Season One | Episode 3
A Match Made in Space: OSIRIS-REx and Bennu, Part II
Thank you to our guests on this episode of Lockheed Martin Space Makers for their time and expertise:
Dante Lauretta from the University of Arizona
Beau Bierhause, Sandy Freund and Joe Landon from Lockheed Martin
To dig deeper into the incredible mission referenced in today’s episode, please follow these links:
[00:00:00] Host: Welcome to Lockheed Martin Space Makers, the podcast that takes you out of this world for an inside look at some of our most challenging and innovative missions. My name is Ben, and I'll be your host. This season, we'll explore the future of space with past and present missions that are shaping our path forward, and chat with experts about what they think the space industry will look like 30, 40, even 50 years from now. Now let's go for launch.
[00:00:35] We are in the middle of a two-part episode about an incredible mission to collect a sample from an asteroid that is sailing through space 200 million miles away. Today in part two, we sail through space towards the Asteroid Bennu, and hopefully by the end of the show, we'll have a sample. And in our flash forward segment, we'll look at how an in-space economy and astropreneurial pursuits will help pave the way for people to live on the moon and even Mars.
[00:01:01] As we jump back into the OSIRIS-REx mission, let's take a moment to review the highlights of the previous episode. Let's start by introducing our guests who are working on this mission.
00:01:10] Beau: My name is Beau Bierhause, and I'm a senior research scientist at Lockheed Martin. I work on active flight programs such as OSIRIS-REx.
[00:01:20] Dante: My name is Dante Loretta. I'm a professor of planetary science at the University of Arizona. I serve as the principal investigator for NASA's OSIRIS-REx asteroid sample return mission. Basically, I'm the scientist in charge of the program.
[00:01:33] Sandy: My name is Sandy Freund. I am the Lockheed Martin OSIRIS-REx mission ops manager.
[00:01:39] Dante: Our goal is to get out to this asteroid, find the best spot on the surface, grab as much material as we can and bring it back to the earth for study in our laboratories. Our mission is really about going back in time to the formation of the solar system, to find the source of organic material that led to the origin of life here on earth.
[00:01:59] Host: With that goal in mind, now all the team had to do was find the right asteroid. It had to have the source material they were looking for and one close enough to earth. They discovered that asteroid as a tiny dot of light against the black void of space, its name was Bennu.
[00:02:15] Dante: Bennu is incredibly rare. It's very accessible from the earth and it's very rich in water and carbon.
[00:02:20] Beau: We think of Bennu as a time capsule. We're reaching back in time and we're pulling material into the present.
[00:02:28] Dante: And so, it really was the best target in the solar system for our mission.
[00:02:32] Host: They have the goal of the mission and the right asteroid. Now, they needed to start thinking through what major challenges the spacecraft would need to overcome to be successful.
[00:02:43] Dante: We were building off of some very capable heritage Lockheed Martin spacecraft, in particular, the Maven mission and the Juno mission.
[00:02:51] Host: And these missions gave the team the ability to get out to Bennu and study it in great detail.
[00:02:56] Sandy: We've got our TAGSAM which is our Touch-And-Go sample acquisition mechanism. So that's new technology that was developed here at Lockheed Martin, and we often describe as a reverse vacuum cleaner, in that once it makes contact with the surface of the asteroid, that triggers the release of the nitrogen gas bottles. That would stir up the surface regulus and cause it to float into the TAGSAM head and become entrained.
[00:03:23] Host: The TAGSAM device would give the team the ability to collect material from Bennu surface.
[00:03:28] Dante: And we were building off another Lockheed Martin heritage mission called the Stardust mission, which returned samples from a comet. And we were using that return capsule, especially it's heat shield.
[00:03:39] Host: The heat shield and the lessons learned from this mission would solve the last major challenge, bringing a pristine sample back to earth. The team had the technical ability and the know-how to build a spacecraft that would successfully complete the mission. Now, they just had to win a highly competitive selection process from NASA.
[00:03:57] Dante: OSIRIS-REx is in NASA's new frontiers program. I like to compare it to the NCAA basketball tournament. NASA says, "Okay, we're gonna open up a competition. One team is gonna win, and your mission's gonna fly somewhere in the solar system, and the other teams are not." And OSIRIS-REx was the team that won, and we were selected to fly in 2011.
00:04:19] Host: It was time to start building OSIRIS-REx
[00:04:22] Dante: And then once the design is locked down, you go into the build phase, and that was really fun. So, you start to see the hardwares coming in from all over the place, the instruments are coming in, the spacecraft structure is coming together, and you start to see your dream become a reality.
[00:04:37] Host: OSIRIS-REx was launched into space on September 8th, 2016. Now, this last piece of information catches us up with where we left off in part one of this series. The spacecraft was now sailing through space with its sights set on Bennu. But because Bennu was on a different orbit and plane relative to earth, you couldn't just fly directly to the asteroid. The team had to design a special maneuver to slingshot OSIRIS-REx towards Bennu.
[00:05:06] Dante: After we launched, we have to rendezvous with the asteroid, and the asteroid is orbiting at an inclined plane relative to the earth. So, one of the first things we had to do is figure out how we were gonna get out of the plane of earth's orbit, which is what we launched into and onto the plane of the asteroid's orbit. And we designed a maneuver called the earth gravity assist, where we came back one year later. We launched in September of 2016, we came back to the earth in September of 2017, and we use the earth's gravity field like a slingshot. And that moved us from the orbital plane of the earth up six degrees to match the inclination of Bennu's orbit and set us up for the rendezvous trajectory. And we were able to cruise along that way until August of 2018 when we got our first view of Bennu.
[00:05:50] Host: OSIRIS-REx finally reached its approach face. Even then it was still about a million miles away, but it was close enough to stretch out its legs. And by legs, I mean its cameras and science instruments. OSIRIS-REx has an amazing payload designed to study Bennu. The science camera's suite was called the OCAM comprised of three different cameras, the MapCam, PolyCam, and the SamCam. Dante starts us off with the MapCam.
[00:06:17] Dante: The MapCam has a series of color filters, so we can take images of the asteroid in four different colors, including one infrared channel, and then look at the geology and the variations in the composition of the surface using that information.
[00:06:31] Beau: The filter specifically selected to match filters that ground-based observations use to get color data of asteroids when looking at them from the earth. So, it was specifically selected to allow an apples-to-apples comparison of how Bennu looks in color with the spacecraft when we're there in person, and we can compare that to the colors that we see with the same set of filters on ground-based observatories, uh, here on earth.
