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The Hyperion proto-supercluster at zvirgul2.5 is the largest and best-studied large-scale structure observed during the peak of the cosmic star formation activity. Hyperion is the most massive overdensity yet discovered in the high-redshift universe comma comparable in size and mass to present-day superclusters comma and is comprised of seven distinct matter peaks comma each corresponding to a proto-group or -cluster exhibiting its own unique activity. These peaks span over an order of magnitude in total mass and show a variety of levels of dynamical maturity. A small portion of Hyperion was serendipitously observed by the 3D-HST survey comma revealing tantalizing indications that stellar mass assembly was proceeding rapidly in member galaxies both through star formation and merging processes. We propose to use HST.s unique capabilities comma combined with existing data comma to perform unbiased studies of environmentally-driven evolution in the early universe. Our program will produce a near complete map of Hyperion with WFC3 spectroscopy and imaging comma confirming virgul150 members (virgul50 in the densest peaks) - doubling the member sample and uniquely sampling the dusty star-forming and quiescent members. With this incredible sample comma we will constrain the relationships between average galaxy star formation rates comma stellar mass functions comma and merging activity and environment. In conjunction with simulations and semi-empirical models comma we will place strong constrains on different avenues of stellar mass assembly at a time when environmental quenching should be imposing itself in earnest and the vast majority of the stellar content of galaxies should be forming.位于红移z≈2.5处的Hyperion原超星系团（Hyperion proto-supercluster）是宇宙恒星形成活动峰值阶段迄今被观测到的规模最大、研究最深入的大尺度结构。Hyperion是高红移宇宙中迄今发现的质量最大的物质过密区，其尺寸与质量可与现今的超星系团相媲美，由7个独立的物质峰构成，每个物质峰均对应一个展现出独特演化活动的原星系群或原星系团。这些物质峰的总质量跨度达一个数量级以上，且呈现出多样化的动力学成熟度水平。3D-HST巡天（3D-HST survey）曾偶然观测到Hyperion的一小部分区域，揭示出诱人的观测迹象：成员星系的恒星质量组装（stellar mass assembly）过程正通过恒星形成与星系并合两种途径快速推进。我们提出利用哈勃空间望远镜（HST, Hubble Space Telescope）的独特观测性能，结合现有数据集，对早期宇宙中由环境驱动的星系演化开展无偏研究。本项目将借助WFC3（广角相机3号，Wide Field Camera 3）的光谱与成像数据，绘制Hyperion近乎完整的空间分布图，确认约150个成员星系（在最致密的物质峰中约50个）——这将使成员样本量翻倍，并能独特地覆盖尘埃恒星形成星系与宁静态星系样本。依托这一优质样本，我们将限定星系平均恒星形成率、恒星质量函数（stellar mass functions）、星系并合活动与环境之间的关联。结合数值模拟与半经验模型（semi-empirical models），我们将在环境淬火（environmental quenching）正切实发挥作用、绝大多数星系的恒星质量仍处于形成阶段的时期，对恒星质量组装的多种潜在路径施加强有力的观测约束。