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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Earth Observing System (EOS) Aqua & Aura Space Weather Effects on Operational Collision Avoidance

This presentation will describe recent EOS Aqua and Aura operational collision avoidance experience during periods of solar and geomagnetic storm activity. It will highlight challenges faced by the operations team during short-notice, high-risk predicted close approaches. The presentation will highlight the evolution of the operational collision avoidance process for the EOS Aqua and Aura missions. The presentation will highlight operational challenges that have occurred, process improvements that have been implemented and identify potential future challenges.

Operational collision avoidance↗
NASA NTRS2017

Earth Observing System (EOS) Aqua and Aura Space Weather Effects on Operational Collision Avoidance

This presentation will describe recent EOS Aqua and Aura operational collision avoidance experience during periods of solar and geomagnetic storm activity. It will highlight challenges faced by the operations team during short-notice, high-risk predicted close approaches. The presentation will highlight the evolution of the operational collision avoidance process for the EOS Aqua and Aura missions. The presentation will highlight operational challenges that have occurred, process improvements that have been implemented and identify potential future challenges.

Guit, Bill↗
NASA NTRS2015

Operational Collision Avoidance

This presentation will describe the early days of the EOS Aqua and Aura operational collision avoidance process. It will highlight EOS debris avoidance maneuvers, EOS high interest event statistic and A-Train systematic conjunctions and conclude with future challenges. This is related to earlier e-DAA (tracking number 21692) that an abstract was submitted to a different conference. Eric Moyer, ESMO Deputy Project Manager has reviewed and approved this presentation on May 6, 2015

collision avoidance↗
NASA NTRS2007

Mars Reconnaissance Orbiter Aerobraking Daily Operations and Collision Avoidance

The Mars Reconnaissance Orbiter reached Mars on March 10, 2006 and performed a Mars orbit insertion maneuver of 1 km/s to enter into a large elliptical orbit. Three weeks later, aerobraking operations began and lasted about five months. Aerobraking utilized the atmospheric drag to reduce the large elliptical orbit into a smaller, near circular orbit. At the time of MRO aerobraking, there were three other operational spacecraft orbiting Mars and the navigation team had to minimize the possibility of a collision. This paper describes the daily operations of the MRO navigation team during this time as well as the collision avoidance strategy development and implementation.

Long, Stacia M.↗
NASA NTRSDate not supplied

Safe Space Conduct: NASA Best Practices Overview

While prevention of launch and on-orbit collisions has been an institutional concern of NASA for several decades (beginning with the Shuttle program), historically the paucity of spaceactors and deployed payloads made the conduct of such protection activities relatively straightforward. With the substantial increases in launched payloads over the last several years, collision avoidance operations have become substantially more complicated. At the same time, many operators are uncertain regarding what collision avoidance activities are appropriate to their missions. The lack of a space traffic management authority to articulate standards and guidelines for such conduct has only increased the confusion.In response to this situation, NASA has published a Spacecraft Conjunction Assessment and Collision Avoidance Handbook, which articulates and explains the launch and on-orbit collision avoidance best practices that the Agency has developed and is requiring of present and future NASA missions. Because the CA2 Handbook is a living document regularly updated to reflect best practices changes as the industry develops, feedback from both NASA missions and other users is continuously collected in order to issue CA2 Handbook updates.This talk will summarize and explain the collision avoidance best practices from the CA2Handbook, along with the key issues that drove the selection of those practices.

Conjunction Assessment↗
NASA NTRSDate not supplied

NASA Best Practices Overview

While prevention of launch and on-orbit collisions has been an institutional concern of NASA for several decades (beginning with the Shuttle program), historically the paucity of space actors and deployed payloads made the conduct of such protection activities relatively straightforward. With the substantial increases in launched payloads over the last several years, collision avoidance operations have become substantially more complicated. At the same time, many operators are uncertain regarding what collision avoidance activities are appropriate to their missions. The lack of a space traffic management authority to articulate standards and guidelines for such conduct has only increased the confusion. In response to this situation, NASA has published a Spacecraft Conjunction Assessment and Collision Avoidance Handbook, which articulates and explains the launch and on-orbit collision avoidance best practices that the Agency has developed and is requiring of present and future NASA missions. Because the CA2 Handbook is a living document regularly updated to reflect best practices changes as the industry develops, feedback from both NASA missions and other users is continuously collected in order to issue CA2 Handbook updates. This talk will summarize and explain the collision avoidance best practices from the CA2 Handbook, along with the key issues that drove the selection of those practices.