[00:06:58] Dante: And that's important because we did wanna make sure we understood the chemistry and that we got the sample from, uh, a nice location that represents the asteroid.
[00:07:07] Host: Then we have our second science camera called the PolyCam.
[00:07:10] Dante: That image Bennu all the way from two million kilometers down to two meters from the surface, and at every distance in between. So, we really got an amazing range of images.
[00:07:20] Beau: So, it's got a much higher resolution, but it's also got a much smaller field of view, for to see the same surface area you actually need to mosaic together a series of images.
[00:07:29] Host: The PolyCam captured the very first images of Bennu from a distance of 1.4 million miles away. That's almost equivalent to six times the distance between earth and our moon.
[00:07:40] Dante: So, we got our first view of the asteroid in August of 2018. And it was just a point of light. It could just barely detect it with our cameras, it was as far away as we could see it, but still it was exciting to know that the destination is in sight. And then over the next four months from August through December of 2018, Bennu got more and more resolved in our field of view.
[00:07:59] Host: And as they got closer, the team would start using the MapCam. These cameras would support their primary goals of the approach phase of the mission, visually locating Bennu for the first time and surveying the surrounding area for potential hazards. They also wanted to collect enough imagery of Bennu so that scientists could generate a detailed shape model of the asteroid, assign a coordinate system, and understand how it was spinning. The other cameras and science instruments onboard OSIRIS-REx would be used as they got closer to Bennu, and some of them much closer like the SamCam.
[00:08:33] Beau: The third science camera was what we called SamCam, and it was specifically designed to monitor the sample collection event itself. So those are the three science cameras.
[00:08:46] Host: OSIRIS-REx reached Bennu in December of 2018. This would begin the preliminary survey phase of the mission marking the first time that OSIRIS-REx would be operating around the asteroid in close proximity. This would also be the first time that the team would begin to use the other science instruments onboard OSIRIS-REx.
[00:09:05] In this phase of the mission, the spacecraft made a total of five passes over the north pole, equator, and south pole. The science team would use the map cam, laser altimeter, and the spectrometers to further their understanding of the asteroid. With each pass, they would learn more about Bennu's mass, refine how they asteroid was spinning, and generate a detailed model of the asteroid. Let's take a look at the two spectrometers they use during this phase of the mission.
[00:09:33] Dante: We have two spectrometers that measure either reflected or emitted radiation. One is called OVIRS which looks invisible and near infrared wavelengths, and the other's called OTES, which looks out in the mid infrared for thermal emission data. That's radiation that's coming off the surface as heat.
[00:09:50] Beau: A spectrometer works by taking light and dividing it up into slices and looking at how much light is in any particular slice. And this is a very powerful technique to understand the composition of the surface. OVIRS and OTES don't exactly overlap in wavelengths, but they get very, very close. So OVIRS goes out a certain distance into the infrared. There's a very small gap, and then OTES starts observing at a little bit longer wavelengths and goes all the way into the formal infrared.
[00:10:21] The combination of OVIRS and OTES provide a tremendous amount of information about the composition and the thermal properties of the asteroid. And you can think of it like a geologist going out into the field. A geologist will take a rock hammer, knock it against the cliff, take that material and bring it back to the lab. But also, that geologists will take a lot of pictures and a lot of data to understand the context from which that sample came. So, when looking at that piece in the lab, you're getting exquisite amount of detail on that one piece of the sample, but then you'll be able to place it in the bigger context of where it came from and be able to make statements about the evolution of that broader area. So, that's the value of these spectrometers. They allow us to put the sample in the context of the overall object that is Bennu.
[00:11:13] Dante: We discovered the claim, and it rules right away that we were hoping to see, that was an early detection, it's a very strong signal, so we're excited about that. We have since found the organics on the surface as well, so everything we hope would be there was confirmed by those spectral instruments. And we were able to measure the thermal properties of the asteroid at high resolution and understand how that influences the future orbit because the emission of thermal radiation actually slows the asteroid down and changes its orbit in the future. Pretty interesting. And we have a scanning laser altimeter called OLA, which fires a laser beam and measures how long it takes to bounce off the surface. And it does that 10,000 times a second and build up amazing three-dimensional topographical maps of the asteroid.
[00:11:54] Beau: It's just an unprecedented data set that we can combine with the image data and the spectral data, and just have this incredibly rich understanding of Bennu as an object in space. And that provides just an incredible context into which we can place the samples that we analyze here in the laboratories on earth.
[00:12:15] Host: Now our next science instrument would discover something that they weren't even looking for.
[00:12:20] Dante: And then finally, we had a student experiment, REXIS, an X-ray imaging spectrometer. Students from MIT and Harvard worked with the spacecraft team to build and deliver this instrument. And it was tough. They didn't get a lot of signal off the surface of Bennu, it turns out not to be the instrument's fault because they found a black hole with their X-ray telescope. But Bennu, for some reason is not emitting X-rays in response to energetic particles from the sun like was predicted. And we don't know why, but there's an interesting science puzzle to be solved there. So the REXIS team still had an important discovery, even if it wasn't what they were hoping for.
[00:12:52] Host: OSIRIS-REx also had navigation cameras that helped them get to Bennu, and would eventually play a critical role in assisting the spacecraft to navigate down to the surface of the asteroid.
[00:13:03] Beau: In addition to the science cameras, we had two navigation cameras, and both were used in support of proximity operations around Bennu, and it was the images from those cameras that supported natural feature tracking.
[00:13:16] Sandy: So that is looking at features on the surface of Bennu that the team picked out ahead of time and loading those up to the spacecraft, that's a way of navigating down to the surface, in that we'll take images real time as we're descending onto the surface of Bennu, and it's able to match those in its onboard catalog to determine exactly where it's at. Is a spacecraft too far off the course? Which direction does it need to go? And its next maneuver to make sure that it's touching right at the sample site that we've selected.
[00:13:45] Host: The next phase would mark the first time OSIRIS-REx was placed into a gravitational bound orbit around Bennu. This would also mark the first of a series of orbital missions designed to practice spacecraft maneuvers and continue to perform science surveys of Bennu. These surveys would reveal a host of surprises and challenges that the team would have to overcome if they were to successfully retrieve a sample from the asteroid's surface.
