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NASA NTRS2021

Leveraging the Atacama Compact Array for Cometary Science: An Interferometric Survey of Comet C/2015 ER61 (PanSTARRS) and Evidence for a Distributed Source of Carbon Monosulfide

We report the first survey of molecular emission from cometary volatiles using standalone Atacama Compact Array (ACA) observations from the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2015 ER61 (PanSTARRS) carried out on UT 2017 April 11 and 15, shortly after its April 4 outburst. These measurements of HCN, CS, CH3OH, H2CO, and HNC (along with continuum emission from dust) probed the inner coma of C/2015 ER61, revealing asymmetric outgassing and discerning parent from daughter/distributed source species. This work presents spectrally integrated flux maps, autocorrelation spectra, production rates, and parent scale lengths for each molecule and a stringent upper limit for CO. HCN is consistent with direct nucleus release in C/2015 ER61, whereas CS, H2CO, HNC, and potentially CH3OH are associated with distributed sources in the coma. Adopt- ing a Haser model, parent scale lengths determined for H2CO (Lp ∼ 2200 km) and HNC (Lp ∼ 3300 km) are consistent with previous work in comets, whereas significant extended source production (Lp ∼ 2000 km) is indicated for CS, suggesting production from an unknown parent in the coma. The continuum presents a point-source distribution with a flux density implying an excessively large nucleus, inconsistent with other estimates of the nucleus size. It is best explained by the thermal emission of slowly moving outburst ejectas, with total mass 5–8 × 1010 kg. These results demonstrate the power of the ACA for revealing the abundances, spatial distributions, and locations of molecular production for volatiles in moderately bright comets such as C/2015 ER61.

Molecular spectroscopy↗
NASA NTRS2021

Concerns About Phytoplankton Bloom Trends in Global Lakes

Satellite remote sensing has been widely used to monitor the water quality of inland and coastal environments. Using satellite data from the Landsat 5 Thematic Mapper (L5TM), Ho et al.1 showed an increase in peak summertime bloom intensity in 68% of the 71 large lakes worldwide from 1982 to 2012. However, we question the veracity of their finding for at least two reasons: (1) satellite-derived reflectance in a single near-infrared (NIR) band is not a reliable proxy for bloom strength, and (2) the infrequent satellite observations from L5TM make it difficult to draw statistically meaningful conclusions.

Lian Feng↗
NASA NTRS2020

Voyager and its Team—A Journey to The Outer Planets and Beyond

The Voyager Program and the twin Voyager 1 and Voyager 2 spacecraft are leg-endary, and the mission they continue to fly achieved significant milestones in the history of solar system exploration. NASA launched the two spacecraft in separate months in the summer of 1977. Eventually, between them, Voyager 1 and 2 would explore all four giant outer planets of our solar system, 48 of their moons, and their unique systems of rings and magnetic fields. To achieve this great success, the Voyager team had to work through a series of anomalies, start-ing with safe mode entries shortly after launch and telecommunications issues in early operations. The Voyager team pioneered deep-space exploration as they learned to solve these and many other problems in the mission’s 40-plus years.

Wolf, Aron A.↗
NASA NTRS2020

Efficient Starshade Retargeting Architecture Using Chemical Propulsion

NASA is studying a possible starshade flying in formation with the Nancy Grace Roman Space Telescope (Roman). The starshade would perform weeks-long translational retarget- ing maneuvers between target stars. A retargeting architecture is introduced that is based on chemical propulsion and does not require ground tracking or interactions with the telescope during the retargeting cruise. Feasibility is demonstrated through a verified covariance analysis of the starshade-telescope relative position over several weeks using realistic sensor and actuator assumptions. Performance is sufficient for Roman to reacquire the starshade after retargeting and the architecture is shown to also be applicable to other mission concepts such as the Habitable Exoplanet Observatory (HabEx).

