[HN Gopher] Hubble telescope has new lease on life after compute...
___________________________________________________________________
Hubble telescope has new lease on life after computer swap appears
to fix glitch
Author : sohkamyung
Score : 479 points
Date : 2021-07-16 12:54 UTC (10 hours ago)
(HTM) web link (www.sciencemag.org)
(TXT) w3m dump (www.sciencemag.org)
| js4ever wrote:
| NASA and Space engineering is fascinating! Being able to do this
| on 30 years old hardware ... In space
| zabzonk wrote:
| Hurrah! We may well need it if the James Webb doesn't go
| according to plan.
|
| But really, aren't these spacecraft, rovers, exploration
| programmes, etc. among the best example of what humans can do if
| they put their minds to it?
| Tomte wrote:
| Hubble "sees" different wavelengths than JWT, also, both are
| overbooked. So we really want Hubble as long as possible, no
| matter how the JWT launch goes.
| Mentoio wrote:
| Hui, does that really matter? or lets ask other: Is JWT able
| to make another but more crazy deep field image?
|
| I think i have to read up on it :D
| smeyer wrote:
| Yes, it really matters. It might not matter from the
| perspective of just making cool looking images, because you
| can do that in any wavelength. But for science, the
| wavelengths matter a lot, and you can learn different
| things at different wavelengths.
| Mentoio wrote:
| Oh no no, i was just worried that JWT would actually not
| be able to do a deep field 2.0. im very curious on
| potentially higher details on this and mentioning that
| JWT and Hubble use different wavelength (or JWT might be
| able to do more?) would have meant that JWT wouldn't be
| able to do the same as Hubble in regards of a deep field.
| rootbear wrote:
| There is great interest in using both instruments to observe
| the same target simultaneously, for example, a new supernova.
| It would be a real loss not to have Hubble available for such
| observations after JWST launches later this year.
| [deleted]
| zinekeller wrote:
| The link is fine, but here's the news from NASA:
| https://www.nasa.gov/feature/goddard/2021/operations-underwa...
| platz wrote:
| The article contradicts itself several times on what the actual
| fix was.
| 2Gkashmiri wrote:
| What is the power generation or storage on Hubble?
| odysseus wrote:
| Finally, for fans of Weird Al Yankovic's White & Nerdy, an excuse
| to reference Norm Sherman's Pimp My Satellite, which is all about
| the Hubble: https://www.youtube.com/watch?v=xMXk5Y7Gv6Y
| cyberlurker wrote:
| " NASA announced that they had identified the Power Control Unit
| (PCU), which is part of the SI C&DH, as the source of the
| problem"
|
| So they had a spare PCU that they switched to. Hubble was
| launched in 1990. Is 30+ years normal for a continuously
| operating PCU? What is the expected lifespan of the "new" PCU
| that has been sitting this whole time?
| ceejayoz wrote:
| Not just continuously operating, but in a _very_ harsh
| environment. Impressive.
| phonon wrote:
| The original PCU was replaced in 2001.
|
| https://esahubble.org/about/history/sm3b_replacement_of_pcu/
| BeefWellington wrote:
| NASA's hardware is deployed in anything but normal
| circumstances, so normal for them vs normal for the consumer
| are vastly different things.
|
| Given the longevity and how well engineered things are for
| their other projects, I'd have to say yeah it seems pretty
| "normal" to me.
|
| It seems like they overengineer and quality control to the
| point of doubling planned mission length, if not longer. My
| cynical take on it is they do it this way because of the nature
| of their funding rather than any specific engineering goal.
| rtkwe wrote:
| Part of the source of the discrepancy is the planned mission
| is basically just what they get initial funding for not
| everything they would like to do and the entire mission
| length they'd like to use. Because launch costs are such a
| big part of the costs of ever replacing a Hubble or a
| Curiosity it makes sense for them to last longer than they're
| funded for because most likely they'll continue to get some
| funding a long as there's good science and the equipment is
| still usable. Also the cost of failure is pretty high, if you
| have something break early there's not another
| rover/satellite program there to replace it the science just
| doesn't get done until the next program in 10 years gets sent
| unless someone else was sending a similar device to that
| destination.
| Steltek wrote:
| Anyone claiming to have a real answer to that would be torn to
| pieces by Richard Feynman. I think you'll need to be satisfied
| with best guesses and a metaphysical "as long as it lasts".
| izacus wrote:
| The designed life expectancy of Hubble as a whole (and thus, by
| extension the minimal designed life expectancy of all
| components) was 15 years. It's now been operating for 30 years,
| doubling its design lifetime and intent to be replaced.
| coldcode wrote:
| It's too bad you couldn't just leave a space shuttle in orbit,
| and then fly to it to use its arm when needed. Or build something
| like a repair "truck" that once launched, never comes back. You
| just load it with fuel and whatever you need, and drive it to
| where it's needed.
| p_l wrote:
| Buran system had designs for that - one of the components was a
| nuclear-powered space tug that could shift satellites around,
| reducing launcher limitations. Design planned for endurance of
| 100 "LEO->GEO" satellite moves.
|
| Hypothetical Hubble with support for such operation would have
| docking port for the space tug, which could bring it back to
| orbit that could be taken by service vessel, then bring it back
| to proper orbit.
| agloeregrets wrote:
| So...are we gonna send up a replacement failover? Seems risky.
| rootbear wrote:
| There is currently no way to service Hubble, now that the
| Shuttle fleet has been retired.
| ordu wrote:
| _> The PCU supplies a steady voltage supply to the payload
| computer and either it was supplying voltage outside the normal
| range or the sensor that detects the voltage was giving an
| erroneous reading._
|
| Swollen capacitors? =)
| yoursunny wrote:
| It's amazing how much redundancy was built into those out-of-
| touch systems, 30 years ago. However, the number of backup units
| is finite, so let's hope the now-operating system can last for
| several more decades.
| hawkesnest wrote:
| The part that caught my eye was redundancy on memory.
|
| >> Hubble's operators initially thought a memory module was at
| fault but switching to one of three backup modules produced the
| same error.
|
| Apparently Hubble has 4 memory modules which are switchable!
| I'd love to see how that works. Actually, I'd be fascinated to
| get a walkthrough of the overall architecture. It might give
| insights for how we keep business continuity by first accepting
| that hardware and software will fail.
| belter wrote:
| Posted this before here. Maybe worthwhile to post again...
|
| Fig 5-10 is the Data Management Subsystem
|
| https://asd.gsfc.nasa.gov/archive/sm3a/downloads/sm3a_media_.
| ..
|
| Concerning the computers:
|
| - First they had a DF-224 flight computer and a
|
| - Science Instrument Control and Data Handling (SI C&DH)
|
| Initially DF-224 between missions got installed a
| coprocessor:
|
| https://asd.gsfc.nasa.gov/archive/hubble/a_pdf/news/facts/Co.
| ..
|
| During another servicing mission they replaced it with
| something called the Advanced Computer with Intel 80486:
|
| https://asd.gsfc.nasa.gov/archive/hubble/a_pdf/news/facts/FS.
| ..
|
| There are some 50,000 lines of code in the C and Assembly
| programming languages. https://www.nasa.gov/pdf/327688main_09
| _SM4_Media_Guide_rev1....
