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Hubble Space Telescope Is In Safe Mode After Gyro Failure (nasawatch.com)
274 points by waserwill on Oct 8, 2018 | hide | past | web | favorite | 132 comments

It was originally asserted that the telescope required three working gyros. Later a method was devised to operate using two. [1]

Background information describing Hubble's Pointing Control System.


[1] 2005 article: https://www.newscientist.com/article/dn7051-gyro-sacrifice-m...

There is going to be no way to use it with just one. If someone figures out a solution they will be the hero of the decade.

To bad the replacement James Webb Space Telescope is not scheduled till March 20, 2021, 14 years past it's initial launch date of 2007.

It's initial budget was 1.6 billion and it will hit over 9.5 billion when it launches, if it launches. In 2011 Congress moved to cancel the whole thing. If the cost estimate exceeds the $8 billion cap Congress put in place in 2011, as is unavoidable, NASA will have to have the mission re-authorized by the legislature.

Fingers Crossed (My Nasa Photo of the Day Wall Paper isn't going to be so great for the next 3 years I am afraid)

Yes, we figured it out years ago. Instead of spending a fortune on manned space flight, spend the money on developing advanced robotics to explore space. In addition, the technology will be usable on earth in manufacturing, etc.

We’ve had this discussion several times:


We can iterate faster, making less costly mistakes, and blanket the solar system with robots.

It took about a decade for humans to get to the moon once America entered the space race. Everything is taking several times longer now.

These are all very practical arguments, but spaceflight is not a practical endeavor. It is fundamentally an emotional activity.

The will to do science originates in the urge to explore. Whether we're spending the money to send people or robots, it's not a rational pursuit. We explore because we want to. Why do we want to? No one knows for sure.

Human spaceflight is valuable because things are emotionally different when a human is doing them. That's why spaceflight is so much more expensive when humans are aboard: because we have higher standards for humans, despite the obvious evidence that human life is abundant and cheap. The value of a human to another human is primarily an emotional calculation, not economic.

Even when the mission remote asset is a robot, we focus on the human element. Coverage of robot missions always includes a lot of people cheering at the launch, reactions in the control room, interviews with project leads, etc.

So, I would not be so quick to dismiss human spaceflight based on metrics of efficiency. The whole thing of exploring space is inefficient, and serves no practical purpose. Spaceflight runs on inspiration, and that's something we haven't figured out how to automate (and IMO never will).

As others have already mentioned, spaceflight has useful applications at creating a long term stable population center outside of Earth. There's also the commercial application of being able to gather vast resources relatively cheaply from the asteroid belts once there's a platform to routinely and cheaply transfer cargo up to space, down is relatively easy. We're going to run out of raw resources at some point and this will be the least costly application. Deep well drilling could access large amounts of trapped resources however the cost is prohibitive for the return.

One important reason to research space travel is to protect our species from disasters that would destroy the Earth. I'd bet our instinctual desire to explore probably evolved for a similar purpose.

Communication, weapons, navigation, and weather forecasting are the modern cornerstones of spaceflight. I bet communication satellites outnumber all others by 10 to 1. I love the emotional aspect of space exploration but I wanted to note that there are established, profitable, and increasingly essential reasons for mastering spaceflight.

NASA's biggest challenge has always been a budgetary one, balancing some pretty stiff political headwinds with their efforts to get things done. People like NASA, and they're proud of it; for decades, the Space Shuttle was probably one of the most obviously American symbols besides the flag itself. People, regrettably, aren't quite as fond of paying for NASA. Even in the heady days after Apollo 11, people thought the money could be better spent elsewhere:

> [Peter Flannigan, Nixon's assistant] also had become attuned to the reality that there was limited public support for ambitious post-Apollo space activities. On December 6, he sent a memorandum to the president reporting that “the October 6 issue of Newsweek took a poll of 1,321 Americans with household incomes ranging from $5,000 to $15,000 a year. This represents 61% of the white population of the United States and is obviously the heart of your constituency.” Of this group, Flanigan reported, “56% think the government should be spending less money on space exploration, and only 10% think the government should be spending more money” (Logsdon, 92).

