Hubble's star refuses to fade | Hacker News Reader

Hubble's star refuses to fade

bbc.co.uk

93 pointssjcsjc46 comments

The deliberate use of the word "observable" when referring to the Universe, is perhaps one of the most profound changes in human thinking the Hubble Space Telescope has contributed.

One falls silent contemplating the images this machine has produced.

I remember in junior high our physics teacher made a huge deal about this when they launched it in 1990. He quizzed us on the article he handed out at the beginning of class, just to make sure we didn't forget how important this was.

Beyond the early failures, it has indeed achieved well beyond what I think most people imagined, bringing us closer to a world we know so little about.

I don't think the Hubble Space Telescope has anything to do with that term. We use "observable" because the Universe is far larger than what we can ever physically see or interact with (there's a growing body of evidence that it's infinite and "flat"). The observable part is an upper bound on the part of the Universe that will ever be relevant to us. Kind of makes me feel insignificant in a weird way :)

Also, the Hubble can't even see most of the Observable Universe; it can see ~15 billion lights years away, whereas the radius of the observable universe is 47 billion light years.

How is that the radius of the observable universe? I thought the observable universe was bounded by the age of the universe, which why the furthest distant observations show the universe close to the time of the Big Bang. Shouldn't the radius of the observable universe = the number of years light has been traveling toward us?

Edit: Wikipedia says I'm wrong about this. What's new?

The radius of the observable universe is the distance the furthest stars we could theoretically observe today.[0] So these stars were a lot closer earlier and we can see the light even though the stars are further away than the age of the universe (times the speed of light).

[0] Technical details omitted.

The universe has been expanding.

So the distances now are vastly larger than they used to be when the light left its sources.

> Also, the Hubble can't even see most of the Observable Universe; it can see ~15 billion lights years away, whereas the radius of the observable universe is 47 billion light years.

There is a subtlety with the size of the observable Universe versus the distance Hubble can see. The radius of the observable universe is 47 billion lights years (the radial distance to the cosmic microwave background[0]). Hubble has spotted galaxies whose distance corresponds to a light travel time of ~13 billion years. However, the Universe has expanded since that light was emitted 13 billion years ago, so the galaxies which emitted that light are now about 30 billion light years away. So Hubble can see objects which are closer to the edge of the observable Universe than the 13 billion year light travel time implies, compared with the size of the observable universe. There are tentative detections of even more distant galaxies.

For reference, I obtained those values using Ned Wright's cosmology calculator[1] with a redshift z=8, and the default values, assuming a flat cosmology. The 13 billion years ago number is the light travel time and the 30 billion light year distance is the comoving radial distance.

[0] If you plug the approximate redshift of the cosmic microwave background (z=1100) into [1], you get 45.5 billion light years.

[1] http://www.astro.ucla.edu/~wright/CosmoCalc.html

Edit: Clarified wording and added CMB distance info.

Or the inspiration that the images have produced.

As a kid Hubble photos made me fall in love with science.

Until I learned all the colors are fake and space is monochromatic almost everywhere.

It's absolutely not monochromatic. It's full of colours that we cannot see, we have to use fake colours to visualize objects from space in all their diversity.

Full of colors that we cannot see. Are you saying its like watching a color TV signal on a black and white TV set? Are we just too far away? Would any of those nebulae show such beautiful colors to the human eye if we were only closer? I can never get a straight answer on that.

But if you look at these objects through a small telescope, you will see white blobs.

Near and far infrared, ultraviolet, x-rays, gamma rays -- there are lots of photons out there. Hubble has many sensors[0], so many of the images taken are from outside the relatively small portion of the spectrum that humans can see and then mapped to the visible spectrum.

Additionally, human vision is dominated by intensity sensitivity, not color sensitivity.[1] So especially with very modest optical equipment and faint light sources you won't see much color.

[0]http://hubblesite.org/the_telescope/hubble_essentials/ [1]http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.ht...

An ngrams analysis doesn't show a significant increase in the use of "observable universe" after 1990. https://books.google.com/ngrams/graph?content=observable+uni... .

While it does increase, it seems to continue the trend which started in the 1940s.

Here's an example of Asimov using "Observable Universe" in "Asimov on Numbers" (1977): https://books.google.com/books?id=el0PAQAAMAAJ&q=observable+... .

Sound engineering often trumps sexier approaches. Legacy systems should not be under rated.

Ya. That said, flying a repair mission to install a corrective lens on a space telescope is/was totally in the realm of 'sexy solutions'.

The problem here is that messing up the mirror on such a project in the first place was not very sound engineering.

Fair point, but 'messing it up' to such a high degree of accuracy that it could be corrected for via COSTAR does show soundness of engineering.

