A Far-UV Micromirror Integral Field Spectrograph for Planetary Science

Goals and Objectives. We propose to study an instrument concept to improve upon current capabilities in UV imaging spectroscopy for planetary uses. The concept is a UV micromirror spectrograph with a wide variety of potential applications including Discovery- and New Frontiers-class missions. The state-of-the-art UV imaging spectrographs, such as the SwRI-built Alice instruments (including Juno UVS, Rosetta Alice and LRO LAMP) and the LASP-built Cassini UVIS and MAVEN IUVS, return useful datasets from their targets and have opened up the field to the next questions to address. Recent technological advances have enabled instrument improvements for the next generation of planetary science missions. Furthermore, a range of possible upcoming missions could successfully utilize such improved UV instrumentation. The goal of this program is to develop a proof-of-concept instrument for integral field far-UV spectroscopy. By utilizing a pair of digital micromirror arrays, this concept instrument will be capable of dissecting the focal plane and re-forming it into a series of slit-shapes to overcome the limitations of spectral confusion. The TRL of the system is currently estimated at ~2. We expect to advance the TRL to ~4 through this PICASSO program to be ready to propose to MATISSE for follow-on work and further TRL advancement. Potential science applications of the instrument include atmosphere characterization, in particular using stellar occultations. A highlight of the micromirror concept is that the array allows for the potential to observe several stellar occultations simultaneously, to probe atmospheric composition and density at multiple locations within a planet's atmosphere. Such a capability will be particularly critical in future missions to Venus and Titan, two worlds likely to be the target of orbiters in the future. Furthermore, thin atmosphere and plume characterization will be useful at upcoming comet missions, an Enceladus orbiter, and perhaps even a KBO mission. The UV capabilities of the instrument will also allow for critical surface composition characterization in addition to the study of gases, particularly useful on asteroid (including Ceres) and Trojan missions, for instance. Another area of importance in the Visions and Voyages planetary decadal survey, and likely important in the next decadal survey as well, is an Ice Giants mission to Uranus and/or Neptune. For such a mission, a capable UV instrument will be of extreme value for studying atmospheric composition as well as for addressing questions about the moons of these planets and whether they harbor subsurface oceans. Methodology We will construct a testbed telescope and spectrograph to measure performance of commercially available micromirror arrays. The UV-visible integral field spectrograph will include electronics to functionalize and steer the micromirrors. With the testbed we will characterize scatter, mirror surface quality, and imaging/spectroscopic performance. We will also determine the compatibility of the micromirror arrays with advanced broadband mirror coatings. We will also perform science trade studies on the instrument architecture as it would be applied to different science targets. We will consider instrument volume and mass, the addition of an internal scan mirror, wavelength coverage, and resolving power. For a range of applications, aperture size will be weighed against field of view and spatial resolution. Significance and Relevance to the PICASSO Program This work is relevant to the PICASSO program because it seeks to advance concepts for instrumentation that will directly address science questions relevant to NASA goals. This micromirror array system shows promise for use in future planetary missions.