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Comment: Re:ATLAST (Score 2) 46

by Trapezium Artist (#46902609) Attached to: Astronomers Calculate How To Spot Life On an Alien Earth

Absolutely right: I was going to point out the same thing. It's many, many years away from any possible launch ...

For reference, the James Webb Space Telescope (or NGST as it was then) was beginning to be picked up as a serious prospect by NASA, ESA, and the Canadian Space Agency in the late 1990's. It's due for launch now in 2018.

(This is not meant as a criticism: I've been closely involved with JWST since 1998 and know how hard it has been in terms of technology, programmatics, and politics to get the good state it's in today, namely mostly built and now entering the comprehensive integration and test phase.)

So, very crudely, I'd say that something like ATLAST might be launched after 2035, if it gets picked up as the highest priority in the next US astronomy decadal survey.

Comment: Re:Surely ironic (Score 2) 276

Good point; I did use the word "we" in a rather catch-all manner there, and I'd also agree that technologists are likely to have a much better record at predicting the future than journalists.

But I'd then turn the tables and say that it depends on the timescale implied by "future". On a ten-year horizon, I'd agree that technologists are likely to have a pretty good idea what's coming, in part because they're likely to be working themselves actively on new technologies and products for release on similar sorts of timescales.

But on a 100 or 50 or even 30 year horizon, as this article refers to? It seems clear to me that on some timescale, even technologists are unlikely to be that close, if only because they're probably called "futurologists" at that point, or "science fiction writers" :-)

On some timescale, almost everyone is going to be pretty much guessing ...

Comment: Re:Surely ironic (Score 3, Interesting) 276

OK, now having read the linked article (oops), I do see that the author (Henry McCracken) realised that the cover painting had a humorous intent (not least that it was the April edition of BYTE), satirising the conservative opinion that future tech was likely to be an extension / miniaturisation of the then-prevalent PC paradigm.

Good to see I got it, though :-)

Comment: Surely ironic (Score 4, Insightful) 276

C'mon, it's entirely obvious that that "PC on a watch" painting is a rather clever piece of irony or even satire, not a meaningful prediction of an actual future piece of technology.

That doesn't mean I disagree with the point of the discussion, namely that we're not that great at predicting the directions of future tech, but using this magazine cover as a direct illustration of that is, IMHO, rather disingenuous.

Comment: Re:What's been the hold up???? (Score 1) 100

by Trapezium Artist (#46688297) Attached to: NASA Laying Foundation For Jupiter Moon Space Mission

Actually, ESA built the Huygens lander which descended to the surface of Titan. It was carried there on the NASA-ASI Cassini orbiter after being launched by a NASA rocket, but Huygens was European-built, with instruments from Europe and the US.

Its the U-571 gambit: keep saying that things were achieved by the US independent of the truth of the matter, and pretty soon it becomes received knowledge.

Comment: Re:What's been the hold up???? (Score 3, Informative) 100

by Trapezium Artist (#46688221) Attached to: NASA Laying Foundation For Jupiter Moon Space Mission

Quite. Rosetta has been on a ten year journey around the Solar System, using Earth and Mars fly-bys to wind its orbit up to meet with 67P/Churyumov-Gerasimenko in August this year. At its most distant point from the Sun, it was beyond the orbit of Jupiter, but the comet rendezvous will take place at about 3AU, before the comet becomes active as it moves closer into the inner Solar System.

As for outer planet missions, the NASA-led and launched Cassini mission also carried ESA's Huygens probe, which performed the most distant ever landing in the Solar System when it landed on the surface of Titan in 2005.

But the elephant in the room here is ESA's JUICE mission, which is a real mission, not a study, already under implementation for a launch to Jupiter and its icy moons in 2022. JUICE will conduct a number of close fly-bys of Europa, but due to the dangerous radiation environment, will ultimately end up in orbit around Ganymede, another icy moon thought to host a deep ocean below the surface. And NASA are also involved in this mission, providing some of the instruments.

Comment: Re:US broke? Do it with Europeans! (Score 1) 216

by Trapezium Artist (#46420561) Attached to: NASA Wants To Go To Europa

I was waiting for someone mention the (funded and being built) JUICE mission: it's astonishing to me that the "if it ain't NASA, it ain't worth jack" attitude generally persists, and that hardly anyone in the media (let alone on /.) bothers to do the slightest modicum of research.

JUICE is under development by the European Space Agency for launch in 2022 (not 2020 anymore) and arrival at Jupiter in 2030. It will tour the Jupiter system, including multiple fly-bys of the giant icy moons Europa, Callisto, and Ganymede. It will end up in orbit around Ganymede, where it will conduct a more detailed survey.

