# Couldn't the Webb telescope get better photos of Jupiter?

Looking at the newly released Webb telescope photo of Jupiter, I know I’ve seen sharper photos than this. If Webb can photograph 13 billion year old galaxies, couldn’t it zoom in a lot closer to Jupiter and get sharper detail? Here’s the photo: https://blogs.nasa.gov/webb/2022/07/14/webb-images-of-jupiter-and-more-now-available-in-commissioning-data/

Probably, but keep in mind that photo you linked is an infrared image, not visible light.

I don’t know but could it be like watching your TV from the couch through a telescope designed to look at the moon?

A lot of those hi-res photos of Jupiter you’ve seen are likely from the spacecraft Juno, which is orbiting Jupiter a few thousand miles above its “surface.” Hard to get better photos than that from here.

Three are lots of great pic of Jupiter, but they were taken by probes that flew right up to the planet to take them. The JWST is still next to the Earth. So you would be comparing the pic to either Hubble or Earthbound telescopes. Hubble has taken some very good pics.

The images taken by Webb don’t look as good as the Hubble ones, but they are test images that have had no special processing done to make them look fabulous for public consumption. They are clearly blown out in the bight areas. They were taken to prove Webb can take such pictures at all. They do however show stuff Hubble can’t. Such as the rings around Jupiter. The Hubble images have been heavily processed to look fabulous. Jupiter doesn’t actually look like that. It is far more muted and drab looking.

This then gets us to the fundamental limits of any telescope. Telescopes actually don’t zoom in on anything. They work at their ultimate capability all the time. So in a sense the JWST is already zoomed is as far as it can go. The limit to what it can achieve is defined by a few things, but ultimately the hard limit is defined by the diameter of the mirror and the wavelength of light it is seeing in. The limit was described by Rayleigh, and known as the Rayleigh criterion. He described the best possible angular resolution an optical element can achieve.

\theta \approx 1.22 {\lambda \over D}
\theta is the angular resolution, \lambda is the wavelength of light and D is the diameter of the telescope mirror.

This is a hard limit. The JWST uses infra-red light, so the resolution drops relative to visible light. You can especially see this is the released images of a planetary nebula, there are two images: one in near infra-red, the other in mid-infra-red. The longer wavelength light image is noticeably less detailed than the one in shorter wavelengths.

But the mirror on the JWST is huge compared to any other space telescope so that claws back everything it loses due to wavelength compared to Hubble and more.

Overall, don’t judge the JWST by these few test images of Jupiter. You can be sure that in the fullness of time they will release some jawdropping new images of Jupiter.

Also remember that the Webb is just one instrument, and there’s an awful lot out there to look at. To get the Webb to take pictures of anything, you need to put in a proposal and convince a committee that your proposal is better than all of the other proposals, and even then you’ll probably be put on a waiting list. How pretty the public pictures will be probably is part of the criteria that committee uses, but it’d be very low on their list of priorities. The big question is always going to be “what can we learn scientifically from this target?”.

In the case of planets in our Solar System, we already have oodles of scientific information from probes that we’ve sent right up to the planets. It’s going to be tough for any telescope near Earth to learn anything about the planets we don’t already know. The Webb pictures we have of Jupiter mostly aren’t to tell us more about Jupiter (though I’m sure that the scientists who study Jupiter are combing through the data to find everything they can), but to tell us more about Webb itself. This works precisely because we do already know so much about Jupiter.

Actually Webb has found a “new” ring system and some more details on the cloud bands and convection cells on Jupiter, which is not only of interest for that planet but in understanding more general phenomena of large “hot giant” planets in general that may aid in intrepreting spectral data on exoplanets. The impressive results of JWST thus far should be an impetus to vastly expand space-based astronomy for the capabilities it offers over ground based telescopes; unfortunately, going from concept to deployment for space observatories is the work of decade. (JWST was formally conceived in 2003 but a near-infrared space observatory replacement for the Hubble Space Telescope was in proposal phase since the early ‘Nineties with the Hi-Z telescope concept.)

With the upcoming heavy lift capability of Falcon Super Heavy and SLS (assuming that one or both are successful) we could launch much larger telescopes that could also make use of advances in membrane and inflatable structures to deploy truly massive collectors for both optical and radio telescopes as well as flying array observatories, which are the only ways we are going to be exploring other star systems for the foreseeable future.

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In the case of the JWST, with a diameter of 6.5 meters and looking at the infrared at 2000 nm, yields a resolution of less than 0.1 arc-seconds (if I have done the math correctly). Since Jupiter can appear as large as 50 arc-seconds, the JWST is capable of resolving a lot of detail.

That’s a virtual ‘pixel’ size of 0.2% of the aspect of Jupiter, or in other words, frame of Jupiter would be 500x500 pixels. It’s more than a blob but if you want to zoom in close detail is going to be lost pretty quickly. Those who have worn NODs know just how much imagery degrades in the near-infrared in infrared region, and how hard it is to make out real detail.

