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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2022

Mission Planning for Trident: Discovery proposal to Neptune’s moon, Triton

Trident was one of the four Discovery-class Step-1 mission proposals selected by NASA in 2020 for further development and study; however, in 2021, the Step-2 proposal was not down-selected to transition into the next phase of mission development, i.e., a mission for flight.Neptune’s largest moon, Triton, was the primary focus of study for Trident. Triton’s physical and orbital characteristics make it a unique planetary target for scientific exploration, providing opportunities for investigations in a wide variety of scientific fields, including geomorphological, atmospheric, geophysical, magnetospheric, and ionospheric studies. The science objectives of the Trident mission encompassed an in-depth interior-to-exterior set of objectives, focused on multiple outstanding questions resulting from the 1989 encounter of Voyager 2, and subsequent analysis.Ball Aerospace Corp. was tasked with building the Trident spacecraft, with JPL responsible for providing Engineering Support (Mission Design & Navigation, Mission Planning, Flight Operations, Ground Data Systems, Systems Engineering) and leading Project Management. The observatory would carry a wide-ranging suite of scientific instruments onboard, including an Infrared Spectrometer (IRS) and Narrow Angle Camera (NAC) to be provided by Ball Aerospace Corp., a Wide Angle Camera (WAC) from JPL, a Magnetometer from UCLA, a contributed Plasma Science Suite from IRF (Sweden), and a contributed Radio Science instrument from ASI (Italy). All of these instruments would be used to collect unique datasets during the Triton encounter. Trident would have taken advantage of an ~13-yr, nearly-ballistic trajectory to Triton, utilizing a timely Jupiter Gravity Assist, to execute a 10-day long encounter in the Neptunian system. Launch was planned for October 2025, with Triton arrival scheduled for December 2038. The timeline for this mission would have been sub-divided into seven major phases: Launch, Commissioning, Inner Planet Cruise, Outer Planet Cruise, Approach, Encounter, and Science Data Return. Multiple planetary flybys were planned to be performed during the cruise, including three Earth flybys and one Venus flyby in the Inner Planet Cruise phase, and one Jupiter flyby in the Outer Planet Cruise phase. Along with conventional (Range and Doppler) tracking data, Delta-DOR and Optical Navigation data were also to be acquired to assist with spacecraft navigation during the Approach and Encounter phases. A 3 meter X-Band High Gain Antenna would allow playback of all science data at 1 kbps within 1 year after the Triton Encounter. The Mission Planning element on Trident encompassed and informed multiple aspects of this proposal, ranging from science observation planning during the Triton Encounter phase, to generation of activity timelines for all mission phases; performing ground coverage analysis for science observations to be acquired by all instruments and tracing them to science requirements; evaluation of spacecraft resources including data volume stored onboard, power/energy consumption, telecom (commanding/telemetry) requirements, and overall, working at the interface of science and engineering teams on the mission. All of these functions that were performed by the Mission Planning team on this proposal are discussed in this paper.

Prockter, Louise↗
NASA NTRS2010

Predictability of Top of Descent Location for Operational Idle-Thrust Descents

To enable arriving aircraft to fly optimized descents computed by the flight management system (FMS) in congested airspace, ground automation must accurately predict descent trajectories. To support development of the trajectory predictor and its uncertainty models, commercial flights executed idle-thrust descents at a specified descent speed, and the recorded data included the specified descent speed profile, aircraft weight, and the winds entered into the FMS as well as the radar data. The FMS computed the intended descent path assuming idle thrust after top of descent (TOD), and the controllers and pilots then endeavored to allow the FMS to fly the descent to the meter fix with minimal human intervention. The horizontal flight path, cruise and meter fix altitudes, and actual TOD location were extracted from the radar data. Using approximately 70 descents each in Boeing 757 and Airbus 319/320 aircraft, multiple regression estimated TOD location as a linear function of the available predictive factors. The cruise and meter fix altitudes, descent speed, and wind clearly improve goodness of fit. The aircraft weight improves fit for the Airbus descents but not for the B757. Except for a few statistical outliers, the residuals have absolute value less than 5 nmi. Thus, these predictive factors adequately explain the TOD location, which indicates the data do not include excessive noise.