|
| They also have a Help Desk...
|
| "Welcome to the Hubble Space Telescope Help Desk"
|
| https://stsci.service-now.com/hst?id=hst_index
| Nition wrote:
| Classic movie scenario. Hubble's down, and we need it now.
| No-one can solve the errors. Old guy walks in, worked on
| Hubble 30 years ago.
|
| "There's a backup module, with an override command to
| activate it, but it won't work with the system down. You'll
| have to use the manual override switch - on the telescope."
| melling wrote:
| ...or as I try to occasionally discuss here... let's simply
| develop the unmanned robotic capability to service Hubble, etc
|
| I found one discussion from 7 years ago
|
| "... I think we should start a more extensive national unmanned
| space program. For example, if the Hubble, or its replacement,
| needs to be fixed, we should have an unmanned answer, for
| instance."
|
| https://news.ycombinator.com/item?id=8540664
| gumby wrote:
| I agree in a more general sense: space is a natural domain
| for robots, not humans, and we should be designing out space
| flight capability with that in mind. We have some almost 50
| year old robots advising us on the heliopause right now.
|
| The general problem of repairing Hubble robotically is
| unlikely to be solvable within the lifetime of the telescope,
| but future devices could be designed with that in mind.
| dr_orpheus wrote:
| While we don't have a direct capability to do this now, some
| of the large programs of record are being built so that
| robotic servicing may be possible.
|
| JWST has a docking port for a future robotic servicing
| mission.
|
| Nancy Grace Roman (formerly WFIRST) space telescope has
| grappling points on the spacecraft for robotic servicing.
| chmod775 wrote:
| I think 'simply' is precisely the wrong adjective.
|
| Plus you'd still need spare parts. Why would I build a robot
| to swap parts, when I can simply put all of the spare parts
| into the telescope and swap over to them electronically?
| melling wrote:
| Knowing what will go wrong is hard to predict. Having the
| capacity to have robots service satellites, etc would be
| extremely useful.
|
| Also, the vision is that robots can build on Mars, for
| example.
|
| "Simply" means fund the research. My comment was from 7
| years ago.
|
| We also need the robots here on earth for dangerous tasks
|
| We'd make impressive progress over each decade with more
| effort.
| gwbas1c wrote:
| > Why would I build a robot to swap parts, when I can
| simply put all of the spare parts into the telescope and
| swap over to them electronically?
|
| What if the system that swaps parts fails?
| Xylakant wrote:
| What if the robot fails?
| melling wrote:
| The robot fails to perform the task or fails reaching
| orbit,etc?
|
| Send up another [improved] robot. These missions are less
| costly than human missions. We get to iterate more often
| kllrnohj wrote:
| > Send up another [improved] robot. These missions are
| less costly than human missions.
|
| Says who? And how? This seems like an unsubstantiated
| claim.
| gwd wrote:
| <pedantic> adverb </pedantic>
|
| The other thing to remember was that Hubble was designed in
| an era that the Space Shuttle was meant to make manned
| missions to repair / upgrade commonplace. My understanding
| is that this was actually done at least once to Hubble
| (maybe more? I forget); but unfortunately for Reasons, NASA
| turned out to be incapable of resisting cutting corners
| which put people's lives at risk (Challenger, Colombia). A
| system designed today would be designed assuming that it
| would be robots or nothing.
| mannykannot wrote:
| I was curious myself, and it turns out there were five
| missions, starting with the one to compensate for the
| incorrectly ground mirror. IIRC the final one was in
| doubt, as there was no possibility of a rescue mission in
| the event of irreparable damage on launch.
|
| https://www.nasa.gov/mission_pages/hubble/servicing/index
| .ht...
| BurningFrog wrote:
| Why don't we just build 5 Hubble copies and send them up?
| Should be much cheaper now.
|
| Is the answer is that NASA doesn't know how to build them
| anymore? Or that it's not politically feasible?
| kitd wrote:
| _Why don 't we just build 5 Hubble copies and send them up?
| Should be much cheaper now._
|
| "Just" is being extensively overused in this thread.
| modeless wrote:
| NASA doesn't know how to do _anything_ cheaply. They have
| two space telescopes sitting in a warehouse since 2011 that
| were donated by the NRO. They 're estimating $4 billion to
| launch and run just one of them, more than a decade after
| the donation. And you know it'll cost double the estimate
| and take an extra 5 years.
| 2Gkashmiri wrote:
| Why dont they just give others to do their work? Last I
| remember india sent a probe to Mars for less than amount
| it took for making the movie Mars featuring Matt Damon ?
| modeless wrote:
| For the politicians that fund NASA, spending money is the
| whole point. They call it "job creation".
| 2Gkashmiri wrote:
| agreed but what job creation is a project sitting dead
| for 5 years? are they giving people salary for not doing
| anything and then claiming too much costs or something
| else?
| Voloskaya wrote:
| Ah yes, let's simply do something very hard.
|
| Huble was never meant for this, if you look at all the
| systems present on ISS for automated docking, none of that is
| on Hubble. Access to modules inside Hubble was never meant
| for robots with very limited dexterity either. Being able to
| do something like that would be a huge feat of engineering in
| my opinion (and extremely expensive).
|
| I am fairly certain it would be faster and cheaper to just
| build a new one from scratch.
|
| And even if you managed to make a robot to service Hubble, it
| then would only be able to service Hubble and nothing else.
| JWT for example is completely different.
|
| On the long term you are right that this is a capability we
| need, but this needs to be taken into consideration while
| building the telescope/satellite/whatever: automated docking
| mechanism, standard ports and dimension of parts etc. etc.
| mikepurvis wrote:
| I'm pretty sure the pitch here is "a robotic being with
| human perception, dexterity, and manipulation, but who
| doesn't breathe air and never gets tired."
|
| So the idea is that you _don 't_ need to specialize it to
| the thing it's meant to work on, because it works on
| whatever a human works on. A similar idea drove a lot of
| the DARPA Robotics challenge, with its emphasis on being
| able to drive a normalish vehicle, open a door, climb a
| ladder, use a regular power tool, etc.
|
| Anyway, I think the state of the art for all this is still
| pretty far away, which is why the instinct is to assume
| we're talking about something specialized.
| Voloskaya wrote:
| > I think the state of the art for all this is still
| pretty far away, which is why the instinct is to assume
| we're talking about something specialized.
|
| Yes, that's exactly what I thought. If we are talking
| about AGI + human level robotic dexterity, then the use
| of "simply" becomes even funnier.
| parsecs wrote:
| I'm not sure about AGI. You can just control the robot
| remotely from earth. Sure, there will be a minor lag but
| definitely won't justify need of AGI.
| writeslowly wrote:
| NASA was experimenting with this in the past with
| Robonaut (apparently it also started as a collaboration
| with DARPA)
|
| https://en.wikipedia.org/wiki/Robonaut
| mikepurvis wrote:
| I believe Robotnaut is back on earth as of sometime in
| 2018, but it was briefly at the ISS and even ran ROS--
| there was an official NASA-supplied Gazebo simulator for
| it: https://www.slashgear.com/nasa-robonaut-2-simulator-
| stack-no...
