Transcript from Jennifer Burt's talk "Future of RV" given at ExoPAG 34 on June 14, 2026. 542 02:58:05.120 --> 02:58:13.990 ExoPAG: Okay, hi folks! My name is Jennifer Burt, I'm a scientist up at JPL, and I am here today to talk to you about the future of radial velocities. 543 02:58:14.750 --> 02:58:18.620 ExoPAG: Okay, and… Green button is click. 544 02:58:21.910 --> 02:58:46.810 ExoPAG: Okay, okay. So I will… I will start with an oft-used quote that the RV field has gotten a lot of mileage out of from the 2018 National Academy of Sciences report that highlights that mass is the most fundamental property of a planet, and knowledge of a planet's mass, along with knowledge of its radius, is essential to understanding its bulk composition and understanding its atmosphere. So masses are the thing that radial velocities provide 545 02:58:46.810 --> 02:58:54.560 ExoPAG: for us when studying exoplanets. And I wanted to highlight a couple of the roles that radial velocities play in the exoplanet field. 546 02:58:54.630 --> 02:59:09.500 ExoPAG: So, first, from a pure RV discovery point of view, long-term radial velocity surveys on ground-based telescopes that generally target bright, nearby stars are allowing us to push to lower masses and wider orbits. 547 02:59:09.500 --> 02:59:19.120 ExoPAG: Almost regardless of the planet's inclination and period. They help us to improve our understanding and modeling of stellar variability as it manifests in the stellar spectrum. 548 02:59:19.120 --> 02:59:30.770 ExoPAG: And right now, we're focusing a lot on vetting the provisional HWO targets that will be likely high up for the Earth Twin search that the HWO will carry out in sometime in the 2040s. 549 02:59:31.770 --> 02:59:47.339 ExoPAG: There's also a lot of synergies with transiting planets, and Tiffany's gonna tackle the future of transiting planets next, so I won't say too much on this, but just to note that we use radio velocities as an independent detection method to confirm the planetary nature of candidates discovered by missions like Kepler and TESS. 550 02:59:47.380 --> 02:59:56.320 ExoPAG: They allow us to measure the mass, the eccentricity, and sometimes the obliquity of the planets, and that is key for, again, determining bulk densities and atmospheric scale heights. 551 02:59:56.320 --> 03:00:08.870 ExoPAG: They provide insights into the stellar variability when thinking about transmission spectroscopy, the transit light source effect, and the havoc that is wrought by star spots your planet might cross in front of as it's moving across the star. 552 03:00:08.870 --> 03:00:15.179 ExoPAG: And then also for the detection of additional non-transiting planets, if our planets aren't exactly in a plane with one another. 553 03:00:15.810 --> 03:00:40.799 ExoPAG: There are also a lot of synergies with other fields that I won't touch on in detail here, but we can assist with doing high-resolution detections of atmospheric abundances for exon and atmospheres, looking for atmospheric escape, again, measuring obliquities. From the solar and stellar astrophysics point of view, lots of work in determining the magnetic cycles, long-term magnetic cycles of stars, trying to spatially resolve 554 03:00:40.800 --> 03:01:02.089 ExoPAG: the surfaces of stars, and then using astroseismology via radio velocities to determine masses and ages. We actually, just this past week, had an online workshop run by the EPRV Research Coordination Network that I had on synergies between EPRV and solar physics. You can see the agenda there. The recordings are all going to be posted online if you're interested later on. 555 03:01:02.090 --> 03:01:09.830 ExoPAG: But we had participation from 15 speakers across 7 countries who were very keen on looking for more ways to build connections between these fields. 556 03:01:11.050 --> 03:01:12.530 ExoPAG: Okay, so… 557 03:01:12.700 --> 03:01:21.250 ExoPAG: kind of mimicking the approach that Scott took, and I think the future speakers will take, I want to talk first about what we can do right now, and then what we're looking to do in the future. 558 03:01:21.250 --> 03:01:34.069 ExoPAG: So, what can we detect right now if we look at the set of confirmed exoplanets that have RV measurements at the 20% precision or better threshold? I'm plotting those here as a function of when they were first published. 