Search NASA⌕ Search

SEARCH · Search NASA

Results for “Elliptical orbits”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Terminator Double Layer Explorer (TerDLE): Examining the Near-Moon Lunar Wake

As the solar wind flows by the Moon, an antisunward-directed low-density wake forms as the plasma expands to fill in the trailing void in the plasma flow. Analytical modeling and modern plasma simulations suggest that plasma quasi-neutrality could possibly be broken close to the terminator obstruction as solar wind electrons expand into the wake ahead of the ions, leading to the formation of a standing (time-stationary) double layer. The objective of the Terminator Double Layer Explorer is to extend the fundamental understanding of the plasma expansion into the trailing near-vacuum wake region by (1) identifying any plasma expansion density anomalies at low altitudes near the terminator wake initiation region, (2) assessing the highly variable solar wind's effect on the low-altitude wake region, and (3) determining if plasma neutrality is maintained or lost during passages through the low-altitude expansion region. The mission concept uses a propulsion-driven CubeSat with ion spectrometer and plasma wave system in elliptical orbit about the Moon with periselene near the terminator. Over the course of the mission, the periselene decreases, placing the CubeSat ever closer to the terminator wake initiation location and the possible nonneutral region.

lunar science↗
NASA NTRS2020

Navigation Design and Operations of Maven Aerobraking

This paper describes the operational design and execution of the MAVEN aerobraking phase at Mars from a Navigation Team perspective. MAVEN was designed to perform atmospheric science in a ~150x6200 km altitude elliptical orbit. After the primary science mission, it was decided that MAVEN should circularize its orbit, as much as feasible from a spacecraft and mission standpoint, to better support relay operations with the landers. As a result, MAVEN performed aerobraking in the first half of 2019 to reduce its orbit to ~150x4500 km altitude. Although MAVEN did not decrease its altitude as low as previous aerobraking missions, it had several unique challenges. Science observations continued to be taken during aerobraking, requiring dramatically better Navigation accuracies than typical for such phases. Furthermore, continuous DSN coverage with 2-way Doppler data was not available. So, with 40% less Doppler data, Navigation had to meet prediction accuracies which were an order of magnitude smaller than in previous aerobraking operations. Spacecraft accelerometer data was included in Navigation analyses in order to meet these requirements.

Jakosky, Bruce↗
NASA NTRS2021

Hiten Mission

The Hiten mission (formerly the MUSES-A) was the first space engineering experimental satellite of the Institute of Space and Astronautical Science (ISAS) and was launched from Kagoshima Space Center (JKSC) in Japan in January 1990. After the successful insertion into a highly elliptical orbit around the Earth, the Hiten mission carried out several objectives to demonstrate space technologies for swing-by (or gravity assist) techniques and insertion of a sub-satellite into orbital space around the Moon. The results from these engineering missions have also led to follow-on missions, including aerobraking techniques and an excursion to the Lagrange points of the Earth-Moon system.

Caitlin Ahrens↗
NASA NTRS2024

Evidence for Surprising Heavy Nitrogen Isotopic Enrichment in Comet 46P/Wirtanen's Hydrogen Cyanide

46P/Wirtanen is a Jupiter-family comet, probably originating from the solar system's Kuiper Belt, that now resides on a 5.4 yr elliptical orbit. During its 2018 apparition, comet 46P passed unusually close to the Earth (within 0.08 au), presenting an outstanding opportunity for close-up observations of its inner coma. Here we present observations of HCN, H13CN, and HC15N emission from 46P using the Atacama Compact Array. The data were analyzed using the SUBLIME non-LTE radiative transfer code to derive 12C/13C and 14N/15N ratios. The HCN/H13CN ratio is found to be consistent with a lack of significant 13C fractionation, whereas the HCN/HC15N ratio of 68 ± 27 (using our most conservative 1σ uncertainties), indicates a strong enhancement in 15N compared with the solar and terrestrial values. The observed 14N/15N ratio is also significantly lower than the values of ∼140 found in previous comets, implying a strong 15N enrichment in 46P's HCN. This indicates that the nitrogen in Jupiter-family comets could reach larger isotopic enrichments than previously thought, with implications for the diversity of 14N/15N ratios imprinted into icy bodies at the birth of the solar system.

