The European Space Agency (ESA) will launch a comet interception mission that does not target any particular comet. Instead, the spacecraft will hang out at the Sun-Earth Lagrange point L2, and move to target an incoming yet undiscovered object that could be found by observatories such as the LSST:
The concept is a three-in-one probe: a mothership and two smaller daughter craft. They will separate near the comet to conduct different but complementary studies. The cost for Esa is expected to be about €150m. As is customary, individual member states will provide the instrumentation and cover that tab.
Interceptor was selected on Wednesday by the agency's Science Programme Committee as part of the new F-Class series - "F" standing for fast. The call for ideas only went out a year ago. There will now be a period of feasibility assessment with industry before the committee reconvenes to formally "adopt" the concept. At that point, the mission becomes the real deal.
The intention is to launch the probe on the same rocket as Esa's Ariel space telescope when it goes up at the end of the next decade. This observatory won't use the full performance of its launch vehicle, and so spare mass and volume is available to do something additional.
And it's Ariel's destination that makes Interceptor a compelling prospect. The telescope is to be positioned at a "gravitational sweetspot" about 1.5 million km from Earth. This is an ideal position from which to study distant stars and their planets - but it also represents a fast-response "parking bay" for any new mission seeking a target of opportunity.
The type of comets being sought by Interceptor tend to give little notice of their impending arrival in the inner Solar System - perhaps only a few months. That's insufficient time to plan, build and launch a spacecraft. You need to be out there already, waiting for the call. This is what Interceptor will do. It will be sitting at the sweetspot, relying on sky surveys to find it a suitable target. When that object is identified, the probe will then set off to meet it.
The Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL), is a space telescope planned for launch in 2028 as the fourth medium-class mission of the European Space Agency's Cosmic Vision programme. The mission is aimed at observing at least 1,000 known exoplanets using the transit method, studying and characterising the planets' chemical composition and thermal structures.
Also at Discover Magazine.
(Score: -1, Troll) by Anonymous Coward on Sunday June 23 2019, @01:10AM
Kudos to ESA for coming up with this explanation, when the reality is that this is a missile equipped satellite being positioned in low earth orbit ready to nuke Mecca next time the moslems try any shit in Europe.
(Score: 2) by Pslytely Psycho on Sunday June 23 2019, @03:58AM (5 children)
IANARSO (I am not a rocket scientist, obviously), but wouldn't this plan take a shitload [*] of Delta-V?
Once you get there and slow down enough to be captured in the La-Grange point, then enough to escape it, plus match orbits......Wouldn't it be simpler and cheaper to just place it in a high orbit if you're going to 'wait for an unknown comet in an unknown orbit?'
To me it seems the best would be just launch toward your intended target, even hanging out in a high orbit might require quite a bit more DV to intercept than a direct mission.
Scott Manley, fire up KSP and tell us!!
Seriously though, someone with the math skills I lack, how is this a good idea?
[*] No, I can't give you a quantitative value of a shitload. Thanks for asking.....(:
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(Score: 4, Informative) by takyon on Sunday June 23 2019, @04:53AM (1 child)
It will do a pretty fast flyby, so it doesn't necessarily have to match orbit. They just need to be in the same place at the same time.
Targets could come relatively close to where it is. There are backup targets:
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(Score: 2) by Pslytely Psycho on Sunday June 23 2019, @06:11AM
Ahh, fast flyby. I think I was confused by the daughter craft, which I apparently thought were landers, although the summery said nothing of the sort.
Read it too quickly on my lunch break, missed some critical information and made assumptions.
On a slower re-read I see now what they are aiming for.
Jumped the gun with my comment.
Thanks Takyon.
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(Score: 3, Informative) by Immerman on Sunday June 23 2019, @03:06PM (2 children)
There's not really a whole lot of slowing down to be done - impart *exactly* escape velocity to something and, in hypothetical infinite flat space, it would move away, slowly losing speed as it was pulled back by Earth's gravity until it came to a complete stop at infinite distance, just as the pull of Earth's gravity falls to zero.
In more practical real-world terms, think of it like rolling a ball out of a skate-park half-pipe or bowl: roll it fast and it will fly up the curved side and go rolling off into the distance, but roll it just right, and it will just barely make it out of the bowl and stop almost immediately.
Of course, space doesn't actually have any gravitational "flat spots" for things to come to rest at, but Lagrange points are the next best thing: points where the gravitational influences of the Earth and Sun (in this case) perfectly balance out with orbital dynamics. If you're not in a hurry you can lob something out of Earth's gravity well with just the right speed that it *almost* gets stuck there - just a tiny bit more thrust to make up for the lack of friction slowing you down and you're good.
That critical balance of influences also makes them useful for course adjustments: skim past a Lagrange point, and very tiny course adjustments on your way in can result in very large differences in the path you take on the way out. The gravitational "mountains" form a dramatic orbital "saddleback" to navigate. - Here's a great "topographic map" of the orbital energy landscape, where the white lines indicate constant orbital potential energy. You can see that L1 and L2 are actually the orbital "low points" for escaping Earth's influence. https://en.wikipedia.org/wiki/Lagrangian_point#/media/File:Lagrange_points2.svg [wikipedia.org]
I imagine there's a similar benefit to using Lagrange points as place to launch from: it takes very little delta-V to get moving, and depending on which direction you launch in you can end up on wildly different trajectories depending on exactly how you ride which slope of the gravitational mountain. From L2 you could move slowly outward beyond Earth's orbit, or slingshot around Earth in any direction, even well outside the plane of the ecliptic, having already "stored up" the orbital orbital potential to mostly escape Earth's gravity and even get a bit further from the sun than Earth is. And of course, add in the moon and it's own Lagrange points, and you have all sorts of additional really interesting slingshot maneuvers you could engage in, if you can wait for the moon to get into the right position.
(Score: 2) by Pslytely Psycho on Monday June 24 2019, @03:42AM (1 child)
Thank you for the comprehensive explanation.
I know a little of this, and now I know a bit more.
The effort is much appreciated.
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(Score: 2) by Immerman on Tuesday June 25 2019, @12:59AM
You are most welcome. I'm always glad to share a bit of knowledge with someone who appreciates it.