Which is ridiculous, and grossly ignores the economic impacts of NASA's efforts (whether manned or unmanned). But no politicians have ever really bothered to make those arguments. During the FY1971 budget process, a robotic grand tour of the solar system[0] (Jupiter, Saturn, Uranus, Neptune, possibly Pluto due to the alignment of the outer planets) was quasi-considered and rejected due to cost. The Voyager program came out of that debate, at least. But FY1971 was a nasty year for budgeting, and NASA's budgeting in particular:

> NASA had been caught up in a chaotic confrontation between budget choices and broader fiscal considerations, reinforced by a breakdown in the White House policy-making process. That chaos obscured a stark reality—that through its decisions on the FY1971 NASA budget, the Nixon White House and ultimately the president himself had significantly reduced the priority of the space program among the whole range of government activities. In the form of modest funds for continued study of the space station and space shuttle, NASA’s hopes for the future were still alive, but just barely (99).

That's from John Logsdon's After Apollo? Richard Nixon and the American Space Program,[1] which is a fascinating glimpse into some of the challenges NASA faced.

You're right that, had we aggressively pursued--and funded--unmanned space flight, we likely could have done more science. But realistically, that was never on the cards. The problem with counterfactual scenarios is that we're often comparing them to an idealized scenario that relies on hindsight bias. In 1971, nobody at NASA genuinely thought we'd be limited to LEO for decades afterwards. Likewise, it's easy to look at STS and how it shaped manned spaceflight, and then come up with a list of better policy alternatives that could have been pursued with the same money.

That ignores how the program's original approval was tied to specifics of the Space Shuttle. The program's approval was, in large part, due to NASA's acceptance of major engineering changes to gain support from the military and intelligence community though most of the capability they demanded was never actually used. Likewise, the expected cost savings of a reusable space plane were fundamental to its approval. Those cost savings never materialized, and in fact things went the opposite direction. We know that today, and there were clues even enough early on. But while there were probably better manned spaceflight options, STS--flaws and all--was able to build a wide enough base of political and institutional support to get approval. Other post-Apollo options didn't and couldn't.

But the biggest factor, I think, is that manned spaceflight has cultural meaning. Politicians might eye NASA's small fraction of the federal budget covetously as something they could probably get away with raiding, but to date no one has had the guts to kill our manned spaceflight program outright. Probably because nobody wants to play the bastard who tells kids "sorry, astronauts aren't an option now" or destroy those childhood dreams adult voters remember fondly. Even if those adults now think money could be better spend "here at home" (as if we're spending it "out there" at a Space-Walmart or something...sigh). Instead of crowding out unmanned opportunities, manned spaceflight served as a sort of umbrella to give them just enough political protection to make it.

Absent those perceptions, I think there's a damned good chance that the alternative to manned spaceflight wouldn't have been unmanned spaceflight. It'd have been no spaceflight. Maybe not right away, but eventually. Perhaps that could have changed had there been a president along the way willing to genuinely fight for NASA and was willing to spend the political capital needed to persuade enough voters to recognize the economic and scientific benefits offered. Unfortunately, the electorate was never interested in it enough and politicians never saw fit to try and change that. Particularly because the political benefits of successful space missions generally accrue years after the politicians who initially funded the program are out of office. Compared to that, a bridge with their name on it is practically an immediate win.

0. https://en.wikipedia.org/wiki/Grand_Tour_program

1. https://www.amazon.com/After-Apollo-American-Palgrave-Techno...

> There is going to be no way to use it with just one. If someone figures out a solution they will be the hero of the decade.

The deputy mission head seems to disagree with you


Maybe someone who knows satellites can help here. I assume with one gyro the satellite still has pointing function because one gyro senses in 3 axis, but that if that one gyro were to go it would no longer know where it was pointing or perhaps without enough accuracy for science.

But... it’s a telescope. Couldn’t it determine direction from images received from a spotting or wide angle lens? Does it not have one?

> I assume with one gyro the satellite still has pointing function because one gyro senses in 3 axis,

Each of the Hubble's gyroscopes only measures rotation around a single axis.

> But... it’s a telescope. Couldn’t it determine direction from images received from a spotting or wide angle lens? Does it not have one?

