The upGREAT Dual Frequency Heterodyne Arrays for SOFIA

Risacher, C.; Güsten, R.; Stützki, J.; Hübers, Heinz‐Wilhelm; Aladro, R.; Bell, Andreas; Buchbender, C.; Büchel, D.; Csengeri, T.; Durán, C.; Graf, U. U.; Higgins, R.; Honingh, C. E.; Jacobs, K.; Justen, M.; Klein, Bernd; Mertens, Marc; Okada, Yoko; Parikka, A.; Pütz, P.; Reyes, Nicolás; Richter, Heiko; Ricken, Oliver; Riquelme, D.; Rothbart, Nick; Schneider, N.; Simon, R.; Wienold, Martin; Wiesemeyer, H.; Ziebart, Monika; Fusco, P.; Rosner, S. J.; Wohler, Bill

doi:10.1142/s2251171718400147

Cited by 90 publications

(80 citation statements)

References 15 publications

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“…The EXES results suggest that dust in the inner-CSE is not significantly heating the gas. At the time of submission of this Letter SOFIA will be observing Betelgeuse with the Far Infrared Field-Imaging Line Spectrometer (FIFI-LS) (Colditz et al 2018a,b), upGREAT (Risacher et al 2018). GMH's research was supported in part by SOFIA grants SOF 05 0073 and SOF 07 0073.…”

Section: Resultsmentioning

confidence: 99%

SOFIA-EXES Observations of Betelgeuse during the Great Dimming of 2019/2020

Harper

DeWitt²,

Richter³

et al. 2020

ApJL

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In 2019 October Betelgeuse began a decline in V-band brightness that went beyond the minimum expected from its quasi-periodic ∼ 420 day cycle, becoming the faintest in recorded photometric history. Observations obtained in 2019 December with VLT/SPHERE (Montargès 2020) have shown that the southern half of the star has become markedly fainter than in 2019 January indicating that a major change has occurred in, or near, the photosphere. We present SOFIA-EXES high spectral-resolution observations of [Fe II] 25.99 µm and [S I] 25.25 µm emission lines from Betelgeuse obtained during the unprecedented 2020 February V-band brightness minimum to investigate potential changes in the circumstellar flow. These spectra are compared to observations obtained in 2015 and 2017 when the V magnitude was typical of brighter phases. We find only very small changes in the gas velocities reflected by either of the line profiles, no significant changes in the flux to continuum ratios, and hence no significant changes in the [Fe II]/[S I] flux ratios. There is evidence that absorption features have appeared in the 2020 continuum. The Alfvén wave-crossing time from the upper-photosphere is sufficiently long that one would not expect a change in the large scale magnetic field to reach the circumstellar [Fe II] and [S I] line forming regions, 3 < R(R * ) < 20. However, the light-crossing time is of order a few hours and a reduction in luminosity may reduce the dust-gas heating rate and [O I] 63.19 µm emission which has contributions from R > 20R * , where significant circumstellar oxygen-rich dust is observed.

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Section: Resultsmentioning

confidence: 99%

SOFIA-EXES Observations of Betelgeuse during the Great Dimming of 2019/2020

Harper

DeWitt²,

Richter³

et al. 2020

ApJL

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“…During this period, the relative humidity varies between 25% and 45%, which in turn changes the absorption and influences the image beam intensity distribution. (2) Power coupling between the pyro-electric detector and the image beams. During the mapping of the image beams, the measured power is angle-dependent, with more power for the beams in the center, but less power for the outer beams.…”

Section: Measurement Setupmentioning

confidence: 99%

81 supra-THz beams generated by a Fourier grating and a quantum cascade laser

Gan¹,

Mirzaei²,

Silva³

et al. 2019

Opt. Express

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J-R. (2019). 81 supra-THz beams generated by a Fourier grating and a quantum cascade laser. Optics Express, 27(23), 34193-34204. https://doi.Abstract: Large heterodyne receiver arrays (~100 pixel) allow astronomical instrumentations to map more area within limited space mission lifetime. One challenge is to generate multiple local oscillator (LO) beams. Here, we succeeded in generating 81 beams at 3.86 THz by combining a reflective, metallic Fourier grating with an unidirectional antenna coupled 3rdorder distributed feedback (DFB) quantum cascade laser (QCL). We have measured the diffracted 81 beams by scanning a single pyroelectric detector at a plane, which is in the far field for the diffraction beams. The measured output beam pattern agrees well with a simulated result from COMSOL Multiphysics, with respect to the angular distribution and power distribution among the 81 beams. We also derived the diffraction efficiency to be 94 ± 3%, which is very close to what was simulated for a manufactured Fourier grating (97%). For an array of equal superconducting hot electron bolometer mixers, 64 out of 81 beams can pump the HEB mixers with similar power, resulting in receiver sensitivities within 10%. Such a combination of a Fourier grating and a QCL can create an LO with 100 beams or more, enabling a new generation of large heterodyne arrays for astronomical instrumentation.

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“…Towards the end of Cycle 4, the HAWCþ (Highresolution Airborne Wideband Camera Plus) far infrared photometer with a polarimetric capability was commissioned (Harper et al, 2018 this issue). A new mode of GREAT, 4-GREAT (Risacher et al, 2018 this issue) achieved¯rst light in Cycle 5. SOFIA's 3rd generation instrument HIRMES will be commissioned in 2019.…”

Section: Science Instrumentation Suitementioning

confidence: 99%

An Overview of the Stratospheric Observatory for Infrared Astronomy Since Full Operation Capability

Ennico

Becklin

et al. 2018

J. Astron. Instrum.

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The Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project between NASA and the German Aerospace Center DLR, provides access to observations of the infrared and sub-millimeter universe. As its development timeline is unique compared to all other NASA astrophysics missions, a milestone called the Full Operation Capability (FOC) was defined to identify the start of science operations. SOFIA reached this in February 2014. With a wide range of imagers, spectrometers and a new polarimeter, SOFIA provides unique scientific results that cannot be obtained with a ground-based facility and any spacecraft expected in the next decade. The airborne platform has continued to mature its mission systems as part of a planned spiral development approach, particularly with upgradable instrumentation that opens up new science directions for the Observatory. A third generation instrument is planned for commissioning in 2019. This paper summarizes the current state of the Observatory with emphasis on the science and instrumentation updates since FOC.

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The upGREAT Dual Frequency Heterodyne Arrays for SOFIA

Cited by 90 publications

References 15 publications

SOFIA-EXES Observations of Betelgeuse during the Great Dimming of 2019/2020

SOFIA-EXES Observations of Betelgeuse during the Great Dimming of 2019/2020

81 supra-THz beams generated by a Fourier grating and a quantum cascade laser

An Overview of the Stratospheric Observatory for Infrared Astronomy Since Full Operation Capability

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