Stell, Laurel L.↗
NASA NTRS2019

Scheduling Improvements Following the Phase 1 Field Evaluation of the ATD-2 Integrated Arrival, Departure, and Surface Concept

NASA is conducting the Airspace Technology Demonstration-2 to evaluate an Integrated Arrival, Departure, and Surface (IADS) traffic management system that extends traffic sequencing for the entire life-cycle of a flight from departure gate to arrival gate within multi-airport, metroplex environments. After development and testing in human-in-the-loop simulations, the IADS system was deployed to Charlotte Douglas International Airport for a three-year field evaluation. From the initial IADS concept development through the end of the Phase 1 field evaluation many lessons were learned with regards to the IADS scheduler. In this paper we describe how data from the Phase 1 field evaluation helped identify scheduler improvements and guided the implementation of refinements. The improvements in the IADS scheduler described in this paper are incorporated into the IADS Phase 2 scheduler enabling strategic Surface Metering Programs and will be evaluated during the field evaluation.

Coupe, William J.↗
NASA NTRSDate not supplied

Human Factors Impact of Different Ramp Controller Scheduling Advisories for ATD-2 Surface Metering in a Human-in-the-Loop Simulation

A human-in-the-loop (HITL) simulation took place in 2019 at NASA Ames Research Center’s Future Flight Central, an airport simulator with a full-scale 360-degree view that showed real-time airport operations at Dallas/Fort Worth International Airport (DFW). The HITL was part of the NASA/FAA Airspace Technology Demonstration 2 (ATD-2) project which involves an on-going field demonstration at Charlotte Douglas International Airport (CLT). In the field demonstration, metering on the airport surface takes place with one of the goals being to reduce runway queue length by holding aircraft at the gate during busy times, thereby reducing fuel burn and CO2 emissions. This goal has been successfully accomplished at CLT by showing Ramp Controllers when to release aircraft at the gate so as to reduce aircraft waiting in the queue. Among the questions that the current simulation at DFW was designed to address were, "Which types of advisories to the Ramp Controllers work best, those that show a ±2 minute window for a release time from the gate, or a ±5 minute window for an arrival time at the spot (where Air Traffic Control takes over) or both?" and "How do these different types of advisories affect Ramp Controller workload and situation awareness?" Another question was, “Does a ramp that is less restrictive than the one at CLT affect compliance with these advisories?”

Bonny K Parke↗
NASA NTRS1994

Differential GPS and system integration of the Low Visibility Landing and Surface Operations (LVLASO) demonstration

The LVLASO Flight Demonstration of ASTA concepts (FDAC) integrates NASA-Langley's electronic moving map display and Transport Systems Research Vehicle (TSRV) (a modified Boeing 737 aircraft); ARINC's VHF data link, GPS ground station, and automated controller workstation; and Norden's surface radar/airport movement safety system. Aircraft location is shown on the electronic map display in the cockpit. An approved taxi route as well as other aircraft and surface traffic are also displayed. An Ashtech Z12 Global Positioning System (GPS) receiver on the TSRV estimates the aircraft's position. In Differential mode (DSPS), the Ashtech receiver accepts differential C/A code pseudorange corrections from a GPS ground station. The GPS ground station provides corrections up to ten satellites. The corrections are transmitted on a VHF data link at a 1 Hz. rate using the RTCM-104 format. DGPS position estimates will be within 5 meters of actual aircraft position. DGPS position estimates are blended with position, velocity, acceleration, and heading data from the TSRV Air Data/Inertial Reference System (ADIRS). The ADIRS data is accurate in the short-term, but drifts over time. The DGPS data is used to keep the ADIRS position accurate. Ownship position, velocity, heading, and turn rate are sent at a 20 Hz. rate to the electronic map display. Airport traffic is detected by the airport surface radar system. Aircraft and vehicles such as fuel trucks and baggage carts are detected. The traffic's location, velocity, and heading are sent to the TSRV. To prevent traffic symbology from jumping each second when a location update arrives, velocity and heading are used to predict a new traffic location for each display update. Possible runway incursions and collisions can be shown on the electronic map. Integrating the different systems used in the FDAC requires attention to the underlying coordinate systems. The airport diagram displayed on the electronic map is obtained from published navigational charts. The charts reference the North American Datum of 1927 (NAD27) or a local state-plane coordinate system. GPS uses the World Geodetic Standard of 1984 (WGS84). Both NAD27 and WGS84 model the Earth as an ellipsoid, however, they use a different origin and different size ellipsoids. Latitudes and longitudes given in these systems can be converted to a Cartesian system with the origin at the Earth's center. The surface radar detects traffic in a locally-level, rho-theta coordiante system. The electronic airport diagram is stored using a flat XY coordinate system. The map origin is at the tower and is referenced as True North up. All ownship and other traffic positions must be converted to the electronic map's frame of reference for display.