Short period comets↗
NASA NTRS1996

Unstable Box Orbits in Cuspy Elliptical Galaxies

The aim of this work is to gain physical insight into the role played by a concentrated central mass in affecting the shape of elliptical galaxies, by examining its effect on the stability of box orbits which are the backbone of triaxial elliptical galaxies. Ample observational evidence is now available for the existence of a central mass concentration or central cusps in galaxies. The central mass is expected to cause orbital stochasticity and chaotic mixing of orbits, which could have ramifications on galactic evolution. We investigate here the interplay between potential cuspiness and eccentricity on the stability of axial orbits in a scale-free potential in a simple, preliminary attempt to characterize this effect.

galaxies central mass concentration box orbits↗
NASA NTRS1990

Examples of the nonlinear dynamics of ballistic capture and escape in the earth-moon system

An example of a trajectory is given which is initially captured in an elliptic resonant orbit about the earth and then ballistically escapes the earth-moon system. This is demonstrated by a numerical example in three-dimensions using a planetary ephemeris. Another example shows a mechanism of how an elliptic orbit about the earth can increase its energy by performing a complex nonlinear transition to an elliptic orbit of a larger semi-major axis. Capture is also considered. An application of ballistic capture at the moon via an unstable periodic orbit using the four-body sun-earth-moon-S/C interaction is described.

Belbruno, Edward A.↗
NASA NTRS1996

Analysis of Apollo 8 Photography and Visual Observations

Apollo 8 was launched from Cape Kennedy, Fla., at 7 :50 a.m., e.s.t., on December 21, 1968. Two hours 50 minutes later, translunar injection was performed; and astronauts Col. Frank Borman, the commander; Capt. James A. Lovell, Jr., the command module pilot; and Maj. (now Lt. Col.) William A. Anders, the lunar module pilot, were on their way to the Moon. The spacecraft was placed in an elliptical lunar orbit at 69 hours 8 minutes after liftoff. After flying two elliptical orbits of 168.5 by 60 nautical miles with an inclination of 12° to the Equator, the spacecraft was placed in a nearly circular orbit of 59.7 by 60.7 nautical miles, in which it remained for eight orbits. At 89 hours 19 minutes, trans earth injection was performed from behind the Moon. A nearly flawless mission was completed on the morning of December 27 when splashdown occurred in the Pacific Ocean after a total elapsed time of 147 hours. Lt. Gen. Sam C. Phillips, the Director of the Apollo Program, announced that such a mission was being considered at a press conference on August 19, 1968. Formal announcement that NASA was preparing Apollo 8 for an orbital flight around the Moon was released to the press on November 12, 1968. The primary purpose of this mission was to further progress toward the goal of landing men on the Moon by gaining operational experience and testing the Apolio systems. However, a great effort was also made to accomplish worthwhile scientific tasks with photography and visual observations by the astronauts. In planning the scientific tasks to be attempted on this mission, it was obvious that one of the prime tasks should be photography of the lunar surface. Such photography would furnish valuable information on the following : 1. Approach topography and landmarks for the early Apollo landings 2. The scientific merit and the roughness of areas for possible follow-on Apollo landings 3. The broad structure and characteristics of the lunar surface During the orbital part of the mission, a major portion of the lunar far side would be in sunlight. Although almost all of the far side of the Moon has been photographed by the automated Lunar Orbiter spacecraft, the photography generally was made with the spacecraft relatively far from the Moon, limiting the Lunar Orbiter photographs to an average resolution of approximately 100 meters. Thus, Apollo photographs of the far side would have much better resolution than existing pictures. Finally, it was recognized that contamination, both as it relates to window fogging (which did occur) and to contamination clouds around t he spacecraft, should be studied for both scientific and operational interests.

Richard J. Allenby↗
NASA NTRS2005

Constellations of elliptical inclined lunar orbits providing polar and global coverage

Prior results have developed a methodology for selecting a long-lived constellation of 3 satellites that provide persistent, stable coverage to either the North or South Pole with no requirement for stationkeeping under the influence of only gravitational perturbations. In the present study, the sensitivity of this coverage in the presence of non-gravitational forces is determined, and a design strategy is formulated that minimizes any potential sensitivity to these accelerations.

lunar constellation design↗
NASA NTRS2012

Space Launch System Mission Flexibility Assessment

The Space Launch System (SLS) is envisioned as a heavy lift vehicle that will provide the foundation for future beyond low Earth orbit (LEO) missions. While multiple assessments have been performed to determine the optimal configuration for the SLS, this effort was undertaken to evaluate the flexibility of various concepts for the range of missions that may be required of this system. These mission scenarios include single launch crew and/or cargo delivery to LEO, single launch cargo delivery missions to LEO in support of multi-launch mission campaigns, and single launch beyond LEO missions. Specifically, we assessed options for the single launch beyond LEO mission scenario using a variety of in-space stages and vehicle staging criteria. This was performed to determine the most flexible (and perhaps optimal) method of designing this particular type of mission. A specific mission opportunity to the Jovian system was further assessed to determine potential solutions that may meet currently envisioned mission objectives. This application sought to significantly reduce mission cost by allowing for a direct, faster transfer from Earth to Jupiter and to determine the order-of-magnitude mass margin that would be made available from utilization of the SLS. In general, smaller, existing stages provided comparable performance to larger, new stage developments when the mission scenario allowed for optimal LEO dropoff orbits (e.g. highly elliptical staging orbits). Initial results using this method with early SLS configurations and existing Upper Stages showed the potential of capturing Lunar flyby missions as well as providing significant mass delivery to a Jupiter transfer orbit.

