 Yeah, okay everybody. Hello and welcome. Are we are you broadcasting? Yes, we're broadcasting. Okay, great. All right, so thanks everybody for coming to this webinar on evolving the Geodetic infrastructure to meet scientific needs Presented by the National Academy of Sciences Engineering and Medicines Committee on seismology and geodynamics. I'm so glad you're able to join us My name is Matt Pritchard. I'm a professor of geophysics at Cornell University and a member of the committee on seismology and geodynamics or COSG. I will be serving as your moderator today, and I'd like to start by telling you just a little bit about COSG and the report So COSG is a committee of volunteer experts in the variety of geophysical disciplines and Serves as the focal point for community discussion on issues related to the structure dynamics and evolution of the earth COSG also provides a forum to bring federal agencies together on these different topics This particular report evolving the geodetic infrastructure to meet new scientific needs was sponsored by NASA and overseen by the COSG The report summarizes progress in maintaining and improving the geodetic infrastructure And identifies improvements to meet the new science needs that were laid out in the 2018 report thriving on our changing planet A decadal strategy for earth observation from space Focusing on sea level change the terrestrial water cycle geological hazards weather and climate and ecosystems The study examines the specific aspects of the geodetic infrastructure That need to be maintained or improved to help answer the science questions that were in the other report Our presenter today is dr. David sandwell chair of the report committee Dr. Sandwell is professor of geophysics at the Scripps institution of oceanography His research interests focus on mapping large scale topographic features beneath the oceans using data collected by remote sensing instruments On satellites orbiting the earth and sonars on research vessels He co-chaired the 2017 decadal survey panel on earth surface and interior and was a member of the committee on natural national requirements for precise geodetic infrastructure Dr. Sandwell is a fellow of the american academy of arts and sciences the american geophysical union and the geological society of america And is also a member of the national academy of sciences He earned his phd in geophysics and space physics from the university of california, los angeles Dr. Sandwell providing a brief summary of the report for the next 35 minutes after that We will shift to a question and answer period Participants in the webinar can ask questions at any time by using the q&a box To ask a question hover your mouse near the bottom of your screen where you should see a button that says q&a Should you have any technical issues? Please use the q&a box to ask about your issue I will try to get through as many questions as I can in the time allotted The webinar will promptly end on the hour at 2 o'clock eastern time As a note the webinar is being recorded so that it can be watched later by interested colleagues So thank you all for this listening at this introduction and I'd now like to hand over to dr. Sandwell for the presentation I'm going to share my screen. Thank you map for the introduction I'm sharing my screen now. I hope Let's see Can you see the screen now? Yes. Yes, I can see it. Great. Thank you Thanks again, matt and thank you all for joining this webinar. I've never done one of these before but it's great We it saves us all a lot of travel And fossil fuels so i'm going to talk about the evolving geodetic infrastructure to meet new scientific needs and You see a list of the authors of this report It was a mix of disciplined scientists and experts on the terrestrial reference frame that i'll talk about in a minute But also we had 12 reviewers that really put in a lot of positive feedback about the report and that really helped us polish it off in the end oops forward Ah Next Okay So what is the geodetic infrastructure and this is what we'll be talking about it really consists of four systems You see the slide here. There's the very long baseline interferometry These are large radio telescopes that distributed around the planet and they're mainly used to Measure the orientation of the earth in the celestial reference frame The second main component here is satellite laser ranging again. These are distributed around the planet And these are mainly used for satellite tracking but also for positioning the center of mass of the earth To take that reference frame at those few points and distribute it around the planet there's a system of gns s or gps stations fixed stations part of the igs and And um, there's about 500 of these and then there's a system called doris That's mainly used for real-time tracking of satellite altimetry You see two different color dots here. The red dots are run by nasa and other us institutions Or hosted by them and the blue dots are the international component. And so you can see this is really an international Reference a geodetic infrastructure. It wouldn't work without all the all these countries involved Hmm Okay, now this report follows from a report in 2010 an nrc report shared by bernard minster on precise geodetic infrastructure And that was really an excellent report and part of our report is to see what has been done in the last 10 years See if we've achieved the recommendations of that earlier report Um, as matt said the other uh document that we're following on to is this thriving on our changing planet A decade old strategy for earth observations from space And this involved all types of science biology oceanography everything to um The objective here was to look at at the existing satellite systems. This would call called the uh program of