Eye on the heavens

The Milky Way

The contract stems from a long-standing collaboration between IRL business unit KiwiStar Optics and the Australian Astronomical Observatory (AAO), a division of that country’s Department of Innovation, Industry Science and Research. It is part of an ambitious AAO project called Hermes, named after the Greek messenger of the Gods, which will provide a unique and powerful new facility for multiobject astronomy.

Over the next four years the primary Hermes science project, the Galactic Archaeology Survey, aims to unravel for the first time the 12-billion-year history of our galaxy, the Milky Way. Of particular importance is the identification of the early activities of primordial stellar fragments that are believed to have been the founding blocks of our galaxy.
 
The Hermes system includes a powerful new spectrograph which will be capable of collecting the light from 400 stars at a time. This is a vast improvement over traditional spectrographs, which can typically analyse light from only one or two objects simultaneously. The high-resolution Hermes spectrograph will be used to capture spectral images of over a million stars.

The head of Mechanical Engineering at AAO, Greg Smith, says the Hermes project is unique in terms of its spectral resolution and ability to look at multiple objects at the same time.

“Extragalactic surveys using the Hermes spectrograph will be the flagship science for the AAT over the next few years. Based on our previous work with KiwiStar Optics, they were an obvious choice to help us create this ground-breaking tool.”

Astronomical spectrographs split the light from a celestial object into a spectrum of colours, in much the same way as a prism does. From this, scientists are able to determine important properties such as the chemical composition and velocity of the object, revealing vital facts that photographs cannot show.

KiwiStar Optics is building some of the main spectrograph components, which work together as one system. The four optical cameras – red, blue, green and infrared – and a collimator, composed of a mirror almost one meter in diameter and two large lenses, will require specialist optical design and fabrication, says technical project manager Peter Connor.

“Each camera consists of five large glass lenses, the largest being 380mm in diameter, that weigh a total of 100 kilograms.

“All the glass, including that in the collimator, must be polished to an extremely precise surface curvature which is accurate to within one wavelength of light. This is less than one thousandth of a millimetre, or about 200 times smaller than the diameter of a human hair.”

IRL’s Measurement Standards Laboratory will provide the measurement expertise to ensure all the lenses are precisely aligned. With Auckland company kanDO Innovation designing the camera housings, and IRL’s Engineering Innovations team and Mechanical Workshop designing and building the mechanical parts of the collimator and the housings, the project is also supporting precision manufacturing industries in New Zealand.

Each component will be sent to the AAO laboratory in Sydney to be assembled into the spectrograph and tested, then to Siding Spring to be installed in a custom-built room adjacent to the AAT.

“Hermes is a spectacular and extremely ambitious project,” says Peter Connor. “It’s another example of the very innovative approach to astronomy in Australia, and it’s good to be a part of it.

About KiwiStar Optics

With a 40-year record in optics research and development in New Zealand, the KiwiStar team has built up a worldwide reputation in optical design and manufacture. KiwiStar’s optics are installed in telescopes in Australia, Hawaii, South Africa and at the University of Canterbury’s Mt John Observatory near Tekapo.

Other lenses can be found in a sophisticated navigation system at the Diego Garcia US naval base in the Indian Ocean and a special camera for a proton radiography experiment at Los Alamos National Laboratory in the US.

Now, with funding from FRST^[?] and co-funding from Agmar Engineering Tools Ltd, they are to produce a highresolution spectrograph for small- to medium-sized telescopes at an affordable price as the basis of a new export industry for New Zealand.