Hubble does have imaging sensors to allow it to track the stars and orient itself. But the orientation needs to be not only measured very accurately (to within a few millionths of a degree), but also kept stable over long periods of time, in order to avoid motion blur. So the attitude control system needs to have low latency.

In principle it would probably be possible to do this using only image sensors, but it would have been very challenging when that Hubble was designed in the 1980s. It has a number of CPUs, the fastest of which is an 80486 running at 25 MHz.

> But the orientation needs to be not only measured very accurately (to within a few millionths of a degree)

The fact that we can even achieve this level of precision from a piece of hardware blows my mind.

One need not have something as expensive as Hubble to have such angle sensitivity.

This instrument can resolve an angle change of < 0.3 millionths of a degree in one second.


Disclaimer -- am an author.

Edit: and this instrument, using the autocollimator above, can do the same thing for inertial sensing. Same disclaimer applies. https://aip.scitation.org/doi/10.1063/1.4862816

> It has a number of CPUs, the fastest of which is an 80486 running at 25 MHz.

Not unexpected but reading that now... Absolutely remarkable.

Specifically, a radiation-hardened 486. The type of equipment that can survive in space lags significantly behind what you would consider modern on a desktop computer. For example, the radiation-hardened PowerPC G3 is a popular choice. It will power the 2020 Mars rover too: https://en.m.wikipedia.org/wiki/RAD750

The 80486 was state of the art in 1990 when the Hubble launched, as it was released in 1989.

Was it installed as a later update? The PowerPC G3 was released in Apple computers in 1997, just a few years later.

Yep, the original main computer was a 1.25 MHz (!) DF-224 [1]. It was augmented on Servicing Mission 1 in 1993 with a 15 Mhz 80386 co-processor [2]. The 80486 was installed in 1999 on Servicing Mission 3A (STS-103) [2].

[1] https://en.wikipedia.org/wiki/DF-224

[2] https://en.wikipedia.org/wiki/STS-61

[3] https://en.wikipedia.org/wiki/STS-103

Reading more about the DF-224...

It was roughly 45 centimeters (1.48 ft) by 45 centimeters (1.48 ft) by 30 centimeters (0.98 ft), weighed 50 kilograms (110 lb)

It had about 96KB of usable plated-wire memory (32K 24-bit words).

That seems like a lot of weight. I wonder how much was radiation shielding?

So not a data center, but like an Arduino.

The amazing thing is that back when the US had a manned space capability, those gyros were replaced. Twice. There were five servicing missions to the Hubble telescope.

IMHO we should let Hubble die and take the funds that repair missions would suck up to deploy an improved replacement (i.e. the James Webb telescope). When Hubble was launched it could take better photos than any Earth-based telescope, but with improvements in technology that is no longer the case. We've become really good at filtering out atmospheric noise and the telescopes we can build on Earth are much bigger than Hubble.

I don't think anyone is planning to send up a repair mission, Hubble is merely being kept alive as long as possible.

Without the shuttle servicing missions are not even possible anymore anyway.

There will be no repair missions because the US has not retained manned access to space for that sort of activity.

But what happens when the folding space blanket fails on Webb? That system seems incredibly flimsy and will be the downfall.

> those gyros were replaced. Twice.

Hmm, I think the second time the gyros needed replacing, and the gyros were the limiting factor on the telescope's lifetime, I'd have installed a redundant set.

Well, except if system wasn't designed to have a redundant set of gyros, it could be that some complexity and risks may be involved. For example, unable to write that without changing some board, reprogramming, etc.

All such satellites (incl. ISS) have 4 gyros while you only need 3, geometrically. That‘s your redundancy. You don‘t add stuff just for the fun of it but you do cost-benefit trade-offs that include e.g. weight (goes directly into launch costs) and design lifetime. And gyros need to be heavy because physics (i.e. you need counter overall mass of spacecraft).

Sure. But not after the fact the satellite is ALREADY there. This was reply to: > Hmm, I think the second time the gyros needed replacing,...

But as other mentioned, they had redundant set of gyros...

You can only replace what‘s already there, otherwise you‘d change the design (here orbital dynamics, thus attitude control system incl. all Math and software behind it) so much that you’re basically building a new one – and that was certainly not the goal of having an on-Orbit repairable satellite.