record And and see whether or not those existing systems will meet all the scientific needs of our communities And if not, there were some recommendations on how to What what new satellite systems would needed to be uh launched to achieve those science needs over the next decade? um Part of the reason we're here is that document Uh was really focused on space based observations um, and it wasn't focused so much on other things that you would need uh other infrastructure ground-based that You would need to achieve these science objectives. And so, um, here you see one of the recommendations from the decade old report But again, I highlight this is space based observations And so there's nothing about or there's little about the terrestrial reference frame the geodetic infrastructure So that was the second reason why we're we're doing this report was to um highlight the need for this foundational part of of this whole space program this geodetic infrastructure Now in that Decadal report, I was co-chair of the earth surface in an interior a chapter and This was focused on things like earthquakes and volcanoes and natural hazards and um Water cycle and other things like that and and we came up with a list of measurements that That we needed to achieve our science over the next decade And I've listed them actually in the order we found them most important The terrestrial reference frame was number one And then we wanted to be able to measure crustal deformation using gps and insar um bare earth topography came out as one of the key measurements Doing that from space is a challenge but aircraft Capabilities available right now hyperspectral imaging Was another important component and also time variable gravity has really been a key measurement for For a lot of our science and also for cryosphere and ocean and so on But you see the terrestrial reference frame is at the top, but it couldn't be included in the decade old survey So that's where we're going right now to try to highlight the need for the geodetic infrastructure that supports our terrestrial reference frame um Just to review here here are the the recommended designated NASA priorities for the next decade and they include Three of the things that we need for earth surface and interior This is mass change From a grace type mission grace follow-on type mission right there is a grace follow-on this would be a Further follow-ons of the grace follow-on And then a hyperspectral mission. It's called surface biology and geology But it's really code for hyperspectral imaging at high resolution lots of channels And then surface deformation change is really something that is needed by a lot of communities So our report had the following tasks First we needed to summarize the progress and maintaining and improving the geodetic infrastructure as detailed in that 2010 report um, and we had a meeting in washington dc in october 2018 where we brought in all the different uh stakeholders in this infrastructure and they reported on on the uh On what they achieved in a decade and what needs to be done and so on the second task was to identify those questions in the decadal survey that depend on the geodetic infrastructure and describe the connections between the the science questions and The geodetic infrastructure and that's basically the heart of this report um Making that connection And then the third thing is to discuss the elements of these science questions that drive future requirements for the terrestrial reference frame geodetic infrastructure What will we need in the next decade? How can we improve things? and then uh For us identify priority improvements. I guess I already said that to the infrastructure Okay, so This is the hard part Why do we need here? Here's a diagram at the bottom is this foundational geodetic infrastructure consisting of vlbi and slr and gnss experts software archives This is the part we're we're focusing on but What we're trying to achieve is at the very top here that he's enabled science applications things like sea level level water cycle geological hazards weather climate ecosystems geodynamics and so on. There's a lot of different science that can be that rely on this infrastructure But the connection between those two There's a lot of steps here And I'm going to in a minute. I'll try to take you through one step where it's obvious how the two are connected, but From the geodetic infrastructure that's used to create something called the terrestrial reference frame that I'll talk about in a minute It's basically just a seven numbers a reference frame and then from that you get Geodetic products like orbits earth orientation gravity field and so on and then That's used to support earth orbiting missions and this is really where that a connection to the decadal missions comes in and then Finally that's used to measure geophysical observables and then the connection to the science So how does this all work? Well Here is one place where we can make a direct connection between satellite laser ranging that's used for orbit Determination which is essential for Measuring sea level change. So this is just one of those connections But there's lots of connections between the infrastructure and the science Okay, a little bit about remote sensing um because really this infrastructure is really only needed for Active remote sensing. What do I mean by that? There are there are two types of Satellite sensors that you can use to look at the earth passive remote sensing would be something like a camera or a thermal infrared Sensor or a microwave radiometer Um, those are passive sensors and then And you can see this diagram here has the transmission. This is how how uh Non opaque the atmosphere is in different bands. We've got optical over here and microwave over here and then And on the