[HN Gopher] Operations begin to de-ice Euclid's vision
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Operations begin to de-ice Euclid's vision
Author : N19PEDL2
Score : 73 points
Date : 2024-03-19 10:48 UTC (12 hours ago)
(HTM) web link (www.esa.int)
(TXT) w3m dump (www.esa.int)
| Loughla wrote:
| Is there not a way to control moisture during assembly? If there
| is, and they did. What amount of moisture are we talking about to
| cause this issue?
| SiempreViernes wrote:
| Well, the deposition is estimated as just a few nanometres
| thick so were talking about something like a grain sand crushed
| to a fine powder, and then a few grains of that...
| chongli wrote:
| Still, I would've thought they'd do a very long vacuum bake-
| out stage before sealing up the satellite inside the launch
| rocket.
| Sharlin wrote:
| It's not going to be in a vacuum inside the payload shroud.
| There's air, and that air contains some amount of moisture.
| And Florida isn't known for its dry air (it was launched
| from Cape on a Falcon 9 - but French Guiana would hardly
| have been better in that respect).
|
| > It was always expected that water could gradually build
| up and contaminate Euclid's vision, as it is very difficult
| to build and launch a spacecraft from Earth without some of
| the water in our planet's atmosphere creeping into it.
| nick238 wrote:
| Satellites are transported in very specialized containers
| that will often be purged with dry nitrogen. Then after
| encapsulation in the faring, conditioned air of whatever
| sort is pumped into the faring from rollout to launch.
| [Example air conditioning duct attached to a Thor-Agena](
| https://space.stackexchange.com/questions/39440/why-use-
| an-a...)
| 0cf8612b2e1e wrote:
| Can ice sublimate at these temperatures?
| SiempreViernes wrote:
| They did:
|
| > This icing issue is not uncommon, and, as a result, part
| of the telescope's commissioning phase included an
| "outgassing campaign." This process involved Euclid turning
| to face the Sun for a total of 96 hours. This process was
| implemented specifically to reduce the risk of ice build-up
| after the agency's Gaia mission faced a similar issue.
|
| Apparently, it wasn't as effective as they hoped.
| seszett wrote:
| They say _Approximately 10 kg of MLI covers Euclid 's two
| science instruments, but this material can absorb 1% of its own
| weight in water_ so at most 100 grams of water.
|
| Assuming they were careful, maybe a tenth of that remains, so
| around 10 grams of water, a small fraction of which sublimates
| and eventually meets a mirror and deposits there. They say it's
| "several layers of molecules".
|
| I suppose they could have used another type of insulation, but
| since they also have very precise temperature requirements,
| maybe it was a trade off they had to make.
| pmontra wrote:
| 500 Internal Server Error, so
| https://archive.is/20240319115956/https://europeanspacefligh...
| WarOnPrivacy wrote:
| > 500 Internal Server Error
|
| Firefox gives a SSL_ERROR_NO_CYPHER_OVERLAP (can't vet cert
| data).
|
| Cert _is_ good.
| https://www.ssllabs.com/ssltest/analyze.html?d=europeanspace...
| pmontra wrote:
| My Firefox doesn't complain both on Linux (123) and on
| Android (latest Nightly)
| perihelions wrote:
| The primary source is this ESA story and it's much better:
|
| https://www.esa.int/Science_Exploration/Space_Science/Euclid...
|
| The current OP is just a summary of this one.
| 1970-01-01 wrote:
| >It was always expected that water could gradually build up and
| contaminate Euclid's vision, as it is very difficult to build
| and launch a spacecraft from Earth without some of the water in
| our planet's atmosphere creeping into it.
|
| If they expect moisture, perhaps final assembly could be done
| in the Atacama?
| SiempreViernes wrote:
| Still need to launch from either Guyana or Florida though, so
| that doesn't solve anything unless you do the integration
| with the final stage in the Atacama and ship the entire
| assembled rocket somewhere.
| bee_rider wrote:
| I wonder if this is actually a good application for orbital
| manufacturing.
|
| Kidding. Kinda...
| perihelions wrote:
| You could do a Starship* hop from Chile to Guyana, and
| there transfer it to the ESA's launch vehicle.
|
| *(Meaning the upper stage by itself, once it has lunar
| lander legs).
| throwway120385 wrote:
| Are you saying ESA should have waited for this to be
| technically possible? Or that it is technically possible
| now and ESA should have looked in to this option?
| perihelions wrote:
| It's a speculative, blue-sky idea--as is the context
| discussion that's proposing to assemble space satellites
| in a remote desert for optimization reasons.
|
| It's not technically implausible. Starship (upper-stage
| only) in principle has a very long hop range--it's almost
| an SSTO by itself [0]. In principle it could also support
| landing on non-spaceport facilities like deserts--after
| all it's explicitly designed for landing on the moon, in
| accordance with the NASA Artemis contract. Would SpaceX
| be thinking about trying long-range hops on Earth, as a
| testing mechanism? I'm not sure it'd be completely crazy
| to consider that.