Lisman, P. Douglas↗
NASA NTRS2020

Event-Driven Modeling and Execution of Robotic Activities and Contingencies in the Europa Lander Mission Concept Using BPMN

TRACE (Traceable Robotic Activity Composer and Executive) is a tool designed to address the model-ing, verification, and execution of planned and con-tingent activities during robotic space missions. These activities can be modeled (i.e., planned) graph-ically in TRACE using the Business Process Model and Notation (BPMN) language. This standardized language is used to model a sequence of robotic ac-tivities tied together by logical constructs, events, and time. TRACE includes verification tools to en-sure feasibility before mission models are executed by TRACE’s executive, which is integrated into the autonomy subsystem via a connector. In this paper, we describe TRACE in detail as it would apply to a conceptual Europa Lander surface mission with planned excavation and sample collection activities, as well as, contingency activities when execution is off-nominal—all highlighting our novel use of BPMN as a lingua franca for the pipeline from mis-sion planning to autonomous execution.

Lim, Grace↗
NASA NTRS2021

Nighttime Convection in Water-ice Clouds at High Northern Latitudes on Mars

We investigate water-ice clouds and their influence on the temperature structure of the Mar-tian atmosphere at high northern latitudes in early summer. New results are obtained throughcoordinated analysis of two types of data from Mars Global Surveyor: atmospheric profiles re-trieved from radio occultation (RO) measurements and wide-angle images from the Mars OrbiterCamera (MOC). Some RO profiles contain a layer of neutral static stability, which indicates thepresence of convective mixing at a local time (about 5 h) when it does not usually occur. Thesenocturnal mixed layers (NMLs) were observed frequently in early summer of Mars year 27 atlatitudes of 53–72◦N and longitudes of 210–330◦E. The base of a typical NML is 3 km abovethe surface, about the same height as the nighttime cloud layer detected by the Phoenix LIDARin early summer of Mars year 29 at 234◦E, 68◦N. The depth of the NMLs ranges from less than1 km to more than 5 km. Comparisons with nearly simultaneous MOC images demonstrate thatNMLs are closely associated with water-ice clouds. There is a dense cluster of NMLs within theannular cloud that appears every year in early summer between Alba Mons and the north polarresidual ice cap. The lighting conditions at this location and season allowed MOC to observe theannular cloud on most orbits, at 118-min intervals. Its appearance varies dramatically with localtime, becoming more symmetrical and better organized at night and dissipating to a crescentshape during the day. According to high-resolution numerical simulations (Spiga et al., 2017),including a large-eddy simulation at the Phoenix landing site, NMLs form when radiative cool-ing by water-ice aerosols causes convective instability; the mixed layer is forced from above bynegative buoyancy. Our results strongly support this conclusion. In addition, MOC images frommidsummer contain eastward-moving frontal clouds. Temperature profiles within these cloudsshow signs of near-surface advection of warm air, which reduces the static stability of the loweratmosphere and contributes, along with cloud radiation, to the formation of an NML.

David Hinson↗
NASA NTRS2016

Enabling International Data Relay at Mars

The most commonly used mode of communications be-tween Earth and a Mars surface mission is ultra-high fre-quency (UHF) radio relay via a Mars orbiter. There are four orbiters and two surface rovers operating at Mars and by October there should be five orbiters and three landers or rovers. There has been some collaboration between ESA’s Mars Express orbiter and NASA’s rovers, but 2016 is when Mars relay becomes fully international. In October, ESA will deliver the ExoMars Trace Gas Orbiter (TGO) and En-try, Descent, and Landing (EDL) Demonstrator Module (EDM) lander to Mars. The ExoMars program includes both ESA and ROSCOSMOS, with NASA participation (the Electra UHF transceiver on TGO). NASA orbiters will pro-vide relay for EDM and future ESA Mars landers and rov-ers. TGO will provide relay for NASA's current and future surface assets (as Mars Express will continue to do). Inter-national collaboration is enabled in several steps. At the in-struction of the space agencies, the Mars mission projects negotiate and write a “Service Agreement.” This describes at a high level how a new Mars orbiter would operate with its corresponding surface missions or how a new surface mis-sion would operate with its corresponding orbiters. It in-cludes the roles of the different projects, how the new mis-sion would communicate with existing or planned missions, the general flow of data and commands, and the capabilities or requirements of the new mission. After completing the Service Agreement, the projects write Interface Control Doc-uments (ICDs), each of which describes data and command flow in greater detail and quantitative aspects of the relay link and operations timeline between an orbiter and a cor-responding lander/rover. Interfaces and operations are test-ed before a new mission arrives at Mars. Once at Mars, a new orbiter performs some “practice” relay contacts with its partners. For a new lander (e.g. EDM), relay operations gen-erally begin before atmospheric entry at Mars, with record-ing of the UHF relay signal from the lander (including open-loop wide-bandwidth recording) as it enters and traverses Mars’s atmosphere and lands on its surface. After Mars EDL or orbit injection, each relay contact is negotiat-ed and scheduled using the Mars Relay Operations Service (MaROS). This paper describes the international approach to develop inter-agency agreements, inter-project interfaces, and specifics of how MaROS is used in actual relay opera-tions between international partners.

