From: Georgia Institute of Technology
Posted: Tuesday, July 28, 2015
Draft Written Statement of Dr. Robert D. Braun Georgia Institute of Technology
U.S. House of Representatives Committee on Science, Space and Technology Exploration of the Solar System: From Mercury to Pluto and Beyond July 28, 2015
Mr. Chairman, Ranking Member Johnson and members of the Committee, thank you for theinvitation to appear before you today to share my view of the exciting future of our nation'ssolar system exploration program. It is an honor to be seated at this table with some of ourworld's planetary science heroes. My name is Robert D. Braun. I'm an engineer and atechnologist. The views I express today have been shaped through a 28-year aerospaceengineering career in government, industry and academia. I started my career as a member of the technical staff of the NASA Langley Research Center. As a young engineer at Langley, I was given the freedom to dream big. I developed advanced space exploration concepts, ledmultiple technology development efforts, and contributed to the design, development, test andoperation of several robotic Mars spaceflight systems beginning with the Mars Pathfindermission, which included the first rover to visit the Red Planet.
Since 2003, I have been fortunate to serve on the faculty of the Daniel Guggenheim School ofAerospace Engineering at the Georgia Institute of Technology. At Georgia Tech, I lead aresearch and educational program focused on the design of advanced technologies andmission concepts for planetary exploration. Judging by the passion and creativity of thestudents I see everyday on the campus of Georgia Tech, this nation's grandest era of spaceexploration is ahead of us. It gives me great pride to work closely with these students, who are on their way to creating economic, national security and societal value for our nation through our space program.
In 2010-2011, I was honored to serve as NASA's first Chief Technologist in more than adecade, creating and leading the development of a spectrum of broadly applicable technologyprograms designed to build the capabilities required for our nation's future space missions. I presently serve as Vice Chair of the National Research Council's Space Studies Board and Chair of the Standing Review Board Chair for the Mars 2020 Project. However, I am here todayas an individual and the views I express are mine alone.
Solar System Exploration
Planetary science is one of America's crown jewels. A unique symbol of our country'stechnological leadership and pioneering spirit, this endeavor has consistently demonstrated that the United States is a bold and curious nation interested in discovering and exploring therichness of worlds beyond our own for the betterment of all. In addition to informing ourworldview, these missions are inspirational beacons, pulling young people into educational andcareer paths aligned with science, technology, engineering and mathematics, the foundation ofcontinued U.S. economic competitiveness and global leadership in a world that is becomingmore technologically advanced with each passing year.
We are not alone in this enterprise. The emergence of the Chinese and Indian space programsand the continued successes of the European and Japanese programs illustrate that, much like scientific knowledge, global prestige and advance technological capability. In the comingdecade, China is preparing a series of robotic lunar missions, Russia is preparing lunar, Venusand Mars missions, India is planning to follow-up on its successful Moon and Marsexperiences, Japan is planning a second asteroid sample return mission, the United ArabEmirates is planning a Mars mission, and following up on the flight of the Rosetta spacecraft and Philae lander, the Europeans are headed to Mercury, Mars, and Jupiter. Clearly, othernations believe that solar system exploration is a worthwhile endeavor and a credible measure of scientific innovation, engineering creativity, and technological skill.
Beginning with the flight of Mariner 2 more than 50 years ago, the United States has consistently led the robotic exploration of our solar system. Decade-by-decade, we havecreated, flown and operated a balanced portfolio of missions to explore destinations acrossthe solar system. In just the past decade, we have proven that large quantities of water onceflowed across the Mars surface, that vast hydrocarbon seas exist on the surface of Titan, andthat there is a diverse set of ice-encrusted worlds in our own solar system waiting to beexplored. Today, as we celebrate the success of the New Horizons mission to Pluto and the Dawn mission to Vesta and Ceres, another U.S. spacecraft is enroute to Jupiter, two U.S. rovers trundle across the Martian surface, and U.S. orbiters at Mars and Saturn are returningtantalizing insights. We have learned that our solar system and other planetary systems areexceedingly diverse. From the dusty plains of Mars to the subsurface ocean of Jupiter's moon Europa to the hydrocarbon seas on Saturn's moon Titan to the thick carbon dioxide greenhouse of Venus, there remains much to discover in our cosmic backyard.
