Far-ultraviolet observations of comets yield information about the energetic processes that dissociate the sublimated gases from their primitive surfaces. Understanding which emission processes are dominant, their effects on the observed cometary spectrum, and how to properly invert the spectrum back to the composition of the presumably pristine surface ices of a comet nuclei are all critical components for proper interpretation and analysis of comets. The close approach of comet 46P/Wirtanen in 2018–2019 provided a unique opportunity to study the innermost parts of a cometary coma with the Hubble Space Telescope Cosmic Origins Spectrograph, rarely accessible with remote observations, at length scales (hundreds of kilometers) and wavelengths (900–1430 Å) previously probed only by the European Space Agency’s Rosetta spacecraft. Our observations show a complex picture for the inner coma; atomic production rates for H and O that show water is the dominant source of both, an abundance of atomic sulfur that is difficult to explain with the lifetimes of common sulfur parent molecules, and a density distribution that is poorly fit with both Haser and vectorial models.

对彗星的远紫外观测产生了有关将升华气体从其原始表面分离的能量过程的信息。了解哪些发射过程占主导地位，它们对观测到的彗星光谱的影响，以及如何正确地将光谱反转回可能是彗星核的原始表面冰的组成，都是正确解释和分析彗星的关键组成部分。2018-2019 年 46P/Wirtanen 彗星的近距离接近提供了一个独特的机会，可以使用哈勃太空望远镜宇宙起源光谱仪在长度尺度（数百公里）和波长上研究彗星彗发的最内部部分(900–1430 Å) 以前仅由欧洲航天局的罗塞塔航天器探测。我们的观察显示了内部昏迷的复杂图像；H 和 O 的原子生产率表明水是两者的主要来源，大量的原子硫难以用普通硫母分子的寿命来解释，并且密度分布与 Haser 和矢量模型都不太吻合.