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[Music]

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[Applause]

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first I really appreciated the

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presentation by a honeybee very nice

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work we also were one of the groups that

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received a cold tech okay

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we received a a cold tech grant and we

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pursued a very specific path with this

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we have had several cryo bot projects at

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the lab now for the past 10 years in

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fact and have looked at a lot of

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different technologies everything from

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melt probes to closed cycle hot water

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drills and a an alternative that we hit

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on back in 2015 was using tuned

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wavelength lasers that match the

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absorption frequency of solid ice and so

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the idea came up as well if you build a

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small highly efficient probe to get

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through a short distance of ice we're

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not talking about a full depth 20

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kilometer penetrator here this is more

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of a lightweight Lander style mission

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whether it's a Martian polar cap or or

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the Europa Lander and we needed a place

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to to test this concept and so there

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really weren't any true cryo bot

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chambers available in which there was a

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large cylinder of ice kept at Europa

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temperatures and and vacuum and so we

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designed and built this facility we're

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operating it now it is active up and

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running in Austin and when we first got

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it running and had had a slug of ice in

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there sitting at liquid nitrogen

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temperature the first thing that we

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wanted to look at was an old question

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that had been kind of raised in the

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2000s regarding whether a pure a passive

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thermal probe was going to stall out

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there were suggestions from this from

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German researcher DLR and so we built a

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three point two centimeter diameter

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system and tested that out in the ice

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fully expecting that

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was going to stall out and so here's a

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video that hopefully will play and this

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is this is sped up about 300 times just

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so you get the idea here that things are

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not happening fast when you're going to

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early passive thermal however the thing

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that surprised everybody was the fact

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that it went down

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we actually penetrated down to about two

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and a half vehicle lengths before we had

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a stall out at the vacuum seal where the

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rod goes into the chamber but nothing

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appears to be stopping at what we did

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see however it was something very

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similar to a dlr saw which is a trumpet

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shaped radiation ablated zone going in

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where you're wasting a lot of energy

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just trying to get started if you plot

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this up you can see the the curve here

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of depth versus energy in a watt hours

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that we're putting in here there was a

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stall point in the middle where the the

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vacuum seal bound up we had to jiggle it

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to get it to keep going the reason we

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were doing this is because we had a

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edged marker on the rod to let us know

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how far the vehicle had gone down per

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watt hour of descent so once it started

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back up and we were below the hole

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closure rate and and by the way the

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supposition that the hole closes is no

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longer conjecture

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we saw it it's real and after a certain

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point it will bind around anything that

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is holding that probe up so anything

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that goes below a vehicle length or two

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is going to have to be free controlled

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from this point forward the nice thing

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about it was that green line that you

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see there was our thermal modeling that

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was built around the a mod equation for

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a traveling vehicle and so that was kind

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of reassuring to know that we're on

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target with our simulations as well

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looking at cryovac behavior the other

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nice thing is we had designed the

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chamber to be large enough so that the

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boundary conditions would maintain

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Europa ice and we tracked that

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performance over more than a kilowatt

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hour of energy being pumped into the ice

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from that probe and you can see from

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that the middle plot they

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we had some minor changes in vacuum why

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because you're sublimating ice out into

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the atmosphere and the three-state pumps

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have to pull that back down the bottom

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line there the green solid line is the

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temperature of the ice near all the

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chamber it's sitting down there at

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liquid nitrogen temperature not doing

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much the dotted line is a string of

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thermocouples that was immediately

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adjacent to the probe itself so you can

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see that we are radiating energy out

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into the ice and it's picking that up so

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the real test was what is going to

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happen if we change the game here

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instead of using a passive probe we pump

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optical power down to the system on a

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spacecraft this would be a card a board

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level laser for the test that we did

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this was an industrial 10 70 nanometer

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laser which we sent by fiber optic

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thread it's about a 200 micron device

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and there were optics inside a Tyrolean

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tellurium copper head here we had two

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different types that we wanted to look

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at to kind of bracket the a mod equation

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one was where we had the portion of the

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beam about 54% of the power being dumped

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into the sidewalls of the vehicle to

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make sure that the vehicle didn't freeze

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in and then the rest of that was going

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out optically into the ice depositing

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over a distance of about a vehicle and a

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half length ahead of the system allowing

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it to move through that Isis it went

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forward and so here's a there's a video

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of this you see all the the refreeze on

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the outside of the probe is dropping off

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now it's turned up we're pumping about

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340 watts through this right now and

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interestingly not the thing that we

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conjectured for a long time is that it

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is sublimating out and forming a nice

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little crystal cone on the outside of

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the of the hole the one thing that was

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kind of a surprise is that we were

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getting extremely high efficiency out of

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this thing okay honeybee can go back and