Moving beyond the investigations carried out by our initial robotic emissaries, there is noshortage today of scientifically compelling mission concepts, designed to answer fundamentalquestions about who we are, where we may have come from, where we are going and perhaps the most fundamental of them allare we're alone? Potential planetary sciencemissions of the next decade include returning scientifically selected samples from Mars, accessing the Mars subsurface, analyzing and returning samples from the nucleus of a comet, sampling the liquid water of one or more ocean worlds, surveying the geology of the Venussurface, sailing the hydrocarbon seas of Titan, exploring the mysterious ice giants Uranus andNeptune that stand like sentinels at the solar system's edge, and perhaps, one day, setting sailon an interstellar journey to another Earth. Clearly, there is no shortage of exciting vistasremaining for us to explore. These missions require technology development to improve orenable scientific return, reduce cost, or improve the cadence of our exploration journey. Usingour past NASA technology development experiences as a guide, I will discuss thesetechnological advances in my testimony today.
As our exploration journey expands, a compelling scientific theme focused on the diversity anddistribution of liquid resources across the solar system is beginning to emerge. On Earth, where there is liquid water, there is life. As such, investigation of our solar system's oceanworlds has potentially profound ramifications for understanding the emergence of life on Earthas well as the potential for life elsewhere in our solar system and across the universe. Inaddition to Earth, our present list of ocean worlds includes Jupiter's moons Europa, Ganymedeand Callisto, Saturn's moons Enceladus and Titan, and Neptune's moon Triton. Enceladus and Europa may be the two worlds in our solar system best suited to search for life as we know it; Titan is likely the best place to search for life as we don't know it.
In my view, accessing water, in destinations where we know it exists, is the next greatplanetary science quest; one that may provide the answers to our fundamental questionsregarding the potential for life across our solar system and the universe. To address these questions, we need to return to the outer planets with regularity and consistency of purpose. We need to work together to ensure future missions access the water at destinations in whichwe know it to exist. It is worth noting that today, even considering the work being donetowards a mission to Europa, there are no planned missions in NASA's planetary scienceportfolio that would accomplish this.
Now is the time to organize and initiate a series of robotic missions focused on thefundamental questions of evolution, habitability and life across our solar system's ocean worlds. It is worth remembering that prior to flight of the Mars Pathfinder and Mars GlobalSurveyor missions in 1997, our nation went 20 years without the Mars Exploration Programthat is today a central part of our U.S. space exploration identity. Spurred by the technologyadvances of these two missions (e.g., direct entry and aerobraking, among others), NASAchanged the game at Mars, successfully implementing these missions for approximately onequarter the price of past mission concepts and unsuccessful attempts. These technologies andapproaches fueled the creation of the Mars Exploration Program and its associated budgetline, allowing for an increase in mission cadence that has enabled our advancement of Marsscientific knowledge over the past two decades.
In a similar vein, direct access to our solar system's oceans is now both technically and fiscallyviable. Recall that it has not been any one mission or science measurement that has singularlychanged our view of Mars. Rather, it has been the synthesis of evidence, gathered through an integrated set of measurements, obtained by a carefully engineered sequence of missions. Advancing Mars science required a prioritization of investigations, opportunities for relativelyfrequent launch, and a building-block approach in which technology advancement was madeacross a series of interconnected missions to improve science return over time. Built uponthese same principles and the scientific foundation obtained from past missions, exploration ofour solar system's ocean worlds is possible today as a result of critical technology investmentsand new capabilities that may bring the outer planets within reach of a broad set of missions.
At present, NASA is formally initiating the Europa Mission in accordance with the objectives ofthe planetary science decadal survey. However, going all the way to Europa without touchingits surface is like driving across the country to Disneyland and then staying in the parking lot.
Viewed through a program lens, the addition of a small, astrobiology-focused lander to directlyaccess the surface of this ocean world should be considered for potential launch with theEuropa Clipper. A science-focused technology demonstration that proves our ability to safelyand precisely access the fundamentally different surface environment of these ocean worldsshould be the primary objective of this first U.S. outer planets lander. Providing unique imageryand chemical analysis of the icy moon terrain, such a mission would be a pathfinder for a suite of future surface and subsurface astrobiology missions to access the water in these ocean worlds. Compiled as a sequence of interconnected missions, this is a journey sure to inspirethe world and maintain U.S. leadership in space exploration.
