A 3,200-pound NASA observatory is careening back toward Earth. Here’s what to know

NASA’s Neil Gehrels Swift Observatory is expected to meet a fiery end early Wednesday morning, nearly 22 years after it launched to study the most powerful explosions in the universe.

While most of the 3,200-pound spacecraft is expected to burn up as it blazes through the thick inner band of Earth’s atmosphere, NASA predicts some pieces of the vehicle will hit the ground.

“The risk of harm coming to anyone on Earth is unlikely, approximately 1 in 2,100,” NASA said in a statement Monday.

Goddard Space Flight Center/NASA

A storied NASA observatory could be weeks away from falling to Earth after failed rescue attempt

The agency also anticipates that Swift’s debris could land somewhere between 20.6 degrees south latitude and 20.6 degrees north latitude — or about 1,420 miles (2,285 kilometers) below and above the equator. That band encompasses much of Central and South America, Central Africa, southern India, Southeast Asia and northern Australia, as well as vast stretches of ocean.

It’s not yet clear exactly when Swift will make its final descent to Earth. Prediction models typically have a margin of error of at least a few hours. An estimate from the nonprofit Aerospace Corporation put reentry 5:19 a.m. ET, plus or minus two hours. A more recent US Space Force projection predicted reentry for 7:42 a.m. ET with the same margin of error.

If Swift were launched today, it would likely have to adhere to far stricter safety guidelines regarding end-of-life planning, according to The Aerospace Corporation, which is a federally funded research and development center.

Current orbital debris mitigation standards , which were updated in 2019, mandate that “uncontrolled reentries have an expected casualty of less than 1 in 10,000,” said Parker Wishik, a spokesperson for The Aerospace Corporation. He noted in an email that, in this context, “casualty” refers to “serious injury or death.”

While NASA has long known that Swift would likely have to make an unpredictable plunge back to Earth, the agency had hoped that a daring rescue mission launched in July could latch on and boost the Swift Observatory as atmospheric drag gradually pulled it from a once-stable orbit. It could have extended Swift’s operating life by a decade or more, but ultimately the effort failed. The spacecraft eventually dropped down to just 171 miles (275 kilometers) above the planet, and the observatory officially stopped gathering scientific data.

“At this point, the spacecraft was no longer able to compensate for the effects of the increased drag and entered safe mode,” NASA said in a news release .

A team of researchers at Penn State — NASA’s partner on the project and home to the observatory’s Mission Operations Center — sent the final kill-switch command to Swift on October 20.

University of Hawaii/NASA

NASA/Swift Science Team/Stefan Immler

NASA/Swift/Stefan Immler

NASA Goddard Space Flight Center

NASA/CXC/Univ. Of Michigan/M. Re/Chandra X-ray Observatory

NASA/Swift/Phil Evans

NASA/ESA/XMM-Newton/Younes et al.

NASA/Swift/Z. Xing et al. 2020

NASA/Swift/A. Beardmore (University of Leicester)

Swift’s demise was hastened by an increase in solar activity over the past couple of years as the sun reached the peak of its 11-year cycle in 2024.

Intense flares and coronal mass ejections caused Earth’s atmosphere to expand, which intensified the drag on Swift, leading scientists to predict it would descend toward our planet this fall.

Arizona-based Katalyst Space Technologies scrambled to put together the last-ditch effort to stabilize the Swift observatory earlier this year, getting the rescue mission off the ground in only nine months. The company rapidly produced a spacecraft called LINK, which aimed to grapple the telescope and lift it back into a stable orbit. But the mission failed a few weeks after LINK’s launch in July as the satellite spun out of control in space before reaching the Swift observatory.

As Swift’s fate was sealed, mission scientists slowly turned the telescope’s instruments back on to collect data and observations right up until the end. The instruments had been shut off for months to save power and mitigate how quickly the spacecraft sank out of orbit.

The Swift Observatory, which does not have an established observational replacement waiting in the wings, has served as an astrophysics multi-tool in low-Earth orbit since it launched in November 2004.

Named after fast-flying birds, the telescope could quickly pivot to observe blink-and-you-miss-it cosmic events such as flaring black holes. The telescope was originally designed to study the most powerful explosions in the universe, called gamma-ray bursts, but scientists have also used it to monitor other types of cosmic flashes as well as asteroids and comets.

NASA/ESA/David Jewitt (UCLA)

Image reveals unprecedented view of the third interstellar object observed passing through our solar system

Despite the failed attempt to rescue Swift, NASA has signaled it may try similar lifeline-extension missions for other valuable space-based instruments. Last week, the agency issued a solicitation — formally called a Request for Proposals or RFP — to commercial companies, asking how they might boost, service or otherwise prolong the life of the iconic Hubble Space Telescope.

NASA’s analysis shows that there’s a 10% chance Hubble will plunge out of orbit by 2032 and a 50% it will deorbit by 2033, according to the RFP. The beloved telescope, launched in 1990, has delivered some of the most recognizable images in astronomy and has transformed scientists’ understanding of the cosmos. There is no replacement for Hubble expected before the 2040s, the RFP states.