top are the active sensors. These are the ones that don't just measure the intensity of the radiation They also measure the travel time and this is where you need precise orbits So things like iSat2 altimeters like SWAT synthetic aperture to radars like NYSAR And then even the grace mission and GNSS radio occultation will talk about all these sensors So it's really just the active sensors that are Are need need this infrastructure The really precise infrastructure Okay, why is that let's take an example here a very simple example of a satellite altimeter It's orbiting the earth And it's measuring the two-way travel time between the radar and the ocean surface To an accuracy of a centimeter or so But to get the height of the ocean surface above Something like the reference ellipsoid or the center of mass You need to know the height of the satellite independently To that same accuracy of a few centimeters to be able to difference those and get the height So that's that direct connection Um, okay. What is the terrestrial reference frame? Well, um, I think I already said this but it's basically Just seven numbers. It's the origin of the earth The orientation of the earth in space and then a scale factor Now one can't actually put a monument at the center of the earth Um, you'd like to be you can't so really this reference frame is defined by All those positions of the geodetic infrastructure, you know, several hundred GNSS and VLBI and SLR and so on now if if any one of those moves due to something like an earthquake down below here That will affect the reference frame and so We need to be able to accommodate motions of Of the geodetic infrastructure as a function of time things like earthquakes. There's a a significant signal associated with snow and water loading an annual cycle And then over larger timescales the position of the center of mass of The earth can drift away From where it is today by up to about 50 millimeters Due to the melting of the ice sheets is a prediction for 100 years But we need to accommodate and understand and measure these motions of of the earth So how do we do that? Well, we have we have these three main systems I'm not going to talk much about Doris, but we have VLBI SLR and GPS And we really need all three of these The VLBI is used to orient the earth with respect to the celestial reference frame It's looking at quasars out in deep space, which are assumed to be fixed Satellite laser ranging is good at measuring the scale Of the earth and also the geocenter because all these satellites orbit the geocenter And then GPS is is used for both of these things but also more for connecting the VLBI SLR reference frame to All our GPS receivers on ships and boats and planes and in your pocket on your cell phone Of course, you don't need that accuracy, but This backbone GPS system it makes the connection here Okay, again back to How are we going to connect? What why do we care about Things like motion of the center of mass of the earth? Well, here's here's that diagram of satellite altimetry over here We're measuring the height of the ocean surface using the two measurements But what happens if and on the right hand side you see a plot of The z component of the center of mass of the earth as a function of time This is actual motion of the center of the mass of the earth with respect to the center figure of the earth And so what would happen if we didn't know about this if we got this wrong? The center of mass would be moving up and down the z axis five millimeters, which doesn't seem like a lot but can be important and But the tracking stations aren't moving. They're on the center of figure and so you'll end up with And the orbit of the earth of course is orbiting around the center of mass So you'll end up with the sea surface look like it's going up and down in a north south in a z direction With an amplitude of about five plus or minus five millimeters So we don't want this because It's not a real signal. This this is not a real oceanographic signal We need to measure these things okay so A little bit more about the connection. This slide has lots of numbers, but um, just to make the point That we have all these decadal missions like jason 3 grace follow on ice set to cosmic to swat nice are These all are active type remote sensors that have to have precise tracking systems They mainly rely on gnss But if what happens if the gnss fails on the satellite you need to have this backup slr system And it's also used for checking the gnss and getting more accurate orbits um The accuracies that we need are If you look at this row here, I don't know if you could see my mouse, but the accuracies are 10 millimeters 20 less than 20 millimeters and so on we're down in the 10 20 30 millimeter range For accuracies Precisions are even more stringent on some of these satellites Jason 3 to measure sea level. We need about 0.1 millimeter a year and so on. So this is really what's driving our Geodetic infrastructure achieving these orbit accuracies for decades and even centuries So task one, um, this was to assess what what's improved or what's lacking since 2010 and We are Really, there's been a lot of progress, but i'm just going to talk about four areas of concern um NASA is still building out their next generation of vlbi and slr systems They aren't complete yet and there needs to be some testing and and and publish studies on their accuracy It's happening, but it needs needs to continue Um There aren't as many Fundamental slr stations, especially in the southern hemisphere to help control that z motion of the center of mass One thing we noted is that there's really No national GNSS observing system That could serve both as a us realization and connection to the itrf. There are Really good gnss stations in the u.s. But um They they're funded