Technology Enables Our Exploration of the Solar System
Numerous engineering and technical challenges need to be addressed to advance U.S. scientific exploration of the solar system. Because the transit times, distances, radiationenvironment and surface environments of these worlds differ so significantly from vistas wehave previously visited and understand, new engineering capabilities and technical expertisemust be developed, particularly to land, rove or dive at one of these destinations. If plannedand managed appropriately, broadly applicable technology investments can be utilized to bring the exploration of these worlds within our reach.
Technology advancements being pursued today can greatly reduce the cost and increase thecapabilities of future spaceflight systems for the exploration of a broad range of destinations, including the outer planets, their ocean worlds, Venus and Mars. Fortunately, many of theneeded technologies, including advanced power systems (both solar and nuclear), radiation protection, sensing, landing, navigation and communications were identified for funding in theFY15 House Appropriations bill. These technology development activities have the potential tobring a broad range of compelling new missions into the realm of possibility, includingDiscovery, New Frontiers and Flagship class missions to outer planet destinations. Coupled, with the fielding of a heavy lift launch capability, presently in development by NASA and U.S. industry, an increased cadence and widening aperture of outer planet missions is possible in the decade of the 2020s.
NASA has a successful track record in the development of game-changing technologies andmission implementation approaches to enable planetary science. Consider the following shortlist of illustrative examples that span propulsion, power and atmospheric entry technologies:
Solar Electric Propulsion (SEP): In 1994, NASA initiated the New Millennium Program todevelop and demonstrate technologies for future space science and exploration missions. TheNew Millennium Program flew its first deep space mission, Deep Space 1 or DS-1, in1998. DS-1 included flight qualification of a dozen new space technologies, most of which have subsequently found their way into current NASA missions. However, the true superstartechnology on DS-1 was the NSTAR solar electric powered ion propulsion system. DS-1 not only successfully demonstrated this revolutionary SEP system, but showed through its primary and extended missions the ability of SEP missions to encounter multiple comets (Braille andBorrelly), a technical feat not possible with traditional chemical propulsion systems. As a directresult of the flexibility of the SEP system (and unlike any previous planetary science mission), the DS-1 mission plan allowed for the selection of which comets to visit and for whattimeframes during the performance of the actual mission.
With the DS-1 mission completed, this technology was ready for mission infusion. The demonstrated SEP efficiency, reliability and mission flexibility carried over directly into thecompetitively selected Dawn mission. Launched in 2007, Dawn is powered by a DS-1 classSEP system operating at 10 kW, and like DS-1, has for various reasons needed to adjust itmission trajectory on the fly. Today, after nearly eight years of operations, and with the firstscientific data set of Ceres continuing to be returned to scientists and the public here on Earth, it is clear that SEP technology has revolutionized the art of the possible in terms of spacescience and exploration. These advances in solar electric propulsion technology are usefulbeyond the scientific domain. Ion thruster technology has been transferred from thesemissions to the commercial satellite industry, and today most of our new geostationarycommunications satellites use ion thrusters to meet their orbital propulsion needs.
Solar Power: Following decades of investment in solar-cell technology by both governmentand industry, NASA conceived, designed and is now operating the first solar-powered roboticmission to Jupiter (Juno). In this case, solar power is used to operate the spacecraft asopposed to power its propulsion system. This distant location from the Sun is a regime whereonly nuclear-powered spacecraft were once thought possible. This breakthrough is enabling collection of planetary science through a New Frontiers mission at a cost not possible through alternative means. This same high-efficiency solar cell technology is now making its way intoother space science missions, including the Europa Mission as well as the solar powerinfrastructure that supports our society here on Earth.