Rankin, James M.↗
NASA NTRS2014

An Evaluation of a Flight Deck Interval Management Algorithm Including Delayed Target Trajectories

NASA's first Air Traffic Management (ATM) Technology Demonstration (ATD-1) was created to facilitate the transition of mature air traffic management technologies from the laboratory to operational use. The technologies selected for demonstration are the Traffic Management Advisor with Terminal Metering (TMA-TM), which provides precise timebased scheduling in the terminal airspace; Controller Managed Spacing (CMS), which provides controllers with decision support tools enabling precise schedule conformance; and Interval Management (IM), which consists of flight deck automation that enables aircraft to achieve or maintain precise in-trail spacing. During high demand operations, TMA-TM may produce a schedule and corresponding aircraft trajectories that include delay to ensure that a particular aircraft will be properly spaced from other aircraft at each schedule waypoint. These delayed trajectories are not communicated to the automation onboard the aircraft, forcing the IM aircraft to use the published speeds to estimate the target aircraft's estimated time of arrival. As a result, the aircraft performing IM operations may follow an aircraft whose TMA-TM generated trajectories have substantial speed deviations from the speeds expected by the spacing algorithm. Previous spacing algorithms were not designed to handle this magnitude of uncertainty. A simulation was conducted to examine a modified spacing algorithm with the ability to follow aircraft flying delayed trajectories. The simulation investigated the use of the new spacing algorithm with various delayed speed profiles and wind conditions, as well as several other variables designed to simulate real-life variability. The results and conclusions of this study indicate that the new spacing algorithm generally exhibits good performance; however, some types of target aircraft speed profiles can cause the spacing algorithm to command less than optimal speed control behavior.

Swieringa, Kurt A.↗
NASA NTRS1998

Ionospheric Signature of Surface Mine Blasts from Global Positioning System Measurements