[00:14:11] Sandy: Our biggest surprises, I would say, really came in flight. We designed a really great spacecraft, really confident in what we were about to do. But then as we got closer to Bennu, we could see this rocky surface, and we were expecting one large boulder on Bennu, and there were hundreds of them visible in the first few images that we started to get of the asteroid.
[00:14:31] Dante: The surface of asteroid Bennu is a rocky, rough, and rugged surface. And we were definitely surprised by some of those images that we saw coming back early on in the mission, because we were expecting this really smooth, what we call literally a beach like surface based on thermal properties that we had measured using telescopes prior to even launching. And instead, we saw this big rough rugged rocky surface.
[00:14:57] The asteroid itself has this amazing shape. It looks like a spinning top. It's almost a sphere except that it's bulging at the equator, and it's bumpy because it has these massive boulders scattered across its surface. So, it's 500 meters in diameter and the largest boulder that we can see is a hundred meters across. So, 20% of the width of the asteroid, you can see expressed in one large boulder on the surface. We have boulders that are tens of meters. We have thousands and thousands of boulders that are meter scale.
[00:15:27] Host: The diameter of Bennu is a little more than five football fields long. And that giant boulder that they were talking about would easily take out one of those football fields. The boulder field, like terrain, was a surprise that posed a domino of problems that the team would have to solve. Mind you these solutions are for problems that are over 200 million miles away. The first being the obvious, they had to find a safe area, big enough for OSIRIS-REx to take a sample from.
[00:15:54] Dante: It was really pretty challenging terrain to navigate a spacecraft down to the surface to collect a sample. And right away it was obvious that the design requirement of a guidance accuracy of 25 meters from a selected location was not going to work.
[00:16:08] Sandy: And that's really where everyone said, "Okay, this is not where we designed to go. So, we're gonna now need to look a lot closer at what we have on board, the spacecraft. How are we going to be able to get this sample?"
[00:16:17] Dante: There was nowhere on Bennu that was 25 meters in radius and safe for spacecraft to contact the asteroid. We had planned to take most of 2019 to map the asteroid in great detail and ultimately select the sample site, but we knew at that point that we were in for a pretty big challenge, and we were gonna have to solve some problems in order to get the spacecraft safely down to the asteroid surface.
[00:16:39] Fortunately, we had anticipated that there might be challenges, and we put a backup system on the spacecraft right around what we call a CDR, a critical design review. The board directed us to say, "Your current guidance technique is great, but it might not work, and so you need a backup capability. And we chose natural feature tracking, which the Lockheed Martin team developed for this mission. And I was able to use the map of the asteroid surface that the science team had put together and identify a catalog of features on the surface of the asteroid. And the spacecraft was able to take an image, find a feature that was in its catalog, and then determine its position and its velocity relative to that feature, and use that information to guide itself to a much tighter location on the asteroid surface.
[00:17:27] Host: The team switched gears to their backup system. By using the navigation cameras on OSIRIS-REx, they could use natural feature tracking to navigate them down safely to a much smaller area. However, the rocky surface in any potential TAG site could still pose challenges that could be catastrophic for the spacecraft.
[00:17:46] Sandy: The rocky surface was problematic in a couple of ways. The rocks on the surface at Bennu are also a hazard for the spacecraft. If we were to put the sampler head on a large rock, we run the risk of tipping over. So, we did a lot of analysis in spacecraft tip over, where could we land? We developed what we call a hazard map that we put on board the spacecraft in flight. And that was a way for the spacecraft to know if it was coming down near one of those large boulders, or if we run the risk of leaning over into a large boulder and perhaps hitting part of the spacecraft structure or the antenna.
[00:18:23] Host: The natural feature tracking and the hazard map would help them avoid unsafe rocky features and increase the accuracy of where they would want the TAG from. The last point brings up the next challenge, the TAGSAM device was designed to collect smaller material than what they were initially seeing.
[00:18:41] Sandy: We wanted to make sure that we got some fine grain material, but our TAGSAM collector is designed to pick up particles that are two centimeters or less in diameter. So not unable to ingest those large rocks, and we wanted to make sure that we placed the TAGSAM head on the surface where we believed there was fine grain or more sand like material in order to make sure that we would pick up an appropriate sample to meet the mission goals.
[00:19:06] Host: As they looked through these navigation cameras to develop their natural feature tracking and the hazard map, they began to see something very strange happening with the asteroid.
[00:19:15] Sandy: And just as we were starting to come to grips with what we were dealing with and discussing changes that we can make to sample collection, we started noticing particles coming off of Bennu. So, about a month and a half after we had arrived at the asteroid and seen this rocky surface, it was essentially spitting rocks at us.
[00:19:32] Dante: We were surprised by Bennu ejecting particles into outer space, and those were only detectable in the navigation camera system. So, all of a sudden, the MapCams became science instruments for particle tracking. And we got a whole bunch of bonus science that we didn't even anticipate before we got there.
[00:19:47] Beau: And this is the great thing about space exploration is, anytime you send a spacecraft somewhere new, you get to answer the questions you knew to ask, but you also realize that there are these amazing questions that you didn't even think to ask that you get to answer. We had no idea that was happening before we got there, and it was totally unexpected, and it caused a scramble for the mission. We had to figure it out whether or not these were gonna be a risk to the spacecraft, and if it was gonna still be safe to orbit Bennu.
[00:20:15] Sandy: So that was another really amazing finding from the science team, but also a little bit scary on the engineering side, in that Bennu was now classified as an active asteroid, where on occasion particles come off the surface and some stay in orbit for a short period of time, others fall right back. So, that was another interesting thing that the team had to come together, characterize those particle-ejection events, decide that the vehicle was going to be safe and then start changing. Everything we had designed for TAG before we left the ground, we redesigned again in flight to accommodate the rocky surface of Bennu.
[00:20:49] Host: These particle-ejection events sound like something straight out of a science fiction movie. Scientists studying Bennu have several fascinating theories on why they think this is happening, but for now we're saving this topic for a short bonus episode. I can say that these rocks being kicked into space from the surface of the asteroid acted as a key, unlocking the team's understanding of Bennu's weak gravitational force.
[00:21:13] The team would take advantage of this bonus science and their initial surprising observations to develop a new plan for collecting a sample. That new plan would require them to find a site safe enough for the spacecraft, and that had small enough material for the TAGSAM device to collect a sample. To find the best location, the engineers and science teams across several organizations would have to work closely as one team.