The last servicing mission they installed 6 gyros. It was designed to operate with three.

Actually it does have a dedicated star tracker, and (the system)[https://www.nasa.gov/content/goddard/hubble-space-telescope-...] is designed to combine gyro measurements with star tracker measurements. Both the Lunar Reconnaissance Orbiter and Mars Reconnaissance Orbiter are dealing with or expecting gyro issues and are currently coming up with and testing control paradigms that only use the star trackers. I think part of the problem with the star trackers is that if you "lose your place" then it's very difficult to get back on track and this could lead to serious problems.

As i understood it the gyros provide Hubble's axial rotation, not merely sensing for positioning (ie there are no fuel jets for orientation) so a single gyro will only allow them to rotate Hubble in 1 axis, regardless of image orientation data or latency issues.

Aren't you confusing gyros with reaction wheels?

No. The gyros are more accurate. If it were to use reference stars, through the big camera, any detected motion would be at least one pixel. So every image would be blurry. It has to react before any drift results in movement more than a pixel.

Actually, you can do substantially better than one pixel, because the point spread function is bigger than one pixel. Even a technique as simple as centroiding will get you sub-pixel accuracy.

Yes but to get there you need detectable movement, a change in the image because of motion. A pixel has to change somewhere, the definition of blur. Sub-pixel blur is still blur.

No, you can get sub-pixel accuracy with a static image. The point is the star takes up multiple pixels, and when it moves by less than a pixel, some pixels get brighter while others get dimmer.

This is a common fallacy in computer vision. Often people get to a within a pixel and stop because they assume they can't get better. Most times you can get substantially better. I worked on a qr-code like system where the scanner could reconstruct the code from an image with (slightly) less pixels than 'pixels' in the code.

If a pixel gets brighter, that is a moving pixel, ie blur. This is scientific observation. Any change to the data because of movement is blur. The rules for computer vision and astronomy are very different.

Interesting observation. This works presumably because the output of a pixel is not just one bit, but some sort of continuous brightness reading (discretised, of course, sooner or later)?

Not obvious a priori, but makes sense.


The light is blurred, with a fairly predictable pattern, so if you fit a function to the shape, you can find the peak of the function and that is the most likely center position for the point source.

GP is right. The point spread function will spread the flux of a point source (eg. a star) across multiple pixels. You can identify the location of the actual star with sub pixel accuracy if you have a good PSF model.

In addition to what others have said, the concern about pixel-imperfect star tracking is somewhat moot, as we're talking about two different cameras. The effect on the imaging camera is very small.

There is the star tracker camera (widefield, fast), and the imaging camera (narrowfield, slow).

Star trackers use a fast widefield camera because it's easy to get a good signal:noise ratio (there is a lot of contrast between the stars and the background).

The imaging camera, on the other hand, generally takes much longer exposures (HST subjects are generally very dim, relative to stars). All those beautiful, nebulous HST photographs you see? Those have exposure times on the order of hours or days. In practice, being off by a pixel momentarily is not a big concern -- the amount of "bad" photons you collect during that time is very small.

Couldn't you measure star motion over longer periods of time, then even minuscule amounts of motion could be detected.

By the time you can see the motion on your image sensors it's too late - you want to detect and correct the motion you need to do it while you're imaging stuff, before it smears all your measurements.

This is nonsense.

The gyros are only used for coarse pointing, guide stars are used for much more accurate and precise position sensing during exposures (which is why they are called Fine Guidance Sensors).

gyros can be used for both sensing motion as well as creating motion (is this true for Hubble's gyros ?), using spinning spheres on each axis of a high enough mass ratio in comparison to the enclosing object similar to haptic ... if so, I wonder if the issue is a degraded gyro is impacting ability to steer the telescope not just to do the sensing

There's no good reason to combine jobs for such devices on spacecraft since the requirements for attitude control and attitude sensing are very different. The gyros on the HST are only for sensing, it uses a combination of reaction wheels and magnetic torque rods for attitude control, which are well suited to orbital observatory application due to their high precision.