Ie, mistakes will inevitably happen. But having the process refined enough to compensate, improvise, and enhance on original plans and imperfections does show good design.

You're right, and it's a funny kind of right.

It's an astounding thing when you're creating a mirror closest to perfection that had ever been made, and missing by 2.2 micrometres ruins it. And given that it was the 1980s and you're dealing with nano scale engineering, it was just that much more incredible.

I should have made my point slightly more clear. I think that the OP's post is actually a non-sequitur. Both statements are generally true, but neither necessarily follows from the other.

Professional engineering practice admits the possiblity of errors and ommissions. Insurance is the technique used to address it. In ordinary practice this is something that is purchased from agents with an associated cost. In the case of Hubble, it was purchased for the cost of making the telescope serviceable. Infallability is not an engineering practice. "Don't screw up" is not an engineering heuristic.

Of course we could have also easily launched 5 redundant space telescopes for the cost of those servicing missions. So, the point still stands sexy engineering is rarely the ideal approach.

EX: Consider how much better the space shuttle would have worked without a cargo bay.

This is just not true. I worked on three of those servicing missions as an engineer. They were required to keep HST running and to enhance it's capability. Adding COSTAR to fix the mirror fuckup was one tiny piece of the servicing missions.

There were 6 Hubble missions all of them where manned.

I suggest that the savings of using unmanned missions, not making a serviceable telescope, and saving 1 full trip would have paid for construction of 4 additional telescopes with minor design updates for instruments and or fix bugs but no changes to major systems. With the added advantage of not risking astronaut lives on a publicity stunt.

How would you have gotten even one HST sized telescope into orbit without a manned mission? Do you know what life span of a Hubble would have been if it were not serviceable? Your approach would have cost more, not less. More manned fights, more time consuming, expensive design and construction. Believe it or not, they thought about this stuff.

How would you have gotten even one HST sized telescope into orbit without a manned mission?

How do we get similar sized spy satellites into orbit without people? http://www.space.com/16000-spy-satellites-space-telescopes-n...

As to lifetime, we don't need a 30 year lifespan. If you average 6 years * 5 satellites you get 30 years and I suspect we could easily average 8-10 years.

As to thinking about this stuff. Clearly, but Hubble was specifically designed to make the Shuttle seem more relevant. Just about all of the major decisions where made for political not technical reasons.

Hubble was specifically designed to make the Shuttle seem more relevant.

It flows both ways. Hubble was designed to take advantage of the planned capabilities of the shuttle, but also, the Hubble was an important use case in setting shuttle requirements. And as I pointed out elsewhere in this thread, the shuttle dropped the ball on many of these, both functionally and in terms of delivery dates.

Every decision at NASA is political - it's a government entity (look up Triana - that's another one I worked on. It's laughably ridiculous). But you're grossly oversimplifying. There isn't a prayer in heaven that would keep Hubble alive for 10 years on its own. Hubble made sense as a shuttle payload for a lot of reasons. I'm sure someone could have cooked up alternatives, but the one we got obviously did some good.

As government programs I think both Hubble and the Space shuttle where significantly better than average. Realistically redundancy is the first thing that gets cut at budget time etc etc.

Still, what makes you think building a Hubble equivalent that would last 8-10 years is outside the realm of the reasonable when Hubble is expected to last 7 or 8 years after the last servicing mission.

I get what you're saying, and I agree it's possible. But I think the position you're taking is too strong, in that you seemed to have accepted that it must be true. I think that what you're saying is reasonable, possible, and could be the case. But I don't think you have enough information to claim so strongly that it is certainly true.

That’s probably the most reasonable statement I have ever seen on the internet.

I try to judge past decisions in context not just based on what worked. At the time we did not know that each of those servicing missions would work or even if the initial launch would work. Though, clearly one path worked and the Servicing missions where incredibly valuable experience. But, they could have also cost a shuttle and several astronauts lives. Granted, the odds of multiple telescopes being sent up in a fairly short time period is tiny so it's only reasonable on a technical level.

In the end I think the Hubble program is completely justifiable, but that justification needs to be about more than just a quest for pretty false color pictures or worse an example of the sunk cost fallacy.

You bring up an interesting point regarding astronaut safety. It's interesting to me because I have the polar opposite opinion. This will sound cold, but astronauts are basically expendable. We can expect a small percentage of them to die. Much like in the military, the mission takes priority over safety, which comes second.

Given that we have no shortage of astronauts willing to accept that, and that we do put a ton of effort into their safety, I have no qualms whatsoever pushing the limits of what is possible. I've met a lot of astronauts - I don't recall meeting a single one who didn't fully understand how dangerous the work is. It's not for everyone. Personally, I think they're nuts to take that risk for what amounts to floating around in a stinky can for a few days, punctuated by brief stints of mechanic duty.