All three moons are thought to harbour giant water oceans under (probably) very thick icy crusts (~100km), although there are debates about which may be the most likely to provide potentially habitable environments deep in these oceans: it may depend on central heat flux from the moon's contraction, flexure due to Jupiter's gravity, heat from radioactive decay, and whether there's a water:rock interface which could provide minerals.

Why Ganymede as the final moon to be orbited? Because Europa is closer to Jupiter and suffers a much higher radiation dose due to high energy particles trapped in Jupiter's magnetic field. Not necessarily an issue for life(?) buried deep in the oceans, but certainly an issue for the survivability of a spacecraft. Through the US's, umm, extensive military experience, NASA has access to higher-grade rad-hard electronics components than ESA, and so JUICE will only fly-by Europa a few times instead of bathing itself in that radiation.

But NASA is involved in JUICE too: several of the (many) instruments on JUICE have US Principal Investigators, funded by NASA. So, NASA is already going to Europa in a very real sense.

Comment: Not likely to happen any time soon (Score 1) 134

I hate to rain on everyone's parade here, but this mission isn't likely to happen soon. The paper referenced in the original post is a write-up of a case made to the call for ideas put out by the European Space Agency for future large missions, specifically looking for one to be launched in 2028 and another in 2034 (L2 and L3, in ESA-speak, with L1 being a mission to Jupiter and its icy moons, selected a year or so earlier).

Problem is, the Uranus/Neptune case didn't win either the L2 or L3 slot. A wide range of scientific ideas and mission concepts were proposed, aired publically, and assessed by a senior survey committee, before the two top-ranked ideas were approved by ESA's Science Programme Committee in late 2013.

And those two future missions will be a new high-energy astrophysics observatory for L2 in 2028 and a gravitational wave observatory for L3 in 2034.

The senior survey committee liked the science case for Uranus and Neptune, saying "The SSC considered the study of the icy giants to be a theme of very high science quality and perfectly fitting the criteria for an L-class mission", but then went on to say:

"However, in view of the competition with a range of other high quality science themes, and despite its undoubted quality, on balance and taking account of the wide array of themes, the SSC does not recommend this theme for L2 or L3. In view of its importance, however, the SSC recommends that every effort is made to pursue this theme through other means, such as cooperation on missions led by partner agencies."

So, it certainly won't be an ESA-led mission in the foreseeable future, but ESA could participate in a wider international mission if someone else leads it.

You can read the whole report here.

Comment: Iain (M) Banks: you will be greatly missed. (Score 4, Interesting) 150

by Trapezium Artist (#43347259) Attached to: Iain Banks: Extremely Ill With Cancer

As I posted a little earlier on The Guardian:

Desperately sad news.

His contemporary and science fiction novels have been an important part of my life for many, many years, and I shall miss knowing that his twisted and brilliant imagination is beavering away at new works.

But if nothing else, looking for a silver lining to this dark, dark cloud, I'm at least happy to have the chance to thank him publicly, before he's gone, for the great pleasure I've had in reading his books.

I'm sure he's greatly loved by many and I hope that that knowledge can go at least some small way to helping him and his wife through the months to come.

Comment: Re:Seems Like a Waste of a Good Mirror (Score 3, Informative) 40

by Trapezium Artist (#43097555) Attached to: For ESA's Herschel Mission, the End Is Near

Problem is that Herschel's primary mirror was only polished to the level of surface roughness required for the telescope to be diffraction-limited (i.e. as good as it gets) at far-infrared wavelengths. It wasn't polished to the level necessary to form good images at optical wavelengths.

Just to put some numbers on that, Herschel's shortest operating wavelength is 70 microns (70 millionths of a metre), whereas the red end of the visible is around 0.7 microns, i.e. 100 times shorter.

Polishing the mirror to a factor of 100 lower surface roughness would have been far more expensive and perhaps even not possible using the underlying segmented silicon carbide technology. (SiC can be polished to optical tolerances, but I don't know if Herschel's substrate was made to the appropriate tolerances).

Comment: Re:Why is it so difficult to cool (Score 1) 40

by Trapezium Artist (#43094963) Attached to: For ESA's Herschel Mission, the End Is Near

Space isn't really cold, not at least when you're close to a star like the Sun. After all, the Earth's isn't cold (well, relatively speaking), despite the fact that it sits in space. Sure, there's some internal heating from our molten core and some greenhouse effect from our atmosphere, but the underlying reason that the Earth is warm (again, relatively speaking) is because it's in thermal equilibrium with sunlight at a distance of 150 million kilometres from the Sun.

So if you stick something in space at L2, it's essentially at the same distance from the Sun as the Earth and thus, roughly speaking, it'll end up at the same temperature as the Earth.