Conjunction Assessment↗
NASA NTRS2017

Filter Tuning Using the Chi-Squared Statistic

The Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) performs orbit determination (OD) for the Aqua and Aura satellites. Both satellites are located in low Earth orbit (LEO), and are part of what is considered the A-Train satellite constellation. Both spacecraft are currently in the science phase of their respective missions. The FDF has recently been tasked with delivering definitive covariance for each satellite.The main source of orbit determination used for these missions is the Orbit Determination Toolkit developed by Analytical Graphics Inc. (AGI). This software uses an Extended Kalman Filter (EKF) to estimate the states of both spacecraft. The filter incorporates force modelling, ground station and space network measurements to determine spacecraft states. It also generates a covariance at each measurement. This covariance can be useful for evaluating the overall performance of the tracking data measurements and the filter itself. An accurate covariance is also useful for covariance propagation which is utilized in collision avoidance operations. It is also valuable when attempting to determine if the current orbital solution will meet mission requirements in the future.This paper examines the use of the Chi-square statistic as a means of evaluating filter performance. The Chi-square statistic is calculated to determine the realism of a covariance based on the prediction accuracy and the covariance values at a given point in time. Once calculated, it is the distribution of this statistic that provides insight on the accuracy of the covariance.For the EKF to correctly calculate the covariance, error models associated with tracking data measurements must be accurately tuned. Over estimating or under estimating these error values can have detrimental effects on the overall filter performance. The filter incorporates ground station measurements, which can be tuned based on the accuracy of the individual ground stations. It also includes measurements from the NASA space network (SN), which can be affected by the assumed accuracy of the TDRS satellite state at the time of the measurement.The force modelling in the EKF is also an important factor that affects the propagation accuracy and covariance sizing. The dominant force in the LEO orbit regime is the drag force caused by atmospheric drag. Accurate accounting of the drag force is especially important for the accuracy of the propagated state. The implementation of a box and wing model to improve drag estimation accuracy, and its overall effect on the covariance state is explored.The process of tuning the EKF for Aqua and Aura support is described, including examination of the measurement errors of available observation types (Doppler and range), and methods of dealing with potentially volatile atmospheric drag modeling. Predictive accuracy and the distribution of the Chi-square statistic, calculated based of the ODTK EKF solutions, are assessed versus accepted norms for the orbit regime.

Covariance Analysis↗
NASA NTRS2019

Analysis of Interactions Between Urban Air Mobility (UAM) Operations and Conventional Traffic in Urban Areas: Traffic Alert and Collision Avoidance System (TCAS) Study for UAM Operations

This paper presents results on potential interaction effects from UAM (Urban Air Mobility) operations integrated into current operational scenarios by evaluating if/where/how Traffic alert and Collision Avoidance System (TCAS) alerts are triggered on-board commercial aircraft. A range of operational scenarios are evaluated with combinations of UAM vehicle route, speed, altitude, and direction along the DFW (Dallas-Fort Worth) "spine route." The effect of UAM altitude uncertainty on the above is also explored. The analysis was done for both South flow and North flow configurations of DFW. When UAM operations are deterministic, no TCAS RAs (Resolution Advisories) are issued. However, UAM altitude uncertainties point out geographic areas of concern with the associated severity of interactions.

Airspace↗
NASA NTRS2019

Analysis of Interactions Between Urban Air Mobility (UAM) Operations and Conventional Traffic in Urban Areas: Traffic Alert and Collision Avoidance (TCAS) Study for UAM Operations

This paper presents a preliminary modeling and analysis of interactions between proposed UAM operations and present-day conventional traffic if UAM operations occurred along FAA- approved helicopter routes and altitude ceilings. It assesses the extent to which the UAM operations will trigger TCAS resolution advisories (RA) aboard the conventional aircraft in the Dallas/Fort Worth (DFW) terminal airspace. It is observed that under deterministic UAM operational conditions, no RAs will be triggered. Furthermore, the impact of UAM altitude uncertainty is also evaluated. It is observed that restricting the UAM cruise altitudes to 990 feet above Mean Sea Level (MSL) or below reduced the chance of triggering an RA to under five percent throughout the day, even in the presence of maximum altitude error of 30 feet.