| cesarb wrote:
| > Access to modules inside Hubble was never meant for
| robots with very limited dexterity either.
|
| It was also never meant for humans with less limited
| dexterity.
|
| I recall one of the Hubble servicing missions I watched on
| NASA TV, in which they had to bolt a special adapter plate
| over a cover, unscrew over a hundred tiny non-captive
| screws (which the adapter plate was designed to catch, so
| they wouldn't float away), and only then could they open
| that cover. That part of the telescope clearly wasn't
| designed to be serviced in space.
| kiba wrote:
| Pretty sure it's much easier and faster to do it with humans
| and Starship, assuming the necessary interface is developed.
| elif wrote:
| starship wouldn't really fit the mission profile of sending
| 2-3 astronauts to hubble orbit for EVA. The same starship
| could instead deliver a fleet of replica hubbles to
| lagrange points autonomously.
| pantalaimon wrote:
| Or built the telescope into Starship and use it as an
| observatory.
| pantalaimon wrote:
| We can put much larger payloads into orbit now and will be
| even moreso with Starship.
|
| It would make sense to start working on a replacement for
| Hubble, even if that means it'll be ready in 20 years.
| Gare wrote:
| Or we could build a cheaper telescope that is less
| redundant more quickly, and launch a new one every 5 years.
| Launch prices are falling, so this could be more economical
| than building expensive long-lasting telescopes.
| gumby wrote:
| Also swarms of telescopes that can collectively take
| higher resolution, broad spectrum photos.
| [deleted]
| nerfbatplz wrote:
| Considering Hubble was an old NRO design that they donated, I
| bet there are more backup parts than are publically known to be
| available.
| hatsunearu wrote:
| If you read up on it, the NRO gave a _shell_ for a Keyhole
| something to do NASA. It had no optics and no sensor AFAIK,
| that was on NASA to build.
| MontyCarloHall wrote:
| Just to clarify: Hubble was not an NRO donation, although it
| bears some similarity to the KH-11, an NRO satellite from the
| 70s. It is not confirmed whether the two actually share
| parts, as the KH-11 is still classified.
|
| The NRO did donate two unlaunched telescopes to NASA in 2012
| (with optics present but sans electronics), which still have
| not yet been retrofitted and launched.
| not2b wrote:
| I hope that as we move more and more to commercial space
| development, we will continue to do the kinds of over-engineering
| and redundancy that make recovery efforts like this even
| possible, but fear that the mindset will shift: out of warranty,
| abandon it, we will sell you a new one.
| throwawayswede wrote:
| I find the constant use of the term "glitch" in the title and the
| lack of actual details of what happened extremely infuriating.
|
| Here's some actual details:
|
| The problem:
|
| > NASA has identified the possible cause of the payload computer
| problem that suspended Hubble Space Telescope science operations
| on June 13. The telescope itself and science instruments remain
| healthy and in a safe configuration.
|
| The payload computer resides in the Science Instrument Command
| and Data Handling (SI C&DH) unit. It controls, coordinates, and
| monitors Hubble's science instruments. When the payload computer
| halted, Hubble's science instruments were automatically placed
| into a safe configuration. A series of multi-day tests, which
| included attempts to restart and reconfigure the computer and the
| backup computer, were not successful, but the information
| gathered from those activities has led the Hubble team to
| determine that the possible cause of the problem is in the Power
| Control Unit (PCU).
|
| The PCU also resides on the SI C&DH unit. It ensures a steady
| voltage supply to the payload computer's hardware. The PCU
| contains a power regulator that provides a constant five volts of
| electricity to the payload computer and its memory. A secondary
| protection circuit senses the voltage levels leaving the power
| regulator. If the voltage falls below or exceeds allowable
| levels, this secondary circuit tells the payload computer that it
| should cease operations. The team's analysis suggests that either
| the voltage level from the regulator is outside of acceptable
| levels (thereby tripping the secondary protection circuit), or
| the secondary protection circuit has degraded over time and is
| stuck in this inhibit state.
|
| Because no ground commands were able to reset the PCU, the Hubble
| team will be switching over to the backup side of the SI C&DH
| unit that contains the backup PCU. All testing of procedures for
| the switch and associated reviews have been completed, and NASA
| management has given approval to proceed. The switch will begin
| Thursday, July 15, and, if successful, it will take several days
| to completely return the observatory to normal science
| operations.
|
| The team performed a similar switch in 2008, which allowed Hubble
| to continue normal science operations after a Command
| Unit/Science Data Formatter (CU/SDF) module, another part of the
| SI C&DH, failed. A servicing mission in 2009 then replaced the
| entire SI C&DH unit, including the faulty CU/SDF module, with the
| SI C&DH unit currently in use.
|
| Launched in 1990, Hubble has been observing the universe for over
| 31 years. It has taken over 1.5 million observations of the
| universe, and over 18,000 scientific papers have been published
| with its data. It has contributed to some of the most significant
| discoveries of our cosmos, including the accelerating expansion
| of the universe, the evolution of galaxies over time, and the
| first atmospheric studies of planets beyond our solar system.
| Read more about some of Hubble's greatest scientific discoveries.
|
| And the fix:
|
| > The switch included bringing online the backup Power Control
| Unit (PCU) and the backup Command Unit/Science Data Formatter
| (CU/SDF) on the other side of the Science Instrument and Command
| & Data Handling (SI C&DH) unit. The PCU distributes power to the
| SI C&DH components, and the CU/SDF sends and formats commands and
| data. In addition, other pieces of hardware onboard Hubble were
| switched to their alternate interfaces to connect to this backup
| side of the SI C&DH. Once these steps were completed, the backup
| payload computer on this same unit was turned on and loaded with
| flight software and brought up to normal operations mode.
|
| https://www.nasa.gov/feature/goddard/2021/operations-underwa...
| 0898 wrote:
| So it's "lease on life" rather than "lease of life"? Never knew
| that.
| baggachipz wrote:
| I remember when this telescope was first launched and deployed,
| and how its initial lackluster performance was a great source of
| mockery and derision of "government overspending for nothing" and
| a general disdain for space-based science. Since then, it has
| absolutely revolutionized our understanding of the universe and
| provided untold inspiration for millions (The famous Deep Field
| image being the prime example). It is a crowning achievement for
| NASA and should be used as an example any time some elected
| official questions the spending on research instruments like
| this.
| jordan314 wrote:
| I can't believe the shuttle chased down a satellite to fix it
| in five spacewalks. How many satellites have had service
| missions like this?
| reportingsjr wrote:
| The public doesn't really know. The shuttle did a handful of
| secret missions that could have involved satellite service.
|
| There is also a sort of mini shuttle that has launched a
| number of times in the last decade called the X-37B which
| some have speculated might be used for servicing satellites.
|
| It's definitely an interesting concept! The way you say the
| shuttle chased down satellites makes me laugh, as if the
| satellites were trying to escape and were zig zagging around!
| In reality, every mission to the ISS does the same thing as
| the shuttle rendezvousing with the Hubble.
| heresie-dabord wrote:
| > mockery and derision of "government overspending for nothing"
| and a general disdain for space-based science.
|
| But nary a word from such commentators when a major commercial
| software product demonstrates yet another catastrophic security
| failure.
