El Hubble Space TelescopeThe Observatory, one of the most emblematic scientific instruments of recent decades, faces an end of life that could be far more difficult than initially thought. Various technical analyses indicate that the observatory, which has been orbiting the planet since 1990, It will eventually re-enter the atmosphere in an uncontrolled re-entry., with a considerable risk to property and people on the surface.
Far from being a simple orbital formality, this final phase has become a delicate matter for space agencies. According to a recent report from NASA Engineering and Safety Center (NESC), available on the agency's own technical reports server, The current trajectory of the Hubble telescope's fall does not currently meet the usual safety criteria.The problem is that the telescope It was never designed to be left to its own devices.but to be recovered or deorbited in a controlled manner.
A veteran of the low orbit with an expiration date
Since its launch into orbit, Hubble has been traveling around the Earth at about 28.000 kilometers per hour, initially at an altitude of about 550 kilometers and currently around 480-500 kilometerswithin what is called low Earth orbit. Although it may seem that up there it is "free" from the atmosphere, There is still a thin layer of air which exerts a constant drag and very slowly slows down the telescope.
During the first decades of its useful life, NASA was able to correct that decline Thanks to several servicing missions of the space shuttle program, between 1993 and 2009. On each visit, in addition to changing instruments and carrying out repairs, the astronauts used the spacecraft's thrusters to push Hubble into a slightly higher orbit and thus extend its operation for a few more years.
When it was launched, the official expectation was that the observatory would operate around 15 yearsHowever, the telescope has lasted much longer than expected, with over 1,3 million scientific observations which have been used to study the expansion of the universe, confirm the presence of black holes at the center of galaxies or detect new moons in the outer Solar System. That longevity, which from a scientific point of view is a blessing, It has now become a headache for planning his retirement.
The big turning point came with the end of the space shuttle program, whose last flight took place in 2011 with Atlantis. The original plan by NASA and the European Space Agency (ESA) envisioned using the shuttle to recover Hubble at the end of its useful life or to direct it towards a controlled reentry.With the disappearance of that capability, the observatory was left in a hybrid situation: it remains operational, but without its own system that allows it to be placed in a safe orbit or deorbited precisely.
In recent years, some of its key components, such as the gyroscopes that allow for highly accurate aimingThey have shown increasingly evident deterioration. Although the telescope continues to operate and send data, Its operating margin is narrowing and, with it, the possibilities of planning complex maneuvers.
A telescope designed to be recovered, not to fall uncontrollably.
The NESC study highlights a key aspect: The Hubble was never designed to handle an uncontrolled reentryIts design was intended so that, upon completion of its mission, a manned spacecraft could dock with it, enabling its rescue or a carefully directed deorbit towards a remote area of ​​the oceanThat option practically disappeared with the withdrawal of the ferries and, to this day, no equivalent alternative has been implemented.
In 2022, Elon Musk He even went so far as to publicly raise the possibility of a mission to SpaceX with the Crew Dragon capsule to raise Hubble's orbit again and give it a few more years of life. That idea was studied in a preliminary way, but It has not progressed nor has it resulted in a formal planSo, for the time being, it is considered, in practice, to be shelved.
Meanwhile, the telescope's orbit is gradually degrading. Hubble is a large structure, with about 13,2 meters long, an approximate diameter of 4,2 meters and a mass around the 12 tonnes Not counting solar panels and mirrors. This size means that, unlike other smaller satellites, There is a significant probability that certain massive fragments will survive passage through the atmosphere.
The NESC analysis emphasizes that Re-entry is not only inevitable if no action is takenbut also requires increasingly precise monitoring as the observatory loses altitude. The combination of its mass, its geometry, and the varying density of the upper atmosphere means that Predicting precisely the time and place of the fall is extremely complexespecially many years in advance.
To make matters worse, factors such as geomagnetic storms and solar activity They can alter the density of the upper layers of the atmosphere, increasing drag on Hubble's orbit. During periods of high solar activity, this atmospheric drag can be significant and accelerate the descent, while during calmer periods the process is somewhat slower.
Probable dates for re-entry: 2029, 2033 or 2040
The most recent calculations use a a time window of about 11 years for the uncontrolled return of Hubble to the dense layers of the atmosphere. Considering "average" solar activity and an effective surface area consistent with the telescope's current configuration, the scenario that experts consider The most plausible scenario places re-entry around 2033.
The technical analysis, also cited by the American Astronomical SocietyHowever, he does not rule out other possibilities. In the most optimistic scenarioWith more favorable conditions, the telescope could remain in orbit until approximately 2040. En el worst case scenarioAnd, still speaking of preliminary estimates, the fall could come significantly earlier and occur as early as [date missing]. 2029.