they don't have permanent funding their nsf funded that kind of thing So there's a threat there and then number four here is this aging workforce We're all getting older and some of the geodetic experts aren't being retrained and replaced so we need to work on that So tasks two and three, um some of the science questions that depend on Geotasy and during that workshop in february we highlighted four areas, um sea level change terrestrial water cycle geological hazards weather and climate and ecosystems And during that workshop and also during the writing of the report we we had discipline scientists working with geodesys to make that connection between the science and The measurements needed from the geodetic infrastructure Okay, i'm going to start with terrestrial water cycle. Um I think it's a good starting point a lot of us know about sea level change, but this is something that's a little bit newer and um and really does require very accurate geodetic infrastructure So the two questions were how do anthropogenic changes in climate land use water use storage interact and modify the water and energy cycles And how does what how does the water cycle interact with other earth system processes? And then the third one i sort of joke laugh at this how how much water is traveling deep underground well deep underground is only you know less than a few kilometers, but uh it's deep for a surface hydrologist So really what's come out in the last decade about The water cycle on the continents is that um When when you have a lot of water piling up on the surface of the earth There's an elastic downward deformation that you can see in the in the gnss data. I'll show an example And that's only if the earth is is elastic in that point if if you have um water Being drained out of aquifers It it looks like a sponge and the in the surface of the earth will go down So we have these two different signals and we can see them both in the gnss and insar Uh data, but it's mainly in the vertical components Um, and we need to measure these vertical components really quite accurately to to see these uh effects so here's a plot of um Vertical land displacement observed by gps in the western north united states from march through 2014 this was a time of drought And if you select the stations that are on The elastic part the hard rock you see that over this period of time. They've rebounded about uh 15 millimeters due to the A loss of water on the surface of the earth but also in the upper most crust Um, and so this is a completely new way of measuring Water availability in the west And i'll show you in a minute. It it actually provides a very different answer than you get from if you just have Say water measurements from snow loading and and other Surface measurements so the top curve here is what you would get from hydrology Uh snow dust model, but the gps is showing um a very different uh amount of water loss especially during 2010 to 2015 um And and the main point here is that the high hydrology models don't include that part In the crust and so they underestimate the water loss by A factor of eight in this case. Um, so it's a new way of looking at at water You can do this with grace also, but uh the spatial resolution is a little better with gps. Actually need both Okay aquifer system compaction, um this this this is creates land subsidence when you do a lot of pumping of of groundwater the land subsides and this is A problem or an issue over many places in the us not just california, but it's also on the east coast Louisiana, texas and so on wherever there's an aquifer that's being Drained of water you get subsidence In california. It's been really uh a big problem Um, especially during the drought. There this is a map of central california central valley and um, you see the subsidence In between that period of time and I think they have the time period wrong here Anyways, this is from sentinel date. I think and um You see there's been, you know, for 41 centimeters 50 centimeters or more of subsidence in various places. Um This isn't anything new. It's been going on since The 1920s, but it's something that we have to be worried about. There's a lot of infrastructure crossing uh these areas the the canals Lose their conveyance capacity because they aren't going downhill anymore and so on so It's something we need to monitor Sometimes the you can't recharge these systems if they if they compact too much I'll say for the terrestrial water cycle Here's the base the bottom line here. We need in all these cases We need to maintain geodetic infrastructure and in some cases we need to enhance The geodetic infrastructure and if you look at this chapter, you'll see We need maintenance. We need satellite orbits for gnss and and insar but um, one of the highlights here was that um To monitor a lot of this uh subsidence. We need to have Maybe better spacing of the gnss receivers. Um, especially in watershed areas So that was one of the takeaway messages for the enhancements water cycle Okay, sea level change. I'm going to have to move to get through all these topics, but um Sea level is really an important issue that we all hear about and there's really two aspects to this sea level change the sea level is going up globally with respect to the center of the earth globally and regionally but also that's absolute sea level but Also, people really care about relative sea level. How is it changing along the coastline? Will my house get flooded in the next big high tide storm and so on and so, um Those are the two things we mainly talked about in the report global sea level rise and coastal Relative sea level rise. So I'll go through those quickly I think you've all seen these kind of curves before this is on the left hand side is sea level global average sea level from satellite