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 was tested 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 leveraged by support from Australia 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 2024; (iii) Our team has extensive experience in designing, building, and commissioning instruments on large telescopes and spacecraft missions.


Broader Impact

This project wil train graduate and undergraduate astronomy students in scientific practices at the interface of photonics and astronomy. It will be the subject of a PhD thesis at Maryland. These students will participate in the final integration, testing, and commissioning of MOHSIS, the GRB science, and extensive user support. This user support will help maximize the scientific output of this instrument, benefiting students and researchers at Maryland and all LDT partner institutions. This project fits the NSF definition of transformative research: as the first photonic OH suppression systm in the world with simultaneous J + H coverage, MOHSIS has the potential to change the way NIR spectroscopy is done from the ground and be a pathfinder to major new instrumentation and scientific discoveries.

This project is supported in part by a grant from the National Science Foundation (Astronomy - Extragalactic and Cosmology)