|
| Musk has extensively talked about the concept of Starship
| (full stack) as city-to-city passenger transport [1].
|
| [0] https://en.wikipedia.org/wiki/Single-stage-to-
| orbit#Starship
|
| [1] https://www.theverge.com/2017/9/29/16383048/elon-
| musk-spacex...
| bee_rider wrote:
| I read the quote and wondered, well, that's sort of a weird
| thing to mess up; if it was always expected then why didn't
| they take care of it?
|
| It in case anyone else is wondering--it sounds like it is a
| very thin layer of water
|
| > A few layers of water ice - the width of a strand of DNA
|
| Sounds like they made it about as dry as possible.
| weebull wrote:
| It's a problem they planned for.
| 7thaccount wrote:
| Sometimes I'm upset that we don't have flying cars or warp drives
| yet, but then I think of the sheer engineering challenges in
| something as mundane seeming as this and can be proud again of
| humanity. I don't know how they ever manage to get these kinds of
| projects right. The JWST was a pretty crazy feat as well.
| DemocracyFTW2 wrote:
| > can be proud again of [del]humanity[/del][ins]humidity[/ins]
|
| I fixed that for ya.
|
| Genuinely my first reading
| rob74 wrote:
| Yeah, those damned science fiction shows make it all look too
| easy...
| 7thaccount wrote:
| You can fix most problems by inverting the field polarity ;)
| the_sleaze9 wrote:
| Enhance!
| hartator wrote:
| 1.4 billion euros over budget, 12 years in, and they still
| can't make it work. I am not sure if I am super proud of this.
|
| Science experiments should have some accountability as well.
| snakeyjake wrote:
| I cut cost overruns for things like this some slack because I
| know, irrefutably, that anyone who thinks they can estimate a
| budget for a one-of-one, never-been-done-before, object like
| Euclid is a liar.
|
| I know all about the techniques. I've been in the meetings.
| I've seen the spreadsheets. Your parametric cost model is
| adorable.
|
| But at the end of the day, you're just lying with math.
|
| And if you have to lie a little bit to get a space telescope
| built... no sweat.
| n4r9 wrote:
| 1.4 billion appears to be the total cost: https://www.esa.int
| /ESA_Multimedia/Images/2023/05/Euclid_an_...
|
| Budget back in 2012 was 600 million:
| https://cerncourier.com/a/euclid-to-link-the-largest-and-
| sma...
|
| I don't know how badly inflation hits these projects, but
| that's around 820 million in today's money, which means
| roughly 580 million over budget. And I've no doubt that 600
| million was only floated around in the first place to satisfy
| a bureaucratic manager who imagines that putting a number
| next to everything makes things efficient.
| throwway120385 wrote:
| Some of this stuff is a gas, and as we know, gases at low
| temperature or high pressure tend to condense into a
| liquid. While gases can be compressed into a small space,
| liquids tend to quite violently exceed the confines of
| their container.
| petschge wrote:
| That's what? Fourteen F-35s? Shared by all of Europe. Or in
| other words 30 cents per European for each of 6 years.
| Science is much cheaper than you think. And much cheaper than
| not doing it.
| munchler wrote:
| How do other telescopes avoid/deal with this problem? I don't
| recall the James Webb telescope having a similar issue, for
| example.
| frederikvs wrote:
| I would expect James Webb has the same issue, and similar ways
| of dealing with it. It's just that it never hits the press,
| since it's a normal part of operations.
|
| I'm not sure why Euclid's icing issue is getting some attention
| now, from the ESA article this was expected. Maybe it's just
| that it's slightly worse than anticipated, and they're changing
| their way of dealing with it?
| Laremere wrote:
| James Webb underwent a very specific cool down procedure. It
| included a phase where everything but the instruments were
| cooled down first, so that water from elsewhere in the
| spacecraft didn't stick to the instruments.
|
| Moving a bit into speculation territory, I can make a more
| specific guess. The article for Euclid specifically mentions
| insulation as the source of the water. It appears that the
| water in the other components were properly accounted for in
| Euclid's cool down procedure. For Euclid, insulation directly
| surrounds the telescope portion. James Webb is build different.
| There's insulation on the solar panel side, but the giant heat
| shield is between that and the mirrors and sensors. I don't
| think there is any insulation on the mirror and sensor side,
| because besides the sun there's no significant sources of heat
| where James Webb is.
| MeteorMarc wrote:
| Why don't they have some strong IR source that can selectively
| heat the water molecules and zap them into space?
| MeteorMarc wrote:
| Why dont they have some IR source that can selectively heat the
| water molecules and zip them into space?
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