[00:21:38] Beau: So, it was a significant parallel effort on two fronts. There was the science front, which was, "Let's start working with that data and scouring the surface as much as we can to find the smoothest spot with the smallest grain size possible." And then on the engineering front, it was, "You know, how small of a TAG site can we target? How accurately can we get the spacecraft to the surface of Bennu?" And it was a huge set of analyses that were done by the science team to work through all of the image data, to work through all the laser altimeter data, to put together maps and analyses to pick out the best spot to sample on Bennu.
[00:22:17] Sandy: For our science team is led by our principal investigator, Dante Lauretta from the University of Arizona, and that's where our science processing center is. So, it's a close working relationship while we were in the science phase of this mission. And it really had to be because we wanted to get as much science as we possibly could while we were there and needing to work closely with them. So even though we were not co-located together, it's a lot of collaboration, sometimes multiple times a day with the partners that are not just here in the University of Arizona, but with our NASA center, which is Goddard out in Maryland, and then of course our navigation team, which was fortunate to be resident here, most of the time.
[00:22:56] Host: Finding the best site would require a symbiotic and coordinated working relationship between the teams located in Arizona, Colorado, and Maryland.
[00:23:06] Sandy: We have quite the site selection campaign, kind of treated it a little bit like a basketball brackets. So, we started with 50 sites, and we got to the sweet 16, and the final four, and then down to our final two sites. And what really drove those ones out was the fact that it looked to have sampleable material, and it's material that's less than two centimeters in size that could be ingested into the TAGSAM head and look to be safe to get there.
[00:23:32] Dante: Ultimately, we selected a location that we named Nightingale Crater as the primary sample site for OSIRIS-REx.
[00:23:38] Sandy: It looked very diverse, so different colors of material, and our science community believed that it was a very diverse site scientifically.
[00:23:47] Beau: The sample site is about eight meters in diameter and that eight-meter circle sits inside a 20-meter diameter crater.
[00:23:54] Dante: The crater itself sounds reasonably large relative to our guidance accuracy, but there's still a lot of hazards around and inside the crater itself. And so that was gonna be kind of a tight fit. We compared it to parking the spacecraft, which is about the size of a passenger van, into a parking lot where only a couple of parking spaces are open for you. And of course, we're doing this over 200 million miles away from the earth.
[00:24:17] Sandy: We did have a very large boulder on the edge of that site that we named Mountain Doom that of course was a spacecraft hazard, and we didn't want to land on Mountain Doom or tip over into Mount Doom. We believed we could get there, and it looked to have that samplable material, so that's what really made that site stand out from the others.
[00:24:36] Host: Through their rigorous selection process, the team finally selected a site, they called Nightingale. Now, Nightingale was a crater that could easily fit a semi-truck with a trailer inside of it. OSIRIS-REx had to navigate into that crater and touch an area that was about the size of a couple parking spots wide. Oh, by the way, the spacecraft also had to avoid a giant two-story sized boulder they named Mount Doom.
[00:25:02] Nightingale was a promising location because it contained the fine grain like material that the TAGSAM device could collect. The team trusted that the spacecraft could get into this small area safely, and now needed to prepare by practicing for the TAG event. OSIRIS-REx's unique design would allow it to maneuver gracefully around Bennu's microgravity environment.
[00:25:23] Dante: We designed this spacecraft to operate it around the asteroid. And one of the key aspects of the spacecraft design was the micro thrusters that were involved, because you're in this micro gravity environment, all little velocities are on the order of centimeters per second. Everything is incredibly slow-motion ballet when you're operating a vehicle around an asteroid. And we had to impart just tiny little thrusts, millimeters per second of velocity to adjust the spacecraft position around the asteroid. And then we had to teach the spacecraft how to do that, how to figure out how much thrust to give the thrusters, depending on where it was and the approach trajectory to the asteroid surface.
[00:26:01] So, it became a very smart spacecraft as a result. And we trained it and we tested it, and we actually rehearsed twice the sampling event before we committed to sending the spacecraft down to the surface. Because we wanted to make sure that all that software was working and that the spacecraft knew how to make the right decisions, and particularly how to make those right calculations for the propulsive maneuvers.
[00:26:22] In April of 2020, we did the first rehearsal we called the Checkpoint rehearsal, which tested out that natural feature tracking software, as well as the ability of the spacecraft to use that information and update firing of its rocket engines to begin to descent towards the surface. We repeated and expanded the rehearsal called the Match Point rehearsal in August of 2020, and that took us within 40 meters of the surface. And the final challenge that we had to solve for the safety of the spacecraft was, even though we thought the guidance was gonna meet the requirements for Nightingale, there was still a chance it was gonna hit one of those large rocks, including what I called Mountain Doom, which was this giant boulder like the size of a two-story building on the eastern edge of the crater. So, we put a final piece of software called the hazard map.
[00:27:07] Sandy: What we implemented was the hazard map that at five meters made the final determination of, on coming down and what is considered a green area versus them coming down and what is considered a red area. So, using our natural feature tracking software, it had a projected, "Here's where I'm going to make contact with the TAGSAM head.," and a check of, "Yep, that's a safe contact," or "That's not a safe contact," at the five-meter mark. Had that not been a safe area, then the spacecraft would have performed that back away burn. But that TAG abort, it was something that we were prepared for. This was a unique event in that we had three opportunities, right? We already had two sites picked out and we had three nitrogen bottle onboard the spacecraft, so if we had gotten close and something had gone wrong, the best thing to do was to have the spacecraft back away, take care of itself, and we would try another day.
[00:27:56] Dante: And we checked that system out in our Match Point rehearsal. So after the second rehearsal, we were fully competent that spacecraft capabilities were exactly as they were needed, the new software was functioning properly, and that we were okay to go in and get that sample in October of 2020.
[00:28:13] Host: OSIRIS-REx is so far away that any communication sent from earth would take 18 and a half minutes to reach the spacecraft. So, having a conversation with OSIRIS-REx would take 37 minutes. This lag time would make it impossible to fly the spacecraft in real time, that meant OSIRIS-REx would have to perform the final TAG maneuver all on its own. To accomplish this feat, the engineering team at Lockheed Martin maneuvered OSIRIS-REx by sending special commands up to the spacecraft. Everything had to be perfect. So, they would always test these commands with their ground simulators. In fact, the Lockheed Martin team would practice the final day of TAG, hundreds of times, working out all of the faults and conditions. When the final go command was sent, OSIRIS-REx would be autonomously performing the maneuvers, meaning it would be making real time calculations and decisions all on its own.