altimetry From the early 90s when the first altimeters were launched till today um, and you see this is in Centimeters the average rate here is about three millimeters a year. It might be closer to four right now People are worried about an acceleration. So you need to measure A fraction of a millimeter a year per decade to to see that signal And it's composed of two parts one is the ice mass loss From the ice sheets water going into the ocean and then there's um thermal expansion of the ocean But those two contribute to the global sea level rise Now people we're also interested in what's happening regionally and that's on the right hand side here There's a plot of regional sea level rise from 1992 to 2018 And you can see that even Even sea level doesn't have it's not a uniform number. There's places where it's mostly it's going up But there's some places where it's actually going down a little bit But we need to measure sea level to about half a millimeter a year over a decade and regional sea level rise to 1.5 to 2.5 millimeters a year and over a decade Okay, ice sheet and glacier mass changes We need to monitor the ice sheets. This is done with a variety of tools Radar altimetry to measure the volume change of the ice sheet, but to measure the mass change, you need things like grace But grace needs to be corrected for glacial isostatic rebound and that depends on models that aren't always that well constrained And so we need gnss receivers to monitor the rebound And and and then also you can measure the outflow of ice Ice streams are using things like interferometry from nice are and as I said before this The problem here is that as the ice sheets melt, they're going to move the center of mass is going to move Away from its current position. And so one has to monitor these things over Lying periods of time and we discussed a lot about Monumentation stable monumentation around the planet Okay, a little bit more about relative sea level. This is what people really care about Relative sea level and it's sea level rise plus whatever is happening land subsidence so so Vertical land motion can be caused by a number of things groundwater extraction hydro hydrocarbon extraction sediment compaction post glacial rebound and tectonics and so In addition to knowing about the ocean, we have to know what the land is doing especially along the the the coastlines and This upper plot. Let me look at the lower plot here first This is relative sea level rise as a function of distance from the center of the lorantide ice sheet So what you see here is that if you live in Churchill Canada sea levels falling at about eight millimeters per year because the land is rebounding at that rate Um, but if you live Out here in Honolulu, you see An average sea level rise about two millimeters a year. This is sort of the just sea level going up If you live here in Hampton Roads, Virginia What's happening is you have a combination of sea level rising and landfalling this is because You're on the peripheral bulge of this rebound and it's collapsing And so this is a place where people really worry about sea level change relative sea level If you look more All around North America here, you can see There are a variety of of causes of vertical land motion for bulge collapse coastal subsidence delta subsidence things like post seismic deformation Rebound and so on in in the Pacific Northwest you have a signal from Subduction zone Locked subduction zone causing changes in in vertical motion so We have to use the tools of nsar and gps to monitor these Vertical land motions and you see the numbers here are pretty small We want to get down to things like millimeters a year And that's going to drive the accuracy of this Geodetic infrastructure Okay, so for sea level change, this is the one that's really driving the infrastructure 0.1 millimeter a year averaged over a decade. We need to maintain this maybe even do better We need altimeter orbits that are very accurate insar orbits that are accurate Maintain the gravity field And then there's some enhancements. We have to improve the TRF accuracy to a millimeter and drift in the TRF origin to 0.1 millimeter per year I think I already said this improving the accuracy of the z component of the center mass and that may be depend on deploying more satellite laser ranging systems in the southern hemisphere, which is sensitive to the center mass and then one thing we pointed out to Tidegates is only measuring the relative sea level because they're on the land And so we need to also know what the land's doing by installing gnss stations that at the tide gauges Okay, geologic hazards and earthquakes This is something that I'm very familiar with and a lot of us are probably very familiar with so i'm not going to dwell on it but The major questions that we came up with is how how can large-scale geologic hazards be accurately forecast in a relevant time frame And then also what do you do after the disaster? How can you deploy your space assets and geodetic infrastructure to Help mitigate the the disaster Try to figure out when the volcano is going to stop erupting that kind of thing Okay, so i'll just give you a couple examples here One of the big hazards in In north america is this cascadia subduction zone It it's capable of generating a large earthquake 8.7 and 9.2 there was there was one in the year 1700 It's about every 300 and 900 years So who knows when the next one's going to be But what happens during that earthquake is you get large amount of coastal subsidence and tsunami generation The the two Models on the left-hand side here just point out that um with our existing geodetic infrastructure We're not really able to understand the locking mechanism Offshore because we don't have good data. We're there. We need some seafloor geodesy to