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[Music]

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[Applause]

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I'm gonna talk about our just a very new

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project called Europa STI where we're

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investigating tethered and free space

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communication techniques for sending

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signals through the ice for a nice ocean

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probe at Europa um so there was a study

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that was done about our Europe a tunnel

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bot mission concept by NASA folks and

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some other folks at Hopkins and Illinois

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and Idaho National Laboratory and the

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technical objective for this type of

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mission is to achieve ice penetration

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into the ocean on an ocean ice ocean

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world particularly we're looking at

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Europa and we needed to do this in about

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three years

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reach a depth we considered 20

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kilometers to be our achievable depth

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there in about three years and/or if we

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determined that there was a water pocket

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within the ice shell at about a four

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kilometer say depth that we could maybe

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determine had connection to the ocean so

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it's being fed by the ocean that might

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also be an objective a place that we

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could achieve our objectives which for

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science are to look for signs of life

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and so the science objectives closely

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followed those of the Europa SDT report

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where we would search for evidence of

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life at Europa we would assess the

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habitability of Europa via these in situ

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techniques which are uniquely available

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for this concept for the tunnel bot and

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then characterize those properties also

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that were the environmental

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characteristics that would either

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support or maybe not so support our

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detection of biosignatures

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so here is the structure of Europa and

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as you can see it's a very interesting

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world we have as time mentioned that's

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basically three layers that you wrote

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but we have the theater thick

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potentially thick ice layer at the top

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which is a brittle upper layer in a more

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ductile lower layer and then the ocean

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beneath and we don't really fully

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understand yet on what this structure is

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like how thick is that brittle layer

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compared to the ductile layer how thick

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is the overall ice shell are there water

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pockets within the ice how briny are

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some of these layers and these are all

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challenges then for a potential mission

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this potential architecture of getting

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through the ice down to the ocean

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sampling on our way trying to understand

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this environment the most thermally and

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mechanically as we design this type of

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mission to achieve our goals so that our

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project is I'm really focused on that

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portion behind the tunnel bot so how do

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we transfer that information that very

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important information from this

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subsurface probe to the landed portion

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that then sends our fantastic science

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data back to earth and so a couple

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strategies have been thought about where

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we're considering a communication tether

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and then also these repeaters on where

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you may be using a free three space type

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of communication to where because of

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these challenges within a rope as ice

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shell the tether may not be the most

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robust to all of these challenges and so

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if you had a repeater that could

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potentially jump across that break in

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your tether you could continue to send

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your information up to the land landed

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portion and so some of these challenges

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on we see evidence of this all over the

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surface you wrote but many faults

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evidence of you know subsumption

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activity potentially where you have

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convergent boundaries on Pascha possibly

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pushing material beneath the surface and

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then divergent boundaries strike-slip

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type of boundaries faults happening

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there so can a tether you know that is

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thin enough right like we also have to

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consider mass for these missions and is

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it thin enough to spool out for a whole

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20 kilometres while still being somewhat

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robust to the potential activity within

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Europa's ice shell and you know if so or

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if not under what conditions are these

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viable options if the tethers not you

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know doable in all the environments of

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europe as ice shell what other options

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you have

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could you use free space communications

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to provide alternative techniques and so

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we're exploring this with our our

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project we have folks from the Woods

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Hole Oceanographic Institute have been

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doing sub-option within the ocean sub

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ice subsea ice type of exploration where

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they have been using tethers for their

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submersibles for some years so we're

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starting out with these types of tethers

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that have been proven in these

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environments which allow on the

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submersibles to move around sort of

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independent of

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the ship is located it can move around

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and do exploration of the seafloor and

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find those really interesting

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hydrothermal vents that we know are

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happening there and so we're starting

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with those tethers on we have

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particularly picked out four types of

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tethers here that we will arm explore

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for their robustness particularly to

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shear motion as we expect there to be

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that to be happening that I'm at the

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faults and we're gonna explore some

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tethers that are more armored for to be

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potentially robust and doing the

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comparison then for how heavy they are

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and how you know much that would require

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four masts for a spaceflight and we're

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also looking at thinner copper ribbons

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potentially they're low-temperature

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ductility may prolong their survival in

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these environments and they're also they

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also have the potential that we could

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maybe heat them and that would have

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relieved some of the stress that may be

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acting upon them in the ice shell and so

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how are we going to do this well first

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we we want to think a lot about the ice

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that they're going to be inside of and

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and and really explore those parameters

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I'm thinking about grain size porosity

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and also potential impurities within the

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ice both composition different

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compositions as well as brines you know

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different amounts of brines and these

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compositions and incorporate those into

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the ice that we built so that we can

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really get a good understanding of how

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the ice mechanics changes with those

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changes in composition thinking about

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where the ice grain boundaries and those

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those impurities happen within between