| renewiltord wrote:
| Well, control is more important than many things.
|
| For instance, I'm happier if I pick my couch and then I'm
| uncomfortable than if the government picks my couch and I'm
| comfortable.
| jrochkind1 wrote:
| you'd be surprised. At a former job (in IT in academia)...
|
| me: I think we can build something in-house here better
| than what the vendor will provide, I think the vendor's
| solution is likely to be a failure for us.
|
| them: Yeah, but if do it in-house and it fails, it's our
| fault. If the vendor's solution fails, it's _their_ fault
| -- plenty of very prestigious universities are using this
| vendor, nobody 's going to blame us for choosing them. [Ie,
| "nobody got fired for picking IBM" basically].
| WalterBright wrote:
| The couch example ins't just hypothetical.
|
| My dad was on an Air Force Base when the base commander
| delegated to his wife picking out all the furniture for the
| base housing. Naturally, every serviceman's wife hated it.
| renewiltord wrote:
| Positively comedic! Thanks for the funny anecdote! I can
| imagine the whole situation.
| BurningFrog wrote:
| You can pick another commercial software vendor.
|
| With government, you can only complain. So you do.
| harry8 wrote:
| >You can pick another commercial software vendor.
|
| With what's left of your budget, which is now very, very
| negative. Better to redefine abject failure as success to
| minimize the chances of it ending your career if you're
| involved in firm purchasing in any way. It's not like
| boards of directors have a clue. The big consulting firms
| will assist pulling the wool and priming the press so they
| can move onto the next mark. It's impossible to by cynical
| _enough_.
| cptskippy wrote:
| Software vendors like Oracle and SAP do everything in their
| power to lock you into their services while doing the
| absolute minimum to fulfill any contract.
|
| It took our IT over 4 years to migrate away from Siebel to
| Salesforce and it's going on 3 years since. I just learned
| the other day we still have a Siebel DB lingering around as
| a dirty little secret.
|
| We move away from Lotus Notes over 10 years ago and we
| still have some Notes Apps used by our Legal Department.
| [deleted]
| throwaway0a5e wrote:
| Oh c'mon. Don't be thaaaat blinded by ideology.
|
| People love to shit on Oracle, IBM, etc when they bungle yet
| another big project that was supposed to fix something.
| WalterBright wrote:
| Once the engineering of the telescope was complete, making
| multiple scopes shouldn't have cost that much more. Launch 'em
| all.
| elihu wrote:
| People underestimate the costs of these kinds of programs, but
| they also underestimate the benefits. In the end it kind of
| works out.
|
| (I came across this idea in a Tom DeMarco book called "Why Does
| Software Cost So Much?": basically people complain about the
| high costs of developing new software, but then for some reason
| they keep paying to develop more software. Even though the
| initial cost estimates may turn out to be fiction, it's still
| worth it because the benefits are so big.)
| [deleted]
| BurningFrog wrote:
| Hubble is 30 years old, and was probably based on a military
| spy satellite (KH-11) design.
|
| I agree it was a milestone for astronomy, but it's been _very_
| long without any progress since. Why don 't we at least have 4
| more Hubbles in orbit?
| patall wrote:
| > Why don't we at least have 4 more Hubbles in orbit?
|
| Kepler, Spitzer, Herschel, WISE and more. I agree that there
| ought to be more by now but its not like we did not see 'any
| progress'. Today we know hundreds of earth sized planets in
| the galaxy. If that's not progress, I feel the telescopes
| JamesWebb and NancyGraceRose will only disappoint you ;)
|
| https://en.wikipedia.org/wiki/List_of_space_telescopes
| geenew wrote:
| There were in fact 4 large observatories, of which Hubble was
| one. Hubble captures light in the visible wavelegnths, the
| others captured light in other wavelenghts. Their pictures
| aren't as pretty so they get less attention. There's also
| JWST, as mentioned elsewhere.
|
| Hubble - Visible / NIR, 1990 - Present
|
| Compton - Gamma Ray / Xray, 1991 - 2000
|
| Chandra - Xray, 1999 - Present
|
| Spitzer - Infrared, 2003 - 2020
|
| https://en.wikipedia.org/wiki/Great_Observatories_program
| pohl wrote:
| Are there any plans for a next generation orbital
| observatory for the visible part of the spectrum?
| NortySpock wrote:
| https://news.ycombinator.com/item?id=27857959
|
| I posted a sibling comment, but both the proposed HabEx
| and LUVOIR space telescope designs would be visible-
| light.
| Intermernet wrote:
| ESA have PLATO (
| https://en.wikipedia.org/wiki/PLATO_(spacecraft) ) Which
| looks very interesting.
|
| Meant to launch in 2026.
|
| "The PLATO payload is based on a multi-telescope
| approach, involving 26 cameras in total: a set of 24
| "normal" cameras organised in 4 groups, and a set of 2
| "fast" cameras for bright stars. The 24 "normal" cameras
| work at a readout cadence of 25 seconds and monitor stars
| fainter than apparent magnitude 8. The two "fast" cameras
| work at a cadence of 2.5 seconds to observe stars between
| magnitude 4 to 8. The cameras are refracting telescopes
| using six lenses; each camera has an 1,100 deg2 field and
| a 120 mm lens diameter. Each camera is equipped with its
| own CCD staring array, consisting of four CCDs of 4510 x
| 4510 pixels.
|
| The 24 "normal cameras" will be arranged in four groups
| of six cameras with their lines of sight offset by a
| 9.2deg angle from the +ZPLM axis. This particular
| configuration allows surveying an instantaneous field of
| view of about 2,250 deg2 per pointing. The space
| observatory will rotate around the mean line of sight
| once per year, delivering a continuous survey of the same
| region of the sky."
| BurningFrog wrote:
| Yeah, I was being overly negative. NASA _has_ produced some
| very good observatories since Hubble
|
| > _There 's also JWST_
|
| Which is 15 years late and still on the ground.
| NortySpock wrote:
| In 2016, NASA began considering four different Flagship
| space telescopes, they are the Habitable Exoplanet Imaging
| Mission (HabEx), Large UV Optical Infrared Surveyor
| (LUVOIR), Origins Space Telescope (OST), and Lynx X-ray
| Observatory. (text from wikipedia)
|
| https://www.greatobservatories.org/about
| dr_orpheus wrote:
| Also Kepler more recently - Visible 2009 - 2018
|
| But again, even though it was "visible" it did not have
| many pretty pictures because the mission was looking at
| brightness variations in particular stars (planet
| transients).
| gizmo686 wrote:
| The James Web telescope was supposed to launch in 2007 (and
| should be launching in November), and began development in
| 1996.
|
| Hubble was launch in 1990, and have 5 servicing missions for
| repairs and upgrades, with the last one being in 2009.
|
| An exact clone of Hubble is not nearly as useful as the first
| one, so it is reasonable to put your resources into a novel
| telescope. Unfourtuantly that telescope hit some scheduling
| challanges.
|
| Not to mention all the other space telescopes
| https://en.m.wikipedia.org/wiki/List_of_space_telescopes
|
| Which includes a _gravitational_ telescope prototype.
