The Polarized Instrument for Long-wavelength Observation of the Tenuous interstellar medium (PILOT) is a balloon-borne experiment that aims to measure the polarized emission of thermal dust at a wavelength of 240 µm (1.2 THz). A first PILOT flight of the experiment took place from Timmins, Ontario, Canada, in September 2015 and a second flight took place from Alice Springs, Australia in April 2017. In this paper, we present the inflight performance of the instrument. Here we concentrate on the instrument performance as measured during the second flight, but refer to the performance observed during the first flight, if it was significantly different. We present a short description of the instrument and the flights. We measure the time constants of the detectors using the decay of the observed signal during flight following high energy particle impacts (glitches) and switching off the instrument’s internal calibration source. We use these time constants to deconvolve the timelines and analyze the optical quality of the instrument as measured on planets. We then analyze the structure and polarization of the instrumental background. We measure the detector response flat field and its time variations using the signal from the residual atmosphere and from the internal calibration source. Finally, we analyze the spectral and temporal properties of the detector noise. The inflight performance is found to be satisfactory and globally in line with expectations from ground calibrations. We conclude by assessing the expected inflight sensitivity of the instrument in light of the measured inflight performance.

中文翻译：

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PILOT气球携带实验的飞行性能

用于对稀薄星际介质进行长波长观测的偏振仪器 (PILOT) 是一项气球载实验，旨在测量波长为 240 µm (1.2 THz) 的热尘埃的偏振发射。该实验的第一次 PILOT 飞行于 2015 年 9 月在加拿大安大略省蒂明斯进行，第二次飞行于 2017 年 4 月从澳大利亚爱丽斯泉进行。 在本文中，我们介绍了该仪器的飞行性能。在这里，我们专注于第二次飞行期间测量的仪器性能，但如果有显着差异，则参考第一次飞行期间观察到的性能。我们简要介绍了仪器和航班。我们使用飞行期间高能粒子撞击（毛刺）和关闭仪器的内部校准源后观察到的信号的衰减来测量探测器的时间常数。我们使用这些时间常数去卷积时间线并分析仪器在行星上测量的光学质量。然后我们分析仪器背景的结构和极化。我们使用来自残余大气和内部校准源的信号来测量探测器响应平场及其时间变化。最后，我们分析了探测器噪声的频谱和时间特性。飞行性能令人满意，并且在全球范围内符合地面校准的预期。