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check these numbers if you wish but we

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were getting three watt hours per

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centimeter of descent this was for a

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three point 2 centimeter diameter of

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probe extremely efficient about sixteen

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times better than what we were seeing

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with the the passive probe we tried a

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shorter version the idea here was okay

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what happens if you dump all the energy

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into the Ison so because we're doing

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this optically we can actually determine

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how far ahead of the vehicle we want to

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deposit the the energy and so here's a

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here's a version of this test here again

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this is sped up about thirty times

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you'll notice our little Lego helicopter

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is moving that's because sublimate is

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flashing out of the hole and creating a

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bit of pressure which is sensed not that

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we put it in there to do that but it was

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a side product you'll notice that you

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can still see just the rear rim of the

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the vehicle in there the reason for that

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is because the backend of the vehicle

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froze down to a temperature at allowed

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it to bind in the hole once we got deep

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enough and so the answer is we had

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correctly bracketed the a mod equation

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what needs to be done now is to tune how

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much of the energy you want to pump into

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the sidewall how you distribute that

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through bimetallic and heat pump systems

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and then how much you put into the the

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nose to get the fastest descent for the

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least amount of energy so we just looks

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for some quick comparison here the red

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line is the passive probe the blue line

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is the longer probe in which we're

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putting a little bit of the heat into

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the sidewalls we're looking at about

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three watt hours per centimeter for the

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laser probe versus about 24 watt hours

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for the the passive probe and the speed

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is about actually nine times faster with

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the the laser probe so we're in the

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limits of what we would expect for

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example to be comparison comparing

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ourselves with a mechanical drill at the

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surface also the interesting thing here

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is that while many people have thought

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there would be a starting problem for

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this class of instrument both the laser

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and the passive probe we've not seen

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okay last slide here before conclusions

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this is comparing the laser probe in

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blue long version versus the short

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version again the issue was that

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eventually we had a lock-up in the

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vehicle in the case of the blue one it

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was not the probe itself it was the

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support rod that we were using to

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measure the descent rate so from this

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point forward what we're doing is

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putting a deployable fiber on the back

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of the vehicle a small fibrous board

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carries about five meters worth the

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fiber and the next tests that are

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scheduled now for September will be free

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fall tests with the probe spooling out

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the fiber as it goes down and hopefully

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we'll get probably on the order of two

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and a half meters worth of penetration

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data so just a couple things for the

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takeaway we have an operational chamber

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right now that is effectively the

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surface of Europa we've got good vacuum

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sitting at 77 Kelvin and 2.3 meters of

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ice that you can go through if anybody

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needs that kind of facility let us know

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we'd be happy to collaborate when we

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look at Europa surface conditions we now

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have hard data showing what some of

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these probes do the hot penny probe

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actually works it's just very slow and

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energy inefficient certainly for the

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initial stage the good news is there

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that several different types of probes

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that are possible candidates for getting

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all the way through the ice cap are now

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enabled by that piece of data it'll take

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a little while to get a couple of

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vehicle lanes through but once you do

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the hole is going to close we saw that

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that's real and then you're going to

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build up vapor pressure to allow melt

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probes to actually work in that

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environment we have a test coming up

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it's called prometheus under the sesame

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program in which we're building a micro

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closed cycle hot-water drill to take off

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once it achieves passive mode descent

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and locks into the ice and then this law

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we're looking at onboard fiber spooling

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for the the Archimedes probe the utility

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of that approach is that if you're

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looking at trying to get information

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in the 1 to 10 even 25 meter descent

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range into ice this is an extremely

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energy efficient approach using the

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laser in fact it it's something that

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would work off a battery powered non RTG

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lander and so for us these were

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surprising pieces of data that have now

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come out of the chamber everyone one

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quick question while we're transitioning

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here Oh super cold bill Sam Howell JPL

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my question is right now you have

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relatively narrow diameter probe and I

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wonder if the ratio of the diameter of

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the column ated beam to the diameter of

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the probe matters where you're actually

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dumping that optical energy into if you

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scale it to the size of something that

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can be instrumented you have to scale up

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the size of the collimated beam

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minnesota's you know the energy required

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to get the optical energy into the

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iscope with like r-squared or something

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we've played with both of these the

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original probe that we developed in warm

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ice had a much bigger lens this was more

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about trying to compare it with an

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existing passive probe that we had so we

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had apples to apples comparison and so

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those are those are experimental

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variables that we are looking at this is

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not really a cryo bot okay in the sense

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that you're carrying an intelligent

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system with you and it's a

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self-contained device it requires a

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surface based laser power supply to do

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that however what I didn't have time to

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go into there is that it will carry a

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fiber Raman a probe that does a side

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look into the ice as it goes time this

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is being developed in parallel on this