Problems with the European Gaia space telescope


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Shades of Hubble: The first data from Europe’s Gaia space telescope, launched to map a billion Milky Way stars, will be delayed 9 months while engineers grapple with several problems.

Gaia managers started taking test images early this year, but soon noticed three issues. For one, more light than anticipated is bending around the 10-metre sunshield and entering the telescope.

Small amounts of water trapped in the spacecraft before launch are being released now that the telescope is in the vacuum of space, and more ice than calculated is accumulating on the telescope’s mirrors. In addition, the telescope itself is expanding and contracting by a few dozen nanometres more than expected because of thermal variations.

Mission managers say the number of stars detected will remain the same even if these complications remain untreated, but the accuracy in measurements of the fainter stars will suffer.

Unlike Hubble, however, there is no way to send a shuttle and a team of astronauts to Gaia to fix it. And it sounds like these issues will have an impact on the telescope’s abilities to gather its intended data.

This story raises my hackles for another reason. Gaia was a very technically challenging space telescope to build, but it was far easier and less cutting edge than the James Webb Space Telescope. It also cost far less. What will happen when Webb gets launched later this decade? How likely is it to have similar issues? Based on a story I just completed for Sky & Telescope on the difficulties of building ground-based telescopes, I’d say Webb is very likely to have similar problems, with no way to fix them. The American astronomy community could then be faced with the loss of two decades of research because they had put all the eggs into Webb’s basket, and thus had no money to build anything else.

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15 comments

  • Orion314

    The failure of “group think” and the results of having committees with decision making powers and little to no oversight….

  • Orion314

    BTW, a really fine book to read about such fiascos is the “Hubble Wars…. Astrophysics Meets Astropolitics in the Two-Billion-Dollar Struggle over the Hubble Space Telescope” by Eric Chaisson

  • Don

    What is the life remaining for Hubble? No way to do any repairs to that either.

  • Actually, as someone who has written a book on the history of Hubble as well as interviewed at length many people who were personally involved with its design, construction, and repair, I can tell you unequivocally that Chaisson’s book is a very unreliable and very inaccurate book. Chaisson had his own person ax to grind, and the truth was not that important to him in grinding it.

    You should read The Universe in a Mirror. You would find out the actually reasons why Hubble was launched with the wrong prescription in its primary mirror.

  • The last servicing mission in 2009 was intended to give it a minimum of five more years of life. Those five years are now complete, and the telescope, with the repaired or new instruments installed during that servicing, continues to function flawlessly.

    It is likely the telescope could operate for years to come, though failure could also come at any time. If it lasts for another five years the technology to fly a robot mission to repair it at that time will have become far more likely, and I would then expect money will be found to fly such a mission, especially because there are as yet no plans to build a replacement optical space telescope.

  • mivenho

    Perhaps the Webb team can learn from Gaia by taking special precautions to reduce adsorbed moisture. Certainly it’s far too late to make revisions to the shielding

  • The concerns with Webb are not the problems that Gaia has, but the problems no one can predict will happen. It is the unknown unknowns with Webb that are causing American astronomers a great deal of stomach pain.

  • Pzatchok

    Of the three problems with the telescope the only one I can see being a real problem would be the extra stray light problem.

    If the machine is reduced in its movements because of that then its a permanent problem.

    The water problem will eventually go away over time. Its just a pain in the butt right now.

    As for the mirror expanding and contracting that little extra bit more than anticipated. That could be “fixed” with a software change. The worst of the visual changes will be around the outer edge. Closer to the center and things will stay pretty consistent visually.
    Even if they are forced to not use the outer 10% or so of the mirror it will just mean a longer time scanning the sky. The photographic overlap will just have to be larger than anticipated thus making them take more photos.

  • Kelly Starks

    Its sad we no longer have, nor are planning to build again the shuttle like abilities. Both Earth orbiting sats and ISS could really use that ability.
    ….Webb is a even bigger issue.

    I’m not optim,istic about robot repairs given the difficulties found repairing sats in the ’80’s. Even the tools and clamps were found to fall short, and the astrounauts needed to do things by hand to compensate. Developing a robot with that detailed a capacity – and one you can’t really test until you get there, is a big problem.

  • Competential

    Kelly Starks,
    Do you know if that 9 months delay is related to the need of extra overlap? Are they starting to do science, but at a slower rate, or are they canceling science for the next 9 months to give engineers time to fix everything? For example by turning the telescope back and forth so that the icy parts are exposed to sunlight until sublimated.

    I agree with you that repairing spaceships has proven to be very inefficient. Making things right to begin with is of course a winning strategy, and it is fabulously happening now! Failed space missions are getting rare. And servicing old satellites with fuel gets less interesting as technological development shortens the economic lifetime of the hardware out there.

    This kind of problem is small and is best solved by having the future science mission design phase learn from unexpected events like this. Not by waiting with everything until some kind of cis-lunar satellite servicing capability has been established. If you build anything which needs service, then you have failed to adapt to the current rate of new discoveries. Gaia 2 would be much more capable anyway, to compensate for much of a ten years delay.

  • Kelly Starks

    no real info. At the least they’ll need to analyze it and study sublimation rates of what’s leaking. Hopefully nothing but pure water got on the lenses – some lubrication films could do wonders for the images. ;/
    Also you’d need to wonder where in the ship the stuffs getting. Freezing joints or distorting gears? Shorts on circuit boards.

    Bottom line they are seeing that the sat isn’t as clean and dry as was expected and designed for — which should cost them a lot of sleep.

    Then there the “more light is getting around the sunshade” comment that’s confusing. With no atmosphere around it (unless theirs a slight fog from evaporation) the sunshade should produce a extremely predictable geometrically perfect shadow. So where the light getting “around” it? Is it bent or damaged?Torn edges?

    I expect the 9 months is just a conservative estimate of how long to turn the sat back and forth to boil off what they can, study the rest and deduce what can be worked around operationally.
    ….or they might think they need that long to find new jobs before the bad news gets out.
    ;)

  • Pzatchok

    I could see a very small two man one week operation shuttle being built just for repair work and refueling.

    But nothing more than that. No capability to return anything to earth like a large satellite or telescope.

    Maybe something about three times the mass of the new US Airforce robotic shuttle.

    Barely room for an airlock and definitely no privacy.

    Small enough to be lifted on something we already have operational.

  • Pzatchok

    How would water get into the craft in the first place.

    I can see some adhesives, paints and or other coatings giving off a little, but those would be known quantities. And more than likely already taken care of long before lift off.

    Did a mouse die inside it? Did someone leave a wet rag in it?

  • Kelly Starks

    Sounds like your describing a X-37C. Though that would be to small to do much repair work with. You really need more of a space truck, then a space taxi.

  • It is actually normal for spacecraft to be launched with some humidity inside them. Remember, they are on Earth when built. There is no way to build them in the vacuum of space.

    Early in the 1960s engineers learned that they had to give spacecraft time to vent out the atmospheric components that the spacecraft had inside it when built. The ice in Gaia is actually not a serious problem. It was expected and they had allowed time for it to vent. What wasn’t expected was the amount, requiring more venting time.

    The more serious issue is the spacecraft’s jitter due to thermal changes. This should have been better estimated during construction, and will cause significant headaches in gathering the data Gaia was designed to gather.

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