In the past few years, the Space Technology Mission Directorate has demonstrated innovativesolar array structures whose mass has been cut in half and packaging volume reduced by twothirds. To further promote science mission infusion potential, NASA has offered this technologyas Government Furnished Equipment in the most recent SMD Discovery solicitation. Couplingthe efficiency improvements of the solar cells themselves with these gossamer solar arraystructure improvements, NASA investments in this technology appears poised to benefit the
U.S. commercial telecommunications industry. SSL, Lockheed Martin, Boeing and ATK have held discussions with NASA regarding future utilization of these solar power systems, improving the performance and affordability, while reducing the mass, of future communications satellites. PICA Heatshield: Following a decade of investment in lightweight carbon ablators, NASAmatured the high-performance thermal protection system PICA that has enabled analysis ofdust samples obtained from a comet following safe completion of the highest speed Earthreentry of all time (Stardust). Demonstrating the broad applicability of this technology, PICAwas utilized to enable entry of the Mars Science Laboratory (MSL) after a potentiallycatastrophic problem was uncovered late in the development cycle of the initially-planned thermal protection system material. NASA's technology development efforts provided themature PICA solution at precisely the needed instant in time, allowing the mission to move forward successfully. Without the prior development and availability of PICA, the Curiositylanding may never have occurred. Since that time, the SpaceX Dragon capsule has adopted a form of PICA as its heatshield material, while the Orion project also considered this material forpotential use.
These examples of technology infusion share a common characteristic -each was maturedfrom broadly applicable space technology roots, not mission-focused objectives. For example, when the time came for flight project development, Stardust and Mars Science Laboratory did not need to be planned inclusive of the cost and risk associated with the maturation of the PICA heatshield material. Rather, technology development efforts external to these flightprograms had already retired these risks and handled these costs. Similarly, Juno did not needto be planned inclusive of the cost and risk associated with the maturation of high-efficiencysolar cells. DS-1 was not planned as a technology precursor to Dawn; however, its successcertainly enabled Dawn's competitive selection as a Discovery mission. Removing thistechnology development risk has been cited numerous times by the GAO as a means to better manage NASA's future spaceflight missions. This is the principle upon which NASA's SpaceTechnology Mission Directorate was built. Such an approach is also one of the cornerstones ofthe N.A.C.A. and the 1958 Space Act that authorized NASA.
Technology Investments Bring the Outer Planets Within Our Reach
A broad range of technology advancements and alternate mission implementation approachesare needed to allow for the conduct of compelling deep-space missions at various scalesincluding NASA's New Frontiers and Discovery-class missions. For example, low massavionics and power systems capable of operating reliably at very low temperatures willenhance or enable a broad set of deep space missions. Listed below are six technology areasthat are critical to explore our solar system's ocean worlds or complete other compellingscience missions outlined in the NRC Planetary Science Decadal Survey.
Radioisotope Power Systems (RPS): Space exploration missions require safe, reliable, long- lived power to provide electricity and thermal energy to the spacecraft and their science instruments. One source of power, particularly for missions far from the Sun, is theRadioisotope Thermoelectric Generator (RTG) that reliably converts heat into electricity through the natural decay of plutonium. RTGs have been safely used on solar system explorationmissions since the 1970s, including Pioneer, Voyager, Ulysses, Viking, Galileo, Cassini, Curiosity, and New Horizons. Such systems were also used in the Apollo program. Today, Multi-Mission Radioisotope Thermoelectric Generators (MMRTGs) are the only viable RPSoption for planetary exploration missions. With a mass of 45 kg, each MMRTG is capable ofgenerating 125 W of power at the beginning of its life. For approximately five years, NASA andthe DOE pursued development of the Advanced Stirling Radioisotope Generator (ASRG). Witha mass of approximately 20 kg, this system was designed to produce 140 W of power at thebeginning of its life while using only one quarter the plutonium of a MMRTG, implying thepotential availability of four times the number of systems with current materials. The ASRGachieves it efficiency through precise and rapid movement of a piston; reliably and accuratelycontrolling this movement for the duration of a deep space mission (potentially a decade or more) is the critical breakthrough required for ASRG feasibility. In 2013, NASA greatly scaledback its ASRG activity and used these funds to maintain the DOE production line.