“No longer in operation” - not strictly true. Looks like it will return to operation soon, but in 1-gyro mode, which means its operations will be restricted.

1-gyro mode..... I am counting on how long can we keep Hubble up there, or how long until we need to put another costly service mission up there.

There are no more Space Shuttles that could service Hubble. When it fails it will simply be dead.

(Cut to Elon Musk, who begins to furiously sketch some plans on a paper napkin)

Cut to Hacker News 4 years ago this month when I tried to make the case for sophisticated unmanned space exploration:

“For example, if the Hubble, or its replacement, needs to be fixed, we should have an unmanned answer, for instance”


The right thing to do would be to launch a bunch of new ones.

(NASA estimated the marginal cost of launching a shuttle to be $450 million, which is going to be most of the cost of assembling a big telescope. Note that I said "assembling" and not "developing".)

Would it be feasible if they "just" rebuild the Hubble with the original plans? I mean it's 30 years old by now but it's a solid device. That would save on development at least.

DOD transferred two "obsolete" KH-11 spy satellites (which are pretty much evolved Hubbles) to NASA in 2012. They've been in storage since. So the scope for a "new build Hubble" is putting instruments on those sats, launching them, and supporting the ongoing mission. That's still substantial, but much less than a new build from scratch.

One of them is, as far as I know, now dedicated to WFIRST:


It was just the mirrors. Earth observing telescopes aren't useful for deep space.

The infrastructure no longer exists. The tooling no longer exists. Miniaturization makes old designs obsolete. Design is now the cheapest part of manufacturing.

(See "Can we rebuild Saturn V in 2018") https://www.youtube.com/watch?v=mhIfeS3OumY

Rebuilding electronics from original plans which are 30 years old will be very hard. Components will have gone out of production, and minor design changes to accommodate new replacements will lead to a cascade of things which need recertifying.

It took over 2 years just to make the wave mirror.

I don't know if NASA will ever plan to send a mission to repair it since it's already well over it's intended lifetime (by well over I mean several years which is a lot).

The decay date for the Hubble is 2030-2040 so we should possibly get another 12 to 22 years.

It only needs to be operational until the James Webb Telescope is available.

As soon as this happens, most astronomers will jump ship anyway

Ha, good one! :D

Like saying "it just needs to work until Longhorn ships" ;)

In any case, JWST doesn't have UV capability, so it is not a straightforward replacement of what Hubble does. It just able to look at more distant objects because they've all been red shifted into the IR.

JWST and HST are not comparable telescopes. Moreover, the idea that astronomers would stop using one world class telescope just because another one (even a better one) exists is sheer lunacy. Even if a space telescope that was worse than Hubble existed it would still be completely 100% booked in terms of observation time, because there is much more demand for those capabilities than there is supply, by orders of magnitude.


Basically it will be launched in March 2021, if at all.

By the way, every-time the launch year approaches they delay it by a good 2 - 3 years, and this has been the case almost forever.

completely different devices built for completely different purposes. there's nothing quite like the hubble.

Sure, but the jump is still tempting for the scientific top brass. There's only so much that can be learned in the visible spectrum and only so many Noble prizes, PhDs, tenures and grants to be had. Staying on Hubble is scraping the barrel when the new sexy JWST promises to open whole new fields of scientific inquiry.

The linked page contains the sentence "There isn't much difference between 2- and 1", so what restrictions are we talking about?

I know the shuttle is long gone but are we at the point where robotic repair could be an option. The Hubble might be out of date but that would be a great exercise in developing repair tech.

Could be wrong but my understanding is the issue preventing repair is the expense in getting to the Hubble.

So whether it's via robot or human spacewalk (though a manned operation is even more expensive obviously) the issue is the prohibitive expense of getting to the Hubble to fix it.

Orbital apogee is only 540.9 km[0]. SpaceX launched a satellite to an orbit of 640km last night for what I presume was it's usual $60m launch price.

So 'getting to the Hubble' is pretty low in price, all things considered. Now the hard part: building something that can fix the Hubble. Humans would be good at making repairs, but the SpaceX Dragon capsule doesn't have an airlock, so that won't work easily. Repairs might be doable by a robot, but I suspect the easier option would be to simply attach new parts to it to perform the broken functionality.