[00:29:09] This is where one of the more spectacular aspects of the mission takes place. At the five-meter mark is the point of no return, and it's here that OSIRIS-REx has the final say. The fate of the entire mission would be up to a spacecraft performing a delicate dance around an asteroid, 200 million miles away. The engineers and scientists have been training OSIRIS-REx for its big day. Still, everyone has their own worst-case scenarios that they're thinking about on the day of TAG.
[00:29:39] Sandy: I think it's probably a little bit different everybody, but coming from a full protection background, I knew the final three minutes, coming into TAG was a vulnerable point for the spacecraft. If this spacecraft were to experience a reboot at that time or have some sort of other failure, it may not recover before it would make an uncontrolled contact with the surface of the asteroid. So that was something that we had identified early on in development that said, "Hey, the final three minutes before contact is a potential loss of mission scenario, if we were to have a really bad day." So, where I was sitting, [laughs] once we passed that three-minute mark, it was okay. We are headed in from a fault standpoint, right? The spacecraft can no longer recover and take care of itself. Now, of course, in parallel, you have the TAG abort running on things like the hazard map to safely back you away, but some of our other faults that we analyzed, and those spontaneous reboots would have been a situation that non-recoverable.
[00:30:36] Dante: The worst-case scenario during sample collection was what the, the spacecraft contacted the asteroid surface and was perturbed substantially to the point where some other piece of the spacecraft contacted the asteroid. And we worry about the solar arrays. Those are big panels that were sticking out from the spacecraft. We put them away, away from the surface, but it was possible that they could either tip over and become damaged by contacting a boulder, or even worse tip over, and then the spacecraft fired its thrusters and flew into one of the large boulders that were nearby the asteroid and then you probably lose the vehicle at that point. And we put in a lot of protection so that it probably wasn't gonna be into an unsafe state, but you never know, nature always has a way of surprising you. It may have determined that the location was safe and turned out not to be, and it was hazardous for some reason and the spacecraft was either damaged or lost during the sample collection.
[00:31:26] Host: On October 20th, 2020, the team sent the final command for OSIRIS-REx to collect the sample. No more training, no more test flights, it was time for its big day with Bennu.
[00:31:37] Sandy: So, the TAG event was all sequenced on board. We sent the final go command, and then we were really hands off because you can't really do much when you're 18 and half minutes away.
[00:31:47] Dante: The entire TAG sequence had to be autonomous. We told it to go for TAG, and it had its programming, and it had its decision-making capabilities, it collected the natural feature tracking imaging data, and it calculated the maneuvers that it needed to get down to the surface. So yeah, it was fully on its own at that point, and we were just watching events play out. We got signals from the spacecraft, and everything that it told us had happened to 18 and a half minutes in the past. So, on the day of TAG, I was hosting NASA's live TV broadcast [laughs] so I was in, in the control room and I could hear the engineer calling out the major milestones in the sequence.
[00:32:23] NASA Broadcast: Checkpoint burn in two minutes.
[00:32:24] Dante: So, we were getting a little bit of information from the spacecraft.
[00:32:28] Sandy: During the TAG event, we had 40 bit per second telemetry, which is insanely slow, but we prioritized that telemetry to only bring down what we needed. And of those pieces of data was the milestones.
[00:32:41] Dante: We thought about each one of those bits, literally like, "What do we wanna know from this spacecraft? What is the most important information?" And so, the spacecraft was telling us its positional estimates using the natural feature tracking software, where is it? And what are the updates to the maneuvers looking like? So, we were getting a pretty good sense that the software was working, the critical guidance software was taking images, it was finding features, it was solving for position and velocity, and propagating that information forward.
[00:33:07] Sandy: I think for a lot of the team, once we got below 25 meters on TAG day, we had done these two rehearsals, we have seen the spacecraft, we had gotten closer and closer, but we passed that 25-meter mark on TAG day and the team got really quiet. And I think that's when most people started to get nervous in that, "Oh man, we're really gonna head in and touch this asteroid."
[00:33:31] Host: As OSIRIS-REx made its descent down to the Bennu, I'd like to imagine what it would have been like if you somehow were in a space suit and could have been there as it happened, just what exactly would you see?
[00:33:43] Dante: You would be watching a spacecraft approaching at an excruciatingly slow rate. It would be literally in the sky above you for hours [laughs] as it began its 10 centimeter per second crawl towards the asteroid surface.
[00:33:56] Sandy: So not moving very fast at all. It would have been a nice, slow ride to the surface.
[00:34:02] Dante: That's one of the things you need to understand when you're operating in these micro gravity environments, everything is an excruciatingly slow motion because it's driven by the acceleration from gravity, which is very, very low. So, you wouldn't even be sure it was moving I think if you were watching it come down, the pace would be so slow.
[00:34:19] Beau: If you were an astronaut, at the end of the TAGSAM arm, coming along for the ride to the surface, you would see a surface that was covered in boulders and rocks of a huge variety of sizes. From the big picture perspective, you're coming down inside of a bowl, and around that bowl, there are these very large boulders, one of which was as big as a two-story building. This giant two-story building is looming over you, especially now, if you're just down to five meters to the surface and getting closer. Then if you direct your attention towards the surface, you'll see rocks scattered all over that are, uh, half a meter in size and larger. Between those rocks, you'll see particles that go down as small as your eye can actually pick out.
[00:35:15] Sandy: And then at five meters, when we saw that the spacecraft had passed that hazard map check is, I think when people got really excited and really nervous, [laughs] and that we were headed in, we were gonna make contact. It was for sure gonna happen.
[00:35:29] NASA Broadcast: Position on certainty is 0.5 meters. [cheering, clapping] Predicted TAG lateral off set is 1.7 meters. Hazard probability is 0%.
[00:35:40] Dante: Right at the five-meter crossing, which is kind of like the point of no return, and that's when the spacecraft could say, "I don't like it. It looks hazardous and I'm backing away." We got a report that the hazard map had calculated 0% probability of hazardous contact and was going in to collect the sample. So that was a huge moment of cheering.
[00:35:58] NASA Broadcast: OSIRIS-REx has descended below the five-meter mark. The hazard map is go for TAG, and the TAG is expected in 50 seconds.
