- We'll have two presentations on Pandora. First will be from Emily Gilbert, and I'll just pitch it by saying, Pandora is very relevant to the work just presented by Nestor.

- So yeah, that was really the perfect intro to this talk, and thanks so much Nestor. And today I'm going to be talking about the Pandora SmallSat Mission. So this is a SmallSat, specifically designed to tackle this issue of stellar contamination. And Pandora is one of four mission concepts, selected for further study in NASA's Astrophysics Pioneers Program. This mission is led by PI, Elisa Quintana based at NASA Goddard. Deputy PI, Jessie Dotson at Ames, and our project scientist is none other than, Knicole Colon. So one of the goals of this pioneers program is to change, train early career researchers. So in addition to my participation on the science team of Pandora, I'm also shadowing Knicole, as the project scientist, to gain experience working on missions. So as I mentioned, Pandora is designed to measure exoplanets and their host stars with long, baseline, simultaneous, and multi-wavelength observation in order to tackle this issue of stellar contamination. By doing so, we're able to disentangle star and planet signal and exoplanet transmission spectra in order to obtain robust measurements of exoplanet atmosphere. A little deeper dive off of what Nestor just said. So exoplanet transmission spectroscopy work by taking differential measurements of the system in and out of transit. So in our transit spectrum here on the left, you can see that the planet atmosphere signal is embedded within the stellar signal. We then subtract off a sector of just the star. And what we are left with is that of the planet's atmosphere. But one problem with this is that this differential measurement works by assuming we know the stellar's stellar spectrum. And typically we assume this to be a uniform light source. But we know that for most stars, it's not the case. We know that there are, active stars can have dark spots and bright faculae regions, that convolve with time and stellar rotation, and then these brightness variations can then be imprinted within observed spectrum and contaminate the planet spectra. If we assume the star is uniform, when in fact it's not, we might end up with misleading planetary spectra. And this issue arises because the planet is only transiting a portion of the star, the transit cord that you can see here. And so we have several cases of where inhomogeneities on the star may exist and how they will impact the planet atmospheric signals from there. So if you have visual inhomogeneities within the transit cord itself, you may see spot crossings like these within your transit light curve. These are somewhat easier to identify as you can just pick them out by eye right here. But we may also have unocculted variability within the stellar curve here, outside of the transit cord. And this is more difficult to identify and quantify and can cause variation in transit depth. So overall, if you have spectral differences between the assumed light source, the whole dip integrated face of the star, and the actual light source with core integrated region, then these variations will be imprinted in your transmission spectrum, leading to stellar contamination in the jue planetary spectra, and the stellar contamination can introduce features in an observed spectrum. And they end up with false positive detections, or you might suppress what might otherwise be an interesting discovery. So this issue of stellar contamination is a particular concern for small stars. We know that small young stars can be highly active on long timescale and stellar rotation can occur on hour to days long timescale. With the spot variability timescale it can be comparable on an orbital period and transit duration. So when you were observing the spectra of a star, you might have different faces of the star showing from transit to transit of the same planet, or even from planet to planet on multi-planet systems. So this makes stellar contamination, even more of a challenge to contend with. You may be asking yourself if low-mass stars are so active, why do we even bother looking at them? They are particularly near and dear to my heart. And so there are a lot of reasons why we should not just copy a star. So for one, they make up the majority of stars in the Milky way. And dwarf stars are more than 70% of all stars. For smaller stars, we also see stronger planetary symbols in detection for both radial velocity and transit. So it's much easier to detect planets around small stars. Building off of that, the habitable zone for smaller stars are closer in, which, again, makes it easier for us to detect planets using both radial velocity and the transit method. So if we want to search for habitable zone planets, where we may be able to look for biosignatures, small stars are the best spots to look given today's technology. And so despite these activities low-mass stars are still the most favorable targets for transmission spectroscopy because the strength of the planetary atmospheres features scales inversely with the square of the star size. This means that planets transiting small stars with stronger features and can therefore be better characterized when stellar contamination is correctly accounted for. So we've shown that HSC has been a powerful tool for identifying the presence of molecules, gases and clouds in the atmosphere of giant exoplanets and the upcoming JWST mission we'll build on the science. So exoplanet atmospheres are a key science driver for James Webb, which will have unprecedented precision to study planets in great detail, including several temperate Earth-sized planets. So as we begin probing the atmospheres of increasingly small planets with high precision, we are under, we need to understand the effects of stellar variability on transmission spectroscopy even more. We already know a little bit about some of the early James Webb targets. So James Webb will be observing 30 transiting exoplanet in both the GTO, Guaranteed Time Observations and Early Release Science programs. And recently the JWST Guest Observer Cycle 1 targets were announced and an additional 38 transiting exoplanets were added. And so a significant number of