Advances in POST2 End-to-End Descent and Landing Simulation for the ALHAT Project

Davis, Jody L.; Striepe, Scott A.; Maddock, Robert W.; Hines, Glenn D.; Paschall, Stephen; Cohanim, Babak E.; Fill, Thomas; Johnson, Michael C.; DeMars, Kyle J.; Sostaric, Ronald R.; Johnson, Andrew

doi:10.2514/6.2008-6938

Cited by 21 publications

(14 citation statements)

References 5 publications

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“…Studies also showed that the size of hazards influenced detection performance, while the distribution of hazards (number of hazards of each size per unit area) influenced the probability of detecting a safe landing site [2]. Consequently, FT1 was designed so that hazards of a variety of sizes, placed in fields with different hazard distribution, could be imaged from different angles and distances.…”

Section: Test Overviewmentioning

confidence: 99%

“…Thus, the HD analysis done up to date has focused on maximizing the detection probability of hazards greater than a predetermined height. A study was conducted to determine the sensor's range precision and field of view needed to detect such hazards [2]. Attempts were made to minimize the false-positive rates by appropriately choosing the detection threshold for such hazards, but there was no clear understanding of the tolerable amount of false positives introduced in the process.…”

Section: Individual Hazard Analysismentioning

confidence: 99%

“…Currently, ALHAT is developing a flash lidar sensor with a 5cm range precision that will be able to detect 30cm-high hazards when viewed from a 1000m slant range at a 15-degree path angle. Slant range is the distance to the target along the line of sight, and path angle is the angle between sensor boresight and the horizontal [2]. The goal of the first Field Test (FT1) was to assess the commercial state of the art by testing a custom-built commercial flash lidar.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of flash lidar field test data for safe lunar landing

Johnson

Keim

Ivanov

2010

2010 IEEE Aerospace Conference

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In May 2008, the Autonomous Landing and Hazard Avoidance Technology (ALHAT) Project conducted a helicopter field test of a commercial flash lidar to assess its applicability to safe lunar landing. The helicopter flew several flights, which covered a variety of slant ranges and viewing angles, over man-made and natural lunar-like terrains. The collected data were analyzed to assess the performance of the sensor and the performance of two algorithms: Hazard Detection (HD) and Hazard Relative Navigation (HRN). The collected flash lidar data were also used to validate a high fidelity flash lidar software model used in ALHAT Monte Carlo simulations. The field test results, combined with prior simulation results, advanced the technology readiness level of the HD algorithm to TRL 5 and the HRN algorithm to TRL 4. 12

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Section: Test Overviewmentioning

confidence: 99%

Section: Individual Hazard Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of flash lidar field test data for safe lunar landing

Johnson

Keim

Ivanov

2010

2010 IEEE Aerospace Conference

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“…The original map was chosen from a synthetic lunar terrain database in an end-to-end engineering landing simulation known as POST II (Program to Optimize Simulated Trajectories II) 13 . The map is classified as a smooth mare terrain type with 10% rock abundance.…”

Section: Numerical Simulationmentioning

confidence: 99%

A super-resolution algorithm for enhancement of FLASH LIDAR data

et al. 2011

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A novel method for enhancement of the spatial resolution of 3-diminsional Flash Lidar images is being proposed for generation of elevation maps of terrain from a moving platform. NASA recognizes the Flash LIDAR technology as an important tool for enabling safe and precision landing in future unmanned and crewed lunar and planetary missions. The ability of the Flash LIDAR to generate 3-dimensional maps of the landing site area during the final stages of the descent phase for detection of hazardous terrain features such as craters, rocks, and steep slopes is under study in the frame of the Autonomous Landing and Hazard Avoidance (ALHAT) project. Since single frames of existing FLASH LIDAR systems are not sufficient to build a map of entire landing site with acceptable spatial resolution and precision, a super-resolution approach utilizing multiple frames has been developed to overcome the instrument's limitations. Performance of the super-resolution algorithm has been analyzed through a series of simulation runs obtained from a high fidelity Flash LIDAR model and a high resolution synthetic lunar elevation map. For each simulation run, a sequence of FLASH LIDAR frames are recorded and processed as the spacecraft descends toward the landing site. Simulations runs having different trajectory profiles and varying LIDAR look angles of the terrain are also analyzed. The results show that adequate levels of accuracy and precision are achieved for detecting hazardous terrain features and identifying safe areas of the landing site.

