Search This Blog

Wednesday, 11 July 2012

Iceberg ahead...

How's my blogging? leave some feedback, I get better at this, you get a more interesting read!

Today NASA has announced the discovery of a tiny fifth moon of Pluto [1] - yet to get a proper name - which is between ten to twenty five kilometres across. It was found by none other than the Hubble Space Telescope, while conducting a ramped up survey of the Pluto system, in preparation for the arrival of New Horizons spacecraft [2] there - and there's a bit more to that then just science. 

 Image above: The fifth moon of Pluto, for now nameless, in one of the the Hubble Space Telescope images. That's alot of moons for something not thought worthy of being a planet. I think Pluto might be laughing at us...Image courtesy of NASA.

The space near Pluto is looking fairly crowded these days. When New Horizons was planned, Pluto had one big moon: Charon [3]. When it launched, six years ago, Pluto had one big moon (Charon) and two small ones (Nix and Hydra [4]). Last year a fourth, tiny, moon was found [5]. Now another one. Simulations predict a ring system for Pluto [6], made of dust chipped off of the smaller moons by micrometeorite impacts. In fact the Pluto system is looking more and more complex all the time.

Video above: The launch of New Horizons. It launched on a mission to a world with three moons, and will arrive at a world with at least five, and possibly a ring system. I'm sure it won't mind. I wouldn't. Video courtesy of NASA.

At some point (metaphorically, and in my head), the New Horizons team have looked at each other across the growing map of Plutonian space, and said:

"Um....Are we about to drive this space probe into something?"

The worry is this: The smaller moons don't have enough gravity to pull debris from meteorite impacts back to the surface. So the debris will hang around the space about Pluto itself. Now almost all of this debris is tiny. Unfortunately, at New Horizons speed of fourteen kilometres a second, hitting something tiny  - millimetres across - will have the same effect on the probe as Simon Cowell has on a talentless X-factor contestants ego.

The leading theory for how Pluto got its moons [7] is that, at some point in its past, Pluto got hit by something big. The explosion knocked a whole bunch of debris into space, some of which accreted back together [8] to become the moons. This theory implies there may be even more tiny moons to be found, so the debris problem might be still more intense.

Are the New Horizons team panicking about flying their spacecraft into a half-seen hailstorm?


A presentation [9] (thanks to Phil Stooke at [10] for this) from the latest meeting of the Small Bodies Assessment Group [11], spells out the NASA plan of action for dealing with this. Hubble hasn't just been mapping the area to help hone the science mission - it has been, and will continue to be, searching for hazards to navigation. As well as Hubble, the Keck [12] observatory, Gemini observatory [13], and European Southern Observatory [14] will be scrutinising the area around Pluto.

Better still, New Horizons own imaging system, called the Long Range Reconnaissance Imager [15], will get switched on 27 days before, and again 18 days before, Pluto is reached. It will have long hard look for any possible hazards.

Video above: A NASA sciencecast, with a bit more information on the LORRI instrument. This sensor is now tasked with making sure there's nothing menacing in the probes way as it approaches Pluto and it's moons. Video courtesy of NASA.

So the team will be going in with a good idea of what's ahead. But, if there is a risk of collision, what can they do?
Adding a foot of flak jacket to the crafts nose is, obviously, not an option at this point  Slowing to one quarter impulse speed, like Cap’n Kirk would, isn’t an option either. Sadly, real astronavigation just doesn’t work that way. 

First the team will be taking out an insurance policy: There will be two extra uplinks of science data - at one and two days before reaching Pluto -  so even if the worst happens, the mission isn't a total loss. Second, the team are planning a 'Safe Haven Bail-Out Trajectory'. This is an alternate course through the Pluto system, avoiding the worst danger zones. Tweaking New Horizons onto a different course is do-able up until ten days before they reach Pluto, meaning that the team have years yet, to asses all the possible hazards, and plot the best course for safety and discovery. 

And that's where we're up to: There is yet another new moon of Pluto. There may well be more. There is danger, flying through such a crowded part of the Solar system, but all over the world astronomers and engineers are working to minimise it....

... and, now, all the rest of us have to do is sit back and wait for July 2015, when we'll get our first up close look at the furthest edge of the Solar System......

List of links:

No comments:

Post a Comment