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the grain boundaries and how that

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affects just the loads that are placed

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on the ice and then subsequently the

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tether you know how that affects the the

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transfer of the loads to the tether and

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how it just all behaves together and of

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course we picked out these certain

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impurities and and things from

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observations that have been done of

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Europa finding both on hydro of sulfuric

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acid water Frost and hydrated salts

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potentially from the ice the ocean and

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rock interactions that's happening um so

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here's the really cool testing apparatus

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pun intended that they had

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at a lamont-doherty Earth Observatory so

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we're again pairing with Woods Hole

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Oceanographic Institute with their

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tethers we're freezing their tethers

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into these ice blocks and then this this

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apparatus is loading apparatus can place

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the loads the shearing loads that we

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want to explore on our tethers and this

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is on the testing you know to our test

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setup is based on the concrete so they

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do the same kind of tests for concrete

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where they have the rebars going through

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the concrete and they do these shearing

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tests to understand their their

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mechanical strengths so we're going to

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doing very similar tests I'm exploring

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temperatures and then the velocities of

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these like potential strike-slip like

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fault shearing armloads and then as we

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move forward past this so again this is

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just some some of the work we've only

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done very initially past this we want to

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also then consider these other

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strategies for communications just in

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the case of where the tethers may not be

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the most robust so these additional

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strategies will include radio frequency

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and other free space communication

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techniques and we're interested in these

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also to understand how they behave and

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the different regimes within the thermal

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mechanical layering and Europa would

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they potentially be most applicable when

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certain regimes in the ice shell where's

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the tether maybe most applicable and

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other regimes trying to really

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understand that and we will further

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explore this through modeling efforts

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just of the Europa's ice shell itself

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we're going to take into account on

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fault movements do fracture mechanics

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modeling consider tidal forcing and

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thermal mechanical characteristics of

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the ice shell blitz viscosities and then

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also one interesting thing that we've

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been thinking about is as so our cry

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about you know melts its way this is a

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concept that we have is melting this way

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so your water is refreezing behind you

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sort of in this column you know is that

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refreezing ice going to be similar to

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the surrounding ice that you've just

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passed through or is it going to

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refreeze in a different way changing

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that compositional layering potentially

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and how would that then affect your

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tether that's within that column of ice

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behind you that's been refrozen as well

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as the RF or you know free space

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communication repeaters that have been

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frozen and behind you as well so we're

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going to be doing further modeling to

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understand that and that's going

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done by folks at John Hopkins Applied

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Physics lab Southwest Research Institute

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and we have University of Southern Maine

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and we're going to be continuing just to

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explore those and try to understand

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where in Europa's ice shell can we you

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know have this strategy of communication

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like where best is the tether gonna be

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from you know doing the best for us with

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a higher probably data rate transfer but

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then when we need a repeater you know

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can it also be robust in certain regimes

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um that we can depend on those so in

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summary our project the Europa SDI

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project is going to characterize the

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deployment capability and mechanical

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strength of these multiple tethers in

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the laboratory sent us situation where

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we are simulating Europa light

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conditions will do a lot of modeling to

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understand the thermal mechanical

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environmental hazards that are possible

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within Europe as ice shell and on that

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kappa tote could be potential risks to

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our communication techniques and then

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we'll evaluate the system performance of

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these free space communication

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strategies to further our understanding

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of where we want to employ certain

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techniques where we want to have you

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know a reliability on these as we as we

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want to go down and explore your roses

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your robust ocean so I'm just like to

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thank everyone for their time and thanks

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to all my colleagues um as we push

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forward

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onward to your row position so thank you

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so we have time for a couple questions

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it just occurred to me that there's an

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experiment in Antarctica called ice cube

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they have 50 to 2.8 kilometer setups

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have you talked to them and gotten

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lessons learned from so um my colleague

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Ralph Lorenz he's kind of more the

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expert on history cuz but he definitely

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we've we've definitely are considering

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that and what they've done to build upon

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their their knowledge that they gained

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there yes thank you I said a question

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about how the ice changes like either

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the radio frequency or the acoustics for

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the repeater mechanism like if you have

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to consider the geometry value sentence

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how

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change your signal that kind of thing do

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you mean like one if a fault happens and

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you have a fault happens or just from

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refreezing or whatever other mechanical

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changes so I think this is these are the

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kinds of things that we'll be exploring

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like we we understand that like with

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with depth you know wrote Europa's ice

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shell is gonna change with fracture

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current you know fracture motion

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happening things are gonna and this is

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exactly what we want to explore to try

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to understand how robust are they to

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these this type of activity how that

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would it change our signal oh and the

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other thing I didn't mention is we

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really want to constrain the attenuation

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of the signal as it moves apart because

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you need to understand like how often

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you need to drop these these repeaters

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off behind you you know how far can your

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signal transfer across if you have a