fill in that area And then down here and the lower left here is a plot of one of these gnss receivers showing The eastward motion that you'd expect from this locked subduction zone But then there's this stair stepping sawtooth backward Stepping caused by slip at the downward part of the subduction zone episodic tremor and slip We'd like to understand this better understand if this is going to be Related to the earthquake if it ever happens And so on so these are the kind of things here's a tsunami model that can be Generated but also we can use Gnss on Platforms out at sea to monitor the tsunami in real time Okay seismic strain Uh one of the things that people have now Understood is that where you have strain rates in the cross where you can measure it with gnss and nsr When they exceed about 50 nano strain per year You're more likely to have an earthquake in those areas and this is just a map showing the population density and the strain rate in Asia But it's similar in Along the san Andreas fault zone in western north america And and the requirement here is sort of 0.5 millimeters a year over 10 kilometer distance The gnss receivers aren't Don't have this spacing to resolve the strain always so we need also insar at Some high repeat rates better than 12 day, which is coming Volcanic hazards Here's an example in hawaii the 2018 killaway eruption It was sort of a slow motion eruption and it's It it doesn't you know, it's not an explosive eruption, but it did cause a lot of damage to property 700 homes or so and Also a lot of damage in the the killaway of park there This is the kind of thing where we would like to monitor the eruption using a combination of gnss and insar And in other cases you'd want to know When is the eruption going to stop? That's was the big question during this eruption People really care, you know, they want to go back to their houses. How long is this kind of last so These tools can help with that provide that information So for geological hazards, we need to maintain the trf Um, we need uh, also I didn't talk about this, but we need uh monthly gravity change measurements to one micro gal at a 300 or so kilometer spatial resolution and we also need to Be able to accommodate quick motions in the In this geodetic infrastructure due to large earthquakes and so on Now I see I only have about five minutes left. So I'm going to Try to get through these last two and into the conclusions But there are two other areas that we looked at weather and climate and ecosystems and in weather and climate The major science questions are Can we improve the forecast? Going forward and then in the climate area, how can we Uh improve the ability to predict local and regional climate response to natural and anthropogenic force things And the main technique we looked at was gnss radio occultation The way this works is you have the high orbiting gnss satellites Transmitting there are signals and these can be received by a lower orbiting constellation of of gnss receivers in orbit cosmic and as the raid path Intersects the upper atmosphere ionosphere It gets delayed refracted and you can measure this and and make profiles vertical profiles of water vapor and temperature and pressure and and the main Benefit of this is that it works over the ocean where we don't have any many other vertical profiles of the atmospheric structure It's also very accurate in the middle atmosphere Two examples here one for weather one for climate In the in the case of the weather there's an atmospheric river example where Something like ssmi only gives you the integrated water vapor through the whole river Whereas the Cosmic cosmic data gnss radio occultation data provide vertical structure And then the one on the right hand side Is a range of different climate model predictions for the pressure change In the middle atmosphere. I didn't really say this but this technique is really Most accurate in the middle part of the atmosphere where we don't have other measurements. So Um We can discriminate between these different models using this type of data Okay, I want to so what are these? What are the requirements here? free open access to the gnss data This is already happening, but it needs to be maintained clocks and orbits are an issue for Getting accurate clocks is really an issue for this technique and then the other thing is that the Upgrading the igs sites to other techniques, not just gps, but Galileo and And glonass and so on what would increase the number of occultations for this technique All right. I have a few minutes ecosystems You know active remote sensing technologies can be used to look at the The biomass on the surface of the earth the volume of the biomass um And that can be used to address issues like carbon fluxes and so on so We looked into the geodetic requirements for some of these measurements and One of them is vegetation dynamics change in biomass and you can use tools of synthetic aperture radar polarimetric, but also insar LiDAR to provide estimates of the biomass lateral transport I think I just had a signal that I have one more minute. So I'm going to go to the conclusions slide So some of the common themes and maintaining and enhancing the infrastructure everyone needs to Need all the science needed to have an accurate and stable trf accurate and stable satellite orbits Maintaining the low degree geopotential harmonics. So we know we can calculate those orbits Augmenting the GNSS network and some for some applications And then supporting software models data and expertise And then here's my final slide I'll wrap it up here What are the priority improvements for the geodetic infrastructure? Number one here is to finalize the deployment and testing of the next generation of the lbi In slr systems. This is happening But we may also need to