[00:36:06] Dante Broadcast: We're going in. We're going in. [laughs]
[00:36:08] Broadcast Host: We're going in. [cheering, clapping] All right.
[00:36:14] NASA Broadcast: Sampling is in progress.
[00:36:17] Sandy: When we made contact, we received a message that said, "Contact detected."
[00:36:22] Dante: There are accelerometers that tell you that the spacecraft has slowed down, and we sensed the initial contact with the asteroid surface, and we got that information right away. And this is where we did get another surprise. The asteroid surface turned out to be really soft. The response I think is best described like a ball pit in a kid's playground. You kind of jump into it and you're gonna sink in pretty deep, the faster you're going, the deeper that you're gonna sink. The asteroid just kind of moved away from us almost like a fluid, which means that there was almost no cohesion between the grains. They were able to move past each other freely without providing any resistance.
[00:36:59] Beau: The TAGSAM head could actually penetrate down into the subsurface a little bit. And that's because in a microgravity environment, particulate material can actually act like a viscus fluid. It's one of the amazing ways in which our 1G intuition is totally wrong in a micro gravity environment.
[00:37:19] Dante: And we sunk in probably 10 centimeters or so, and then fired that gas bottle. And then all hell broke loose.
[00:37:35] Sandy: You could see rocks flying everywhere. We left what we believed to be quite the large crater on Bennu. That would have been a very high energy moment.
[00:37:44] Beau: Because of the microgravity environment of space, a gas can accelerate a lot of the particles outside the TAGSAM head extremely quickly. So, in the images, you'll see the stream of material moving radially away from the TAGSAM head.
[00:37:59] Dante: We were in contact for about six seconds before the back away thrusters fired. And this was a large burn, 40 centimeters per second. A lot of velocity was added to the spacecraft. And then those thrusters hit the surface of the asteroid. There was four locations where the thrusters hit the asteroid surface. They each kicked up a wave of material, and it looked like tsunamis were kicked up.
[00:38:20] Sandy: There is rocks flying everywhere, uncovering surface that we had not seen before for those few seconds before then the spacecraft started to back away.
[00:38:30] Dante: The thing that struck me the most watching those images, is that the material looked really like sand. And I said, finally, we promised that the surface of the asteroid was going to be beach like, we got there, and we saw this rugged rocky material all over the place. But as soon as we dug down a little bit into the surface, that's where the sandy material is. And that just got blown all over the place, both from the TAGSAM gas and kind of from the thrusters as the spacecraft backed away.
[00:38:56] Sandy: It would have been a gentle ride on the way in, and then quite the event at contact before backing away. And we of course backed away faster than we came in. We wanted to get away safely from the asteroid and from the rocks that we sent flying. And of course, it had happened 18 and a half minutes earlier, but we cheered as though it was happening now.
[00:39:16] NASA Broadcast: [indistinct radio chatter] Sample collection is complete and the back away burn has executed.
[00:39:24] Dante Broadcast: All right, we are on our way back. [laughs]
[00:39:31] Dante: It was emotional for sure. It had been almost seven months and I'd seen the team in Denver, and, you know, we're like a family. It's really tight-knit group. We've worked hard together, we'd solve problems together, and so it was just exuberant. I mean, everybody was thrilled. I was able to come to Denver for the big TAG events and be with the spacecraft team. It was really overwhelming and powerful, joy, excitement, pride, and also trying to keep my cool 'cause I knew how to get back on TV and get back to the cameras and tell what was going on.
[00:40:00] Beau: The moment of TAG and realization that TAG was successful, it's indescribable. I started working on this mission in 2004 and here it is 2020, 16 years later. So, it's this very odd juxtaposition of time scales, where you have 16 years and thousands of hours of effort, and all of that gets distilled down into just a few seconds at the surface of an asteroid. It's just indescribable. It's amazing. It's a thrilling experience. It's extraordinary.
[00:40:35] Sandy: It's a little bit surreal. I mean, many of us have been working for a number of years in all the planning, um, and preparation and all the curve balls that got thrown along the way to finally be there executing TAG. It was a little bit of disbelief that we had finally gotten to that point. This thing we planned forever was actually happening. I still think that even a couple weeks later, we still have a lot of us that are walking around going, "Wow, that's actually over."
[00:41:07] Host: It's fun to hear Dante, Sandy and Beau recall that day with all the information they have now. In actuality, everything they saw happen 18 and a half minutes earlier, and they were essentially reading numbers from a screen. The team would have to wait several hours before witnessing the drama of the TAG unfold before their own eyes. You see, the SamCam, the camera mounted on the arm of the TAGSAM, had been observing the TAG event the whole time.
[00:41:34] As they waited for these images, I'm awestruck at the thought that these teams were about to be the first humans in the entire world to see these pictures. And what they saw was nothing short of incredible. And much of what you just heard them describing is what happened in those images.
[00:41:51] Dante: Everything went according to plan, and we got confirmation. At least the spacecraft did exactly what it was supposed to do. How the asteroid behaved, we wouldn't know until a few hours later when we were able to bring the images down and analyze those and see, in fact that everything looked fantastic. The surface responded in the best possible way. The TAGSAM head was buried deep before the gas fired.
[00:42:15] Quite honestly, it was 2:00 AM, in the morning after tag, when those images came down and I stayed up and waited for that information. And as soon as I saw the first image of the TAGSAM head pushing into the surface before the gas bottle fired, I knew we had it. I was like, "We got it. We got the sample and we're good to go." So, I'll never forget staring at that image, I blinked back and forth before contact and after contact, hundreds of times just watching the spacecraft push into that asteroid surface, and I felt great. I was like, "Mission success."
[00:42:44] Host: Well, almost over. OSIRIS-REx has safely stored the precious sample of Bennu in its return capsule. It performed one last fly via Bennu capturing a final observation of the Nightingale sample site before making the long flight back to earth. The spacecraft is scheduled to deliver the sample to earth on September 24th of 2023.
[00:43:05] Beau: I am very excited about the space industry. We're in an incredible age of planetary exploration. There are more planetary missions happening now than have happened ever before. So, if you're excited about space, come on in, it's an amazing place to be now, and it's just gonna get even more amazing in the years to come.
00:43:31] Host: The future of deep space exploration is exciting, and the private sector will play a significant role in making those future missions possible. Missions like sending humans back to the moon to stay and beyond to Mars. In today's flash forward segment, we will look at how the space industry will shift to an in-space economy supporting the missions of the future. I'm joined today with Joe Landon, and let's start off by telling me a little bit about what you do here.
