The next sixth generation (6G) networks are envisioned to integrate sensing and communications in a single system, thus greatly improving spectrum utilization and reducing hardware costs. Low earth orbit (LEO) satellite communications combined with massive multiple-input multiple-output (MIMO) technology holds significant promise in offering ubiquitous and seamless connectivity with high data rates. Existing integrated sensing and communications (ISAC) studies mainly focus on terrestrial systems, while operating ISAC in massive MIMO LEO satellite systems is promising to provide high-capacity communication and flexible sensing ubiquitously. In this paper, we first give an overview of LEO satellite systems and ISAC and consider adopting ISAC in the massive MIMO LEO satellite systems. Then, the recent research advances are presented. A discussion on related challenges and key enabling technologies follows. Finally, we point out some open issues and promising research directions.

翻译：第六代（6G）网络被设想为将感知与通信功能集成于单一系统，从而显著提升频谱利用率并降低硬件成本。低地球轨道（LEO）卫星通信与大规模多输入多输出（MIMO）技术相结合，有望以高速率提供泛在无缝连接。现有集成感知与通信（ISAC）研究主要集中于地面系统，而在大规模MIMO低轨卫星系统中运行ISAC，则有望实现泛在的高容量通信与灵活感知。本文首先概述低轨卫星系统与ISAC技术，探讨在大规模MIMO低轨卫星系统中采用ISAC的可行性；随后介绍最新研究进展，并讨论相关挑战与关键使能技术；最后指出若干开放性问题及具有前景的研究方向。