| wedesoft wrote:
| The James-Webb telescope is supposed to launch this year:
| https://www.nasa.gov/mission_pages/webb/main/index.html
| [deleted]
| cptskippy wrote:
| Apart from the continued devaluing of Science in our country
| and severe underfunding of any scientific institution?
| adventured wrote:
| > severe underfunding of any scientific institution
|
| NASA is well funded, not underfunded. It receives over
| three times the funding of ESA by comparison.
|
| Why aren't the Europeans funding their scientific
| institutions better? Because the combination of soaring
| entitlement costs and stagnant growth robs them of the
| necessary tax revenue for that. Which is exactly what's
| happening in the US, and it's going to get a lot worse yet.
| The US has a bit less of an excuse, seeing as it could
| safely cut $200b off of its military. However, that $200b
| spread around to every squeaky wheel still won't go very
| far (it's equal to a mere ~2.3% of total government
| spending), you might be able to fairly boost NASA's budget
| by $3b per year if you slashed the military. Back in
| reality, that $200b in cuts should probably be entirely
| allocated to healthcare, which brings us right back to the
| central issue of priorities; and the Europeans know that
| quite well, which is why ESA is poorly funded.
| lizknope wrote:
| Ground based telescopes have improved significantly in those
| 30 years.
|
| The mirror in Hubble is 2.4 meters
|
| Large ground based telescopes now have mirrors in multiple
| segments with motors keeping them at the right curvature.
|
| The largest has 10.4 meter mirror. That is about 11 times
| larger area than Hubble.
|
| https://en.wikipedia.org/wiki/List_of_largest_optical_reflec.
| ..
|
| One of the original reasons for Hubble was to have a
| telescope above the atmosphere. The atmosphere distorts the
| light as it passes through making stars "twinkle."
|
| Now we we use a laser beam to energize sodium atoms in the
| upper atmosphere. We see how that is distorted by the
| atmosphere so that with software we can cancel it out.
|
| https://en.wikipedia.org/wiki/Laser_guide_star
|
| Combined with lucky imaging where instead of taking a single
| long exposure we take thousands of images in the 100
| millisecond range. We can toss out the images where the
| atmosphere was moving a lot and combine the other good
| images.
|
| https://en.wikipedia.org/wiki/Lucky_imaging
| cowmix wrote:
| So I worked on a contract for STScI (the peeps who wrote all
| the Hubble software). The turnover there is insanely low. As of
| a few years ago, almost ALL the people I worked with had been
| there since the initial launch of the Hubble. Anyway, as you
| walk around the cubes in their offices, many had copies of the
| political cartoons from the time which mocked the Hubble as a
| total failure. They are all mission focused, took the initial
| failure very, very seriously.
| vidanay wrote:
| And that's on top of the fact that the original problems were
| the epitome of "That's a hardware problem, not a software
| problem."
| spookthesunset wrote:
| The hardware dudes have it harder than software dudes. It's
| easy to fix software. Hardware, not so much.
|
| I guess the worst thing you can fuck up in space fairing
| software is the boot loader. Mess that up and you can't
| update the software.
|
| Note: I have never designed software for space. I have no
| clue what I'm talking about.
| RobertoG wrote:
| >>"I have no clue what I'm talking about. "
|
| Nobody told me we have to specify that! I thought that
| was the default and we only have to say when we are
| experts in something!
|
| Now I have to delete all my posts.
| WalterBright wrote:
| That's why you _always_ have an independent backup
| system. One that uses different software, developed by a
| different team, using different languages, and different
| algorithms.
| NortySpock wrote:
| I thought one of the Viking landers was lost when a
| software update pointed the big antenna at Mars rather
| than at Earth... hard to send software updates after
| that.
| zarq wrote:
| That's an easy fix; just put a repeater on Mars...
| cowmix wrote:
| I mean, it really was a hardware problem. However, the
| software guys were not pointing any fingers.
| dylan604 wrote:
| Hubble is a great example of just working the problem.
| xhkkffbf wrote:
| I sometimes eat lunch with friends at the STScl. When they
| were in the middle of the fix, I'm told that some of the
| engineers stayed up all night at the office. Not because
| there was anything to do. Just because they wanted to see
| what would happen and the Internet wasn't so pervasive back
| then. They couldn't log in remotely and do much.
| jordache wrote:
| Are these people highly compensated?
| cowmix wrote:
| They are all considered to be in academia I think so you
| can put them in that bucket. My impression they all did OK
| in the compensation department however I'm sure they all
| could make much more in the private sector. EVERYONE I
| worked with on that project was a high performing / expert
| level.
| smabie wrote:
| I'm going to guess, no.
| saganus wrote:
| Any particular reason that they stay for so long at their
| jobs?
|
| Obviously working on such cool projects must be a major
| factor, but it's probably not the only one.
| fidesomnes wrote:
| Government job. Low pay. Much stability.
| cowmix wrote:
| They all really, really believe in the mission. Many are
| well into their 60s and are waiting for JWST to launch to
| finally retire. It was supposed to launch YEARS ago, so
| they are (as a group) getting antsy.
|
| The project I worked one was migrating data from their in
| house ticket tracking system to Jira. I was importing
| tickets from 1985 into Jira which obviously didn't exist at
| that time.
| saganus wrote:
| Interesting.
|
| Thanks for the insight!
|
| I guess it IS very different to believe, for decades, in
| a mission that includes space telescopes than in the
| latest SaaS or productivity app or something more
| "mundane". Not that there's anything bad working on those
| kind of projects, but it sure has a different scope (no
| pun intended)
| elliottkember wrote:
| I just wanted to let you know that "mundane" is an
| excellent pun when talking about space projects, because
| it means "of this earthly world rather than a heavenly or
| spiritual one". The original word is "mundus", meaning
| "world" - "monde" in French today.
| raverbashing wrote:
| They're probably at a "local optimum" (maybe even global)
| in their careers. Peak salary, peak expertise match, etc.
|
| Though probably a "different world". It would be hard to
| retrain to do react development, for example.
| spookthesunset wrote:
| I mean at the age of 60... it's gonna be hard to top a
| career that had you writing code sent to space.
|
| That being said, I imagine it would be very hard to be a
| junior employee in such an environment. Fresh and green
| behind the ears, full of ideas and surrounded by people
| almost ready to retire and pretty set in their ways.
|
| Who knows. Maybe these folks make an effort to stay
| current with progress in development tools and whatnot.
| But it is easy to imagine them being very stuck in their
| ways. Some for good reason but some because "that's how
| we've always done it".
|
| I'd love to be told I was wrong and all their shop did a
| good job staying on top of industry wide progress.
| cowmix wrote:
| True. These guys were maintaining (and updating) software
| for a hardware platform that was 35+ years old.
| jimhefferon wrote:
| > That being said, I imagine it would be very hard to be
| a junior employee in such an environment.
|
| My father was a senior admin in the vendor that made the
| mirror, so I had summer jobs working on Hubble-adjacent
| projects. One summer my cubicle was next to the cubicle
| of a new engineer who worked on it.
|
| They ground the mirror in one facility and then trucked
| it to another one, many miles away, for silvering. This
| new engineer was tasked with drawing up the protocol for
| loading it on the truck (it was driven down in the early
| morning on a Sunday to reduce problems with traffic).