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Well, we could do that. But this fellow named Musk wants to put people on Mars. What to do?

On the topic of “Shit Elon Musk Says”:

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The remarkable thing about landing things on Mars for cheap is that it implies launching things into Earth orbit for really cheap.

The first real job of Starship will be filling out the Starlink constellation. They’ll load the satellites in like a Pez dispenser and they’ll pop out of a little slot.

Starship will launch 100+ tons into low Earth orbit at a time, though. We should be designing telescopes on a common 8-meter platform, designed to be cheap and not light, and build a dozen at a time.

JWST is remarkable but with the same money we could have had far more capability if it had been designed with cheap lift in mind.

We could also have far more capability if we’d designed it based on the principles of unicorn eyes.

When and if cheap lift ever becomes a reality, then we’ll start designing for it. Musk’s vehicles are likely to make it cheaper than it currently is, but even the best projections for them are still pretty expensive. And there’s still considerable difference between the best SpaceX projections and the worst, and we don’t know yet what the reality will be.

The issues with orbiting observatories aren’t weight-limited; aside from the optics, the heaviest components are the batteries and flywheels for maintaining orientation. Having an 8 meter payload width and essentially no limit on weight does make for a lot of design options that don’t require so many compromises but there is also the issue of being able to build a collection structure of that size that would survive the launch loads and environments, or a deployable membrane structure of many tens of meters in diameter that can realistically be tested in the ground environment.

Optical satellite observatories are very complicated systems because of the required precision of the optical systems—far more difficult to design, build, and test than big telecom birds or even most Earth observation satellites—and are always going to be billion-dollar instruments. Realistically, the manufacturing and test infrastructure would not support building them “a dozen at a time”; it is difficult enough to pipeline about half a dozen interplanetary spacecraft and satellites at any given time even though you would find the demand for optical satellite observatories would grow to any number of observatories that were deployed.

It may be possible to build radio-frequency orbiting observatories for much cheaper but they also require a large amount of power which is another challenge; not getting the power, which can be generated from solar insolation, but dealing with waste heat and thermal effects. Still, having multiple radio frequency observatories capable of flying in a well-regulated formation would definitely allow for really long baseline interferometry that isn’t possible from the ground as well as sampling in bands that are screened by the atmosphere.

But first, ‘Starship’ has to demonstrate reliable launch capability instead of repeatedly blowing up on the pad, because even if the launches are cheap, the observatories are not, and nobody likes seeing their payload on a rocket that turns into a fireball or careens into the ground seconds after liftoff.

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Although, if you can get launch prices down low enough, you don’t need to launch the delicate instruments, or test them on the ground: You instead launch all the infrastructure for making them, and build and test them in orbit.

Though you’d probably need launch costs an order of magnitude or two less than even the optimistic SpaceX projections to make that practical.

I would not be surprised if there was some room in there for “wow” shots to be used for promotional purposes. Certainly the telescope’s purpose is for hard science and not pretty pictures of Jupiter but the public likes pretty pics of Jupiter and such things help keep the public enthusiastic and, by extension, funding rolling in. I’d be willing to bet they have a little time carved out in their schedule for such things.

Although launch costs are not insignificant, for a billion dollar payload they are not the driving factor. James Webb Space Telescope (JWST) grew from an initial estimate of US$1B at the program start in 1998 to over US$5B by Preliminary Design Review (PDR) in 2008 and then to US$6B at Critical Design Review (CDR) in 2010. Program delays and schedule slipped cost additional cost increases up to an estimated US$9.7B by launch (in part because of some additional testing and rework and inflation but mostly just for the need to keep the support team and activities in place and stretched out over those years instead of the scheduled deployment date in the 2015-2016 timeframe at CDR).

Space observatories are a very sophisticated and very niche space application and both the engineering expertise, skilled fabrication and assembly labor, and the facilities to test such a large spacecraft to the required conditions are all very limited and perennially in high demand (as they are essentially the same as unnamed national security payloads operated by the National Reconnaissance Office that frequently take priority), so even if launch was so dirt cheap that it was just a rounding error in total budget (which for JWST it effectively was) you still wouldn’t launch an observatory without extensive testing because of the lost of invested effort and cost that would represent. Large telescope optics are always ‘delicate’ instruments that require the highest possible precision feasible.

The “launch your sat into space and see how it does, then iterate as necessary” is a workable philosophy with CubeSats that are assembled by interns and low-cost junior engineers so enthusiastic about getting their foot in the door in the satellite industry that they’ll work for peanuts and mostly worthless stock options but is never going to be a viable approach with large satellite observatories or other really complex payloads. Space ‘enthusiasts’ often make the mostly artificial distinction between ‘NewSpace’ and ‘OldSpace’ companies, but the actual functional distinction is between microspace and macrospace: that is, payloads that are easy to fabricate and dirt cheap, doing simple things that aren’t mission critical or can be iterated quickly; and larger complex payloads that take years to design, fabricate, assemble, and test because of their innate complexity and mission critical need. Large space observatories are inherently in the macrospace category just because of the size, complexity, and necessary precision of the imaging systems regardless of how cheap the ride to orbit is.