Sources such as atmospheric or buried explosions and shallow earthquakes are known to produce infrasonic pressure waves in the atmosphere. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these acoustic and gravity waves induce variations of the ionospheric electron density. The Global Positioning System (GPS) provides a way of directly measuring the total electron content in the ionosphere and, therefore, of detecting such perturbations in the upper atmosphere. In July and August 1996, three large surface mine blasts (1.5 Kt each) were detonated at the Black Thunder coal mine in eastern Wyoming. As part of a seismic and acoustic monitoring- experiment, we deployed five dual-frequency GPS receivers at distances ranging from 50 to 200 km from the mine and were able to detect the ionospheric perturbation caused by the blasts. The perturbation starts 10 to 15 min after the blast, lasts for about 30 min, and propagates with an apparent horizontal velocity of 1200 meters per second. Its amplitude reaches 3 x 10 (exp 14) el per square meters in the 7-3 min period band, a value close to the ionospheric perturbation caused by the M = 6.7 Northridge earthquake. The small signal-to-noise ratio of the perturbation can be improved by slant-stacking the electron content time-series recorded by the different GPS receivers taking into account the horizontal propagation of the perturbation. The energy of the perturbation is concentrated in the 200 to 300 second period band, a result consistent with previous observations and numerical model predictions. The 300 second band probably corresponds to gravity modes and shorter periods to acoustic modes, respectively. Using a 1-D stratified velocity model of the atmosphere we show that linear acoustic ray tracing fits arrival times at all GPS receivers. We interpret the perturbation as a direct acoustic wave caused by the explosion itself. This study shows that even relatively small subsurface events can produce ionospheric perturbations that are above the detection threshold of the GPS technique. By sensing derivative signals, which can be detected over a relatively broad region, it appears that GPS might be particularly useful for source characterization within the first acoustic quiet zone where infrasound would probably be ineffective. This suggests that dual-frequency GPS monitoring could contribute to Comprehensive Nuclear Test Ban Treaty verification.

Calais, Eric↗
NASA NTRS2018

Quantifying the Early Snowmelt Event of 2015 in the Cascade Mountains, USA by Developing and Validating MODIS-Based Snowmelt Timing Maps

Spring snowmelt serves as the major hydrological contribution to many watersheds of the US West. Since the 1970s the conterminous western USA has seen an earlier arrival of spring snowmelt. The extremely low snowpack and early melt of 2015 in the Cascade Mountains may be a harbinger of winters to come, underscoring the interest in advancements in spring snowmelt monitoring. Target-of-opportunity and point measurements of snowmelt using meteorological stations or stream gauges are common sources of these data, however, there have been few attempts to identify snowmelt timing using remote sensing. In this study, we describe the creation of snowmelt timing maps (STMs) which identify the day of year that each pixel of a remotely sensed image transitions from "snow-covered" to "no snow" during the spring melt season, controlling for cloud coverage and ephemeral spring snow storms. Derived from the 500 meter MODerate-resolution Imaging Spectroradiometer (MODIS) standard snow map, MOD10A2, this new dataset provides annual maps of snowmelt timing, with corresponding maps of cloud interference and interannual variability in snow coverage from 2001-2015. We first show that the STMs agree strongly with in-situ snow telemetry (SNOTEL) meteorological station measurements in terms of snowmelt timing. We then use the STMs to investigate the early snowmelt event of 2015 in the Cascade Mountains, USA, highlighting the protected areas of Mt. Rainier, Crater Lake, and Lassen Volcanic National Parks. In 2015 the Cascade Mountains experienced snowmelt 41 days earlier than the 2001-2015 average, with 25 percent of its land area melting more than 65 days earlier than average. The upper elevations of the Cascade Mountains experienced the greatest snowmelt anomaly. Our results are relevant to land managers and biologists as they plan adaptation strategies for mitigating the effects of climate change throughout temperate mountains.

snowmelt timing↗
NASA NTRS1990

Delivery and application of precise timing for a traveling wave powerline fault locator system

The Bonneville Power Administration (BPA) has successfully operated an in-house developed powerline fault locator system since 1986. The BPA fault locator system consists of remotes installed at cardinal power transmission line system nodes and a central master which polls the remotes for traveling wave time-of-arrival data. A power line fault produces a fast rise-time traveling wave which emanates from the fault point and propagates throughout the power grid. The remotes time-tag the traveling wave leading edge as it passes through the power system cardinal substation nodes. A synchronizing pulse transmitted via the BPA analog microwave system on a wideband channel sychronizes the time-tagging counters in the remote units to a different accuracy of better than one microsecond. The remote units correct the raw time tags for synchronizing pulse propagation delay and return these corrected values to the fault locator master. The master then calculates the power system disturbance source using the collected time tags. The system design objective is a fault location accuracy of 300 meters. BPA's fault locator system operation, error producing phenomena, and method of distributing precise timing are described.

