Light travels through the telescope’s optical system and down towards its focus, where it reaches the science fold mirror,
through port location can achieve more accurate polarimetric measurements.
THE MOTION SOLUTION The ability to switch the light beam to or away from the straight-through port in a matter of seconds is vital to capture the fleeting celestial activity. To prevent obscuration of the light beam, the focal station’s mirror must rapidly move out of the light’s path. This will be achieved by mounting the mirror on a platform that can move laterally at high speed, carried by a linear motion system with a ball screw actuator. “The mirror and its support structure weigh
52 DESIGN SOLUTIONS DECEMBER/JANUARY 2024
around 70kg, and we need to move this mass quickly and accurately, within five seconds,” said Adam Garner, control & automation engineer for the NRT at LJMU. “A separate motor and gearbox solution would achieve the required accuracy, but not at the speed we needed, so we specified a direct drive system that directly connects to the ball screw, eliminating the mechanical losses that additional transmission would introduce.” Garner engaged with maxon’s Young Engineer Program (YEP), which provides engineering expertise and beneficial rates for academic projects. maxon engineer, Ronak Samani, specified a maxon IDX direct drive. Quickly moving the linear stage and its mirror into place also has to be achieved with pinpoint accuracy, and the IDX direct drive ensures micron-level precision. This is reached using a design that combines a
brushless DC motor with an integrated encoder, as well as a positioning controller that enables smooth modulation of position and speed. The motion system is also controlled with command signals carried over the EtherCAT communications protocol, where real time data exchange optimises precision coordination. As the NRT operates autonomously, and without maintenance engineers on site, reliability is also crucial. This requirement extends to the motion system. The island’s proximity to the Sahara means that, after six months of operation, the sensitive equipment is covered with a film of dust that can cause damage. However, the direct drive motor’s IP65 rating will seal it from dust and ensure long-term, reliable operation.
INSPIRING FUTURE GENERATIONS With its speed of reaction, combined with sensitivity, the NRT is set to provide new discoveries on the evolution of the cosmos and our understanding of physics. The new telescope is, however, also intended to inspire future generations of astronomers.
maxon UK
www.maxongroup.co.uk
DRIVE SYSTEM
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