|
| He finishes the document draft and calls down the senior
| engineer for a look-over. They are discussing the part
| where the cranes (kind-of like fork lifts) lift the
| mirror. There are three cranes, and three places built
| into the mirror where they hook on.
|
| "How do you know the cranes will take the load?"
|
| "Here are the manufacturer's specifications, saying that
| each will take more than half the total weight. There are
| three cranes, so there is sufficient capacity even if one
| crane fails."
|
| "How do you know the crane will take the specified
| weight?"
|
| "They were vendor certified last week; I was there."
|
| "That's not enough. The night before, you and another
| engineer will personally go down there and personally
| load the specified weight on each crane. Then you will
| each sign a paper. The mirror will not move without that
| paper, containing both your personal names."
|
| Made a big impression on me.
| TeMPOraL wrote:
| Amazing story!
|
| In space projects there's no space for human error.
|
| Reminds me of that one SpaceX mission failure, with F9
| exploding shortly after launch. IIRC, it was quickly
| determined that the cause was a strut from a third-party
| vendor that wasn't up to declared spec.
| patrickthebold wrote:
| I'm still anxious about the James Webb Space Telescope though.
| Fingers crossed.
| BurningFrog wrote:
| One reason JWT has taken so long and is so expensive is that
| launch costs used to be "astronomical".
|
| In the SpaceX era of reusable rockets, those costs become 1-2
| orders of magnitude smaller, and I expect a flurry of simpler
| space telescopes in the nearish future.
|
| That's the theory. Does anyone know if such things are being
| worked on?
| terramex wrote:
| Not to my knowledge. Actually, it was said that lack of
| smaller space projects was catalyst for creation of
| Starlink. They expected tons of launches once launch prices
| dropped but it never materialized so they decided to become
| their own biggest client.
| henrikeh wrote:
| Who's theory?
|
| JWST costs upwards to 9 billion USD. An Ariane 5 launch
| maybe 200 million.
|
| Just because the launch is cheaper doesn't make the rest of
| the project less complicated and costly.
| BurningFrog wrote:
| JWST costs $9B when NASA does it.
|
| I think other actors can do similar things _much_ cheaper
| and faster.
| qayxc wrote:
| > I think other actors can do similar things much cheaper
| and faster.
|
| Think again. JWST was criticised for being too ambitious
| and rightly so. It uses technology that was (and in some
| areas still is) cutting edge.
|
| It baffles me how people always seem to assume that some
| company can miraculously solve scientific and engineering
| challenges quicker and cheaper than the teams that are
| working on it.
|
| JWST was designed with no serviceability in mind, that
| is, unlike HST it _absolutely_ has to work. Every detail,
| from the folding mirror, to the sun shield, to the
| computer systems to the instrumentation. ZERO room for
| error and no "fail early, fail often"-option here.
|
| Most of the delays have been caused by engineers and
| scientists wanting to make 100% sure they get it right,
| because there's no STS servicing for fixing imperfect
| mirrors or switching out hardware.
| spullara wrote:
| We live in an age where companies can and do almost
| miraculously solve technical problems that the government
| has failed to do, so it isn't surprising to me.
|
| https://www.youtube.com/watch?v=Tkk9VIKWw2w
| qayxc wrote:
| It wasn't "the government" that built JWST, though, it
| _was_ companies (and universities). edit: I 'm also
| getting tired of the "but rockets!"-trope. It's not a new
| invention, Saturn V was more powerful, and a rocket is
| not a space telescope.
| spullara wrote:
| I don't think you understand how contracting works, but
| ok.
|
| The James Webb Space Telescope (JWST or "Webb") is a
| joint NASA-ESA-CSA space telescope
| HenryKissinger wrote:
| If the rocket explodes on the launch pad, it will be a bad
| day.
|
| At the same time, it shouldn't take twenty years to build a
| space telescope, especially since it's not like it's the
| first one ever. The first atomic bomb was built in 4 years.
| rtkwe wrote:
| It is a completely novel design for a space telescope
| though. On top of that there's no capability [0] to go
| patch up a sloppy job like we did with Hubble.
|
| [0] Currently at least. Starship could I guess but it was
| planned way ahead of Starship even being a glimmer in
| Musk's eye. Do they have any grapple points on it as
| insurance? I would at this point, just put one of the posts
| they use on the ISS for Canada Arm to grapple.
| frosted-flakes wrote:
| There is a docking ring on the JWST.
| dr_orpheus wrote:
| Yeah, there is a docking ring as a "maybe we can design
| something to use this in the future". Since JWST is going
| out to a Lagrange point it would definitely be robotic
| servicing at this point unless our human spaceflight
| capabilities expand very significantly.
|
| The Nancy Grace Roman (formerly WFIRST) space telescope
| also has grappling points for robotic servicing so it is
| something that is being considered in designs for
| programs of record.
| spookthesunset wrote:
| And that is the problem with 20 year (30 year?) product
| lifecycles. A _lot_ can change in 20 years. For example
| the ability to service it might now be feasible. But
| since it's almost entirely built, good luck making it
| serviceable!
| wizzwizz4 wrote:
| The first atomic bomb was nowhere near as precisely-built
| as the James Webb telescope has to be.
| scrozart wrote:
| It's not the first space-based observatory, but it's still
| a _wholly novel_ device, containing instrumentation
| designed by scientists and engineers in concert to leverage
| every piece of bleeding edge technology available at the
| time, and some throughout the process. Everyone of the
| flagship observatories is moon shot. It's not a mass-
| produced helicopter or missile. This project in particular
| is easily one of the wildest feats of science and
| engineering _ever_ just like Hubble, Cern, and LIGO.
|
| Regarding the bomb, we were trying to end a global
| conflict, so the comparison couldn't be further off base.
| airstrike wrote:
| Plus the bomb was built with the literal opposite purpose
| of the JWST: blowing up!
|
| Worst case scenario it doesn't blow up exactly right and
| you just build another one?
| cmpb wrote:
| I see your point, but you could also argue that worst
| case scenario for atomic bomb malfunction is much more
| awful than worst case for JWST
| lazide wrote:
| With the mindset at the time, the worst case scenario for
| the atomic bomb would have been it not going off in
| anyway way, and then they just handed their greatest
| enemy dud version if a top secret weapon.
|
| Since it likely would have just blown up (fizzle) even if
| it didn't fully detonate that is a pretty remote
| possibility.
|
| Second worst would be it went off on a base somewhere and
| nuked a US base. Considering the location of these bases
| and the nature of the war at that point, it would have
| been a footnote causality wise, but embarrassing.
| retzkek wrote:
| The worst case considered at the time was an uncontrolled
| chain-reaction annihilating the planet. It was calculated
| to be impossible, but it still weighed on the minds of
| many scientists involved, even well into the hydrogen
| bomb era.
|
| https://www.insidescience.org/manhattan-project-
| legacy/atmos...
| [deleted]
| dekhn wrote:
| there has never been and never will be anything like the
| Apollo or Manhattan projects. They had levels of
| productivity that are not normally seen.