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Eh, telescope time is rare and precious, but EPO interns are abundant and cheap. You’re going to be getting some sort of images or other from the telescope even if you put your priority 100% on the science, and it’s not too hard for the EPO interns to massage whatever images you’ve got into something that’ll make the public go “ooh, wow”.

Not directly, maybe, but if launches were trivial in cost, that would drive down all of the other costs. A great deal of the cost of space missions is because they need to be extremely reliable. You can make a much cheaper spacecraft if you’re willing to accept, say, a 90% mission failure rate, and you can afford a 90% mission failure rate if that cheap mission is so cheap that you can afford to launch it ten times. As it is now, no matter how cheap the mission itself is, you can’t afford to launch it ten times, because the launches themselves are expensive, but if the launches were cheap, maybe we could go with that paradigm.

I don’t know that the numbers are quite that extreme, but we do put a whole bunch into adding another 9 onto that reliability.

If they had only had a 90% confidence that JWST would perform as it has, they never would have launched it. Even 95, 99 or 99.9% probably isn’t good enough.

But, if we can reduce the reliability from 99.99% to 90% and cut the price in half, then overall we come out ahead on science per buck. It’s not worth it when launch costs are a significant part of the overall cost, but as they drop, it makes more sense to have less reliability and make up for that in quantity.

No, not really. I know it is an article of faith among the ‘space enthusiast’ community that space launch costs drives everything and if you had dirt cheap launch capability it would suddenly result in space industries, mining, colonizing the Moon and Mars, et cetera, but that is a naive assumption that is demonstrably not true. To be sure, the cost of space launch has been a limitation on low cost micro/nano satellites that have been largely limited to rideshare opportunities on bigger launches (and even with the emergence of RocketLabs, Virgin Orbit, Relativity, Firefly, et cetera it isn’t clear that smallsat launch is a fiscally sustainable industry for more than a couple of launch providers) but for larger complex satellites and interplanetary missions the launch costs, while not insignificant, are not the main drivers. Aside from the inherent costs of fabricating spacecraft and instruments—which even done absent to the extensive ground testing will still be quite expensive for the kind of spacecraft and instruments useful for interplanetary exploration and large space observatories—there is the opportunity cost that is lost every time a mission fails because it is much better to spend 20% to 30% of your budget than to spend three or more years building up a payload to launch it only to have it fail and have to go back through the entire acquisition/contracting/fabrication cycle, especially if you have a mission critical need for your program or company.

I know space enthusiasts try to apply the paradigm of smallsats to everything and assume that that design-build-break-redesign is the way to go which works fine with CubeSats and other small satellites that you can handle without large cranes and fixtures and that cost a few tens of thousands each with a fab cycle of a few weeks, but when you get into the tens or hundreds of millions per unit and a design/fab cycle of years, that entire notion just completely breaks down, again both because of the invested engineering and labor as well as the opportunity cost lost versus a successful mission. The CubeSat was originally conceived as an educational project that would enable literal hands on experience with satellites that were quick enough to build and cheap enough to rideshare that college students could build them, and the CubeSat form has grown into a commercially useful platform for certain applications and even considered for certain types of low cost interplanetary missions, but neither it or other smallsat form factors are suitable for the entire array of satellite and spacecraft applications, and in particular you are never going to build a space telescope that can look back into the origins of the universe in a 6U or 12U form factor. This is precisely what I mean about the functional distinction between microspace and macrosapce; for the missions that low cost, small form factor spacecraft will work, they are as great an innovation as the PC was over mainframe computing, but there are many applications where those types of spacecraft just won’t work and aren’t desirable regardless of how cheap the launch cost is.

As for accepting an estimated “90% failure rate” I guarantee that nobody is going to go for that in the million dollar or higher spacecraft category. It is difficult enough to get acceptance of a mission risk that is at 5% probability of failure because, again, nobody wants to lose either the invested value in building the spacecraft nor the opportunity cost versus a more successful mission. These are the kinds of wild-ass notions that space enthusiasts throw around without knowing anything about the actual space industry or the engineering behind complex spacecraft. There are just marginal limits on how cheaply and quickly you can make a spacecraft of some particular level of capability (mostly based upon the instrumentation it has to carry and support) regardless of how much of a production line you conceive of building it on. While there is merit to common spacecraft systems and buses, you just can’t assembly a JWST-like observatory from off-the-shelf spare parts regardless of how innovative or entrepreneurial you believe yourself to be. And again, for these larger complex missions, the actual ride to orbit is only a small fraction of the total cost and making it even cheaper is only shaving a few points off of the total mission cost, so it just isn’t the main driver or opportunity for cost reduction that people believe it to be.

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