Winton, Alistair J.↗
NASA NTRSDate not supplied

Upgrades to the Single Stage Axial Compressor and Fan Facility For Low Pressure Ratio and Boundary Layer Ingesting Fan Research

Next generation aircraft engine efficiency goals will be met through high bypass ratio engines. To achieve these goals, a combination of small core and low pressure ratio fan technologies will be necessary. Additionally, advanced propulsion air-frame integration concepts, such as boundary layer propulsion, and distributed electrically driven fans with short inlets or wing integration strategies, are beginning to be investigated for their potential fuel burn savings. In order to realize the potential fuel savings from these technologies, it is necessary to have testing capabilities for the components. The NASA Glenn Research Center (GRC) Single StageAxial Fan and Compressor Facility (also called the GRC W-8Facility) has recently undergone several significant upgrades in order to effectively test low pressure ratio fans and various inlet distortions. This paper will outline various challenges to testing low pressure ratio fans and the methods implemented to ensure that the W-8 facility is capable of performing these tests and acquiring high quality data. The upgrades include significant pip-ing upgrades to reduce pressure loss and turbulence, capability for inlet total pressure and swirl distortion, increased test section length including a longer shaft, a two component balance, an up-graded rotating data system, and a new temperature characterization to reduce uncertainties in thermocouple measurements

W-8 Facility↗
NASA NTRSDate not supplied

Free-Flight CFD Simulations and Dynamic StabilityAnalysis of the Orion Crew Module

Dynamic stability analysis of the Multi-Purpose Crew Vehicle (MPCV) is performed us-ing the US3D flow solver and a plugin library to solve rigid-body dynamics, Free-Flight CFD(FF-CFD). Previous efforts investigated the free-flight behavior of higher speed, open-backaeroshell shapes. Three primary experimental sources are used to evaluate the predictivecapability of the FF-CFD solver in the low supersonic range (Mach≈1). First, the ballisticrange results obtained at the HFFAF facility at NASA Ames is used to verify the six degree-of-freedom (6-DoF) dynamic capability of the FF-CFD solver. Next, FF-CFD simulationsare preformed using restricted motion and the resultant trajectories are post-processed toobtain pitch damping coefficient as a function of angle-of-attack. The comparison of thepitch damping results obtained with one degree-of-freedom (1-DoF) FF-CFD compare wellwith experimental fits derived from ballistic range data. Finally, the atmospheric flight ca-pability of FF-CFD is compared to data from the Ascent Abort-2 (AA-2) flight experiment.Two simulations were performed using forced and forced-free flight to investigate surfacepressure predictive capability and free-flight aerodynamic performance through a varyingatmosphere at low speed (Mach 0.6-0.2). Surface pressure predicted with FF-CFD agreeswell with experimental trends, with slight over-prediction near the end of the trajectory.The total angle-of-attack for the free-flight portion agrees well with experimental data.