[00:44:00] Joe Landon: Cool, thanks Ben. I lead Lockheed Martin's space exploration strategy, and my team is responsible for the strategy growth and research and development for our commercial civil space business, which includes human and robotics space exploration, uh, and also weather and earth science, and commercial communications markets.
[00:44:17] Host: It seems like there's really two sides to your role, exploration and development. Can you speak into what do those roles look like at Lockheed Martin, and, you know, where do they intersect?
[00:44:28] Joe Landon: Yeah, that's a really good question. And there's a, a distinction there that is often missed. You know, space exploration is about science, right? It's about the platforms and the missions that expand human knowledge, discover how our solar system works, and also to extend human and robotic presence within the solar system. So, it's really a science goal and the mission is about science. And Lockheed Martin has really been the leader in this area for many decades.
[00:44:52] Space development is different from space exploration. First, it's not purely about science, it's about commerce and other things. It's a broader subject. So, developing infrastructure to support economic activity and space. For example, that economic activity might be science. So, NASA might have a mission to the moon, but is the power station that serves that mission, that's, the purpose of that power station isn't science, even though it's serving a science mission, the purpose is commerce and development. Communication services, other types of services will start by supporting science, but then other missions, other types of purposes can grow from that.
[00:45:29] Host: I've heard you use the term astropreneurs and I was hoping you could explain a little bit more about what you mean by that? And how do you see a space economy supporting missions of the future?
[00:45:41] Joe Landon: What I'm excited about in the future is we're starting to see at least the early signals of an in-space economy. And this idea of an astropreneur is really just a mashup of astronaut and entrepreneur. I like this term because there's lots of opportunities for new companies and people to start companies in space that are growing. And really over the past 10 years, the growth of the commercial space economy has really created these opportunities. And a lot of money has gone to launch vehicles and to earth orbiting satellites. That's where most of the astropreneurial opportunities have been. But the area I'm most excited about is beyond earth to the moon and beyond. It's almost like when you move into a new apartment, you need to set up power, water, and cable. Those are the same things you'll need when you get to the moon. And it's a business opportunity to provide those services and to create those capabilities.
00:46:25] Host: So where do you see this in-space economy really being implemented to support or even create this infrastructure?
[00:46:33] Joe Landon: Really for me, in and around the moon makes the most sense to develop this type of infrastructure right now, because you, you're kind of far enough from earth to make things, doing things locally has a lot of value, but you have time delays and just the distance and the difficulty of operating at the moon makes it valuable to have some local storage or local services there. Things like power, communications, data storage, even data processing.
[00:46:56] You know, one opportunity is communications, let's say at the moon. So, right now, every single mission that goes to the moon has to close the entire communications link and have a full system to communicate back to earth. So, what if instead there were satellites orbiting the moon or cell towers on the surface of the moon. If I'm designing a mission, I can assume the communication capability is gonna be there. I don't have to build that into my system. I just have to talk to the nearest cell tower. I don't have to close that link all the way back to earth. So that's the type of opportunity where a small investment in a capability like communications around the moon can just create a whole lot of value for the whole space economy.
[00:47:34] Host: As we've heard about, in this episode, OSIRIS-REx successfully captured a sample of Bennu, and we're also learning that in some ways it's working out some of the technologies you would need to one day mine asteroids as astropreneurial pursuit. Do you think something like that could be possible in the future? And how do you see us using those resources?
[00:47:57] Joe Landon: Yeah, so I, I really do think this is possible and a big opportunity for the future, and not just asteroid, just the general idea of resources in space. The real value there is being able to find stuff you need in space that you don't have to bring with you from earth, it costs a lot of money, and it takes a lot of energy to get stuff from the surface of the earth, even into low earth orbit. But once you're in low earth orbit, you can move around with relative ease and very little amount of energy to almost anywhere else in the solar system.
[00:48:25] Thinking about resources in space, there's really three main types of resources we'd look for. And there's an order of a priority, which I think we'll need them. So, water is number one. The space economy is really fueled by the water economy in space. We need water to make propellant, and propellant is energy to get around and move around, if we can find water on asteroids or on the moon. So being able to find things like water to sustain human activity, or to split that water molecule into hydrogen and oxygen and it becomes a rocket fuel, at that point, propellant. Being able to find those things in space, there's a lot of economic value to that. And it could be from asteroids, or it could be from the surface of the moon, you know, there's water on the surface of the moon, so we can create propellant on the moon and use it to get back off the moon.
[00:49:08] The next thing we'd look for is building materials. So, it could be as simple as using lunar regolith, and instead of having a surface that's all full of rocks and craters, like maybe we can just create some bricks and make a landing pad. Like very simple use of resources on the moon. But there's also on the moon and in asteroids, metals and other types of things that we could feed into 3D printers to use as building materials in space.
[00:49:31] Today, if you look at how we built the International Space Station, we built it on earth in little pieces, and then had to put those pieces onto rockets and launch them into space. I mean, that's like building a dam in Seattle and shipping it to a river in India. Like it makes no sense, right? Can we get those building materials from space from where we need to use them?
[00:49:50] And then third tip of space resource is industrial metals and other types of things for manufacturing. And this is where a lot of the public attention has been put on like platinum and platinum group metals. But re- that's really the last. Like, once we have factories in space, that's when we'll start looking for those types of materials.
[00:50:06] Host: As you know, there are very real initiatives to go back to the moon and stay. So, what are some of the practical steps that we will need to do to make this happen?
[00:50:16] Joe Landon: First, the goal really should be research stations on the moon. I think that's what we'll see first. We know there's water on the moon that could be used to sustain humans and create propellant, so I think the first real step towards sustainability is, can we live off the land even just a little bit, because then we start to not have to bring everything with us. In order to do that, you need technologies like In-Situ Resource Utilization. Like how do you find and make usable those resources that are on the moon?
[00:50:41] And then in space manufacturing and assembly, like once you have resources, you need the technology to do something with it. Some of these will involve human interactions, but most will need to be robotic, and perhaps even autonomous or semi-autonomous so that, you know, we can land a, uh, spacecraft on the moon that can go find some water, create propellant and have it waiting for the astronauts when they land.
[00:51:03] Host: And what would you use the propellant for?
