Fast single-dish scans of the Sun using ALMA
Neil Phillips, Richard Hills, Tim Bastian, Hugh Hudson, Ralph Marson, and Sven Wedemeyer

TL;DR
This paper presents the development and testing of high-speed scanning software for ALMA antennas to observe the Sun, enabling detailed, high-temporal-resolution solar brightness maps and variability analysis.
Contribution
It introduces a novel control and data acquisition system for ALMA that allows complex, high-rate solar scans with detailed characterization of noise and signal fluctuations.
Findings
Achieved Nyquist sampling of the Sun at 230 GHz in 60 seconds
Mapped brightness temperature variations up to 1000 K
Detected time-series variability of about 0.5% RMS over minutes
Abstract
We have implemented control and data-taking software that makes it possible to scan the beams of individual ALMA antennas to perform quite complex patterns while recording the signals at high rates. We conducted test observations of the Sun in September and December, 2014. The data returned have excellent quality; in particular they allow us to characterize the noise and signal fluctuations present in this kind of observation. The fast-scan experiments included both Lissajous patterns covering rectangular areas, and double-circle patterns of the whole disk of the Sun and smaller repeated maps of specific disk-shaped targets. With the latter we find that we can achieve roughly Nyquist sampling of the Band~6 (230~GHz) beam in 60~s over a region 300 in diameter. These maps show a peak-to-peak brightness-temperature range of up to 1000~K, while the time-series variability at any given…
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Taxonomy
TopicsRadio Astronomy Observations and Technology · Solar and Space Plasma Dynamics · Astronomy and Astrophysical Research
