Microshutter Array-based Multi-object Spectrograph

We were recently awarded a $1M grant from the Canada Foundation of Innovation and the Ontario Research Fund to construct a novel infrared multi-object spectrograph that uses next-generation James Webb Space Telescope technology. The heart of this instrument is a MEMS device called a microshutter array. To understand why this is innovative choice, one needs to understand what the challenges of an infrared multi-object spectrographs are.

The key issue is that a lot of interesting astronomical sources are faint and telescope time is expensive. Multi-object spectroscopy where multiple spectra are obtained simultaneously has become a solution to this problem. There have been numerous surveys done in the visible wavelengths to obtain spectra of galaxies simultaneously (e.g. SDSS). The same is true in the near-infrared, but the instrumentation solution becomes more challenging because the thermal background needs to be kept to a minimum to maximize sensitivity. Traditionally, slit masks, commonly laser machined plates, are put in the input focal plane of the spectrograph to select sources. In the case of an infrared spectrograph, these slit masks need to be cooled to cryogenic temperatures to reduce their thermal infrared background. This makes very challenging to change the slit masks on-the-fly. Frequently, one needs to warm up part of the cryostat to replace these masks.

The microshutter array is an elegant solution to the problem. As its name implies, it has multiple microshutters that can be individually actuated electromagnetically in a cryogenic environment. This means that slit masks can be generated on-the-fly as needed without the need for complex mask exchange systems. This significantly improves the scientific utility of the instrument. Below are two images that shows aspects of the microshutter array. On the left is a picture of the actual microshutter array consisting of 60,000 individual shutters (Li et al. 2010). On the right shows a close-up of two of the shutters (Credit: NASA).

microshutters

 

Stay tuned for more information as this project progresses!

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