[en] As one of the three payloads for the Advanced Space-based Solar Observatory (ASO-S) mission, the Lyman-alpha (Lyα) Solar Telescope (LST) is composed of three instruments: a Solar Corona Imager (SCI), a Lyα Solar Disk Imager (SDI) and a full-disk White-light Solar Telescope (WST). When working in-orbit, LST will simultaneously perform high-resolution imaging observations of all regions from the solar disk to the inner corona up to 2.5 R_⊙ (R_⊙ stands for the mean solar radius) with a spatial resolution of 4.8″ and 1.2″ for coronal and disk observations, respectively, and a temporal resolution of 30 – 120 s and 1 – 120 s for coronal and disk observations, respectively. The maximum exposure time can be up to 20 s due to precise pointing and image stabilization function. Among the three telescopes of LST, SCI is a dual-waveband coronagraph simultaneously and independently observing the inner corona in the HI Lyα (121.6±10 nm) line and white light (WL) (700±40 nm) wavebands by using a narrowband Lyα beam splitter and has a field of view (FOV) from 1.1 to 2.5 R_⊙. The stray-light suppression level can attain <10⁻⁶ B_⊙ (B_⊙ is the mean brightness of the solar disk) at 1.1 R_⊙ and ≤5×10⁻⁸ B_⊙ at 2.5 R_⊙. SDI and WST are solar disk imagers working in the Lyα line and 360.0 nm wavebands, respectively, which adopt an off-axis two-mirror reflective structure with an FOV up to 1.2 R_⊙, covering the inner coronal edge area and relating to coronal imaging. We present the up-to-date design for the LST payload. (paper)

[en] As one of the payloads for the Advanced Space-based Solar Observatory (ASO-S) mission, the Lyman-alpha (Lyα) Solar Telescope (LST) is aimed at imaging the Sun and the inner corona up to 2.5R_⊙ (mean solar radius) in both the Lyα (121.6 nm) and visible wavebands with high temporo-spatial resolution, mainly targeting solar flares, coronal mass ejections (CMEs) and filaments/prominences. LST observations allow us to trace solar eruptive phenomena from the disk center to the inner corona, to study the relationships between eruptive prominences/filaments, solar flares and CMEs, to explore the dynamical processes and evolution of solar eruptions, to diagnose solar winds, and to derive physical parameters of the solar atmosphere. LST is actually an instrument suite, which consists of a Solar Disk Imager (SDI), a Solar Corona Imager (SCI), aWhite-light Solar Telescope (WST) and two Guide Telescopes (GTs). This is the first paper in a series of LST-related papers. In this paper, we introduce the scientific objectives, present an overview of the LST payload and describe the planned observations. The detailed design and data along with potential diagnostics are described in the second (Paper II) and third (Paper III) papers, respectively, appearing in this issue. (paper)