HIRMES is a far-infrared spectrometer that was chosen as the third generation instrument for NASA's SOFIA airborne observatory. HIRMES promises background limited performance in four modes that cover the wavelength range between 25 and 122 μm. The high-spectral resolution (R ≈10<sup>5</sup>) mode is matched to achieve maximum sensitivity on velocity-resolved lines to study the evolution of protoplanetary disks. The mid-resolution (R≈12,000) mode is suitable for high sensitivity imaging of galactic star formation regions in, for example, the several far-infrared fine structure lines. The low-resolution (R≈2000) imaging mode is optimized for spectroscopic mapping of far-infrared fine structure lines from nearby galaxies, while the low resolution (R≈600) grating spectrometer mode is optimized for detecting dust and ice features in protostellar and protoplanetary disks. Several Transition Edge Sensed (TES) bolometer arrays will provide background limited sensitivity in each of these modes. To optimize performance in the various instrument modes, HIRMES employs eight unique fully-tunable cryogenic Fabry-Perot Interferometers (FPIs) and a grating spectrometer. Here we present the design requirements and the mechanical and optical characteristics and performance of these tunable FPI as well as the control electronics that sets the mirror separation and allows scanning of the FPIs.
We will present a status update on the development of HIRMES, the third generation instrument for SOFIA (Stratospheric Observatory for Infrared Astronomy).
HIRMES (HIgh Resolution Mid-infrarEd Spectrometer) will cover the wavelength range between 25 micron and 122 micron with a spectral resolution of up to R~100,000. It will use two arrays of Transition Edge Sensed (TES) bolometers. One of the arrays consists of 8 16-pixel strips, for the high-resolution mode, where the pixel area and backshorts are optimized for 8 different wavelength regimes. The second detector consists of a 16x64 array with excellent sensitivity over the full wavelength range, and it will be used for the mid-resolution (R~19,000) and low-resolution (R~2,000 and R~600) observing modes. Both detector arrays will have background limited performance with NEPs of < 2E-17 W/Hz^(1/2) for the low-resolution array and < 3E-18 W/Hz^(1/2) for the high-resolution array.
HIRMES will employ several Fabry-Perot Interferometers (FPI) for the low- (R~2000), mid- (R~19,000), and high-resolution (R~100,000) observing modes. In addition, three gratings with resolutions of R~600 will be used to order-sort FPI transmission peaks, and also to obtain low resolution broad bandwidth spectra.
HIRMES's main science goals are to study the evolution of protoplanetary disks as well as to investigate the origin of Hydrogen and Deuterium in the Solar System.
The high spectral resolution observations of the HD 1-0 R(0) line at 112 micron will determine the gas mass and kinematics in protoplanetary disks, while the observations of the [OI] 63 micron and H2O lines reveal the amount of Oxygen and H20 within the snowline. Low spectral resolution observations of solid-state H20 ice features at ~43 and ~63 micron will determine the amount of water ice beyond the snowline. Measurements of the molecular hydrogen line and numerous HD lines at mid-resolution will help to estimate the H/D ratio in the Solar System. In addition, the low-resolution FPI is well suited to map fine-structure line emission from nearby galaxies.