美国宇航局的尼尔·格雷尔斯·斯威夫特天文台预计将于周三清晨燃起熊熊烈火，结束其近 22 年的使命——研究宇宙中最强烈的爆炸。

虽然这艘重达 3200 磅的航天器的大部分预计会在穿越地球大气层厚厚的内层时烧毁，但美国宇航局预测，航天器的部分碎片将会坠落到地面。

美国宇航局周一在一份声明中表示：“地球上任何人受到伤害的风险都很小，大约为 1/2100。”

戈达德太空飞行中心/美国国家航空航天局

在一次失败的救援尝试后，美国宇航局一座历史悠久的天文台可能在几周内坠落地球。

该机构还预计，斯威夫特卫星的碎片可能会落在南纬20.6度至北纬20.6度之间的某个区域——也就是赤道上下约2285公里（1420英里）的范围内。这一区域涵盖了中美洲和南美洲的大部分地区、非洲中部、印度南部、东南亚和澳大利亚北部，以及广阔的海洋区域。

目前尚不清楚“雨燕”号卫星何时最终返回地球。预测模型通常至少有几个小时的误差。非营利组织航空航天公司估计，卫星将于美国东部时间凌晨5点19分重返大气层，误差范围为正负两小时。美国太空军最近的预测则认为卫星将于美国东部时间上午7点42分重返大气层，误差范围相同。

据美国联邦资助的研究和开发中心——航空航天公司称，如果 Swift 火箭今天发射，它可能需要遵守更严格的报废规划安全准则。

美国航空航天公司发言人帕克·威希克表示，现行的轨道碎片减缓标准（于2019年更新）规定，“不受控制的再入事件造成的伤亡预期低于万分之一”。他在一封电子邮件中指出，在此语境下，“伤亡”指的是“重伤或死亡”。

尽管美国宇航局（NASA）早就知道“雨燕”号探测器很可能要经历一次难以预料的坠落，但该机构曾寄希望于7月发射的一次大胆的救援任务能够抓住并提升“雨燕”号的轨​​道，使其免于被大气阻力逐渐拉离原本稳定的轨道。这项任务本可以延长“雨燕”号的运行寿命十年甚至更久，但最终以失败告终。最终，这艘探测器坠落到距离地球仅171英里（275公里）的高度，天文台也正式停止了科学数据的收集。

美国宇航局在一份新闻稿中表示：“此时，航天器已无法补偿增加的阻力带来的影响，并进入了安全模式。”

宾夕法尼亚州立大学（NASA 在该项目上的合作伙伴，也是该天文台任务运行中心所在地）的一个研究团队于 10 月 20 日向 Swift 发送了最终的终止开关指令。

夏威夷大学/美国国家航空航天局

美国国家航空航天局/Swift科学团队/斯特凡·伊姆勒

NASA/Swift/Stefan Immler

美国宇航局戈达德太空飞行中心

美国国家航空航天局/CXC/密歇根大学/M. Re/钱德拉X射线天文台

NASA/Swift/菲尔·埃文斯

NASA/ESA/XMM-牛顿/Younes 等人

NASA/Swift/Z. Xing等人，2020年

美国国家航空航天局/Swift/A. Beardmore（莱斯特大学）

过去几年太阳活动加剧，加速了斯威夫特的消亡，因为太阳在 2024 年达到了其 11 年周期的顶峰。

强烈的耀斑和日冕物质抛射导致地球大气层膨胀，加剧了对雨燕卫星的阻力，科学家们预测它将在今年秋季坠向地球。

今年早些时候，总部位于亚利桑那州的卡塔利斯特太空技术公司（Katalyst Space Technologies）紧急筹备了一项旨在稳定雨燕天文台的最后努力，并在短短九个月内启动了这项救援任务。该公司迅速制造了一艘名为LINK的航天器，其目标是捕获望远镜并将其送回稳定的轨道。然而，LINK在7月发射几周后，任务失败了，因为卫星在抵达雨燕天文台之前就在太空中失控旋转。

随着“雨燕”号的命运已定，任务科学家们缓慢地重新启动了望远镜的仪器，直至最后一刻仍在收集数据和观测结果。这些仪器此前已关闭数月，以节省能源并减缓航天器脱离轨道的速度。

自 2004 年 11 月发射以来，雨燕天文台一直作为近地轨道上的天体物理多功能工具发挥作用，目前还没有成熟的观测替代设备。

这架以飞行速度极快的鸟类命名的望远镜，能够快速旋转，观测转瞬即逝的宇宙事件，例如爆发的黑洞。该望远镜最初的设计目的是研究宇宙中最强烈的爆炸——伽马射线暴，但科学家们也利用它监测其他类型的宇宙闪光以及小行星和彗星。

美国国家航空航天局/欧洲航天局/大卫·朱伊特（加州大学洛杉矶分校）

这张图像以前所未有的视角展现了观测到的第三个穿越我们太阳系的星际天体。

尽管拯救“雨燕”卫星的尝试失败了，但NASA已表示可能会尝试类似的延寿任务，以拯救其他重要的太空仪器。上周，NASA向商业公司发出了一份征求建议书（正式名称为“提案征集书”或RFP），询问他们如何才能提升、维护或以其他方式延长标志性的哈勃太空望远镜的寿命。

根据美国宇航局发布的招标书，其分析显示，哈勃望远镜在2032年之前有10%的概率脱离轨道，在2033年之前有50%的概率脱离轨道。这架备受喜爱的望远镜于1990年发射升空，拍摄了许多天文史上最具代表性的图像，并彻底改变了科学家对宇宙的认知。招标书指出，在2040年代之前，预计不会有哈勃望远镜的替代品。