Multiple analyses project that Hubble’s uncontrolled re-entry could occur as early as the late 2020s. Photo credit: Rawpixel.com/Shutterstock
The Hubble Space Telescope, one of the most productive scientific observatories ever launched, is in a gradual but inevitable downward spiral towards Earth due to atmospheric drag acting on its low-Earth orbit. Launched in 1990 and orbiting at an altitude of roughly 540–560 km, Hubble’s orbit decays slowly because even the tenuous upper atmosphere exerts a drag force that diminishes its altitude over time. Without corrective action, this will ultimately lead to its re-entry into the Earth’s atmosphere.
The telescope was periodically boosted into a higher orbit during servicing missions by space shuttle crews between 1993 and 2009. Since the retirement of the shuttle fleet, those opportunities have ceased, leaving Hubble’s orbit unchecked. Without active boosts or a controlled de-orbit mission, the telescope’s descent will continue as atmospheric drag gradually slows its orbital speed.
Predictions for re-entry vary
Models forecast re-entry by the 2030s
Multiple analyses project that Hubble’s uncontrolled re-entry could occur as early as the late 2020s to the mid-2030s. Solar activity plays a significant role in determining the rate of orbital decay, as increased solar radiation heats the upper atmosphere and expands it, increasing drag on satellites at Hubble’s altitude. This variability introduces uncertainty into precise timing estimates for re-entry, but the long-term trend of descent remains clear.
Risks posed by uncontrolled descent
Debris and safety considerations
Hubble was not designed for uncontrolled re-entry. Should the telescope re-enter without a controlled de-orbit plan, much of its structure would burn up during atmospheric entry, but some larger components could survive and reach the ground. Experts note that the probability of debris impacting populated areas is low, but non-zero, because re-entry from a decaying orbit can scatter surviving fragments over a wide geographic range.
Space agencies generally plan controlled de-orbits for large spacecraft to direct any surviving debris to uninhabited regions, such as remote ocean areas, in order to minimise risk. A docking adaptor fitted during Hubble’s final servicing mission in 2009 could facilitate a future controlled re-entry, but no mission to employ it has been scheduled.
Potential mitigation efforts
NASA and private sector proposals considered
In response to the decay issue, NASA and Space X have explored options that would extend Hubble’s operational life or enable a safer end-of-life scenario. One concept under discussion involves a private sector mission to rendezvous with Hubble and boost its orbit, postponing re-entry and potentially allowing a later controlled de-orbit when its mission is complete.
Such proposals remain in the planning or study phase, and none have been formally adopted as of early 2026. Should a reboost mission be pursued, it could significantly delay the telescope’s descent and reduce the risk associated with uncontrolled re-entry.
Key points
- Hubble’s orbit is gradually decaying due to atmospheric drag.
- Re-entry is expected sometime between the late 2020s and mid-2030s.
- Most of the telescope will burn up, but some debris could reach the ground.
- No controlled de-orbit mission has been scheduled.
- NASA and Space X proposals to boost Hubble’s orbit remain in planning.
Broader context for the telescopes re-entry
Uncontrolled re-entry is not unique to Hubble
Many satellites and spacecraft in low-Earth orbit eventually re-enter the atmosphere uncontrolled unless actively de-orbited. Space agencies generally aim to mitigate these risks through design, end-of-life planning and controlled de-orbit missions, but the large size and high scientific value of assets such as Hubble complicate the planning of final disposal strategies.
For its part, Hubble continues to produce valuable scientific observations while engineering teams monitor its health and plan for its eventual retirement.