deploy new slr systems in the southern hemisphere We need to increase the capability for measuring the center of matched motions Especially over the next hundred years due to the melting of the ice sheets And then finally I didn't stress this enough work with the international community to Implement a fully time-dependent trf it again. This is really an international cooperation It couldn't be done without all the other countries and and actually Europe and others are are leaning the way on this And so we we need to have maintained this international community So what I'm going to do is stop sharing Or maybe I should continue if I want to show my slides, but Matt Great. No, thanks, Dave so much for your presentation And I'll just know we have over a hundred people online listening. So it's a great response And if anybody wants to ask a question, please remember to move your mouse to the bottom of the screen to the little button marked q&a Try to type in your question as quickly as you can I'll try to get to as many as I can in the next 14 minutes or so But john labreck already has a question for you, Dave Hi, john I'll try to read it off That's does the study address real-time GNSS to address geohazards because real-time crustal displacements in ionospheric disturbance Has been shown to provide accurate and rapid estimates of service deformation and tsunami hazards Yes, there is some of that in the study. It wasn't We didn't focus on that a lot the real-time aspect, but Of course, it is needed for this hazard response question. And and I think that's in the study in a couple chapters Okay, next question is from rebecca bendick and her question is What is your sense of the capacity for funding to implement some of your key recommendations? Wow You know, that's that's something I really can't answer. I think part of the point of doing this study was to highlight the need for this infrastructure so that NASA and other international partners can really understand How important it is and put some of the funding there, you know, the decadal missions have a huge resource and some of that should go towards This infrastructure, but I don't know the numbers Yeah Great. So we're still waiting for some more questions to come in. Please remember to use the q&a We have some openings, but I guess I'll ask a question, Dave You sort of ended at your talk on talking about the international community I guess can you talk briefly about how you engage the international community in this report and and What efforts might need to be done to expand that engagement in the future? Okay, that's a great question. Let me share my screen again because I had A slide on how this international community works together to There we go How does this all work? Well We have this geodetic infrastructure VLBI SLR GNSS and Doris and this is global infrastructure run by lots of different countries And they all work together to send their data to these data analysis centers Part of the international association of geodesy IGS ILRS IVS IDS and And this is where the cooperation and collaborations come in we We didn't really focus on the international part, but we Or we did have reviewers international reviewers, but But we did Understand and recognize the need to really maintain this this IIG components So those analysis centers are key. They're working together Actually, they there are several centers that provide results cross-checking each other and then that goes um to this earth rotations service and then Finally to define this ITRF so Our report is really mainly focused on on maintaining and enhancing the u.s. infrastructure, you know nasa was funding it, but um But we really really need this international component. It wouldn't work without that. So I don't know if I answered the question. Great. No, thanks, Dave So next question is from Jeremy Maurer. Um, his question is in terms of uh, societally relevant forecasting related to earthquakes, volcanoes and other hazards Can you elaborate a little bit more on what the report is thinking about? And what specific aspects need to be pursued to make that better? That'd be a great question for you matt um Earthquakes something I know a little bit about, you know, we can't actually predict earthquakes, but with geodetic tools we can measure the seismic moment accumulation rate um along a lot of these major Faults and from that we can estimate how much moment has accumulated since the last earthquake and and come up with a Forecast for the size of the earthquake that kind of thing. We can also Estimate seismicity of different areas by looking at the strain rate and the strain rate exceeds You know 50 or 100 nanostrain per year. We usually get higher seismicity. So those those two things volcanoes Maybe matt should answer this question. Do you want to answer this question matt? No, I'll defer it to later I mean I I'm not a volcanologist, but uh Geodetic tools are really good for looking at the deformation from the earthquake. I mean from the volcanoes before during and after the eruption and um I think in some cases the deformation provides a forecast, but some cases It doesn't work. So, uh, yeah I'm not an expert, but good. Well, here's a good question for you. Um from daniel a wine star He says you mentioned an aging aging cast of experts for the reference frame studies Where would you suggest pointing younger scientists to be active? Oh That's a great question. Um One of the things one of the issues that we have and actually nga national geospatial agency Just sent us a questionnaire on What were our capabilities for training? geodesists and And they identified 12 12 places in the u.s. That have some Geodetic training and the problem is um None of us really teach geodesy per se. We teach around geodesy. So, uh The centers are like