| sebzim4500 wrote:
| If the Starship program succeeds in reaching the moon in
| the next few years then I think that is comparable to
| Apollo. Ofc it is easier to do things the second time
| than the first but safety standards are higher and this
| time it will have been done at an enormously reduced
| price.
| Swenrekcah wrote:
| Well, there were the Egyptian Pyramids, Great Wall of
| China, Roman Aqueducts and a whole bunch of Great
| Projects in the past and I certainly hope there will be
| lots more in our future.
| spenczar5 wrote:
| Those projects took centuries to complete.
| DLWormwood wrote:
| Or just a few turns, depending on your difficulty
| setting. (-;
| delecti wrote:
| As far as I know, the pyramids were each constructed for
| a single pharaoh, and during their single lifetime. I
| don't know about all of them, but that's at least true of
| Great Pyramid of Giza.
| dmos62 wrote:
| We don't know how some of the Egyptian pyramids were
| constructed, or when, or how long it took.
| gumby wrote:
| It took 25 years to replace the SF Bay Bridge, a much less
| complex endeavor.
|
| It's simply how things are done around here these days.
| m0llusk wrote:
| That is not a good comparison. The SF Bay Bridge
| replacement project was conducted as a competition. The
| design that won was so much more complicated than all the
| other entries that at first it was not clear that it
| could be built and in fact the finished product is flawed
| with cracks and other failures. There is nothing
| particularly complex about the basic problem and the
| simple viaduct design that was advocated by the Governor
| at the time was expected to involve an order of magnitude
| less cost and time of construction but was rejected for
| being too simple and not beautiful enough. This
| management structure and these considerations have not
| been used for any space missions.
| belter wrote:
| Keep in mind its an orbiting Infrared Observatory so not an
| alternative to Hubble. Of course it will be an amazing
| scientific instrument and we should hope that nothing happens
| during launch.
| CWuestefeld wrote:
| My grandfather worked on the Hubble's mirror - the part with
| all the controversy. It was, simultaneously, both what he was
| most proud of and most ashamed.
|
| One thing he would point out, that I never see discussed, was
| that at the time they built the mirror, there was an
| expectation that it may not be perfect, on account of how the
| Earth's gravity would slightly deform the mirror during
| manufacturing. As he tells the story, they'd tried to factor
| that into the design, but had less confidence in it. This, of
| course, was not the reason for the eventual problems, but to
| illustrate that this _kind of_ thing was understood.
|
| The big picture of the failure relates to the Shuttle program
| as well. At the time Hubble was being developed, its mission
| was supposed to allow for a lot more around the "shuttle"
| aspect: not just that it could be reused, but that it could be
| reused in an actual shuttling capacity, like an orbital pickup
| truck. So it was supposed to be possible to bring the telescope
| up into orbit (away from gravitational stresses), see how it
| worked, and if necessary, bring it back down for corrections.
| Since the end result of the Shuttle design cut down
| significantly in its capabilities in this regard, the Hubble
| program was left without its "Plan B".
| walrus01 wrote:
| In the end it turned out that for the life of the shuttle
| program, each launch ended up costing between 700 million and
| 1.2 billion, so the 1970s goal of an economically reusable
| spacecraft was definitely not achieved.
| jessaustin wrote:
| _This, of course, was not the reason for the eventual
| problems, but to illustrate that this kind of thing was
| understood._
|
| For some reason I had thought this (gravity stuff) was the
| problem. What was the actual problem?
| azernik wrote:
| A device for measuring the final grinding had been
| miscalibrated (by a known, constant amount). The result was
| a spherical aberration, of a kind that is familiar to a lot
| of users of cheaper lenses and mirrors but on a much
| smaller scale.
| krisoft wrote:
| Exactly as azernik says. If you are interested in a lot
| more detail this reports spills the tea:
| https://www.ssl.berkeley.edu/~mlampton/AllenReportHST.pdf
| dr_orpheus wrote:
| It still amazes me that one, the mirrors are sensitive enough
| to the deformation of Earth's gravity to have an effect and
| two, that we are now very good at compensating for this now.
|
| Also consider that the mirrors on James Webb space telescope
| need to account for both deformation from gravity when they
| are manufactured but also that they are manufactured at room
| temperature and will be operated at cryo temperatures. But
| JWST is also special since they have actuators to put stress
| on the mirror segments to be able to reshape them slightly
| on-orbit to focus.
| downrightmike wrote:
| To be fair, Kodak made a sister mirror that wasn't chosen
| to go up, and when the issue on Hubble was found out,
| Kodak's mirror was found to be perfect.
| jcims wrote:
| It's fun to think that there is a bullet list of
| directions that would take me from where I'm typing this
| comment to standing in front of that exact mirror.
| eckmLJE wrote:
| Great tidbit -- found this in the NYT archive (likely
| paywall): https://www.nytimes.com/1990/07/18/us/hubble-
| has-backup-mirr...
| CWuestefeld wrote:
| My same grandpa that worked on the Hubble mirror also
| worked on anti-ICBM lasers back in the 70s. Apparently
| these devices had a tendency to melt their own mirrors, and
| that led to the development on self-deforming mirrors to
| deflect heat from hotspots.
|
| (He also worked on the TEAL AMBER and TEAL BLUE satellite
| surveillance systems, and probably others that he never
| even talked about.)
| tobmlt wrote:
| Hey I saw self deforming mirrors as a missile defense
| intern circa 15 years ago! I thought they were dang cool
| at the time myself. I recall (for these designs) self
| deformation being used to help with tracking and
| compensate for, ya know, the shock of a little steering
| boost motors lighting off and such, in some cases.
| 23B1 wrote:
| Is there a good book I can read about all of this cold-
| war era tech? I find it endlessly fascinating the number
| of programs and technology advancements that happened
| during this period.
| patrick0d wrote:
| There's a book called "Skunk Works" by Ben Rich about the
| making of different spy planes. There's some mentions in
| the book about satellites and what existed at the time
| how projects were carried out.
| panda88888 wrote:
| Skunk Works is a great read. Highly recommend it for
| people interested in the defense technology.
| ChuckMcM wrote:
| You may (or may not :-) find it surprising that there is
| a vibrant ecosystem of research and development on both
| defensive and offensive systems on going to this day. The
| IEEE used to give a talk about "Black Silicon Valley"
| which was not about people of color and their
| contributions (although that would be an awesome talk
| too) but about the origins of the technology focus in
| Silicon Valley with regard to radio and RADAR development
| starting in WW2 and continuing on to this day. When I
| first moved to Sunnyvale my neighbor worked at Lockheed
| and all he could tell me was that he worked with
| electricity :-). He said he hoped that some of the stuff
| he had worked on was disclosed in the future so that he
| could tell is kids and/or grand kids about it.
|
| Having gone to school in LA where, at the time, ALL of
| the EE jobs were in the Defense sector, I specifically
| moved up to the Bay Area to work on cool stuff I could
| actually talk about with others[1].
|
| One thing of note is that ageism is MUCH less of an issue
| in jobs that require security clearances. So a number of
| engineers who are suddenly perceived as "too old" to
| contribute to the latest hot startup find themselves
| recruited by the Raytheons and General Dynamics type
| companies that recognize their skills are valuable.
