NASA engineers have recently inspected a new piece of technology developed for the James Webb Space Telescope (JWST), the Micro-Shutter Array (MSA), with a low light test at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Developed at Goddard to allow Webb’s Near Infrared Spectrograph (NIRSpec) to obtain spectra of more than 100 objects in the universe simultaneously, MSA uses thousands of tiny shutters to capture spectra from selected objects of interest in space and block out light from all other sources. The array is composed of four independent quadrants, each one housing a Micro Electro-Mechanical Systems (MEMS) array, made up of 365 x 171 shutters, whose dimensions are only 80 µm x 180 µm. There are more than 1000 electrical connections obtained with bump bonding and hair-thin wire bonding techniques between each array and its quadrant. Each quadrant also houses four electronic chip controls and monitors the functionality of the shutters.
Each of the quarter of a million shutters can be addressed independently to obtain any pattern of opened/closed ‘slits’. A narrow, strong quadrupole magnet, mounted on a linear moving arm, sweeps up/down across the magnetically sensitive shutters pushing them open. Electrical signals, synchronised with the sweep, are applied to the shutters and to their side walls causing them to electrostatically latch open against the walls. On the return sweep of the magnet, the desired pattern of open shutters is achieved by allowing walls that are not required for the slit pattern to discharge and to gently close the shutters by the dampening magnetic force.
“To build a telescope that can peer farther than Hubble can, we needed brand new technology,” said Murzy Jhabvala, chief engineer of Goddard’s Instrument Technology and Systems Division. “We’ve worked on this design for over six years, opening and closing the tiny shutters tens of thousands of times in order to perfect the technology.”
Harvey Moseley, the Microshutter Principal Investigator, adds, “The microshutters are a remarkable engineering feat that will have applications both in space and on the ground, even outside of astronomy in biotechnology, medicine and communications.”
JWST will be a large infrared telescope with a 6.5-meter primary mirror. The project is working to a 2018 launch date.
Webb is an international collaboration between NASA, the European Space Agency (ESA ), and the Canadian Space Agency (CSA ). The NASA Goddard Space Flight Center is managing the development effort. The main industrial partner is Northrop Grumman; the Space Telescope Science Institute will operate Webb after launch.