FFCFD↗
NASA NTRS2021

Autonomy for Deep Space Communications and Navigation

In more than 50 years of deep space exploration, the number and complexity of the world’s space missions have continued to increase. This has placed increasing demands on deep space communication and navigation. However, these demands have been met in spite of an essentially level overall budget. One of the reasons for this this has been the continual application of autonomy in various forms. The NASA Deep Space Network’s implementation of “Fol-low the Sun Operations” is a recent example – but certainly not the only one. During this same period, the end-to-end information system has been increasingly automated through the application of packet telemetry and virtual channels. Fully autonomous spacecraft navigation has been demonstrated, and more limited autonomy has been applied to the operational navigation process. This paper will show how autonomy and automation capabilities have been infused into operational deep space mission communication and navigation in both flight and ground systems as appropriate. It will further discuss ongoing work aimed at increasing the level of autonomy in the future, leverag-ing recent research and application of autonomy in everyday life.

Chang, Susan↗
NASA NTRSDate not supplied

Error Sources and Mitigation Strategies for Thermocouples Integrated in Flexible Thermal Protection System Materials

Brief Presenter Biography:Ruth Miller is an aer-ospace systems engineer in the Entry Systems and Ve-hicle Development Branch at NASA Ames Research Center.Introduction:The flexible thermal protection sys-tem (FTPS) on NASA’s Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) vehicle will be in-strumented with thermocouples (TCs) to measure the in-depth thermal response during entry into Earth’s atmos-phere[1, 2]. Accurate flight temperature measurements are critical for verifying vehicle performance during the flight test and reducing uncertainties in the thermal models.However,the deployable nature of inflatable decelerator technology presents challengesfor integrat-ing TCs, specifically the TCsneed to be compactableand cannot damage the FTPSnor the inflatable structure(IS).Unlike traditional rigid aeroshells, routing TCsthrough the thickness of the FTPS could cause signifi-cant damage during packing of the deployable aeroshellbecause the different layers may shift small amounts in relation to each other imparting strain on the TCsand FTPS materials. The LOFTID TCleads are routed from the measurement location back to the data acquisition system in the vehicle centerbody within the same FTPS layer that they are monitoring the temperature. This ap-proach eliminates the need to put holes in the FTPS lay-ers,butas a consequence,the insulated TCleads travel for an appreciable distance through a region that will expose them to high temperaturesand large thermal gra-dients.LOFTID’s TCswere baselined to be commercially available Type K TCswith a binder impregnated glass braid insulation. These TCswere chosen because they had been used successfully on IRVE-3 and in ground-based arc jet testing. Additionally, these TCsdid notdamage the FTPS nor IS during packing and deploy-ment testing. However, the glass braid insulation is only rated to a maximum continuous use temperature of 482ºC. For reference, the duration of the heat pulse on the LOFTID vehicle is on the order of minutes and themaximum predicted temperaturebeneaththe outermost FTPS layersis 1350ºC.Ground-based testing in a tube furnace at NASA Ames Research Centerwas conducted to determine if the baseline TCsrouted through FTPS samples would survive and provide accurate temperature measure-mentsat LOFTID flight-relevant temperatures[3].The test results showed large measurement errors occurred beginning at approximately 400°C due to conductive deposits on the TCinsulation electrically shorting the TCleads.The conductive deposits and thus electrical shorting weredetermined to be caused by twoerror sources:1.The organic binder on the TCinsulation carbon-izingin a high temperature, low oxygen envi-ronment2.Decomposition products from the FTPSperme-atingthe braided TC insulationFurther testing in the tube furnace demonstrated that heat cleaning the TCinsulation effectivelyremovedthe organic binder andeliminatedthe first error source.The second error sourcewas shown to be mitigated by the addition of amica wraparound each individual TCleadtoact as an impermeable barrier.To understand the applicability of theground-based tube furnace test results to flight,anarc jet testseriesat Boeing’s Large Core Arc Tunnel (LCAT) facilitywas conducted[4].The error sourcesand mitigation strate-giesidentified in the tube furnace testing were substan-tiatedin the arc jet testing.However, the arc jet testing also revealed three new error sources:1.Glass TCinsulation meltingwhich resultsin electrical shorting of the TCeither through di-rect contact between the two leads or through the electrically conductive FTPS materials2.TCwire meltingwhich results in a noisy and/or open-loop TCresponse3.Type K TCwire green-rotwhich results in large calibration errors Scope of the Presentation:This presentation will include a brief discussion onthe effect of electrical shorting on the output of a TC(i.e. how to identify elec-trical shorting in TCdataand what the associated erroris).The tube furnace and arc jet test resultswill be dis-cussedand the solutions LOFTID is implementing to mitigate the error sourcesidentified in the tube furnace and arc jet testingwill be presented.Additionally, futureresearch and development work to eliminateTCerror sourcesfor future missionswill be recommended.