559 03:01:34.070 --> 03:01:39.840 ExoPAG: The red circles are RV-only detections, and then the blue circles are transit follow-up detections. 560 03:01:39.870 --> 03:01:53.780 ExoPAG: And for a bit of nomenclature, I'm gonna use PRV in general to talk about detections at the 1 meter per second or above level. That is kind of what we are consistently doing now, that is not so much a struggle with modern instruments. 561 03:01:54.340 --> 03:02:07.260 ExoPAG: Eprv, proper EPRV, is getting down to 10 centimeter per second detections, and this is what we need if we're looking for Earth twins. The RV signal of the Earth around the Sun is about 9 centimeters per second. 562 03:02:07.910 --> 03:02:24.440 ExoPAG: And then this kind of E in parentheses, PRV, we haven't done a great job with the nomenclature here, is the 30 to 50 centimeter per second region. This is the current bleeding edge of the field, so this is what the best instruments are producing, over the last few years. 563 03:02:25.540 --> 03:02:39.950 ExoPAG: And if we translate those lines of RV sensitivity and put them on top of these same planets, but now plot it as a function of orbital period versus the planet mass, the masses for most of those transiting planets are inferred from mass-radius relationships. 564 03:02:39.950 --> 03:02:55.149 ExoPAG: You can see that 1 meter per second gives us the ability, with a long enough baseline, to detect planets like Jupiter and Saturn. 30 centimeters per second gets us to our outer ice giants, but getting down to Earth and Venus really does require that 10 centimeter per second precision. 565 03:02:57.140 --> 03:03:14.179 ExoPAG: So I want to talk a little bit about what we're able to do in the field right now in terms of real detections, and so this is a recent paper that came out on the STAR HD161098. This is leveraging data from HARPS and Espresso, and HARPS North, taken over almost two decades. 566 03:03:14.180 --> 03:03:24.720 ExoPAG: So you can see the time series there, the radial velocities are the top panel, and then a whole variety of different metrics we use to assess the variability of the star are shown in the lower panels. 567 03:03:25.320 --> 03:03:44.890 ExoPAG: After a lot of work to characterize and then mitigate the effects of both the magnetic cycle, which is a roughly decade-long signal you can see underlying those radio velocities, and also rotation signals, they're left with two signals that pop up in the periodogram, one at 72 days and one at 687 days. 568 03:03:45.720 --> 03:03:56.599 ExoPAG: And if we derive the planetary parameters for those, that outer signal is something like an 8-Earth mass planet that is actually too far out from its star. 569 03:03:56.600 --> 03:04:14.410 ExoPAG: So we've skipped right over the habitable zone, which is, like, the struggle that we're desperately trying to reach right now, and this guy is on the outer edge of the optimistic habitable zone. But I think this is an encouraging sign that we do have the sensitivity to start reaching, certainly to super-Earth mass planets in the habitable zones of sun-like stars. 570 03:04:14.670 --> 03:04:30.240 ExoPAG: A couple other recent examples of that that I'll highlight. The top left here is looking at a star going through a Monder minimum phase right now, so it's quite quiet in its activity cycle, but the green bars, or the colored bars on each of these, represent the habitable zones of the stars. 571 03:04:30.240 --> 03:04:41.189 ExoPAG: And in that top left, this is a K2 star, HD166620. We have a mass sensitivity down to about 2 to 4 Earth masses in the habitable zone of the star. 572 03:04:41.190 --> 03:05:02.600 ExoPAG: And in the top right, looking at Tau Ceti, which is one of our favorite stars to look at, very bright, very nearby, very much like the sun, and very quiet, using roughly 150 points taken by espresso over a four and a half year span, we have a habitable zone sensitivity of two to five Earth masses on the inner and outer edges of the habitable zone. 573 03:05:02.760 --> 03:05:27.739 ExoPAG: We determine these sensitivities by taking the radial velocity measurements, doing our best to remove the impacts of instrument systematics and stellar activity, and then injecting large grids of synthetic planets with different combinations of orbital periods and masses into the data, and then trying to recover those planets. And so, when we say we have a sensitivity of something like 2.4 Earth masses, it means planets at that mass or above, we can 574 03:05:27.740 --> 03:05:33.969 ExoPAG: reliably recover from the data. Planets below that mass we cannot recover. So it sets a boundary or a threshold. 