Bulusu, Vishwanath↗
NASA NTRS1990

Collision avoidance of a redundant manipulator operating through a window

The problem of collision-free operation of a redundant robot manipulator through a window is addressed. The window is modeled by a polygon with the sides representing the edges of the window. A performance criterion is defined to maximize the shortest distances between the arm link axes and the edges of the window. An efficient gradient projection optimization scheme for the kinematic control of manipulators with multiple degrees of redundancy is developed and used. The effectiveness of this scheme and the validity of the performance criterion are verified through simulations of the seven-degree-of-freedom NASA Laboratory Telerobotic Manipulator (LTM), where controlling only the position of the end-effector provides three degrees of redundancy.

Zghal, H.↗
NASA NTRS2019

Multivariate Normality of Cartesian-Framed Covariances: Evaluation and Operational Significance

Collision avoidance relies on representative Cartesian uncertainty volumes in order to calculate probabilities of collision. Among the potential shortcomings of a covariance matrix representation of state errors, the most worrisome is the coordinate mismatch between the Cartesian framework in which these matrices are distributed and the curvilinear path that satellite orbits actually follow. The present study compares curvilinear-based and Cartesian covariance representations for ~50,000 conjunctions to determine the frequency in which significant deviations from Gaussianity are observed, then compares the 2-D Pc result from the Cartesian covariance to a Monte Carlo Pc conducted in element space to assess operational significance.

Lechtenberg, Travis F.↗
NASA NTRS2019

Multivariate Normality of Cartesian Frame Covariances: Evaluation and Operational Significance

Collision avoidance relies on representative Cartesian uncertainty volumes in order to calculate probabilities of collision. Among the potential shortcomings of a covariance matrix representation of state errors, the most worrisome is the coordinate mismatch between the Cartesian framework in which these matrices are distributed and the curvilinear path that satellite orbits actually follow. The present study compares curvilinear-based and Cartesian covariance representations for ~50,000 conjunctions to determine the frequency in which significant deviations from Gaussianity are observed, then compares the 2-D Pc result from the Cartesian covariance to a Monte Carlo Pc conducted in element space to assess operational significance.

Lechtenberg, Travis F.↗
NASA NTRS2007

Proceedings of the 20th International Symposium on Space Flight Dynamics

Topics include: Measuring Image Navigation and Registration Performance at the 3-Sigma Level Using Platinum Quality Landmarks; Flight Dynamics Performances of the MetOp A Satellite during the First Months of Operations; Visual Navigation - SARE Mission; Determining a Method of Enabling and Disabling the Integral Torque in the SDO Science and Inertial Mode Controllers; Guaranteeing Pointing Performance of the SDO Sun-Pointing Controllers in Light of Nonlinear Effects; SDO Delta H Mode Design and Analysis; Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter; Broken-Plane Maneuver Applications for Earth to Mars Trajectories; ExoMars Mission Analysis and Design - Launch, Cruise and Arrival Analyses; Mars Reconnaissance Orbiter Aerobraking Daily Operations and Collision Avoidance; Mars Reconnaissance Orbiter Interplanetary Cruise Navigation; Motion Parameters Determination of the SC and Phobos in the Project Phobos-Grunt; GRAS NRT Precise Orbit Determination: Operational Experience; Orbit Determination of LEO Satellites for a Single Pass through a Radar: Comparison of Methods; Orbit Determination System for Low Earth Orbit Satellites; Precise Orbit Determination for ALOS; Anti-Collision Function Design and Performances of the CNES Formation Flying Experiment on the PRISMA Mission; CNES Approaching Guidance Experiment within FFIORD; Maneuver Recovery Analysis for the Magnetospheric Multiscale Mission; SIMBOL-X: A Formation Flying Mission on HEO for Exploring the Universe; Spaceborne Autonomous and Ground Based Relative Orbit Control for the TerraSAR-X/TanDEM-X Formation; First In-Orbit Experience of TerraSAR-X Flight Dynamics Operations; Automated Target Planning for FUSE Using the SOVA Algorithm; Space Technology 5 Post-Launch Ground Attitude Estimation Experience; Standardizing Navigation Data: A Status Update; and A Study into the Method of Precise Orbit Determination of a HEO Orbiter by GPS and Accelerometer.

Woodard, Mark↗
NASA NTRS2015

Launch COLA Operations: An Examination of Data Products, Procedures, and Thresholds

NASA GSFC and KSC, acting in response to headquarters NASA direction, performed a year-long study of launch collision avoidance (LCOLA) operations in order to determine and recommend best risk assessment and mitigation practices. The following condenses the findings and recommendations of the study into one short summary, a more expanded version of which appears as Section 10.

Launch COLA Operations: Revision A (12 JAN 2014)↗