Street, Michael A.↗
NASA NTRS1998

Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales

Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

Schenk, P.↗
NASA NTRS2007

Laser Range and Bearing Finder with No Moving Parts

A proposed laser-based instrument would quickly measure the approximate distance and approximate direction to the closest target within its field of view. The instrument would not contain any moving parts and its mode of operation would not entail scanning over of its field of view. Typically, the instrument would be used to locate a target at a distance on the order of meters to kilometers. The instrument would be best suited for use in an uncluttered setting in which the target is the only or, at worst, the closest object in the vicinity; for example, it could be used aboard an aircraft to detect and track another aircraft flying nearby. The proposed instrument would include a conventional time-of-flight or echo-phase-shift laser range finder, but unlike most other range finders, this one would not generate a narrow cylindrical laser beam; instead, it would generate a conical laser beam spanning the field of view. The instrument would also include a quadrant detector, optics to focus the light returning from the target onto the quadrant detector, and circuitry to synchronize the acquisition of the quadrant-detector output with the arrival of laser light returning from the nearest target. A quadrant detector constantly gathers information from the entire field of view, without scanning; its output is a direct measure of the position of the target-return light spot on the focal plane and is thus a measure of the direction to the target. The instrument should be able to operate at a repetition rate high enough to enable it to track a rapidly moving target. Of course, a target that is not sufficiently reflective could not be located by this instrument. Preferably, retroreflectors should be attached to the target to make it sufficiently reflective.

Bryan, Thomas C.↗
NASA NTRS2004

Possible and False Biomarkers from Space

The Search for life in the Solar System is one of NASA's main goals for the coming decade. We may never observe alien life directly; we or our robotic craft may always be removed from it by many years, or meters of crust. If we do find evidence of Life elsewhere in the Solar System it will probably be in form of chemical biomarkers, quintessentially biological molecules that indicate the presence of micro-organisms. What molecules would be truly indicative of alien life? Chlorophyll fragments, which are often used by geochemists are probably far too specific. Simpler molecules, such as fatty acids, amino acids and nucleo-bases might seem to be biomarkers, but they can form non-biotically in space. Alkyl substituted aromatics in ALH 84001 have been invoked as biomarkers, but they are not strong evidence in and of themselves. Understanding the range of nonbiological organic molecules which could act as false biomarkers in space is a prerequisite for any reasonable search for true biomarkers on other worlds. When simple organics arrive at the surface of a body like Europa, either from below or from space, how long do they survive and what do they make? How can we distinguish these from real biomarkers? In this talk I will present some ideas about what might be useful qualities to consider in a potential biomarker, and will ask for advice from the attendant geochemists.

Bernstein, Max P.↗
DOE OSTI2026

3D seismic imaging of a fracture damage zone controlling reservoir compartmentalization at the Raft River EGS using multi-azimuth walkaway VSP

Accurate imaging of steeply dipping fracture zones in crystalline enhanced geothermal systems (EGS) is critical for constraining permeability architecture and guiding stimulation design. However, such structures remain poorly resolved by conventional surface seismic methods. We present a fully three-dimensional (3D) elastic-waveform inversion-migration workflow applied to multi-azimuth walkaway vertical seismic profiling (VSP) data acquired in a deviated borehole at the Raft River EGS. The workflow integrates first-arrival traveltime tomography, multi-scale elastic waveform inversion (EWI), and elastic least-squares reverse-time migration (ELSRTM) to recover high-resolution compressional-and shear-wave velocity models and to image structural discontinuities in the crystalline basement. The results reveal a laterally continuous low-velocity anomaly, with shear-wave velocity reductions of 25-30%, consistent with fractureinduced mechanical weakening. Two steeply dipping discontinuities bound a 50-80 m wide fracture damage zone. Independent constraints from microseismic clustering and geochemical compartmentalization corroborate the geometry and structural significance of this feature. Synthetic modeling further confirms that structures of this scale are resolvable (~30 m). These findings indicate that the Narrows structure is a distributed fracture damage zone rather than a discrete fault plane. By resolving fracture-zone geometry at the tens-of-meters scale using a single borehole, this workflow provides a practical and transferable approach for improving structural characterization, reducing uncertainty in permeability architecture, and supporting reservoir modeling and stimulation design in fractured crystalline EGS reservoirs.