575 03:05:34.440 --> 03:05:55.640 ExoPAG: And I show these, in part to highlight that we are doing pretty well in the radial velocity field. We're not down to an Earth-mass planet on exactly a one-year orbit around a Sun-like star, but these are… the three of these are sun-like stars where our sensitivity in the habitable zone is below 10 Earth masses, so we are comfortably reaching down to super-Earth planets. 576 03:05:55.640 --> 03:06:08.949 ExoPAG: The one in the lower right is a little different. This is using MaroonX data and looking at Barnard's star. So these are planets on much smaller orbits, much closer in orbits, but highlights that we can do this type of work on M dwarfs as well, which I think is nice to see. 577 03:06:10.700 --> 03:06:24.059 ExoPAG: So in terms of what sets our RV capabilities, there are three major contributions to RV uncertainties. One is the photon noise as dictated by the size of your telescope, the throughput of your instrument, and the SED of the star. 578 03:06:24.130 --> 03:06:47.279 ExoPAG: Second is the drift or uncertainties from the instrument, so that includes things like long-term drifts, calibration uncertainties, pixel inhomogeneities, things like that. And then the last one is the contributions from the star, and so this is capturing spots and faculae, rotational modulation, pulsations within the star, granulation and supergranulation, and those long-term magnetic cycles. 579 03:06:48.660 --> 03:07:04.169 ExoPAG: And so the most recent generation of instruments, we are reaching down to total instrument systematic floors of about 30 centimeters per second, which is what's allowing those detections of 30 to 50 centimeter per second planets around these sun-like stars that I showed a moment ago. 580 03:07:04.980 --> 03:07:16.400 ExoPAG: And so the main focal point recently has been on stellar variability, and that is a challenge because all of these different phenomena on stars occur at different RV amplitudes and on different timelines. 581 03:07:16.400 --> 03:07:34.600 ExoPAG: And so, in order to actually model and mitigate these signals, we need to be able to sample our stars at cadences that cover each of these different types of signals to try and actually resolve them and treat them as individual signals in the data, rather than a rolled-up jitter or kind of, like, white noise term. 582 03:07:36.440 --> 03:08:01.339 ExoPAG: And so there have been a number of surveys that started in the last, let's say, 5 to 10 years that have been trying to do this. I list a number of them here, but there are many more that are led at the PI level. Most of these have really targeted a specific set of stars, often at the few dozen stars level, and decided to commit to high cadence, high signal-to-noise observations of those stars, so trying to go 583 03:08:01.440 --> 03:08:05.759 ExoPAG: Often and deep, rather than hitting as many stars as possible. 584 03:08:05.850 --> 03:08:12.539 ExoPAG: I highlight one example here on the right, which is one of the interim reports on the NEWID Earth Twin Survey, or NETS. 585 03:08:12.540 --> 03:08:35.239 ExoPAG: And this shows the stars that they have been observing over a 4-year time span, I believe, in this figure. And the bars show you the RMS of the radial velocities of those stars, and you can see that many of them are already reaching to, you know, 3 meters per second or below, which suggests that the stars are quite quiet. This is before doing a full analysis of the stars on a star-by-star basis. 