This always struck me as a major disconnect between the brass at NASA and the engineers. The higher up the chain you went, the more concerned with safety, politics, and perception they were, and the less concerned with what I would say the true goals of the space program are - the actual exploration of space.

What you're saying isn't crazy. I guess I don't have a lot of faith in their estimates. NICMOS was supposed to last something like 4 years if I remember correctly. It died in about two. A whole slew of gyros failed, degrading performance, and jacking up schedules so we could replace them. COSTAR is a pretty obvious failure that wasn't fully recovered from (COSTAR took up one of four slots that were meant for instruments). Lots of stuff goes wrong. But maybe they could have designed a Hubble-class telescope that would last ten years back then. I don't know for sure. My gut says the first one would have been a piece of crap with a bad mirror and shitty gyros. That's a lot of work to throw away.

Either way, would launching three (or six or whatever) of those on rockets really have been cheaper than the Hubble in terms of science/dollar? I have some serious doubts. Throw in the politics and overhead of three major missions, and you're talking big numbers.

And that ignores the intrinsic value of manned missions for their own sake - you must do them to get good at them. There are people who say that we should never do a manned mission, and that all the data we want to collect can be had by unmanned satellites and whatnot. While it may be very close to true, that's a very short-sighted point of view in my opinion.

The James Webb Space Telescope is ~5x larger than HST, and it will be launched on an Ariane 5 rocket, with a lifespan goal of 10 years and no opportunity for repair or replenishment. You should ask them how they can deploy such a large telescope without a crew. Or ask the NRO how they launch a KH-11 spy satellites, which is the same size as Hubble, and launched on a Delta IV Heavy rocket.

Hubble was built assuming shuttle launches would be cheap. It wasn't.

Fair point on launching big stuff - I suppose that a Hubble derivative could have been designed to work with one of the bigger rockets. But a hoped for lifespan of 10 years is not even close to what you get out of Hubble servicing missions. The ability to improve and repair a working telescope is not without value. Things go wrong all the time with these instruments. No serviceability = higher risk.

You can indeed adapt your designs for unmanned launches and get a good life span out of them, but there are significant tradeoffs to doing so that impact the mission.

Further, there is value in manned missions just because. How are we to gain experience operating in space without sending people there?

Yes, Hubble has been around for 25 years.

There's a question of cost though. Each repair job costs about $1 billion and has a ~1% chance of killing the crew. (When Hubble was designed, it was thought that the Shuttle would be cheaper and safer than it was.)

If we could build an launch a Hubble for $1 billion, then it's obviously cheaper to send up a new one than repair it each time. If it lasts for 10 years, then if the unit cost to launch were under $3 billion then it would still be cheaper to launch a new one than fix one in-place.

So how much did Hubble cost? Wikipedia says $2.5 billion to construct. http://www.nasa.gov/pdf/499224main_JWST-ICRP_Report-FINAL.pd... says "Again, to put this in context, HST, which was a much less complex mission [than Webb], had a total cost-to-launch of approximately $5 billion in current dollars. Hubble’s LCC was approximately double this because of servicing costs over 20 years." (Those are 2010 dollars.)

Hubble also had huge cost overruns. The KH-11 has an estimated unit cost, including launch, of US$2.26 to 3.16 billion in 2015 dollars, says http://en.wikipedia.org/wiki/KH-11_Kennan#Cost . We've built several of those, which I assume helps reduce the per-unit costs.

If we could get the Hubble-like unit cost, including launch, down to $2.5 million, and with a 10 year life time, then we could launch 4 for what we've spent on Hubble, and lower risk through redundancy. "No serviceability" = "cheaper design" = "can launch more" = "lower risk". Again, this is based on the experience since the 1970s that manned missions are expensive and risky.

Regarding just because - your original question was "How would you have gotten even one HST sized telescope into orbit without a manned mission?" That's all I'm addressing.

Yeah - I take it back - I spoke too quickly. You can certainly launch large satellites with rockets. I was too focused on Hubble specifically.

That said, I remain deeply skeptical of the idea of being able to do so cost effectively or in a way that allowed for iteration and development of the systems. That's a lot of eggs in one basket to make 4 duplicates - they'd all fail in the same ways (which Hubble did early and often) and they'd be space junk in a heartbeat. You'd also want different cameras, which would have different requirements, etc. Once the contractors got a hold of that, they'd wind up 4 separate projects costing a fortune, and you'd be right back where you started, except without the budget. Keep in mind how long it took to build the HST. A servicing mission turned around in about 3 years.