58 GEOSCIENCES↗
NASA NTRS1999

Mars Global Surveyor Thermal Emission Spectrometer (TES) Observations of Dust Opacity During Aerobraking and Science Phasing

The Mars Global Surveyor (MGS) arrived at Mars in September 1997 near Mars southern spring equinox and has now provided monitoring of conditions in the Mars atmosphere for more than half a Mars year. The large majority of the spectra taken by the Thermal Emission Spectrometer (TES) are in a nadir geometry (downward looking mode) where Mars is observed through the atmosphere. Most of these contain the distinct spectral signature of atmospheric dust. For these nadir-geometry spectra we retrieve column-integrated infrared aerosol (dust) opacities. TES observations during the aerobraking and science-phasing portions of the MGS mission cover the seasonal range L(sub s)=184 deg - 28 deg. Excellent spatial coverage was obtained in the southern hemisphere. Northern hemisphere coverage is generally limited to narrow strips taken during the periapsis pass but is still very valuable. At the beginning of the mission the 9-(micron)meter dust opacity at midsouthern latitudes was low (0.15-0.25). As the season advanced through southern spring and into summer, TES observed several regional dust storms (including the Noachis dust storm of November 1997) where peak 9-(micron)meter dust opacities approached or exceeded unity, as well as numerous smaller local storms. Both large and small dust storms exhibited significant changes in both spatial coverage and intensity over a timescale of a day. Throughout southern spring and summer the region at the edge of the retreating southern seasonal polar ice cap was observed to be consistently more dusty than other latitudes.

Smith, Michael D.↗
NASA NTRS2010

Interaction of Airspace Partitions and Traffic Flow Management Delay

To ensure that air traffic demand does not exceed airport and airspace capacities, traffic management restrictions, such as delaying aircraft on the ground, assigning them different routes and metering them in the airspace, are implemented. To reduce the delays resulting from these restrictions, revising the partitioning of airspace has been proposed to distribute capacity to yield a more efficient airspace configuration. The capacity of an airspace partition, commonly referred to as a sector, is limited by the number of flights that an air traffic controller can safely manage within the sector. Where viable, re-partitioning of the airspace distributes the flights over more efficient sectors and reduces individual sector demand. This increases the overall airspace efficiency, but requires additional resources in some sectors in terms of controllers and equipment, which is undesirable. This study examines the tradeoff of the number of sectors designed for a specified amount of traffic in a clear-weather day and the delays needed for accommodating the traffic demand. Results show that most of the delays are caused by airport arrival and departure capacity constraints. Some delays caused by airspace capacity constraints can be eliminated by re-partitioning the airspace. Analyses show that about 360 high-altitude sectors, which are approximately today s operational number of sectors of 373, are adequate for delays to be driven solely by airport capacity constraints for the current daily air traffic demand. For a marginal increase of 15 seconds of average delay, the number of sectors can be reduced to 283. In addition, simulations of traffic growths of 15% and 20% with forecasted airport capacities in the years 2018 and 2025 show that delays will continue to be governed by airport capacities. In clear-weather days, for small increases in traffic demand, increasing sector capacities will have almost no effect on delays.