586 03:08:35.240 --> 03:08:43.850 ExoPAG: The two others that I have at the bottom in asterisk are upcoming surveys, the Terra Hunting Experiment, which will be on HARPS3, and the second Earth Spectrograph, or 2ES. 587 03:08:45.350 --> 03:08:58.900 ExoPAG: And a thing to be aware of, we're sending announcements around this around in the next week or so, but there's a new key project call that will be going out for NUID as the NUID team's GTO program rolls off, and we will be soliciting proposals for folks 588 03:08:58.900 --> 03:09:03.320 ExoPAG: To make use of up to 12 nights a semester over 4 years. 589 03:09:03.320 --> 03:09:25.019 ExoPAG: Specifically, we are keen on programs targeting HWO stars and thinking about ways to provide precursor science support, and there is funding at the level of up to $300,000 a year. So, we'll… there will be emails about this out through EXOPEG Announce and through the EPRV RCN, so you should take a look at that. There's a notice of intent due at the end of July. 590 03:09:26.160 --> 03:09:41.169 ExoPAG: Okay, so that is a little bit of where we are in the EPRV field right now. We are able, with much care and much individual, like, bespoke star-by-star work, to get down to the super-Earth mass level in the habitable zone of sun-like stars, which is great. 591 03:09:41.170 --> 03:09:47.399 ExoPAG: One of the questions I was asked in preparing for this talk was, should we do EPRV in space? 592 03:09:47.400 --> 03:09:50.779 ExoPAG: And so, I resisted the urge to just say, no. 593 03:09:50.980 --> 03:10:00.920 ExoPAG: Period. And decided I would at least try to do a little bit of back-of-the-envelope work, because I think there are a lot of challenges to this, but it is always worth considering if it makes sense. 594 03:10:01.730 --> 03:10:11.730 ExoPAG: So I'll start with 3 of the space-based observation benefits that people often highlight and say why the first two, I think, are not as much of a concern as they used to be. 595 03:10:11.730 --> 03:10:34.400 ExoPAG: So going to space gets you out of the atmosphere, and that removes toleric contamination. And that is especially handy when we are looking for planets with periods close to a year around other sun-like stars, because it turns out if your planet is moving on a period of just about a year, then you can see your atmospheric line shift with that same periodicity on top of your stellar spectra, and that can be a real headache. 596 03:10:34.800 --> 03:10:59.299 ExoPAG: Now, thankfully, because of how well stabilized and controlled the more modern RV spectrographs are, Danny Krolikowski has led some excellent work using the nuanced spectrograph and the data they're taking to use the instrument profile and combine that with transmission model grids from the HITRAN groups to actually improve their telluric modeling, and so this is a more accurate treatment of using 597 03:10:59.300 --> 03:11:24.229 ExoPAG: exactly what we know about the instrument on an observation-to-observation basis to understand what those telluric lines might be doing. And you can see in the bottom figures there the improvement from the before the telluric correction in blue to the after the telluric correction in, like, magenta, and the fact that it is removing, in the periodogram to the right, most of these yearly signals that cause such headaches for us. So, we think we have steps forward for addressing the toleric contamination 598 03:11:24.230 --> 03:11:27.920 ExoPAG: Especially in the visible wavelengths where we do most of our EPRB work. 599 03:11:28.940 --> 03:11:35.970 ExoPAG: Another one is getting additional blue and really near UV wavelength coverage from space, which we can't do from the ground. 600 03:11:35.970 --> 03:12:00.100 ExoPAG: This figure shows you the Doppler information that is contained in the stellar spectrum as a function of wavelength on the x-axis, and the bluer colors are the areas that contain more Doppler information, so they are more useful to us, they contribute less uncertainty to our RB measurements, the red areas contain less Doppler information, and so you can see that as we move bluer, and this is true as we continue out to 3,000 angstroms. 601 03:12:00.100 --> 03:12:07.600 ExoPAG: There's less Doppler information there, so we don't actually build up a lot of additional RV information content by having these bluer wavelengths. 602 03:12:08.770 --> 03:12:25.169 ExoPAG: But the one that is important, and the one that we keep coming back to in the RV field, is the fact that going to space means that there's no weather losses and no day-night cycles. And that is very helpful to us, both on the long-term scale of thinking about yearly weather impacts. 