Given the presently planned cadence of deep space missions in need of a radioisotope powersystem (about one per decade), the reliability issues surrounding the ASRG, and the costinvolved, NASA's decision in 2013 was certainly understandable. However, in making thisdecision, NASA has boxed itself into a future in which expanding the pace of outer planetexploration may not be possible. Compounding this situation, NASA is currently expendinglittle effort on MMRTG alternatives, including the previous system used by Cassini, Galileo andNew Horizons which provided about double the performance (W/kg) of the MMRTG. As such, should our nation decide to increase the pace of outer planet exploration, there may be few, if any, technologies ready for NASA to apply to this challenge. A long-lived Europa lander will certainly not be solar powered; neither will a Europa submarine, or missions to explore Uranusor Neptune, sail the seas of Titan, or follow-up to New Frontiers' discoveries at Pluto. Furthermore, NASA's 2013 decision certainly penalizes potential Discovery class missionsmore significantly than potential Flagship missions (that can likely afford the mass impactassociated with the MMRTG) at a time when we should be doing all we can to enable a diverse suite of low cost exploration missions to flourish. In my view, this is a technology problemwhose solution must be addressed as part of plans to expand the exploration of the oceanabodes of our solar system. This investment in a high reliability, high performance RPS mustprecede the mission development funding. Without this investment, numerous deep spacemissions are likely to remain unattainable.
Deep Space Atomic Clock (DSAC): Precise timekeeping is essential to navigation. As the Earth and the planets move about the Sun at different rates, an accurate estimation of time is a critical part of obtaining precise position and velocity estimates. Ground-based atomic clockshave long been a cornerstone of deep space vehicle navigation, providing the baseline datanecessary for precise positioning through two-way communication. The Space Technologyfunded DSAC project is developing a smaller and lighter version of the refrigerator-sizedatomic clocks used as part of this process today at NASA's Deep Space Network (DSN) tracking stations. Use of an accurate onboard clock eliminates the navigation need to sendsignals from Earth to a spacecraft and back, optimizing use of the DSN to enable more efficientdata return while simultaneously improving navigation performance. DSAC has directapplication to gravity science and atmospheric sounding missions and is about an order ofmagnitude more accurate and stable than the GPS clocks in use today at the Earth, while alsobeing smaller and lighter. Upon completion of a 2016 low Earth orbit demonstration mission, this technology will be ready for infusion on deep space missions in the early 2020s. SMDlisted this technology as Government Furnished Equipment in its most recent SMD Discoverycall and the DSAC is expected to be included in the same manner in the upcoming SMD NewFrontiers solicitation.
Deep Space Optical Communications (DSOC): Because the power required for radio frequencycommunications increases with the square of the distance, the efficient and reliable return ofscience data to Earth is a challenge for deep space missions. For missions to Jupiter and beyond, the demands of returning science data to Earth may dominate the power budget of aspacecraft. As we look to accomplish more scientifically ambitious missions to Mars orconsider the scientific exploration of Europa and other ocean worlds, a shift to a differentcommunications architecture may be necessary. Through a partnership between SMD and STMD, NASA is incentivizing the flight of a DSOC system aboard the next Discovery mission. The system will provide a factor of ten increase in bandwidth for the same power (and at farlower mass) compared to a state-of-the-art radio frequency communications system. Thesystem under development for this Discovery opportunity will be directly applicable to aEuropa mission, providing a factor of 10 increase in bandwidth relative to traditionalapproaches. More importantly, the DSOC system represents the beginning of a transformation to optical communications that is occurring not only for deep space missions, but alsopotentially to NASA's Tracking and Data Relay Satellites (TDRS) as well as for commercial communications satellites. Within NASA, STMD is the stakeholder investor across this opticaltechnology spectrum. Through a partnership with NASA's SCaN Office, other governmentagencies, and satellite manufactures, STMD will build and demonstrate the Laser Communications and Relay Demonstration (LCRD) in geosynchronous orbit.
Terrain Relative Navigation (TRN): Most planetary landing systems utilize onboard inertialnavigation to compute position and velocity based on accelerometer and gyroscope measurements. In TRN, a vehicle's position is estimated by autonomously comparing localterrain measurements (e.g. imagery) with an onboard map. In this manner, the vehicleeffectively navigates using the local terrain and can land with great precision relative to localterrain features of scientific interest. For example, recent Mars landing studies have estimatedthat with TRN, the approximate +/-10 km Mars Science Laboratory landing footprint couldhave been reduced to +/-100 m. This technology may also be fused with science sensors orother sensor measurements to create and intelligent landing system capable of setting down close to scientifically interesting locations, dramatically reducing, and, in the extreme, possiblyeliminating the need for significant surface mobility. This technology would significantly improve science return at locales, such as Europa and Titan, where only cursory landing site information may be available. Such a system may enable feasible surface science missionswith greatly reduced mobility requirements (and associated cost). In addition to the outerplanets, TRN is applicable to Mars landings (this technology is presently under considerationfor flight on the Mars 2020 mission) and was baselined in prior plans for human exploration ofthe Moon.