It wouldn't be duplicates. A better plan would reuse the same chassis, and have a staggered production. There have, after all, been 16 KH-11 satellites over 30+ years; they surely didn't all use the same technology.

Part of the reason for the expense of HST comes from the delay after Challenger. Hitching it to the success of the Shuttle helped make it more expensive.

You are right though that it plays to the sunken cost fallacy. Hubble happened because the initial budget was low. Then it ballooned. Congress would likely not have budgeted $10 billion if they knew that was going to be the final cost of Hubble. It's even less likely they would have funded four space telescopes for that price.

> Of course we could have also easily launched 5 redundant space telescopes for the cost of those servicing missions.

Maybe not. Hubble ended up costing over $2.5bn https://en.wikipedia.org/wiki/Hubble_Space_Telescope by launch day while a Shuttle launch cost around $450m https://en.wikipedia.org/wiki/Space_Shuttle . Certainly there would have been economies of scale, but it doesn't seem assured you would have got another four Hubbles for ~$500m extra. Moreover I'm not sure whether the redundancy would have dealt with the lens problem, or whether the same error would just have been replicated in all five satellites.

I don't think we would send them up in the same month so that's plenty of time to check for design flaws. Also, Hubble was far from useless before correction it was still the sharpest telescope ever. Anyway, my point was not sending up more Hubble’s my point was a comparable telescope not a sexy mission. Still, for fun let’s go for something ambitious.

Shuttle launch cost around $450m x 6 = 2,700 million. Hubble mass: 11,110 kg

http://en.wikipedia.org/wiki/Delta_II 6,000kg to LEO launch costs ~51 million.

So if we went with a modular design vs user serviceable we could get a Hubble equivalent in ~2 Delta II launces (6,000 x2 kg to LEO = 12,000 kg) for 102 million x 5 = 502 million.

2,700 million - 502 million = 2.2 billion to build 4 more copies of a similar design plus some extra design costs etc.

PS: There were plenty of other options including arrays of smaller telescopes. For a recent example the Delta IV heavy can launch more mass to LEO than the shuttle $375 million per launch so the shuttle tax was very real.

Sorry, I missed that you were comparing five Hubbles to five resupply missions, not to one. But I'm not sure you would have been able to get five Hubbles for an average of ~$500m each either.

(OTOH, all this is just considering what the best option for Hubble was, taking the existence of the Shuttle as a given. Justifying the existence of the Shuttle partly in terms of the Hubble would be more difficult: that $450m-a-flight figure doesn't seem to include development costs...)

Well, if you allow for waiting long enough they come for free as spy satellite surplus.

http://en.m.wikipedia.org/wiki/2012_National_Reconnaissance_...

My grandfather worked on the Hubble mirror. It was, at the same time, one of his proudest accomplishments as well as a source of embarrassment.

Everybody agrees that the mistakes with the mirror were a real screw-up, something that should never have happened with better management and organization.

However, my grandfather also pointed out that there's another direction to point the blame finger, that actually never enters into the discussions. According to gramps, it was understood that they wouldn't be able to get the mirror perfect (admitting, of course, the actual error was worse than any spec allowed for). Apparently they knew they weren't able to control perfectly for the distortions that would arise from moving the mirror from Earth's gravity to weightless, and perhaps other factors.

But the original goal for the space shuttle was supposed to make it relatively easy to bring the thing up into space, try it out, and tweak it or even bring it back for repairs. According to gramps, this was always a fallback possibility, and the fact that it was so difficult and expensive in practice reveals as much about the failures of the space shuttle program as it does about the Hubble mirror - but the latter is always the focus of the discussion. Indeed, the shuttle gets credit as the savior, if anything, rather than any blame for how poorly it served its intended mission (including how many years its own program delays resulted in delays for the Hubble itself).

Caveat: this is all completely based on the opinion of one guy as communicated to his grandson, and potentially suffers from all the errors that this might imply.

EDIT - fixed mis-wording in para 3.

My PhD was made possible by the great HST. True testament to the infinite science made possible by great Space telescopes. Here's hoping JWST [1] is considered in a similar light 20 years from now.

[1] http://www.jwst.nasa.gov/

I am very excited about the prospects of the JWST and the LSST.

One of my favorite Hubble images is the eXtreme Deep Field, which shows galaxies from 13.2 billion years ago. https://en.wikipedia.org/wiki/Hubble_eXtreme_Deep_Field

This is a product... What one produces when you have the commitment and dedication of the brightest minds. Precision hand crafted, every piece installed by hand and custom made.

Nanometer precision and dedication, ownership produces a top notch product like this that just keeps working... No pun intended to the Kepler team.

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