603 03:12:25.170 --> 03:12:42.289 ExoPAG: So I'm showing here another figure from that NEWIT Earth Twin survey paper from NETS that highlights the monsoon season in Arizona, which wipes out observations from Kitt Peak for something like 1 to 2 months per year. And so behind those monsoon season blocks, there are no observations being taken. 604 03:12:42.420 --> 03:13:01.200 ExoPAG: Additionally, when we think about signals like granulation and super granulation, which manifest on timescales of hours to about 20 hours for sun-like stars, there's a real challenge from trying to observe from a single telescope, because your nightly cycle is too brief to capture the longer-term… 605 03:13:01.200 --> 03:13:16.450 ExoPAG: variations on those stars. And so, a single site does not allow you to do a good job of modeling the supergranulation, which is becoming more and more of a concern from an EPRB point of view, now that we have beaten down the rotational modulation and the magnetic cycles pretty well. 606 03:13:17.840 --> 03:13:34.949 ExoPAG: So, I took a look at, the… the EPRV amenable stars defined quite loosely as V cyanide less than 5 kilometers per second, and effective temperatures less than 6,000 Kelvin. There are about 76 of them on the provisional HWO list from XF. 607 03:13:35.480 --> 03:13:43.760 ExoPAG: And then I used, the NUID exposure time calculator in a very back-of-the-envelope way. I want to stress, like, I did this last night. 608 03:13:43.760 --> 03:14:07.770 ExoPAG: It was… it's a decent guess at it, but there's more work to be done here, where I assumed we took an instrument like Neweit, we attached it to something like Roman's primary mirror, so the collecting area of Roman. I gave it a 20% throughput bump to address the fact that there's no atmosphere in the way, I set the seeing to as low as it can physically go in the ETC, which is 0.3 arcseconds, to say there's also no seeing impacts. 609 03:14:07.850 --> 03:14:25.049 ExoPAG: And then I calculated what it would take to observe each of these targets once to the 10 centimeter per second level, and then also bend down over the stellar pulsations, because that is a common technique nowadays. And to look at each of these 76 stars once, that would take 17 and a half hours. 610 03:14:25.050 --> 03:14:30.830 ExoPAG: This does not include anything about slew time or acquisition, because I do not know how those work in space. 611 03:14:31.100 --> 03:14:49.229 ExoPAG: So what this tells us is that with a mission the size of Roman, you would only be able to look at your stars basically once a day. And if we are keen on this idea of observing stars at shorter cadences, such that we can resolve those super granulation and granulation signals, that might not be enough. 612 03:14:49.290 --> 03:15:05.979 ExoPAG: And my worry is that asking some… an agency like NASA to launch a mission on a Roman-sized telescope to say, please look at these 75 stars, and only these 75 stars ever is for, like, 5 to 10 years in a row is a little bit of a hard sell. 613 03:15:07.080 --> 03:15:30.510 ExoPAG: Other high-level concerns is that right now, the wavelength calibration subsystems we use are not reliable enough to go into space and work for 5, 2, 10 years. They take a lot of love and cajoling on a regular basis to continue working the way we want them to. Cosmic ray contamination, we often use 9K by 9K detectors, and we use almost all of the surface area on those. 614 03:15:30.510 --> 03:15:36.470 ExoPAG: Between the spectra themselves and the calibration traces, and so we would get beat up quite quickly by cosmic rays. 615 03:15:36.470 --> 03:15:44.860 ExoPAG: And then thermal cycling concerns based on the mission orbit. We care very much about having very, like, to the millikelvin stability in our instruments. 616 03:15:44.860 --> 03:16:01.920 ExoPAG: So this is… my pitch for going forward is not EPRV in space, at least not with my understanding of it right now. Instead, I think we could, at a similar scale of effort and cost, actually a much cheaper cost, focus on ground-based efforts. 