university of texas, ohio state and so on So what would a young person study? I mean The science is really great. I mean think doing cryosphere or sea level um, or so on but to really To really learn the inner workings of geodesy Places like texas offer things on orbits. Um, we discussed this if you if you went and worked at a place like jpl or nasa goddard Learned from some of the top geodesists there Europe Europe has probably more geodetic Capability and and education. So that's a tough question. I yeah Yeah, well, we've got another question here from uh, jeff freymueller and his question is What were some of the most surprising or hidden? infrastructure dependencies that you identified uh dependencies Well, you know, I wasn't I'm not an infrastructure person. And so I had to learn all this from scratch and I think satellite laser ranging is maybe underestimated for its need to Uh Get the center mass get the satellite orbit serve as a backup system I think if we lost slr Uh, we would be really in bad shape VLBI also, but and then I guess another thing I've learned is that, um The gnss system is really Starting to take over and provide a lot of this information. We still need slr, but uh, I think actually john Put had worked with the Dov to get, uh Retroreflectors on the gnss some of the gnss satellites and that's helped to, uh Collocate those things in space and and so on so I guess The answer is I just It was new to me. So I'm uh, but maybe not to other people All right, another question from tim parker, which was um along the west coast of the us There are seismic and geodetic integrating stations. Are these um Is is the geodesy densifying with the seismic stations for the earthquake early warning and if not why not? Okay, that's a really good question one thing that we had when we did this report You know when I showed the plot of the igs gnss stations is only 500 or so stations yet There's thousands of stations that are important for science. So we had to Draw a line between science and infrastructure and this is a constant Battle because we'd like to go and say well, we want to do more with the science There were lots of things about soil moisture and um You know d gnss reflections for tide gauges and all that but we had to Try to stay focused on the infrastructure, but I you know, it's really important that the uh Seismo geodesy We we have a little bit about um seafloor geodesy um, we have a little bit about soil moisture, but um, we didn't want to go too far down that road because We had to stay on this infrastructure path All right, um next question from frank lemoine, uh, which was did you discuss the impact of how geodesy funding Is dispersed across agencies in the us where in other countries like australia A single agency is responsible for the national geodetic activities Is there a need for a better and more active coordination of different agencies for geodesy in the us? hmm, that's a great question we didn't discuss that in terms of V lbi and slr, but we did discuss that in terms of this backbone gnss because uh the What what everyone wants in terms of the gnss receivers are ones that are well monument Monumented and have more than 10 or 20 years of a record and a lot of those are run by um, you navco and uh, and so on and nga, but and and ngs, but um There's not a lot of coordination and the in the problem that A number of our gnss experts brought up was that um If something like you navco disappeared, what would happen to all those stations? Who's gonna run them all um, and so there needs to be better Funding coordination, especially on the gnss best, but it's maybe also true for slr and v lbi, you know, there's v lbi run by The navy and and also astronomers and geodesists and so on so It's a great question another study All right, we've got about two minutes left here, but I got a couple more questions. I'll try to sneak in Okay Nimit says the u.s. National Geodetic Survey has an upcoming mandate to the national spatial reference system that will closely align with the geodetic infrastructure And then and the itrf To include crustal motion, but with respect to the geoid How do you suggest we manage multi temporal data when the with the geoid aligned to the new spatial reference system to be more dynamic than it is today Yeah That's a great question and I'm not an expert, but I guess it We did We did discuss this issue of Of the changing geoid or the changing center of mass of the earth and how that Affects the infrastructure and so on so we talked about Monumentation for a hundred year time frames, but we didn't get down to Sort of continental scale geoid changes how that affects the vertical Reference friend that would be a great study. I think yeah All right, so this might be the last question from glenn madioli How valuable and what do you think the impact will be of the planned and already initiated upgrade of the gps stations To multi constellation gnss Okay, that's a good question Um for this gnss radio occultation That was their main Request that um the At least the space born ones all go to multi Systems so that they can get many more occultations In terms of the earth systems Um I think it it does better in real time things when you have shaking and earthquakes and so on You need to have more sources to view Better data. It's great for um positioning yourself Without a permanent station that kind of thing. Um I'm not the expert on that, but I I think it's going to be really important to to use all those Okay, thanks, dave. We are out of time Thanks I've got to end but i'm just going to note that your slides will be available online along with a recording available in the next seven to ten days So watch your email for announcements about future events. Thanks again for everybody participating. Yeah, thank you everybody