Programmable Aperture Masks for JWST Near Infra-Red Spectrometer (NIRSpec)
Alexander Kutyrev
We are developing two-dimensional microshutter arrays for the ESA Near Infrared
Multiobject Spectrograph (NIRSpec) for James Webb Space Telescope (JWST). One of
the primary goals of NIRSpec is to study primordial galaxies evolution
spectroscopically. Selecting large number of objects on a sparsely populated
field is required to increase the spectrometer efficiency. Microshutter arrays
will function as a 2D programmable aperture mask, opening and closing the
shutters with random access addressing. The NIRSpec aperture mask is a 2x2
mosaic of four microshutter arrays of 175 x384 shutters (35mm x 38.4mm area).
The mosaic will cover NIRSpec 3.6 x 3.6 arcminutes field of view allowing
simultaneous observation of about a hundred of objects. Microshutter arrays
themselves are micro-electro mechanical system (MEMS) devices produced on a
thin silicon nitride membrane on 100um by 200 um pitch. They are actuated
magnetically and latched and addressed electrostatically. The shutters a
re closely packed to provide high transmission efficiency for the selected
objects and high open to closed contrast ratio at the 35 K operating
temperature of JWST.
Though microshutter arrays are being built for JWST NIRSpec, they can be used
in a variety of applications where high contrast and random access addressing
is required. Smaller version of the arrays with 128 x 64 elements have been
produced and have been demonstrated for actuation and addressing both at room
temperature and cryogenic environment.