|
| [1] As an new college grad [NCG] I was not yet aware of
| the myriad ways in which employers would use non-
| disclosure agreements to thwart such conversations.
| dundarious wrote:
| Not a book, and not Cold War, but I think this talk does
| a good job outlining just how much of the silicon
| revolution came directly from WW2 military research. It
| also does a decent job of explaining how technologically
| advanced the aerial part of that war really was.
|
| https://youtu.be/ZTC_RxWN_xo
| toss1 wrote:
| I don't have a good book to recommend offhand, but
| wandering a bit offotpic here, I know someone who worked
| on a military orbital program in the late '70 that was
| transmitting data from orbit at 800MB/s.
|
| Some congressmen had not heard of this technology and
| were working to fund a completely different (iirc,
| civilian) program intending to develop essentially the
| same capabilities. They had to go give a few TS briefings
| to the congressmen to dissuade them from writing the
| redundant funding into the next defense spending bill.
| reflectiv wrote:
| Just wanted to say your grandpa sounds pretty damn cool
| yawz wrote:
| Definitely sounds like a very cool grandpa!
| Florin_Andrei wrote:
| > _It still amazes me that one, the mirrors are sensitive
| enough to the deformation of Earth 's gravity to have an
| effect and two, that we are now very good at compensating
| for this now._
|
| I make telescope mirrors.
|
| This problem was well understood since the time of
| Herschel. We just have better solutions now.
|
| The fact that this is a space scope is irrelevant to the
| fact that gravity will cause issues. For any telescope, you
| have to account for differences in the way the mirror is
| deformed in manufacturing vs in actual usage, and the ways
| the deformation will change in usage as the scope is
| leaning at different angles. That is _always_ a thing.
|
| What is particular to the Hubble is that the load in usage
| is zero (which is unusual), so you have to think about it
| that way in manufacture. But deformations in manufacture
| are always an issue you have to account for somehow.
|
| Look at it this way: there is an ideal shape that the
| mirror needs to have, usually a revolution surface of some
| conic section (parabola, hyperbola, ellipse, circle). The
| performance of the mirror will track the difference between
| the ideal surface and the actual mirror. The error
| allowance depends on the wavelength l of the observed
| radiation.
|
| Telescopes where the error is greater than l/4 just suck,
| and are unusable. Good performance begins around l/8. A
| great mirror may do better than l/20.
|
| For visible light, l/4 is 100 nm, or 0.1 microns. That's 10
| thousand times less than 1 mm. On that scale, the mirror is
| made of jelly. If you put it on a rough surface, it will
| deform. If you put your thumb on it, hold it for a minute
| so it heats up from your skin, then pull away, there will
| be a "mountain" left behind on the mirror, under your
| thumb, until it cools off again.
|
| In many cases, the support structures for large mirrors are
| complex mechanisms that ensure the force is uniformly
| distributed across a large number of points on the back of
| the mirror. Even amateur telescopes built using the
| Dobsonian template use passive self-balancing support with
| 3, 6, 9, 18, or even more points, depending on the size /
| thickness ratio.
| petertodd wrote:
| > My grandfather worked on the Hubble's mirror - the part
| with all the controversy. It was, simultaneously, both what
| he was most proud of and most ashamed.
|
| I think a simple way to explain what your grandfather should
| feel proud of, is they documented the construction process so
| thoroughly that they were able to _precisely_ figure out what
| they did wrong, and fix it, on their first try!
| CWuestefeld wrote:
| That's a really positive way to frame it. Thanks for the
| perspective.
| spullara wrote:
| Fascinating story about how the null corrector that was
| supposed to ensure that the mirror was correct was flawed:
|
| https://en.wikipedia.org/wiki/Null_corrector
| awiesenhofer wrote:
| Thats great news! I wonder though, if there will ever be a need
| for another repair mission, could ie. Crew Dragon support such a
| mission or has that possibility passed with the retirement of the
| shuttles?
| trashface wrote:
| Scott Manley had a video on you tube about this recently, don't
| remember which one, but it may have been where he was talking
| about the computer problem itself.
|
| As I understand it, there is no current vehicle that combines
| the Space Shuttle's ability to both dock with a satellite (via
| a docking arm) and allow astronauts to do EVA.
|
| So I guess James Webb is possibly screwed if it has a problem
| in orbit like the Hubble's mirror issue. Too bad we won't bring
| back the Space Shuttle.
| blhack wrote:
| Does crew dragon have the appropriate airlock to allow for a
| spacewalk?
| mLuby wrote:
| I don't think it does. But what's to stop the whole (limited)
| crew from suiting up (without MMUs), slowly venting the
| interior air, doing the EVA, then returning and re-
| pressurizing the atmosphere from interior tanks? My guess is
| it's just uncertified for that procedure, not that it's
| impossible. And there's no recourse if one of the suits fail.
| mikepurvis wrote:
| This is how it worked for all of the capsule-based
| missions-- the entire cabin space is the airlock.
| p_l wrote:
| There might also be not enough space to move with a full
| EVA suit - which is a wildly different thing from in-
| capsule survival suit.
| jvzr wrote:
| In case it wasn't a rhetorical question, Crew Dragon does not
| have an airlock that would allow for a suited astronaut to
| leave the craft while maintaining atmosphere inside it. Plus,
| a big thing missing is a manipulator arm, such as Canadarm,
| which was used to capture the telescope, and essentially make
| the shuttle and telescope one body.
| nomadluap wrote:
| I always thought it would be interesting if Spacex
| developed a "dragon utility module". It would launch in
| Dragon's trunk and consist of a docking port on one end, an
| airlock on the other, a miniature manipulator arm and a
| bunch of cargo mounted around the outside. After separating
| from the second stage the Dragon would flip around and dock
| to this module, which would give it all the extra bits
| needed for a mission like servicing the Hubble.
| krylon wrote:
| I was 9 years old when Hubble was launched, today I am 40 years
| old, so it has been around for all of my adult life and then
| some.
|
| Also, it has provided lots and lots and lots of beautiful
| pictures that are stunning to look at even for people who
| otherwise do not care about astronomy at all. I think it's fair
| to say that no other project/mission/device since the Moon
| landing had a bigger impact in making astronomy "cool". The
| Hubble Deep Field pictures alone are breath-taking, and they may
| very well have had as much of an impact on our current model of
| the universe as Hubble's original discovery of an expanding
| universe, at least from the perspective of a non-scientist.
|
| As far as I can recall, Hubble was supposed to go down in flames
| quite a few years ago, but it just kept working, and no
| equivalent replacement was available. James Webb Space Telescope
| is not _exactly_ a replacement, as it is an infrared telescope.
| It will be quite interesting to see how long they can keep Hubble
| working. It had a rough start, but the fact that after some
| initial corrections, it has lasted way longer than it was
| supposed to speaks of the quality of engineering that created it.
| javier10e6 wrote:
| Ah! Another case of who police the police. The police police the
| police. Good news that the spare PCU took over and it was good.
| We all hope that the spare PCU was not part of an unlucky
| manufacturing batch. Great article.
| zamalek wrote:
| The Hubble Telescope is a gift that keeps on giving. I'm starting
| to wonder if the thing will survive the heat/entropy death of the
| universe.
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