If you can build the new piece for $40m, that's $100m to add another 20+ years to the lifespan of this incredible piece of equipment. Heck, sounds like something Bezos might do just for fun and as a test for his New Glenn rockets.

[0] https://en.wikipedia.org/wiki/Hubble_Space_Telescope

> the SpaceX Dragon capsule doesn't have an airlock

Neither did the Apollo moon landers, or the Gemini missions where NASA first tested spacewalks. Instead they just depressurized the whole cabin, making it into one big airlock. Presumably this would work for the Dragon as well.

I hadn't realized that! Well, potentially possible then.

> Humans would be good at making repairs, but the SpaceX Dragon capsule doesn't have an airlock, so that won't work easily

Can Dragon 2 do what most capsules do and just cycle the capsule interior into vacuum then open the door? (With everyone in suits first, obviously).

Rather than repair it in space, would it be easier to bring it back to earth, refurbish it and relaunch? That would be $120M plus refurbish costs. Or am I underestimating how hard it would be to bring it back to the ground?

> would it be easier to bring it back to earth, refurbish it and relaunch?

At that point you’d just launch a new one. Earth’s gravity well assesses a steep tax.

This would be incredibly difficult, sadly.

The key thing to remember when it comes to space is energy/momentum. Right now, the Hubble Space Telescope is 24,000 lb of mass moving at 4.7 miles per second. To get it back down to earth, you need to somehow slow it down. First, slow it down enough to reach the atmosphere and then protect it as the atmo drag slowed it the rest of the way. I don't even think the Space Shuttle, were it still around, would be capable of doing that.

The only thing that was ever designed to bring substantial mass back from orbit was the Space Shuttle Orbiter, which is decommissioned. Even then, I'm sure Hubble was not designed to fold back up and fit into that cargo bay.

I think it's instructive that they never tried that with any of the earlier Hubble repair missions.

The Dextre robot on ISS was originally proposed for the last Hubble repair mission. All it takes is money and initiative to send up another.

What about just building a new one to spec and launching that?

It's in Low Earth Orbit. I think we could get a rocket to it if we launched from the same location that the Shuttle launched from when it went to repair it.

Remote repair using a robot is a whole other issue, and I don't think we have the tech developed to do this reliably any time soon.

I don't know of anything with an appropriate form factor, unfortunately. You can't just do a normal rocket launch- you need to either develop an entire controlled vehicle to meet up with the Hubble (unless that exists already), or something that can exit a crew capsule. That's a surprisingly demanding task.

I think you'd basically have to engineer something from scratch, which is a big ask. It would be really interesting though! Imagine if you just left the robot up there, plugged in and on standby- ready to activate and do some repairs as needed. We should have one on every major satellite. Give him a box of spares, plug the remote into a 12 year old hopped up on adderall, mute the mic and watch it go.

And in 5 years, we would need to send a robot to fix the robot.

You could use an X-37B to meet up with Hubble.

However, figuring out budget (X-37B is a USAF asset, not a NASA vehicle), designing & constructing a robotic repair system that fits in the cargo bay, etc. would be nontrivial both in terms of price/ROI and the hopefully impending debut of the Webb telescope.

I think you're overestimating the capabilities of current robotics. The Hubble wasn't designed to be repaired by robots. Technically, it wasn't designed to be repaired at all. If a robot is going to do the job, it will need to at least match the dexterity of a human in a space suit, and be able to react quickly to unexpected circumstances. Neither teleoperation nor AI is there yet. Maybe in a few decades.

I have no expertise in any area related to this, other than having watched humans do a repair, and talk about the repair, which leads me to believe while a robot repair would certainly be possible in theory, is probably beyond us for a quite a while.

but, please, change my mind and fix it! =)

Why is the Hubble out of date?

28 years in space is a long time, and the new JWST has a 5x larger collection area and is fundamentally capable of detecting a much larger spectrum (the mirrors are kept colder). The HST has cost more to keep operational than it did to build at this point, and its construction was not smooth. Money might be better spent elsewhere.

However, there is a HUGE amount of data still to collect from space-based telescopes. Even a crippled HST is a desperately wanted resource. It benefits us to have as many space telescopes as we can right now.

