NASA is again asking for ideas to raise Hubble’s orbit. Thin air at its altitude slowly drags the telescope down, and no spacecraft can currently reach it to give it a boost. An earlier request, four years ago, came to nothing.
The Hubble reboost problem
The Hubble Space Telescope is a large observatory orbiting Earth. It is high enough to sit above most of the atmosphere, but not high enough to escape it completely. At that altitude there are still traces of gas. Each pass through this thin air takes a little speed from the telescope, so its orbit shrinks slowly. Engineers call this orbital decay.
A satellite with its own engine can fire it now and then to climb back up. Hubble has no propulsion system, so it cannot do this. Unless something pushes it higher, it will keep sinking until it re-enters the atmosphere. A “reboost” means using another spacecraft, or a device attached to the telescope, to raise its orbit and buy it more years of life. The “certain death” in recent headlines is that uncontrolled descent.
Ars Technica reports that NASA has once more asked outside parties to suggest how such a reboost might be done. It notes that the agency asked a similar question four years ago and that those proposals did not lead anywhere.
Origins of the issue
Hubble was launched by the Space Shuttle in 1990. From the start it was designed to be visited. Astronauts flew to it on several servicing missions, swapping instruments, replacing worn parts and fixing problems, including the well-known flaw in its main mirror. During some of these visits the shuttle also raised the telescope’s orbit, which made up for the height lost to drag.
The Space Shuttle was retired in 2011, and that ended the regular way of reaching Hubble. No other vehicle in service had the same mix of cargo bay, robotic arm and crew access that the servicing missions relied on. Since then the telescope has kept working with what it had at the last visit, and nothing has made up for the slow loss of altitude.
The earlier request for ideas, which Ars Technica dates to four years before the current one, explored whether commercial spacecraft could fill the gap. According to the publication, it produced no mission. The source does not give the reasons in detail, and this article does not speculate about them.
The situation today
Hubble is still operating and producing science. It does so alongside newer observatories rather than being replaced by them, because it observes in parts of the spectrum, especially visible and ultraviolet light, that other telescopes cover differently or not at all.
The rate at which its orbit decays is not fixed. It depends heavily on solar activity. When the Sun is more active, the upper atmosphere heats and expands, which raises drag at Hubble’s altitude and speeds up the descent. In quieter periods the decay slows. For this reason, any projected re-entry date carries real uncertainty, and the source material does not give one.
A reboost mission would face several technical hurdles. Hubble was not built with a docking port for modern spacecraft, so any vehicle would need a safe way to grip or attach to it. The telescope is large and delicate, and it must not be knocked or contaminated. Any visiting craft would also need enough fuel to raise a heavy object by a useful amount. Cost, risk to a working observatory and the question of who pays all shape whether a proposal moves forward. Ars Technica’s report places the new request in this context, but what NASA will do with the responses is not yet known.
Common misconceptions
One common mistake is to think Hubble has already stopped working, or that the James Webb Space Telescope replaced it. Webb is designed mainly for infrared light and sits much farther from Earth. The two instruments complement each other, and Hubble continues to observe.
A second misconception is that Hubble is about to fall. Orbital decay is gradual. The concern is about the long term: without help, the end is unavoidable, but it is not imminent in the sense of weeks or months.
A third is that Hubble could simply fire its own thrusters. It has no rocket engine for changing its orbit. It points itself using internal devices such as gyroscopes and reaction wheels, which turn the telescope but cannot raise it.
People also sometimes assume a reboost would be the same as a servicing mission. Raising the orbit and repairing or upgrading the hardware are separate goals. A mission could do one without the other, and a reboost alone would not fix any ageing components.
Finally, a request for ideas is not a commitment. Asking industry for proposals is a way of gathering information. As the earlier round showed, it does not guarantee that a mission will follow.
Frequently asked questions
Why is the Hubble Space Telescope losing altitude?
Hubble orbits at a height where traces of Earth’s atmosphere remain. Each orbit, this thin gas creates a small amount of drag that slows the telescope and lowers its orbit. The effect is gradual but constant. It gets stronger when the Sun is more active, because solar activity heats and expands the upper atmosphere. Hubble has no engine to climb back up.
Can Hubble boost its own orbit?
No. Hubble has no propulsion system for changing its orbit. It uses internal equipment such as gyroscopes and reaction wheels to point at targets, but these only rotate the telescope and cannot raise it. In the past, the Space Shuttle raised Hubble’s orbit during servicing visits. Any future reboost would need an external spacecraft or an attached device.
Has NASA tried to reboost Hubble before?
According to Ars Technica, NASA asked for ideas on reboosting Hubble four years before its latest request, but those proposals did not lead to a mission. Before that, Space Shuttle crews raised the telescope’s orbit during servicing missions. Those visits stopped when the shuttle was retired in 2011, and nothing has replaced them since.
When will Hubble re-enter the atmosphere?
No precise date is known. The rate of orbital decay depends heavily on solar activity, which changes over time and is hard to predict far ahead. Without a reboost, re-entry is considered inevitable eventually, but it is a long-term prospect rather than an immediate one. The source material behind this article does not give an estimated date.
Is Hubble still working?
Yes. Hubble continues to make observations and produce science. It has not been replaced by the James Webb Space Telescope, which observes mainly in infrared light from a much more distant location. Hubble’s strengths in visible and ultraviolet light mean the two observatories complement each other rather than overlap.
Sources and further reading
- Ars Technica: report on NASA’s renewed request for ideas to reboost Hubble
- NASA: Hubble mission pages and operational status updates
- Space Telescope Science Institute: background on Hubble’s science operations and instruments
- Space agency and university educational material: explanations of orbital decay and atmospheric drag
Surfaced from the rss:arstechnica signal “Hubble orbit rescue request”. AI-assisted draft, editorially reviewed.