R A Miller↗
NASA NTRS2022

CLEAR: Boosted Ly alpha Transmission of the Intergalactic Medium in UV-bright Galaxies

Reionization is an inhomogeneous process, thought to begin in small ionized bubbles of the intergalacticmedium (IGM) around overdense regions of galaxies. Recent Lyman-alpha (Lyα) studies during the epochof reionization show growing evidence that ionized bubbles formed earlier around brighter galaxies, suggest-ing higher IGM transmission of Lyαfrom these galaxies. We investigate this problem using IR slitless spec-troscopy from the Hubble Space Telescope (HST) Wide-Field Camera 3 (WFC3) G102 grism observations of148 galaxies selected via photometric redshifts at6.0< z <8.2. These galaxies have spectra extracted fromthe CANDELS LyαEmission at Reionization (CLEAR) survey. We combine the CLEAR data for 275 galaxieswith the Keck/DEIMOS+MOSFIRE dataset from the Texas Spectroscopic Search for LyαEmission at the Endof Reionization Survey. We then constrain the Lyαequivalent-width (EW) distribution at6.0< z <8.2, whichis described by an exponential form,dN/dEW∝exp(-EW)/W0, with the characteristice-folding scale width(W0). We confirm a significant drop of the Lyαstrength (orW0) atz >6. Furthermore, we compare the redshiftevolution ofW0between galaxies at different UV luminosities. The UV-bright (MUV<−21, orLUV> L∗)galaxies show weaker evolution with a decrease of 0.4 (±0.2) dex inW0atz >6while UV-faint (MUV>−21,orLUV< L∗) galaxies exhibit a significant drop by a factor of 0.7-0.8 (±0.2) dex inW0fromz <6toz >6.Our results add to the accumulating evidence that UV-bright galaxies exhibit boosted Lyαtransmission in theIGM, suggesting that reionization completes sooner in regions proximate to galaxies of higher UV luminosity.

Intae Jung↗
NASA NTRSDate not supplied

Hypervelocity Dust Impact in Olivine: Fib/Tem Characterization and Comparison of Experimental and Natural Microcraters

The flux of objects impacting the surfaces of solar system airless bodies is dominated by micrometeoroids less than 1 mm diameter whose impact effects play a major role in the space weathering of airless body surfaces. To obtain better understanding of how small scale impact effects vary as a function of impact speed in an important lunar and asteroidal mineral, we produced artificial microcraters in San Carlos olivine using Fe metal dust particles 0.10 to 5 µm in diameter electrostatically accelerated to speeds between 0.35 to 25 km s-1. The crater morphologies, size distrrubiton and microstruc-tures were characterized by field-emission SEM (FE-SEM) and also by FIB cross sectioning of selected craters for field-emission scanning transmission electron microscopy (FE-STEM). These same techniques were also applied to study a natural 20 µm-diameter microcrater in a olivine grain on the surface of lunar rock 12075. Measured microcrater diameters in the experimental sample range between 0.20 to 5 µm with larger craters having more irregular outlines dominated by spallation fractures. FE-SEM and FE-STEM imaging docu-ment the formation of shock melt in the size population of experimental craters below approximately 1 µm in diameter, corresponding to particle impact speeds in the 10-25 km s-1 range. The natural olivine crater exhibits similar shock melt features along the perimeter of its cavity, but the shock melt also contains nanophase Fe metal particles, something not observed in the experimental samples. FE-STEM imaging of the experimental craters reveals complex shock-generated dislocation and nanofracture microstructures in zones extend-ing 1-2 µm into the olivine from the crater cavity. The natural microcrater shows a lower density of shock-generated disloca-tions that extends a factor of 2 deeper into the the olivine than in the experimental samples.

