ESA Releases Lutetia Flyby Images

The European Space Agency has released images from yesterday's close approach of asteroid 21 Lutetia by the Rosetta probe. At its closest, the probe was a mere 3,162 km from the asteroid, passing at 15 km/s and snapping photos sharp enough to make out features as small as 60 meters. "Rosetta operated a full suite of sensors at the encounter, including remote sensing and in-situ measurements. Some of the payload of its Philae lander were also switched on. Together they looked for evidence of a highly tenuous atmosphere, magnetic effects, and studied the surface composition as well as the asteroid’s density. ... The flyby marks the attainment of one of Rosetta's main scientific objectives. The spacecraft will now continue to a 2014 rendezvous with its primary target, comet Churyumov-Gerasimenko. It will then accompany the comet for months, from near the orbit of Jupiter down to its closest approach to the Sun. In November 2014, Rosetta will release Philae to land on the comet nucleus." There is also a replay of the media event webcast on the ESA's website.

Comments

Fake!!!

[Anonymous Coward]

When NASA faked the Moon landings they needed an entire film studio. Here all the ESA needed was a potato.

Re:Great.

[ColdWetDog]

It's a rock.

What did you expect? A moon?

Question for the rocket scientist(s)...

[wisebabo]

As an armchair astronomer, I'm as always, extremely impressed by stuff like this. I know the level of precision to pull this off is nothing more than astounding, involving very complex math, deep knowledge of astrophysics and out-of-this-world engineering.

Still I was wondering; why didn't they aim the flyby a little closer, say 100km and not 3500? I believe they had an earlier flyby which did just that at another asteroid so I assume they had the requisite level of precision. I know this might have required them to be off "course" by a few thousand kilometers but in a journey with hundreds of millions to go it would seem to be a detour requiring very little delta-v (and thus very little propellant). Wouldn't the instruments be able to get much better data from a much closer object? Or maybe the position of this asteroid wasn't precisely known, not only giving a (small) risk of collision but making observation via pre-programmed instruments with narrow fields of view impossible. If anyone has a clue, pray tell!

Re:Question for the rocket scientist(s)...

[Chris Tucker]

Probably due to the mechanics of the 2014 encounter with the comet.

For every ounce of fuel needed to change trajectory, an ounce of scientific optics and electronics has to be sacrificed.

A lot of good science can be done with a flyby of this nature, as well as allowing for the calibration of some instruments needed for the comet encounter.

Every mission of this nature is one of compromises.

How close can we get to the asteroid?

How much instrument weight can be devoted to asteroid only observations?

Can we use one instrument to serve several mission objectives at the asteroid and the comet, and can this be done without compromising the amount and granularity of the data returned?

And of course: How much money do we have to spend on the vehicle itself and the scientific packages installed in the vehicle?

Can we sacrifice something in order to have a bigger and better sensor package?

If so, what gets sacrificed?

All things considered, this looks like a very good return of data and science from the asteroid flyby.

Re:Question for the rocket scientist(s)...

[Tablizer]

why didn't they aim the flyby a little closer, say 100km and not 3500?

For one, at that close the instruments and/or craft must be coordinated to move in a way that keeps the target area in view of cameras and instruments. Features would pass by at a rather quick pace. Handling such adds to the complexity of the craft and mission. It's designed to study comets, not asteroids, and one must keep a distance from a comet because of the dust. (It has a detachable comet lander dedicated to such with dust protection engineering.)

Second, they didn't know the shape of the asteroid very well until they actually got there. If you plan a close flyby and part of the asteroid juts out, El Klunnnng!

Third, some asteroids have their own little moons. The closer you get, the more likely you are to "eat" one.
     

Re:Question for the rocket scientist(s)...

[Tablizer]

For one, at that close the instruments and/or craft must be coordinated to move in a way that keeps the target area in view of cameras and instruments. Features would pass by at a rather quick pace. Handling such adds to the complexity of the craft and mission.

This is similar to a key issue with the New Horizons (NH) Pluto/Kuiper-Belt mission. It's moving so fast that it doesn't have a long time at targets. The Voyager crafts had separate, semi-dedicated platforms for each instrument or instrument group. Thus, each could be aimed to work at its optimum pace.

However, that was deemed too expensive for NH, so instead they designed the *whole craft* to move via gyros and pressurized gas to aim each instrument. Many instruments thus have to take turns. It's not the ideal, but it cut costs. If you get too close, then there's no time for each instrument to get a look. You have to pick and choose. Maybe one instrument may get a good look, but the returns are diminishing.

For example, it may be cheaper to have a bigger telescopic lens rather than an independent camera platform and study the target from a medium distance.

Re:Question for the rocket scientist(s)...

[BlindRobin]

Obviously the persons in charge of the mission didn't evaluate the risk using the same criteria as you and deemed the risk to be greater than the benefit.