both of these groups are planets orbiting small stars. So it looks like this issue of stellar contamination is here to stay, we know that some of these James Webb stars are indeed active. So how do we best mitigate the effects of stellar contamination? So, one way to do this is with photometric monitoring, as you heard, and photometric monitoring provides the measurements on the brightness of the star over time. And so you're able to see how the brightness varies as dark and bright spots rotate in and out of the field and rotate in and out of view as the star rotates, probing stellar variability. So Pandora is specifically going to use this method in order to study stars. So this SmallSat is designed to observe transiting exoplanet and their host stars with long baseline, simultaneous visible photometry and infrared spectroscopy. The two main science objectives for this mission are one, to determine the spot and faculae covering fractions of exoplanet host stars and the impact that these active regions have on transmission spectra of planets, and two, to identify exoplanets with hydrogen or water dominated atmospheres and determine which planets are covered by clouds and hazes. So Pandora aims to meet these science goals, using visible and infrared channels to characterize their planets and their host star. So there's visible photometry that you can see up here, places constraints on spot coverage, which in turn allows us to disentangle stars kind of spectra in infrared spectroscopy. So here you can see a simulation showing the challenges of observing planets around an active star. So this red line here is the true final spectrum and the gray and shaded region is an area of inferred planetary spectra for a number of different stellar rotation phases. So depending on the phase of the star, the stellar contamination due to spot can enhance or knock features in the planetary spectrum, resulting in this range of inferred spectra, but Pandora will enable robust measurement of stellar contamination, and thus will allow us to determine the true planet spectrum. So Pandora's infrared band allows us to explore a region where water is a strong, absorber in both H2 and water-dominated atmospheres. Pandora aims to detect H2 dominated atmospheres in one transit. And water dominated atmospheres in ten transits. And if we don't detect spectral features consistent with H2 or water dominates atmospheres, this implies that the planet has either clouds or hazes obscuring atmospheric features, or that the atmosphere is dominated by heavier molecules. But in either case we will have removed spectral contamination from the planet spectrum. This will allow us to put robust limits on the detection of atmospheric features, thanks to these multi-wavelength observations. So even in the absence of detectable spectral features, it will be possible to place rigorous upper limits on atmospheric composition. We can use this information as a driver for additional follow-up observations with facilities like JWST. So here you can see a simulated observing plan for one of our Pandora targets, K2-33. And the observing plan for, for Pandora is to observe 10 transits of each planet with 24 hours of observations per visit. So here you can see like light curve of K2-33, where you see the rotational modulation rotational modulation with a period of 6.3 days. And this variability is caused by spots rotating on the surface of the star. And then this star have a planet, K2-33b with transits every 5.4 days, and the colored regions on this light curve show what Pandora will observe for 24 hours centered on each transit. And this is photometry here. And we will also obtain simultaneous incorrect spectroscopy, which is not shown. And so, as you can see down here, the transit span a wide range of rotational spaces, which will introduce variability in spectra if not properly accounted for. So here's our notional target list of 20 stars. Some, like multiple planets that we've planned to observe. And we have selected targets to span a wide range of stellar types and planet sizes. So we're still a few years before launch. This is subject to updates pending further tests for other facility discoveries. But as you can see here with that, our range of stars and planets spanning from C3 to M8 stars, with a variety of rotational periods for the stars themselves, we have some fast rotators, slow rotators that UCC and the planet radii range in size from about one earth radius up to around the Jupiter radius. Pandora is really important in that it fills a niche that no other facility is able to meet on its own. So Pandora will wavelength range similar to HFC, WC3IRG141 band, and it has the sensitivity approaching that of HST that HSC does not perform simultaneous observations in optical and infrared. Similarly with JWST, JWST is not observed in the optical which is critical for identifying stellar contamination, because this is where the spot contrast is greater. So Pandora science goals cannot be achieved using alternative approaches, including observations from the ground, existing mission or planned space missions that will operate before or concurrently with JWST. Our top speakers here shows how Pandora fits in with this timeline of other missions. We will overlap with JWST potentially HST, pending a quick fixes, hopefully. And maybe additionally, it will observe simultaneous with TESS and it will be able to work in conjunction with the missions or to coordinate targets and observation. So my last slide here. Thanks.

- [Host] Yeah, perfect. I was just going to let you know, two more minutes. Thanks.

- [Emily] Okay. So Pandora will provide the first data set to simultaneous multi-band visible and infrared long baseline observations of exoplanets and their host stars to address this issue of stellar contamination. And this will fill a crucial gap in NASA's roadmap to characterize the atmospheres of small Earth-like planets, like we heard about earlier, the mission is slated to launch in the mid 2020s to a dawn/dusk sun-synchronous orbit, with a nominal mission lifetime of about a year. And this is a SmallSat mission with around a half meter diameter telescope. And I will toss it over to Jordan now to tell you more about the spacecraft itself.