Out of curiosity, what costs so much in terms of operations?

There are a crew of engineers maintaining the satellite's position and operation while another team of scientists operate the telescope, review proposals, and schedule science time. Time also has to be scheduled for the TDRSS ground stations for data downloads. NASA is not the majority user of that system so there isn't a lot of time available. The data then needs to be adjusted and translated into something that can be given to scientists. There is an entire institute, the STScI, that manages missions for Hubble and will someday do the same for JWST and WFIRST. I'm sure there are at least a few dozen engineers and scientists that keep Hubble operational and busy.


Hubble has been in the orbit since 1990, out of curiosity, what is the designated program life and what replacements are scheduled?

There have been five (5) successful missions to Hubble—beginning in 1993, then 1997, 1999, 2002, and 2009.[1]

The final mission, STS-125/SM4 (servicing mission 4), was done to prolong the life of the telescope. During the 12-day mission, they installed two (2) new instruments and performed two (2) repairs of failed equipment, and six new batteries in addition to replacing gyroscopes. This expected to extend Hubble’s lifespan by five (5) years from 2009.[2] So we were looking at an expected 2014 EOL date.

The 2009 mission was an interesting event in itself with Hubble’s durability aside. During a talk from Dr. Andrew Fuestel, he mentioned how NASA developed specialized tools for him to repair Hubble mid-orbit—which he said were the scariest times of his life—during his three (3) spacewalks.

[1] https://asd.gsfc.nasa.gov/archive/hubble/missions/sm4.html


Any idea what made it the scariest times?

I mean, obviously going on a spacewalk must be pretty intense. But is there a particular difference in doing it to the Hubble?

Or was it scary because he was repairing a very expensive piece of equipment?

IIRC, there were a few different reasons why it was scary.

One of the first was this mission was the last one, it was a difficult repair—SC4 did the first in-orbit repair—to do at the time, especially outside of the telescope. Because when you leave the safety of the shuttle, you’re traveling at a rate of ~17,000MPH and where the hubble orbits, there is a much higher chance of debris floating around than as if they were lower in the atmosphere. So in laymen terms, you’re attached to a cord that is supplying you with O2 and spinning at 17,000 MPH while trying to avoid rocks and other dangerous floating objects.

One other danger was the O2 levels. He said the suits are heavy, all of your tools are attached to you via cords and you have limited time to be outside. If something where to happen in this situation, not only would you become unconscious within seconds from the lack of O2, you’d pretty much be a forever piece of debris floating around the galaxies as your body will never decompose or fall from orbit.

The latter part was one of his biggest worries. He knew that he’s on limited time, he also had to renter the shuttle slow because it’s similar to divers and decompression. If for some reason he went too fast or there was a leak somewhere, his suit would have instantly filled up and the pressure would have blew him apart inside the suit.

Oh wow. Awesome.

Definitely not a walk in the proverbial park.

Thanks for the details!

Is there a video or (hopefully) transcript of that talk somewhere? It sounds interesting!

This presentation is from a different college speech and a couple years earlier than when I saw him but he seems to be talking the same general information about SC4. — https://www.youtube.com/watch?v=fZh60_CxxJM

[1] this article speculates operation upto 2008 (article was dated 2005)

[1] https://www.newscientist.com/article/dn7051-gyro-sacrifice-m...

Can`t wait for James Webb telescope to be launched! And I`m a bit anxious about the process of putting it safely into space.

Why anxious? They’ve put other telescopes into space before. Is that one more sensitive or something?

Apart from being the largest and most complex of its kind ever sent to space, the tricky thing is that it will be positioned at the Sun-Earth L2 point, far beyond the orbit of the moon.

Hubble was as successful and long-living as it was because of several manned maintenance, upgrade and repair missions mentioned by others already - but Hubble is in a LEO, only a few 100km from Earth. The JWST? 1.5 million km. So missions like these aren't going to happen, this has to work on the first try.

Have the Hubble servicing missions been actually cost-effective or was that more something that could be done because the Space Shuttle existed, although building a replacement would have been cheaper? (The latter would probably have had a problem having its budget approved, compared to the servicing missions, I guess.)