Palopo, Kee↗
NASA NTRS2002

The Crustal Thickness of Mars: Accuracy and Resolution

Since the arrival of the Mars Global Surveyor (MGS) spacecraft at Mars and its entry into its mapping orbit in February 1999, the radio tracking and altimetry data from the mission have been part of the systematic mapping of the planet and used to develop very precise models of the gravity field and topography of Mars. Until the altimetry function of Mars Orbiter Laser Altimeter (MOLA) failed on June 30, 2001, the instrument had acquired close to 700 million measurements of the planet's radius, the majority of which have been used to develop a model of the topography with horizontal resolution of about 500 m and radial accuracy of better than 1 m. Concurrently, Doppler and range tracking of MGS by the Deep Space Network at X-band frequencies, with accuracies of about 50 microns/s and about 5 m respectively, have provided orbital knowledge of MGS to the few meter level and enabled the gravity perturbations of the spacecraft to be used to develop a improved gravity models of Mars. The recent models have horizontal resolutions of about 200 km, or degree 65, when expressed in spherical harmonics, and have accuracies of the order of a few mGals at the poles and about 10 mGals at the equator at the highest resolution.

Smith, David E.↗
NASA NTRS2004

The Challenges of Landing on Mars

Humans have been fascinated with the idea of exploring Mars since the very beginning of the space age. Largely due to the belief that life may have at one time existed in some form, surface exploration has been the ultimate ambition of this exploration. Unfortunately engineers and scientists discovered early on that landing a spacecraft on the surface of Mars was to become one of the most difficult and treacherous challenges of robotic space exploration. At arrival to Mars, a spacecraft will be traveling at velocities between 4 and 7 km/s. 100% of this kinetic energy (KE) must be safely removed for a lander to deliver its payload to the surface. Fortunately Mars has an atmosphere substantial enough to allow the combination of a high drag heatshield and a parachute to remove 99% and 0.98% respectively of this kinetic energy. Unfortunately the atmosphere is not substantial enough to bring a lander to a safe touchdown. This means that an additional landing system is required to remove the remaining kinetic energy. On all previous successful missions the landing system has consisted of 2 major elements, a propulsion subsystem to remove an additional 0.002% (approx.50 - 100 m/s ) of the original KE and a final dedicated touchdown system. The first generation Mars landers used legs to accomplish touchdown. The second generation of Mars lander touchdown systems used airbags to mitigate the last few meters per second of residual velocity. NASA is currently developing a third generation landing system in an effort to reduce cost, mass and risk while simultaneously increasing performance as measured by payload fraction to the surface and accessible terrain roughness.

sky cranes↗
NASA NTRS2016

Final Mission and Navigation Design for the 2016 Mars InSight Mission

Project Overview: NASA’s 12th Discovery Program mission that will place a single geophysical lander on Mars to study its deep interior using seismic (tidal, marsquake, and impact), rotational, and thermal measurements -First mission to unveil the composition, structure and thermal state of martian crust, mantle and core; Rebuild of the Phoenix flight system, upgraded with Juno/GRAIL avionics -Phoenix cruise stage: 3-axis stabilized, 3.2 square meter UTJ (Ultra Triple-Junction) solar array, X-band telecom -Phoenix aeroshell (heat shield, backshell, parachute) -Phoenix lander: radar, pulsed thrusters, legs, payload deck, 5.1 square meter UTJ solar arrays, two redundant Li-ion batteries, UHF (Ultra High Frequency)/X-band telecom -Dual string: Internally or functionally-redundant equipment; Science Payload -SEIS (Seismic Experiment for Interior Structure) / CNES (Centre National d’Etudes Spatiales); Three-axis seismometry, to measure seismic waves traveling through the interior -HP3 (Heat Flow and Physical Properties Probe) / DLR (German Aerospace Center) -Subsurface heat probe, to measure the heat flux from the interior - RISE (Rotation and Interior Structure Experiment) / JPL (Jet Propulsion Laboratory) -Radiometric geodesy, to determine precession & nutation of the planet’s rotation axis. 2016 Disclaimer: The InSight launch in 2016 was suspended due to critical issues with the Seismic Experiment for Interior Structure (SEIS) instrument that could not be fixed prior to the planned launch period. This presentation and its corresponding paper represent the state of the design for the 2016 mission. No attempt has been made to reflect the latest developments. [2018 Note: InSight (Mars Lander) was later launched and arrived on Mars on Nov. 26, 2018.]

Abilleira, F.↗