Narrow Results

The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was a suborbital experiment designed to map magnetic fields in order to study their role in star formation processes. BLASTPol made detailed polarization maps of a number of molecular clouds during its successful flights from Antarctica in 2010 and 2012. We present the next-generation BLASTPol instrument (BLAST-TNG) that will build off the success of the previous experiment and continue its role as a unique instrument and a test bed for new technologies. With a 16-fold increase in mapping speed, BLAST-TNG will make larger and deeper maps. Major improvements include a 2.5-m carbon fiber mirror that is 40% wider than the BLASTPol mirror and ~3000 polarization sensitive detectors. BLAST-TNG will observe in three bands at 250, 350, and 500 μm. The telescope will serve as a pathfinder project for microwave kinetic inductance detector (MKID) technology, as applied to feedhorn-coupled submillimeter detector arrays. The liquid helium cooled cryostat will have a 28-day hold time and will utilize a closed-cycle ³He refrigerator to cool the detector arrays to 270 mK. This will enable a detailed mapping of more targets with higher polarization resolution than any other submillimeter experiment to date. BLAST-TNG will also be the first balloon-borne telescope to offer shared risk observing time to the community. This paper outlines the motivation for the project and the instrumental design.

We have developed a lightweight low-cost attitude sensor, based on a Raspberry Pi, built with readily available commercial components. It can be used in experiments where weight and power are constrained, such as in high-altitude lightweight balloon flights. This attitude sensor will be used as a major building block in a closed-loop control system with driver motors to stabilize and point cameras and telescopes for astronomical observations from a balloon-borne payload.

MCP-based detectors are widely used in the ultraviolet (UV) region due to their low noise levels, high sensitivity and good spatial and temporal resolution. We have developed a compact near-UV (NUV) detector for high-altitude balloon and space flights, using off-the-shelf MCP, CMOS sensor, and optics. The detector is designed to be capable of working in the direct frame transfer mode as well in the photon counting mode for single photon event detection. The identification and centroiding of each photon event are done using an FPGA-based data acquisition and real-time processing system. In this paper, we discuss various algorithms and methods used in both operating modes, as well as their implementation on the hardware.

We have developed a balloon-borne far-infrared interferometer, the Far-infrared Interferometric Telescope Experiment (FITE). The final goal of spatial resolution was one arcsec at 100$\mu$m. As a first step, we aimed to achieve a spatial resolution of five arcsecs at 155$\mu$m with a 6-m baseline. FITE is a two-beam interferometer like Michelson’s stellar interferometer. Positions and attitudes of all mirrors required to have their alignment checked and possibly adjusted before launch and were checked during observation. We had to satisfy three requirements: the coincidence of the phases of each beam (wavefront error), image quality of the two beams at the (common) focus, and no optical path difference between the two beams for celestial objects. In order to achieve the former two requirements, we developed an interferometer adjustment system that used a newly-developed interferometer measurement instrument. This instrument adopted a Shack–Hartmann wavefront sensor to measure wavefront errors of the two off-axis parabolic mirrors, simultaneously. With this system, the adjustment of the FITE interferometer was carried out at the Alice Springs balloon base in Australia as the JAXA’s Australia balloon experiment campaign of 2018. On-site adjustment was successful; wavefront errors of the two off-axis parabolic mirrors were 1.78$\mu$m and 4.99$\mu$m (peak-to-valley), and the Hartmann constant was 13 arcsecs. As for the optical path difference, we achieved the requirement by step-wise displacement of a folding plane mirror. Results satisfied the requirements for an interferometer designed for a wavelength of 155$\mu$m. Improvement of spatial resolution at far-infrared wavelengths is undoubtedly important for research on protoplanetary disks, circumstellar dust shells of late-type stars, and star-forming galaxies. The method we have developed is also useful for future space interferometers.