星链正降低数千颗卫星的轨道高度，以减少碰撞风险。
内容总结：
美国太空探索技术公司（SpaceX）旗下星链（Starlink）计划于今年内对约4400颗卫星实施轨道调整，以提升太空安全水平。该公司工程副总裁迈克尔·尼科尔斯近日在社交媒体平台X上宣布，将启动"星座重构计划"，把运行在约550公里高度的卫星集体降至480公里轨道。
此次调整旨在通过降低轨道高度，使卫星进入空间碎片较少区域，从而显著降低碰撞风险。尼科尔斯特别指出，在即将到来的2030年代初太阳活动极小期，大气密度降低将导致卫星自然衰减时间延长，而此次降轨能使卫星衰减时间从4年以上缩短至数月，提升失效卫星离轨效率。
该决策发布前，星链系统近期接连遭遇太空安全事件：一颗卫星因异常产生碎片，另有多颗卫星曾与未提前协调的他国卫星群发生近距离接近。尼科尔斯强调，此次轨道调整将有效应对"其他卫星运营商未协调的机动与发射"等难以控制的风险。
随着全球近地轨道卫星数量持续增长，太空交通协调问题日益凸显。星链此次大规模轨道调整，或将为行业建立更安全的轨道运行规范提供实践参考。
中文翻译：
星链计划降低数千颗卫星轨道以降低碰撞风险
星链工程副总裁表示，原在约342英里高度运行的卫星将降至约298英里。
星链工程副总裁迈克尔·尼科尔斯称，今年将把约4400颗卫星的轨道高度降低作为安全措施。尼科尔斯在X平台发帖称，公司"正启动大规模卫星星座重构计划"，所有原在约550公里（342英里）高度运行的卫星将降至约480公里（298英里）。此举旨在降低碰撞风险，将卫星转移至更空旷区域，并在发生意外时能更快脱离轨道。
尼科尔斯写道："降低轨道高度将压缩星链卫星的分布空间，从多个维度提升太空安全。"他同时指出即将到来的太阳活动极小期（太阳约11年周期中活动较弱的阶段）是调整轨道的原因之一。下一个太阳活动极小期预计在2030年代初。"随着太阳活动极小期临近，大气密度降低意味着特定高度的弹道衰减时间延长——降低轨道将使卫星在极小期的弹道衰减时间缩短80%以上，从4年以上缩减至数月。"
此次声明发布前数周，星链曾通报其一颗卫星发生异常产生碎片并失控翻滚。更早几天，尼科尔斯曾披露星链卫星与中国某批新发射卫星发生近距离接触事件，称后者发射时似乎未与现有卫星运营商进行协调。在最新声明中，尼科尔斯补充道，降低轨道"将进一步提升星座安全性，特别是应对其他卫星运营商未经协调的机动和发射等难以控制的风险"。
英文来源：
Starlink is lowering thousands of satellites' orbits to reduce risk of collisions
Satellites orbiting at around 342 miles will be dropped down to about 298 miles, Starlink's VP of engineering says.
Starlink will lower the orbits of roughly 4,400 satellites this year as a safety measure, according to engineering VP, Michael Nicolls. In a post on X, Nicolls wrote that the company is "beginning a significant reconfiguration of its satellite constellation," in which all satellites orbiting at around 550 kilometers (342 miles) will be lowered to around 480 km (298 miles). The move is intended to reduce the risk of collisions, putting the satellites in a region that's less cluttered and will allow them to deorbit more quickly should an incident occur.
"Lowering the satellites results in condensing Starlink orbits, and will increase space safety in several ways," Nicolls wrote, also pointing to the coming solar minimum — a period in the sun's 11ish-year cycle when activity is lower — as one of the reasons for the move. The next solar minimum is expected to occur in the early 2030s. "As solar minimum approaches, atmospheric density decreases which means the ballistic decay time at any given altitude increases - lowering will mean a >80% reduction in ballistic decay time in solar minimum, or 4+ years reduced to a few months," Nicolls wrote.
The announcement comes a few weeks after Starlink said one of its satellites had experienced an anomaly that created some debris and sent it tumbling. Just a few days earlier, Nicolls posted about a close call with a batch of satellites he said were launched from China seemingly without any attempt to coordinate with operators of existing satellites in the space. With his latest announcement, Nicolls added that lowering Starlink's satellites "will further improve the safety of the constellation, particularly with difficult to control risks such as uncoordinated maneuvers and launches by other satellite operators."