[00:51:05] Joe Landon: So, the propellant really is gonna be used for rocket systems. So rocket landers, ascent vehicles to get off the moon, landers to stop and land softly on the moon. That's what the propellant will be used for. For rovers, it'll be electrically powered. So then if you have a rover that has batteries and electrically powered, whether that rover is carrying humans or not, you need to recharge that rover somehow. So then there needs to be a source of electrical power on the moon as well. Whereas the old chemical power, the propellant, is used for rockets, the electrical power is used for almost everything else.
[00:51:37] And there's gonna be two ways that we generate that electrical power on the moon. First, it will be solar power. There's abundant solar resource on the moon, and we can use solar panels and other techniques to generate power. However, the night on the moon lasts 14 days. So we'll need nuclear power on the moon that can work in space and can generate large amounts of power over long periods of time, are gonna be really valuable technology.
[00:51:58] Host: I mean, you're talking about using the moon's natural resources to, you know, basically live off the land. And it seems like you would have to move around quite a bit on the moon to make that happen. So, ho-how do you see that being possible in the future?
[00:52:12] Joe Landon: Yeah, I think the vision for lunar exploration that we have now is really different. I mean, we wanna be able to cover much more ground and mobility on the surface of the moon, it's really important. So, you're right, the Apollo astronauts, they landed at a landing site, and the most they ever traveled, including with the lunar roving vehicle that they had was 4.5 kilometers. And NASA really didn't want the crew to go further on the vehicle than they could walk back in case something went wrong. So, we really wanna take a different approach this time.
[00:52:41] And, you know, I'd like to see everything on the moon that ever lands, it should have wheels. I mean, we need to move things around and develop technology to provide mobility for science purposes, for moving humans around. And this is really the idea behind our collaboration with General Motors, is really to bring the best together on how to create mobility capability on the moon and provide humans opportunity to move around, but also science payloads, and other space development payloads, power stations, and whatnot, to be able to move them to the best place. And then when Artemis astronauts land on the moon, they'll already have their supplies and materials prepositioned where they land. And then when they leave, all the stuff will move to the next landing site in time for the next set of astronauts to land.
[00:53:27] Host: How do you see these foundational technologies used on the moon helping us go to different places like mars?
[00:53:34] Joe Landon: The moon really is a great proving ground. It's, it's relatively closer to earth so we have shorter communications delays, and also, it's a lot shorter trip if you need to get home. And some ways, the moon is even a harsher environment because you don't have an atmosphere, and we'll figure out all kinds of problems that we even know existed on the moon that will be able to figure out and develop the right technologies to enable that, that feature on Mars.
[00:53:56] To get to both the moon or Mars, we really need everything. Like all the technologies that we talk about in the space sector, finding and using resources, being able to manufacture things in space and additive manufacturing, power generation, solar and nuclear, deep space communications technology. Also, habitation, where are the humans going to live and how do we take care of them? One thing that we're working on on is technology for expandable or even inflatable habitats that can be on a planetary surface or an orbit. One technology we need to get to Mars is the technology to actually get to Mars. Like it's a, it's a long trip to Mars. We need to be able to sustain the humans on that trip out to Mars. So those same technologies, those habitats and that those power and life support systems can be tested out lunar gateway or on lunar's surface. And then that helps us put together a system that will work to get to Mars.
[00:54:46] Host: So, I'm curious to know, is there any technologies that you are particularly excited about that could play an important role in, in shaping the future?
[00:54:55] Joe Landon: Yeah, there's really two technologies that I'm really excited about and I think are really critical. So, space-based nuclear power and propulsion, the whole idea of space-based nuclear technology is really important. We've used nuclear technology in space before. Most of the missions like Cassini and others have used RTG, which is basically using the heat from the decay of nuclear material to provide power. And this technology is completely different. We're actually using a nuclear reactor in space to accelerate propellants. So, in order to generate large amounts of power far from the sun, a nuclear reactor is a really great way to do that.
[00:55:29] But nuclear propulsion is also really critical. So, by using a nuclear reactor to accelerate propellant, uh, basically nuclear-powered rocket, we can cut down these vast distances between places in the solar system and create a much more efficient propulsion system. Uh, and we're working on this with both NASA and DARPA to generate these nuclear thermal propulsion systems. So, it's about three times more efficient, a nuclear system versus a chemical propulsion system. So, it needs less propellant mass to go the same distance so you can take more stuff with you. It also enables a faster trip to Mars. So, it could take a three-year trip and reduce it down to two years round trip, which is, you know, pretty significant reduction in time. So that makes the whole task of keeping the humans safe during that trip easier.
[00:56:12] And then in order to achieve nuclear thermal propulsion and nuclear power in space, we need to be able to store cryogenic propellants in ways that really just don't have of the technology for now. So propellants like hydrogen and oxygen need to be kept really cool and under, uh, high pressure. And right now, we can't store large amounts of hydrogen in space for very long, 'cause it just leaks out of the containers we try to put it in. So, we're also developing technology for long term, large scale cryogenic fluid transfer and storage in space.
[00:56:42] So nuclear thermal propulsion is very efficient. The real benefit is the efficiency. So, instead of having single use vehicles, you could just make your fuel that you bring and you have last a lot longer and do multiple missions. So, you can go to multiple destinations on science missions. Or you can go back and forth between different places in space. Like in the moon and Mars, you can have vehicles that just go back and forth multiple times because you have such efficient propulsion.
[00:57:15] Host: This series is dedicated to Dr. Michael Drake, who served as a director of the lunar and planetary laboratory at the University of Arizona. He was a husband, father, friend, and mentor. His brilliance will be missed.
[00:57:29] This concludes our two-part series about OSIRIS-REx and the asteroid sample return mission to Bennu. If this mission interests you, stay tuned for bonus shows and mission updates. You've been listening to Dante Lauretta from the University of Arizona, Beau Bierhause, Sandy Freund and Joe Landon from Lockheed Martin. And they are space makers. Whether you're a software engineer, systems engineer, finance, or HR professional, we need space makers like you to make these seemingly impossible missions a reality.
[00:58:01] Please visit this episode show notes to learn more about the OSIRIS-REx sample return mission to Bennu or the careers available at Lockheed Martin. If you enjoyed this show, please like and subscribe so others can find us and follow along for more out-of-this-world stories from Lockheed Martin Space headquartered in Littleton, Colorado. Join us on the next episode, as we introduce you to more space makers.
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