The big difference, however, is that there's no atmosphere to transport heat by conduction or convection, so the side of the object that's facing the Sun will get hot and the other side, in the shade, will be colder. Of course, conduction by the object itself can transport heat from the hot side to the cold side, evening things out a bit. But if you can thermally isolate one side from the other, the side facing away from the Sun can get really, really cold, as it radiates any excess heat into the 3K "heat sink" of the Universe.

Which is exactly what spacecraft at L2 do. They have a hot side, facing the Sun and Earth, generating power to run the satellite and to communicate data back to Earth. Then they have a cold side, separated from the hot side by a sunshield and facing out into space, which can then get very, very cold, provided the two sides are thermally decoupled. You stick your telescope and instruments on that side and you can get nice and chilly.

(That said, you can only reach about 30–50K or so, which is fine for near-infrared observatories and their instruments, but the instruments used by far-infrared and sub-millimetre observatories need to be much colder, down around absolute zero, in order that their detectors don't blind themselves. That's why Herschel has liquid helium and why it will go blind when it runs out. Being at L2 is only half the story for Herschel.)

The beauty of L2 is that you keep the Sun, the Earth, and the Moon shining permanently on one side of the spacecraft, but never on the other side, if designed well. Spacecraft like Hubble in low-Earth orbit have to contend with half the sky being permanently filled with a big hot object called the Earth, and as you go around in orbit, the combined Earth and Sun illumination is constantly changing: not a good place to get a spacecraft really cold.

Comment: Re:leave it at L2 (Score 4, Informative) 40

by Trapezium Artist (#43094769) Attached to: For ESA's Herschel Mission, the End Is Near

It's not being moved because it will clutter up L2. Indeed, such satellites don't sit exactly at the L2 point, but travel around it in orbits which are hundreds of thousands of kilometres wide. There's effectively no danger of any satellites at L2 hitting future ones.

No, the reason is that L2 isn't a stable location: the gravitational potential there is saddle-shaped. Very crudely, along the line of the orbit around the Sun, the satellite sits at the bottom of a curve. Move forward a bit and the Earth's gravity pulls you back. Fall behind a little bit and the same happens. However, perpendicular to the orbital track, in the plane of the ecliptic (the plane containing the planets), it's more like the top of a gravitational hill. Fall a little away from the Earth and bingo, the Earth is no longer strong enough to pull you back and you fall off, outwards.

But if you fall inwards, towards the Earth, the Earth's gravity gets stronger and pulls you even closer. So much so, that you might end up hitting the Earth.

So that's the reason why Herschel and other satellites there (WMAP in the past, Planck today, Gaia and JWST in the future) are pushed off L2 while the satellites still have propellant and are functional (if not scientifically) into heliocentric orbits, to prevent the possibility of the falling onto the Earth in an uncontrolled manner later.

Space

+ - ESA's Herschel mission: the end is near

Submitted by Trapezium Artist
Trapezium Artist (919330) writes "The European Space Agency's far-infrared space observatory, Herschel, will soon run out of its liquid helium coolant, ending observations after more than three years of highly successful scientific operations. Predictions by ESA engineers are that Herschel will run out of helium later in March, at which point its instruments will warm up, rendering them effectively blind.

Herschel was launched in 2009 along with ESA's Planck satellite to the Sun-Earth L2 point, roughly 1.5 million kilometres from Earth. At that location, the Sun and Earth remain along a more or less constant vector with respect to a spacecraft, meaning that it can cool to very low temperatures behind a sunshield. At such a large distance from Earth, however, there is no way of replenishing the coolant, and Herschel will be pushed off the L2 point to spend its retirement in a normal heliocentric orbit.

With the largest monolithic mirror ever flown in space at 3.5 metres diameter and three powerful scientific instruments, Herschel has made exciting discoveries about the cool Universe, ranging from dusty starburst galaxies at high redshifts to star-forming regions spread throughout the Milky Way and proto-planetary disks of gas and dust swirling around nearby young stars. And with an archive full of data, much of it already public, Herschel is set to produce new results for years to come."

Comment: Re:That "full moon" "after" shot... yeah... no. (Score 3, Insightful) 218

by Trapezium Artist (#43077109) Attached to: Canon Shows the Most Sensitive Camera Sensor In the World
Since you are posting as an AC, I have no idea whether you are one or two people, but under the assumption that the AC who posted this line:

Especially with the sky being blue from the full moon alone.

is the same as the AC who then posted this one:

I obviously didn't object to it being that hue, dumbass. I objected to it being *that* bright. It was a day shot. And obviously so.

then I'd say that's exactly what you did say.

And as for your assumption that I'm an American ... well, you haven't got a clue, mate. You're many thousands of kilometres off. There are other countries in the world where English is the native language, after all. "We have 2013" indeed.

Sometimes I really do wonder whether /. is worth the trouble.

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