Re-entry models also indicate that Hubble would leave behind a rubble footprint which could extend between 350 and 800 kilometers along the surface path. This does not mean that the entire strip will be devastated, but rather that fragments that survive the atmospheric fire could be dispersed along that corridor.
It is important to emphasize that, as of today, It is not possible to know exactly where it will end up fallingThe telescope's orbit crosses a wide band of latitudes, so, from a purely theoretical point of view, re-entry could occur over the ocean, over sparsely populated areas or over densely populated regions, in Asia as well as in America, Africa or Europe.
As the actual reentry date approaches, the predictions will be refined. The report's authors recommend regularly updating the models and better integrating the effect of variations in solar activity and assess the remaining room for maneuver to reduce the risk by small orbital adjustments, if the condition of the telescope allows it.
What real risk exists for the population?
The big question, beyond pure scientific curiosity, is to what extent That fall could pose a danger to people on the ground.The NESC study has addressed this issue using different simulation methodologies, which consider both the observatory's trajectory and the behavior of its components during re-entry and the population distribution on the surface.
According to these models, a substantial part of the Hubble structure would disintegrate due to the extremely high temperatures and mechanical forces that are generated when passing through the atmosphere at high speed. However, it is expected that some more robust elements —for example, certain sections of the main body or dense parts of the instruments— they can reach the ground or the sea as fragments.
Researchers quantify the risk in terms of probability of individual victims globally, across the entire path of the telescope. In the medium scenario, the study calculates an approximate probability of 1 out of 330 that at least one casualty will occur in the latitude range crossed by the Hubble orbit. In remote areas, such as the least populated region of South PacificThat probability is reduced significantly, to around 1 out of 31.000.
The worst-case scenario would occur if the remains of the telescope fell on densely populated metropolitan areas, such as certain regions of India or Southeast AsiaIn simulations with particularly adverse conditions, the report estimates probabilities close to 1 in 22 that victims are registered in an extreme case, with cities like Macau, Hong Kong or Singapore as examples of areas where one might expect between one to up to four potential victims.
These figures should be interpreted with caution, but they serve to illustrate why the issue is a concern for space agencies. NASA's own regulations, specifically the standard NASA-STD-8719.14C, establishes that The acceptable risk to the public in re-entries of this type must be equal to or less than 1 in 10.000In other words, the values ​​calculated for Hubble exceed the security threshold that the agency considers acceptable, which necessitates studying additional solutions.
In the European and Spanish context, potential risks are also assessed in terms of international coordinationSpain, like other member states of the European Union and the European Space Agency, participates in spatial surveillance and monitoring programs that allow monitoring the position of large objects in orbit and anticipate re-entry scenarios with some advance noticeIn the event that predictions point to a possible trajectory of debris over European territory, the mechanisms of civil protection and emergency management They would be activated in a coordinated manner.
Measures under study and scope for action
Given this scenario, the NESC report does not limit itself to quantifying the problem, but also raises a series of recommendationsOne of the main ones is to continue refining the models of orbital decay and reentry, incorporating new data on the structure of the telescope, the behavior of its materials at high temperatures and the evolution of the upper atmosphere.
Another line of work involves re-analyze the intervention options before the orbit descends too low. Although the initial proposal of SpaceX and the Crew Dragon capsule While it may seem unlikely today, space technology is changing rapidly, and it's possible that new technologies will emerge in the coming years. new commercial or institutional solutions that would allow, at least, raising the orbit a few kilometers to gain time or even plan a deorbiting directed towards a less critical ocean zone.
The possible missions of this type are not trivial: they would require vehicles capable of safely coupling to a large and relatively old structure, with a very specific electrical and mechanical system. Furthermore, it would be necessary to assess costs, risks and scientific priorities, comparing the effort required to partially "save" Hubble with other ongoing missions, such as the James Webb Space Telescope or future European and American observatories.
Until there is a clear decision on a targeted salvage or deorbiting operation, everything points to the main strategy being closely monitor the orbital evolution of HubbleThis involves tracking campaigns from ground stations, deep-space telescopes, and specialized radar systems, many of them integrated into space surveillance networks in which Europe participates.
With regard to the population, including cities and rural areas of Spain, experts insist that The absolute risk of being affected by debris from the telescope is very low.Most of the planet's surface is covered by oceans or sparsely populated areas, and the probability of a specific fragment impacting a specific location is extremely low. However, the fact that the calculations exceed NASA's official thresholds necessitates keeping the issue on the space safety agenda.
After more than three decades in service and with a scientific legacy that is hard to match, the future of Hubble enters a phase in which Technical, security, and international cooperation issues carry as much weight as purely scientific ones.What happens in the coming years—whether a mission to raise its orbit is approved, whether a controlled deorbit is chosen, or whether unguided reentry with mitigation measures is assumed—will determine not only how the life of this historic telescope will endbut also the way in which the major space powers will now manage the end-of-life of large orbital infrastructures.