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“…The trajectory design must account for providing a landing approach that enables adequate viewing of the landing area by the both the crew and the hazard detection system. [5][6][7][8][9][10] If a new landing location is selected, the target is updated in the GN&C software and the guidance calculates an updated trajectory that delivers the vehicle to the new location. This changes the throttle and attitude profile for the remaining portion of the phase.…”

Section: Approachmentioning

confidence: 99%

Altair Descent and Ascent Reference Trajectory Design and Initial Dispersion Analyses

Kos

Polsgrove

Sostaric

et al. 2010

AIAA Guidance, Navigation, and Control Conference

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The Altair Lunar Lander is the linchpin in the Constellation Program (CxP) for human return to the Moon. Altair is delivered to low Earth orbit (LEO) by the Ares V heavy lift launch vehicle, and after subsequent docking with Orion in LEO, the Altair/Orion stack is delivered through translunar injection (TLI). The Altair/Orion stack separating from the Earth departure stage (EDS) shortly after TLI and continues the flight to the Moon as a single stack.Altair performs the lunar orbit insertion (LOI) maneuver, targeting a 100-km circular orbit. This orbit will be a polar orbit for missions landing near the lunar South Pole. After spending nearly 24 hours in low lunar orbit (LLO), the lander undocks from Orion and performs a series of small maneuvers to set up for descending to the lunar surface. This descent begins with a small deorbit insertion (DOI) maneuver, putting the lander on an orbit that has a perilune of 15.24 km (50,000 ft), the altitude where the actual powered descent initiation (PDI) commences.At liftoff from Earth, Altair has a mass of 45 metric tons (mt). However after LOI (without Orion attached), the lander mass is slightly less than 33 mt at PDI. The lander currently has a single descent module main engine, with TBD lb f thrust (TBD N), providing a thrust-to-weight ratio of approximately TBD Earth g's at PDI.LDAC-3 (Lander design and analysis cycle #3) is the most recently closed design sizing and mass properties iteration. Upgrades for loss of crew (LDAC-2) and loss of mission (LDAC-3) have been incorporated into the lander baseline design (and its Master Equipment List). Also, recently, Altair has been working requirements analyses (LRAC-1). All nominal data here are from the LDAC-3 analysis cycle. All dispersions results here are from LRAC-1 analyses. Descent PhaseThere are three subphases comprising the descent phase of the Altair mission: the braking burn (BB), the approach, and terminal (note a short pitch-up maneuver will be executed near the beginning of approach). The descent subphases are depicted shown in Figure 1.Implicit guidance algorithms will be used to design the reference trajectories in all these descent subphases. In this approach, we can define, in advance of the mission, a reference trajectory as a vector polynomial function of time that evolves backward from the target state. But the reference trajectory cannot be expected to intersect the initial state of the vehicle due https://ntrs.nasa.gov/search.jsp?R=20100035768 2018-05-13T06:16:06+00:00Z to navigation and control dispersions. Implicit guidance will generate acceleration commands that consist of that computed using the reference trajectory plus two feedback terms. The first "feedback" acceleration correction is proportional to the difference between the actual and reference vehicle's positions. The second term is proportional to the difference between the actual and reference vehicle's velocities. Implicit guidance algorithm will "drive" the vehicle to achieve the target state in the presences of controller errors, na...

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Advances in POST2 End-to-End Descent and Landing Simulation for the ALHAT Project

Cited by 21 publications

References 5 publications

Analysis of flash lidar field test data for safe lunar landing

Analysis of flash lidar field test data for safe lunar landing

A super-resolution algorithm for enhancement of FLASH LIDAR data

Altair Descent and Ascent Reference Trajectory Design and Initial Dispersion Analyses

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