Roy Gray Christoffersen↗
NASA NTRSDate not supplied

Compact Coronagraph (CCOR) Accommodation on GOES-U

The CCOR-1 will monitor our Sun’s Coronal Mass Ejections (CMEs). It will reside on the Sun-Pointing Platform (SPP) of the Geostationary Operational Environmental Satellite (GOES) -U in a geostationary orbit. As a member of the GOES-R Series of satellites, GOES-U will pro-vide advanced imagery and atmospheric measurements of Earth’s weather, oceans and envi-ronment, real-time mapping of total lightning activity, and as well as monitoring of solar ac-tivity and space weather. GOES-U is the final satellite in the GOES-R Series, with an expected launch date in April of 2024. The Compact Coronagraph (CCOR) instrument was designed, built, and tested by the Unit-ed States Naval Research Laboratory. CCOR-1, the first in a series of coronagraphs, is funded by the National Oceanic and Atmospheric Administration (NOAA), is managed by the National Aeronautics and Space Administration (NASA), and will ultimately be operated by NOAA. Us-ing a series of images of the Sun’s coronal white-light, scientists at NOAA’s Space Weather Prediction Center (SWPC) and National Centers for Environmental Information (NCEI) can de-termine the size, velocity, and density of these CMEs. This information can then be used to assess and prepare for potential impacts of these solar storms on infrastructure here on Earth, as well as assets in space. CCOR-1 has completed instrument-level Integration and Testing (I&T), delivered to the GOES-U satellite vendor and is now mechanically integrated with the spacecraft. The GOES-U satellite has completed spacecraft-level integration and test activities. This poster presents the details on the CCOR-1 instrument, its integration onto the GOES-U satellite bus, ground system, and operations, as well as the expected performance.

White Light Coronagraph↗
NASA NTRS2023

Daytime Sky Quality at El Leoncito, Argentina

We characterize the daytime sky quality in terms of brightness, cloud coverage, and mainweather variables at the Carlos Ulrico Cesco station of the Felix Aguilar Astronomical Ob-servatory (OAFA), located in El Leoncito National Park, San Juan, Argentina. We have col-lected more than 15 years of daily observations from the auxiliary sky brightness detectorsof the Mirror Coronagraph for Argentina (MICA, in operations from 1997 to 2012), includ-ing daily observing reports. We additionally present data from two meteorological stationsoperated at the site from 2000 to 2020. We determine the main statistical properties andseasonal variability of daytime sky brightness, clear sky time fraction (CSTF), precipitablewater vapor (WV), temperature, humidity, and wind speed, which are relevant for solar,particularly coronal observations.Our results confirm that El Leoncito is an excellent place to perform daytime astro-nomical observations. We measure a median sky brightness of 15.8 ppm, estimated at526.0±1.0 nm and 6 solar radii from the solar disk center; a median CSTF of 0.7; anda median WV below 6 mm. These values, and those of other relevant weather variables, arecomparable to the levels found among the best astronomical observing sites in the world.Due to the extended period of time analyzed and high sampling frequency, the novel dataand results presented in this report contribute to the analysis and interpretation of historicalsky brightness data and are of great value for the future planning of daytime astronomicalinstrumentation at El Leoncito.