Ocean Worlds Landing Testbed: Because landing on an ocean world requires overcomingdramatically different challenges than those destinations at which the U.S. has landedpreviously, development of an ocean worlds landing testbed (analogous to the JPL Mars yard used for rover testing) is needed to allow advancement of the broad range of landingarchitectures, technologies and capabilities required for safe access to the new and diverse surface and subsurface environments found at these vistas. This testbed would also enable development and testing of ocean worlds surface and subsurface mobility systems (e.g., meltprobes).
Heatshield for Extreme Entry Environment Technology (HEEET): Today, many of the sametechnologists at the NASA Ames Research Center that developed PICA are maturing a woventhermal protection system material capable of withstanding the harsh aerothermodynamicenvironment associated with flight through the atmospheres of Saturn, Uranus or Venus. Thistechnology development is enabling to several potential missions described in the NRCPlanetary Science Decadal Survey. Without HEEET, these missions are significantlyconstrained by the use of heritage carbon phenolic materials that have not been manufacturedin more than a decade. Funded by the Space Technology Mission Directorate, this technologywas offered as Government Furnished Equipment in the recent SMD Discovery call and isanticipated to be included in the same manner in the upcoming SMD New Frontierssolicitation. Without this technological solution, it is likely that missions to the surface of Venus, or to study the atmospheres of Saturn or Uranus would not be feasible. The partnership between STMD and SMD to develop and potentially infuse HEEET is representative of howNASA can effectively manage technology development for future missions, allowing potentialNASA science missions that otherwise would simply not be possible.
Within NASA today, much of the longer-term technology development work is performed withinthe Space Technology Mission Directorate, with nearer-term, science mission technologyinvestments largely managed within the Science Mission Directorate. Clearly, this approachrequires STMD and SMD to work together for the advancement of planetary science. There isample evidence to suggest that this relationship is flourishing. For example, the latestDiscovery call included the NASA provision of five STMD developed technologies: DSAC, DSOC, HEEET, Advanced Solar Arrays, and a Green Propellant technology alternative tohydrazine. STMD and SMD are also co-funding and number of advanced development efforts. Equally important, without the technology investments contained within the Space Technologybudget line, missions to access the Mars subsurface, analyze and return samples from nucleusof a comet, sample the liquid water of one or more ocean worlds, survey the geology of theVenus surface, sail the hydrocarbon seas of Titan, or return to Pluto will likely remain just out ofreach of lower cost and potentially higher cadence mission opportunities.
Planetary exploration is a unique symbol of our country's technological leadership andpioneering spirit. We are fortunate to be part of a society that can fulfill the responsibility ofexpanding humanity's reach from the cradle of Earth throughout the solar system. Working atthe intersection of science, engineering and technology, our solar system exploration missionsyield a return far greater than the funding invested. The challenges of these missions inspireour children, build the scientific and engineering literacy of our country, and increase oureconomic and technological competitiveness. We have now completed a first investigation ofeach major body in our solar system. There is still so much to learn. Fueled by newtechnological capabilities and mission implementation approaches, compelling scientificdiscoveries are within our grasp. However, without appropriate technology investment, thesedreams will not be realized.
Now is the time to accelerate, not curtail, the pace and scope of our nation's solar systemexploration program. Our nation needs to dream big, and achieving large goals is preciselywhat America has come to expect of NASA's solar system exploration program. Through ourexploration missions to date, a major scientific quest focused on fundamental questions of evolution, habitability and life across our solar system's ocean worlds has begun to emerge. Coupling our scientific drive with investment in the critical technologies required to accomplish these future missions at a risk posture commensurate with robotic exploration is the only wayto achieve the grand objectives of these future missions within reasonable cost and time scales.
Investments in NASA technology produce benefits far beyond the Agency's missions, influencing the commercial sector and society as a whole. Positive outcomes that are likelyfrom an investment in the technologies required for our planetary science program includeeconomic, national security, global leadership and societal benefits. As illustrated by some ofthe examples I have discussed today, these advances will serve to enable solar systemexploration missions that would not otherwise be possible, spark a technology-based economy, and highlight internationally our country's scientific innovation, engineering creativityand technological skill.
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