617 03:16:02.150 --> 03:16:12.740 ExoPAG: And so this idea has come up a number of times over the last decade. It was first put forth in the EPRV Working Group's final working report back in 2021, where we looked at 618 03:16:12.750 --> 03:16:37.550 ExoPAG: having a network of EPRV instruments across the globe at 6 different sites and a bunch of different architectures. Future or later work from that that involved more considerations of stellar variability by Jacob Lund showed that if you had a 10-year survey and you allocated 100% of a bunch of 3-meter telescopes to do this, you could get, 5-sigma detections of 80% of the HWO stars that he was considering for that. 619 03:16:39.170 --> 03:17:02.220 ExoPAG: A nice aspect of this, of having multiple instruments, is also that if you have your RV data that contains inherently both the stellar variability and the instrument systematics, and because the stellar variability should be about the same, you can decouple the two from one another and get at what the underlying instrument signals are by saying, when I look at the data from three different facilities, what is 620 03:17:02.220 --> 03:17:05.100 ExoPAG: Common to each of the datasets, and what is individual? 621 03:17:06.250 --> 03:17:31.219 ExoPAG: That is mostly true, modulo the fact that all of our instruments are often using slightly different wavelengths, the band passes, slightly different resolutions, and so they do see the stellar activity a bit differently from one another. So that is a challenge of trying to do this after the fact with existing instruments, where you need to handle the fact that our activity is chromatic, and so that means that the spot modulation doesn't show up exactly the same if you 622 03:17:31.220 --> 03:17:33.770 ExoPAG: You are looking at different parts of the wavelength spectrum. 623 03:17:34.490 --> 03:17:54.719 ExoPAG: Another consideration is that given the aperture and the throughput of your telescope, the exposure time you need in order to reach the same signal-to-noise can be quite different. And if you don't handle that accurately, if you don't address the fact that you can have different amounts of overlap between your observations, as is showcased here in a recent paper from Jacob Lund, that 624 03:17:54.800 --> 03:17:55.480 ExoPAG: Whoop! 625 03:17:55.480 --> 03:18:20.460 ExoPAG: If you don't address that, you can see in the top right there, trying to model the stellar variability can be a very confusing process, because you are capturing or binning over different percentages of those different activity cycles in each of the instruments. But if you do take the time to correct for it, then you can actually do a very nice job of starting to deal with the activity correctly between each of the instruments, and so the residuals of your model 626 03:18:20.460 --> 03:18:22.749 ExoPAG: It'll shrink down, quite impressively. 627 03:18:23.170 --> 03:18:42.269 ExoPAG: And so, he's been doing some additional work on this using data, first collected by Lily Zhao as part of the Extreme Solar Signals project back in 2023, and then more recently with KPF and new solar data to look at comparing those, modeling them, and then trying to separate out the instrumental drifts from the solar drifts. 628 03:18:42.670 --> 03:19:02.079 ExoPAG: We're trying to do this on a stellar aspect as well, and so via a set of coordinated ground-based efforts in the Research Coordination Network, where we submitted proposals to a whole bunch of techs in late 24 and early 25. We were mostly successful with this, which was very exciting to us. We did not expect so many TACs to sign on, because it required 629 03:19:02.080 --> 03:19:24.550 ExoPAG: at least 4 or 5 of them to say yes for this project to work, so that was a big risk. But we got positive feedback. This is just a quick glimpse at the data from Tau Ceti that was taken in 2024. The analysis of the 2025 data is still underway, but we're, again, looking to use this to see, common signatures between the G-type stars that we observed versus the instrumental systematics. 