F A Iglesias↗
NASA NTRS2021

Design of Solar Sailing Trajectories Resilient to Safe Mode Events

Solar sails are an enabling technology for stand-alone small-satellite deep-space exploration. However, their always-on nature, combined with the time of flight required for deep-space missions, makes them particularly susceptible to safe mode events. Unlike missions using electric propulsion, exclusively solar sail- ing missions cannot carry extra propellant to make up for a safe mode event, and more powerful methods like expected availability cannot be directly applied. This work extends the expected availability and duty cycle approaches to solar sailing. Through an application to NASA’s Solar Cruiser mission, a 46 % increase in tra- jectory resilience is obtained at negligible change in the mission’s time of flight. Additionally, it is shown that when a safe mode event stops the spacecraft from reaching its target orbit, the developed methods reduce the expected final error by approximately an order of magnitude.

Johnson, Les↗
NASA NTRS2022

Going to Extremes: Architecting Holographic Microscopes for Extreme Environments

Bacterial life exists on earth in extreme environments. These are environments described by large temperature excur- sions, large pressure excursions, and large radiation excursions from the nominal conditions near sea level which are largely populated by humans. These extreme locales represent such places as the ocean ice, the briny pools of Death Valley and deep mines, the acidic hot springs of the High Sierra or Yellowstone, or even the clouds of our upper atmosphere. The preponderance of bacterial life in these extreme environments here on earth suggests that bacterial life might likely exist in the extreme environments of our own solar system, such as the icy moons of Europa or Enceladus. Thus, architecting instruments for detect- ing life in these extreme environments on earth builds confidence that we can architect such instruments for flight missions. In this paper, we discuss our experience with designing digital holo- graphic microscope instruments to enable detection of bacteria in several extreme environments. In particular we discuss three different instruments. The first is our field instrument which is a small, portable instrument for examination of remote sites. The second is submersible instrument which enables exploration of deep aquatic environments and is deployed on a ocean-going drone. The third is a balloon-borne instrument to examine the bacterial content of the upper atmosphere. We will provide a review of each instrument and discuss aspects of instrument engineering for each particular application.

Ramirez, Alex↗
NASA NTRS2021

Assessment of M2020 Terrain Relative Landing Accuracy: Flight Performance vs Predicts

Terrain Relative Navigation (TRN) was a critical enabling Entry, Descent, and Landing (EDL) technology that enabled Mars 2020 mission Perseverance rover to land at Jezero crater. TRN pro-vides real-time, autonomous, map-relative position determination and generates a landing target based on a priori knowledge of hazards. The required performance for TRN was to land within 60m of the selected target. The required 60m was sub-allocated to various error sources in three major categories: targeting error, knowledge error, and control error. The targeting error is the error in selecting an appropriate landing target and the knowledge of the target on the surface. It includes the Lander Vision System (LVS) position localization with respect the ground, the synchronization between the Lander Vision System measurement and the main Navigation filter, and errors associated with the LVS Reference Map and Safe Target Selec-tion (STS). The knowledge error is the contribution of knowledge growth from the synchronization with LVS to touchdown. The control error encompasses how accurately the system could stay on the desired reference trajectory. The TRN error budget uses a combination of analysis, simulation, and hardware test-ing results to bound the various error contributions obtained during the verification and validation process. This paper first presents a description the TRN system, focusing on the architecture of LVS and STS. The paper then gives detailed overview of the TRN error budget, with a description of the major error contribu-tions in each of the three categories. Next, the paper gives the results for three versions of the error budget, pre-launch, in-flight pre-landing, and post-landing. The paper compares the pre-flight analysis, the pre-landing analysis using in-flight data during cruise, to the post-landing analysis of the TRN performance. Pre-landing analysis best estimate of the landing performance was 33m, compared to the 60m require-ment. Post-landing analysis estimated a landing accuracy of 8.53m or better, much better than the 33m pre-landing estimate. The actual post-landing imagery calculated the distance of the rover to the targeted location to be 5m. The post-landing analysis closely bounds the image-based assessment of landing accu-racy, indicating the success of the error budget architecture in bounding the landing accuracy, as well as the fidelity of the simulations used to model and predict performance.

Chen, Allen↗