Future space-based multi-object spectrographs (MOS) in the Ultraviolet (UV), as those envisioned for LUVOIR, have the potential to enable studies of the chemistry of protoplanetary disks in nearby star forming regions, of mass accretion in young stars, of massive star formation in the Local Volume, of the inter-galactic and circum-galactic media, of spatially resolved feedback throughout star-forming galaxies, of Lyman escape photons in nearby star forming galaxies, of AGN and their host galaxies, and more.
Technological advancements are required to improve the performance of space-based MOS. A crucial component of a MOS is the object-selection device. Digital Micromirror Devices (DMDs) are currently the only alternative to micro shutter arrays (MSAs) as slit selection mechanisms for space-based MOS. DMDs consist of an array of mirrors that can be individually tilted in 2 different states. "ON"-mirrors can send light to a spectrograph, "OFF"-mirrors reflect it away (see Figure 1). NASA-funded tests have concluded that DMDs are highly-reliable systems, resilient to heavy radiation and with outstanding response to vibration testing. DMDs have been used in visible and near-IR astronomical instruments. One of such instruments, SAMOS, is currently being developed by our joint STScI/JHU group.
We recently obtained a large grant that will enable testing of the DMDs optical performance in the near- and far-UV. Our optical bench will be hosted within the Makidon Lab at STScI. The Instrument Development group at Hopkins (JHU/IDG) has a very importnat role in designing, building, and conducting the necessary experiments.
Thanks to our study, we will achieve significant progress toward a Technology Readiness Level that will make DMDs a viable alternative to MSAs for NASA explorer, probe or even flagship class missions.
While our main goal is to characterize the UV properties of the DMDs in the lab, there is potential for further development. Our mid-term (5-10 years) goal is to build NUV and FUV DMD-based MOS for small-sized satellite missions. Our project will contribute to making future UV MOS more likely, and thus help increasing access to the UV sky for the coming decades.
Figure 1, Left: Exploded view of a DMD pixel consisting of the micromirror itself, two electrode layers, and a CMOS memory layer; two DMD pixels in opposite operational states. Right: DMD array chipset.