630 03:19:25.900 --> 03:19:50.790 ExoPAG: And I'll note that the U.S. and NASA are not the only ones, or the RCA are not the only ones thinking about this. There is a proposal that's been started as part of the United Kingdom Science and Technology Facilities Council, led by Annalise Mortier and Heather Segla, to design and develop a fleet of stabilized, high-resolution spectrographs. So again, building on the idea of, if we design these things intentionally, then we can make sure they have the same way 631 03:19:50.790 --> 03:20:12.490 ExoPAG: the same wavelength coverage, the same precision, the same mostly instrument systematics, the same exposure times, removing the need to add all of these additional variables to our models, and maybe streamlining the analysis approach a bit. This is in the very early stages. They, I think, put in the equivalent of a notice of intent, but it's great to see that other countries and other scientists in the field are thinking along these lines as well. 632 03:20:13.200 --> 03:20:38.179 ExoPAG: I focused a lot on this kind of fleet of RV spectrographs. I want to also acknowledge that there are a lot of individual improvements that can be made to specific spectrographs as we think about the next generation or improvements to the instruments that already exist. I'm not going to read these out, but there's a new review paper that myself, Xavier Dumousk, and Sam Halverson led for annual reviews of astronomy and astrophysics. The advanced copy shows 633 03:20:38.180 --> 03:20:59.909 ExoPAG: be out later this month, the full volume comes out in August, and we break down all of the main areas of EPRV and the challenges we face, and then try to highlight the ways that we think we could move each of those sub-areas forward. So I encourage you to give that a read if you are interested. Also, should hopefully be a good resource for new students getting involved in the field. It's pitched at kind of the grad student level, so… 634 03:21:00.260 --> 03:21:25.250 ExoPAG: And the last point I want to make before I wrap up is that every bit of improvement counts here. So we spend a lot of time in the context of NASA and HWO talking about reaching the ability to detect Earth analogs, and that is a goal that the whole community is focused on, but there are many benefits along the way. So right now, we're at 30 to 50 centimeters per second, which is great. Pushing to 20 still opens up a lot of discovery space 635 03:21:25.250 --> 03:21:30.390 ExoPAG: And a lot of follow-up space for small planets, around, around bigger stars. 636 03:21:30.530 --> 03:21:46.610 ExoPAG: And so, it is not all or nothing that we have to get to 10 centimeters per second, or there was no point to it. We add, you know, big ranges of both orbital period space and planet mass space with every centimeter per second we manage to claw out. So as the field is kind of working its way slowly forward from 637 03:21:46.610 --> 03:21:52.960 ExoPAG: 5 Earth mass sensitivity to 1 Earth mass sensitivity, I think we'll end up with a lot of exciting discoveries over the coming years. 638 03:21:53.760 --> 03:21:57.720 ExoPAG: Okay, with that, I will say thank you so much for your attention, and ask if there are any questions. 639 03:22:06.360 --> 03:22:12.120 ExoPAG: All right, again, we've got time for maybe one question while Tiffany gets set up with the next set of slides. 640 03:22:15.910 --> 03:22:26.619 ExoPAG: Being none, I'll ask one. Jen, you mentioned something like 76 EPRV-amenable HWO targets, which is less than half of the list of 160 or so. Is that an implicit 641 03:22:26.620 --> 03:22:51.619 ExoPAG: advocation for high-precision astronometry to get the bulk of the sample to measure masses of planets that we might find there? Yeah, I think it's a great lens to say, like, we should do both of these things. You know, Eduardo and I will happily advocate for our preferred detection method, but I think the real answer is we should do both of them. And from the EPRV point of view, there are stars that are just too hot, or that are rotating too rapidly for us to reach the precision necessary 642 03:22:51.620 --> 03:23:09.760 ExoPAG: to get to those planets. From an astronometry point of view, more of the stars are accessible, but if the, you know, cost of running that long-term survey becomes exorbitant, we can split those populations and do an intentional survey design that really leverages or optimizes across the two detection methods. 643 03:23:11.470 --> 03:23:13.660 ExoPAG: Okay, thanks so much, folks!