Overview

Intellectual Merit

A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations from the ground due to the extreme brightness and variability of the night sky at these wavelengths. The atmospheric emission at 1.0 – 1.7 um arises almost entirely from a forest of extremely bright, very narrow OH emission lines that vary on timescales of minutes. Infrared astronomers have long envisaged the prospect of selectively removing these lines, while retaining high throughput between the lines. Such a filter has now been realized at 1.5 – 1.7 um by members of our team; it is called GNOSIS and is in use for science with IRIS2 on the AAT. The unique approach of GNOSIS relies on using fiber Bragg gratings (FBGs). These gratings are fabricated by imposing variations of the refractive index along individual optical fibers. Here we seek to apply this same technology to commission the Maryland OH Suppression IFU System (MOHSIS, pronounced “Moses”) for the Rapid IMAger-Spectrometer (RIMAS), a first-light facility instrument for the 4.3-meter Discovery Channel Telescope (DCT). MOHSIS + RIMAS will be much more powerful than GNOSIS + IRIS2 for three reasons: (1) MOHSIS will remove the ∼300 strongest OH sky lines at ∼1.0 – 1.7 um, covering the critically important J band and removing ∼3 × more lines than GNOSIS. (2) RIMAS will have 2-3× higher throughput and lower background noise than IRIS2. (3) DCT will deliver image quality at least ∼2× better than the AAT. MOHSIS + RIMAS will become one of the premier instruments for deep near-infrared spectroscopy. The ∼40× lower sky brightness of this instrument over conventional spectrographs will result in an effective ∼6× gain in sensitivity to faint sources. The commissioning of MOHSIS is highly leveraged by support from U. Sydney and from NASA Goddard Space Flight Center and U. Maryland (who are providing RIMAS). This is a project with low risk: (i) MOHSIS uses the same proven technology as GNOSIS; (ii) RIMAS is based on a simple double-beam design and on schedule for first light in 2018; (iii) Our team has extensive experience in designing, building, and commissioning instruments on large telescopes and spacecraft missions.


Broader Impact

The broad J+H band coverage of MOHSIS will make this instrument the first of its kind. This project fits the NSF definition of transformative research: it has the potential to change the way we do near-infrared ground-based spectroscopy and lead to major new technologies and scientific discoveries. Graduate and undergraduate students at Maryland will benefit from this effort through direct involvement in the integration and commissioning of MOHSIS, the science, and extensive user support. This user support will help maximize the scientific output of MOHSIS and RIMAS, benefiting students and researchers not only at Maryland but also at Lowell, Boston University, University of Toledo, and Northern Arizona University, the other DCT science partners. Discovery Channel’s motivation for investing in DCT is to use results from “its” telescope for television and web programming. This has the potential to bring results from MOHSIS + RIMAS to 99 million households in the U.S. and nearly 1.5 billion subscribers worldwide. Discovery Channel has extensive programming targeted toward the nation’s schools, with an active effort underway in response to the President’s STEM initiatives, and we expect DCT and therefore Maryland to enter these efforts as well.

This project is supported in part by a grant from the National Science Foundation (Astronomy - Advanced Technologies and Instrumentation)