Glad to see that you jumped in on this: good description.
Because the comet is so small, the gravity changes a lot with "altitude" from the surface. For a 2-km diameter sphere, say, then the difference in gravity between an altitude of 2-km and 6-km (i.e. between 4 and 8-km from the centre of the sphere) is a factor of 4. On the Earth, it barely changes at all between altitudes of 2 and 4-km, because this is a tiny change relative to the 6400-km radius of the Earth.
So, yes, at 100-km and 50-km, we'll be flying these hyperbolic arcs (slightly bent by the very weak gravity), using thrusters to "turn the corner" at the end of each leg. But at 30-km, we'll be on closed more-or-less circular orbits: I'm pretty sure that it is natural orbit though (and thus fairly long in duration), but not powered.
I do work on the project, albeit not on the flight dynamics side. One of our experts on this, Frank Budnik, did give a talk on this in the science session I moderated yesterday afternoon, starting at 11:28 into the recording of the live stream here:
That said, there are some colleagues I tried to have volunteer to go
Our live webcast will be at www.esa.int starting at 10:00 CEST / 08:00 UT. Should be some cool new pictures of the comet to see.
(Disclaimer: I'll be one of the speakers
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.
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
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
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.
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.
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.
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
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.
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.
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.
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).