Hard to put a price on astroscience or cosmology. Hubble was just recently assisting in the search for the very first discovered exo-moon.


In the mid-1990s, after Hubble had its optics corrected, researchers were already planning its successor. The catch phrase in NASA at the time was “faster, better, cheaper.” JWT was announced in 1996 to a standing ovation, yet it's current planned launch is due 25 years after that announcement. (note that it's infrared, not optical)

> Hard to put a price on astroscience or cosmology.

It's pretty easy. Did those missions cost more or less than making a copy of Hubble and launching it?

The cost assessment of service missions take into account all the experience gathered when performing them. Even if a replacement telescope is cheaper, you do not learn anything.

What you learn is mainly about engineering challenges of servicing satellites though, and if that's not a cost effective solution due to launch costs it does not seem that important.

I think it's still valuable since we have tons of waste in our orbit that has already proven to be problematic. Maybe it's not cost effective if you only consider the cost of sending a new satellite vs the costs of repairing an old one, but if you take into account the reduced waste and the problems you avoid by having a cleaner orbit it may be worth the extra money.

Deorbiting is the reasonable way of keeping the orbit clean until there is actually anyone up there that can recycle in situ.

No, you learn about servicing things in space. If we are to ever send humans far from earth (mars perhaps) they need to have the ability to service their craft should something break. If a satellite breaks in space sending a new one is probably the most cost effective thing to do. However I have a moral problem with the idea that humans sent to mars would be told to die if something goes wrong. That means the ability to repair the things that go wrong.

It is crazy expensive and the "unpacking" process that happens in space seems very fragile.

And they're probably scared because of the Galileo antenna[0]. Of course, this was a long way back and they should've learned... But still until it deploys succesfully, they'll be anxious.

[0] https://en.wikipedia.org/wiki/Galileo_(spacecraft)#Main_ante...

They are having troubles with the folding space blanket on ground tests. Can you imagine this system being robust in space?

There's a video showing the JWST deployment sequence. It's set to calm orchestral music, and the visuals are just 3D renters of the spacecraft.


This video makes me far more nervous than "7 Minutes of Terror", depicting Curiosity's entry/descent/landing sequence. Far more things have to go right in order for JWST to become operational.


Doesn't it have the crazy unfolding hexagonal mirror thing?

I guess the increased complexity will increase the risk of failure.

Would it be possible to dock a second satellite, with new gyros, to he deorbiting rendevouz ring they installed a few years ago?

Scott Manley released an excellent video today about what this really means in the context of Hubble's various attitude sensing and control systems: https://www.youtube.com/watch?v=MY169HtCazE

What about these two other, very similar space telescopes that were made available by some intelligence service (CIA?) to NASA?

Ah yes, that's the context I was looking for: https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...

Firstly, they aren't telescopes let alone spacecraft, they are mostly just optical assemblies. Secondly, there are plans to make use of them in space telescopes but it will cost billions and take years to get them built and launched. WFIRST has already been planned and budgeted, though there is a proposal to slow down the program to accommodate JWST cost overruns.

This situation makes me wonder when, if ever, this country will create a "technical congress". One that, given a reliable, non-revocable budget, makes the kinds of budgeting decisions that are best NOT left to the tech-ignorant politicos.

Oh no :( Safe mode is bad! The pictures will be limited to 640x480x256. Looking into the neighborhood will not be possible, too.

You created a throwaway account to post this? Lately the regulars have no courage.

I genuinely want to thank you for that full throated chuckle I had from this comment

Let's hope they select "Safe Mode with Networking" otherwise they'll have a "brick" in orbit ;-) As a side note (nightmare scenario), image if HST had Windows 10 and was forced to do the fu$%ed up updates from M$ every now and then :-)

Slashdot is that way, buddy.


Hi, you appear to be shadowbanned.

No I'm not, profile loads fine in an incognito window and another device. The comment is shaded because it got downvoted, which was probably appropriate given the snark.

No, I vouched for your comment so I could tell you. The comment has now disappeared because I have now unvouched.

Url changed from http://Twitter.com/NASAWatch/status/1049111536550273024, which points to this.

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