Design and characterization of a balloon-borne diffraction-limited submillimeter telescope platform for BLAST-TNG

Abstract

The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the ∼0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium. With three detector arrays operating at 250, 350, and 500 µm (1200, 857, and 600 GHz), BLAST-TNG will obtain diffraction-limited resolution at each waveband of 30, 41, and 59 arcseconds respectively.To achieve the submillimeter resolution necessary for its science goals, the BLAST-TNG telescope features a 2.5 m aperture carbon fiber composite primary mirror, one of the largest mirrors flown on a balloon platform. Successful performance of such a large telescope on a balloon-borne platform requires stiff, lightweight optical components and mounting structures. Through a combination of optical metrology and finite element modeling of thermal and mechanical stresses on both the telescope optics and mounting structures, we expect diffractionlimited resolution at all our wavebands. We expect pointing errors due to deformation of the telescope mount to be negligible. We have developed a detailed thermal model of the sun shielding, gondola, and optical components to optimize our observing strategy and increase the stability of the telescope over the flight. We present preflight characterization of the telescope and its platform.

Design of a Dynamic Secondary Mirror Truss Adjustment Mechanism for Large Aperture Telescopes

“…Therefore, the adjustment mechanism of the secondary mirror must be designed as a system with at least three DOFs. The BLAST-TNG telescope uses three linear actuators to adjust the three DOFs of the secondary mirror piston/tip/tilt [3,4]. The William Herschel Telescope uses four Focus Translation Units to correct the primary focus for the three DOFs of the piston tip/tilt [5,6].…”

Optical Design of the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)

“…The combination of quasi-optical metal-mesh filters, on-chip filters, and spectrometer design defines the EXCLAIM observing band of 420-540 GHz. The MKID arrays for the six spectrometers use a microwave multiplexing readout scheme with heritage from The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) 16 and the Far Infrared Observatory Mounted on a Pointed Balloon (OLIMPO). 17 The EXCLAIM gondola design, attitude determination and control system, and flight electronics are based on those of PIPER with modest modifications and improvements.…”

The Balloon-Borne Large Aperture Submillimeter Telescope Observatory

“…2,3 Finally, in 2020 we flew a completely new experiment with 10 times the detectors which had been upgraded to polarized MKIDs. 4,5 These experiments have flown a total of five times 1,2 and provided a wealth of technological and scientific advances, from showing that the dominant star-forming period occurred at z>1 6 to mapping the magnetic fields within star-forming regions of our own galaxy 7 and demonstrating the viability of kilopixel MKID arrays on stratospheric balloons.…”