Monk, Timothy↗
NASA NTRS2014

Orbit Determination Accuracy Analysis of the Magnetospheric Multiscale Mission During Perigee Raise

The Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) will provide orbit determination and prediction support for the Magnetospheric Multiscale (MMS) mission during the missions commissioning period. The spacecraft will launch into a highly elliptical Earth orbit in 2015. Starting approximately four days after launch, a series of five large perigee-raising maneuvers will be executed near apogee on a nearly every-other-orbit cadence. This perigee-raise operations concept requires a high-accuracy estimate of the orbital state within one orbit following the maneuver for performance evaluation and a high-accuracy orbit prediction to correctly plan and execute the next maneuver in the sequence. During early mission design, a linear covariance analysis method was used to study orbit determination and prediction accuracy for this perigee-raising campaign. This paper provides a higher fidelity Monte Carlo analysis using the operational COTS extended Kalman filter implementation that was performed to validate the linear covariance analysis estimates and to better characterize orbit determination performance for actively maneuvering spacecraft in a highly elliptical orbit. The study finds that the COTS extended Kalman filter tool converges on accurate definitive orbit solutions quickly, but prediction accuracy through orbits with very low altitude perigees is degraded by the unpredictability of atmospheric density variation.

Determination↗
NASA NTRS2014

Orbit Determination Accuracy Analysis of the Magnetospheric Multiscale Mission During Perigee Raise

The Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) will provide orbit determination and prediction support for the Magnetospheric Multiscale (MMS) mission during the mission's commissioning period. The spacecraft will launch into a highly elliptical Earth orbit in 2015. Starting approximately four days after launch, a series of five large perigee-raising maneuvers will be executed near apogee on a nearly every-other-orbit cadence. This perigee-raise operations concept requires a high-accuracy estimate of the orbital state within one orbit following the maneuver for performance evaluation and a high-accuracy orbit prediction to correctly plan and execute the next maneuver in the sequence. During early mission design, a linear covariance analysis method was used to study orbit determination and prediction accuracy for this perigee-raising campaign. This paper provides a higher fidelity Monte Carlo analysis using the operational COTS extended Kalman filter implementation that was performed to validate the linear covariance analysis estimates and to better characterize orbit determination performance for actively maneuvering spacecraft in a highly elliptical orbit. The study finds that the COTS extended Kalman filter tool converges on accurate definitive orbit solutions quickly, but prediction accuracy through orbits with very low altitude perigees is degraded by the unpredictability of atmospheric density variation.

Multiscale↗
NASA NTRS1980

Diurnal, seasonal, and nighttime variations of atomic nitrogen in the equatorial thermosphere

The open source neutral mass spectrometer on board the equatorial Atmosphere Explorer E satellite (AE-E) measured atomic nitrogen densities at frequent intervals during both the elliptical and circular orbit phases of satellite operations. Elliptical orbit data presented here by means of empirical models at 225- and 300-km altitude provide diurnal and seasonal profiles at altitudes lower than previously possible. Data from individual circular orbits later in the AE-E mission confirm essential features of these models, particularly the diurnal density profile. At lower altitudes, considerable variation is evident near midnight, with density enhancements correlated with increasing levels of geomagnetic activity.

Engebretson, M. J.↗
NASA NTRS1986

Tether propulsion

The principle and applications of tethering are examined. Tethering works by momentum transfer; the center of mass of a system consisting of (for example) a Space Shuttle and a tethered payload such as the Advanced X-ray Astrophysical Facility continues to follow the original orbit. Given a slight outward velocity, the payload begins to lag behind because it has the same linear velocity as the Shuttle but is at a greater distance from the earth. Any displacement from the local vertical causes a restoring force at each end tending to restore the system to a vertical orientation. When vertically above the Shuttle, the payload has the same angular velocity but a greater linear velocity; thus momentum is transferred from the Shuttle to the payload. It is computed that a tether 32 nautical miles long could deploy AXAF into a 320-nautical mile orbit from a lower, elliptical Shuttle orbit, thus saving 5000 pounds of Shuttle propellant. Various types of tether are considered: Kevlar and steel, uniform and tapered. Numerous cases appear to be feasible for boost and deboost as well as momentum transfer, using such reaction masses as the Space Station, a lunar orbiter, the Martian moons Phobos and Deimos, various asteroids, and moons of the major planets.

Bekey, I.↗
NASA NTRS1999

Comets: Very Eccentric Characters

Astronomical distances, even within our own solar system, are very difficult for anyone, let alone children, to imagine. In this month's space-program-related activity, students have the opportunity to create a visual and kinesthetic model of the solar system on a scale that may begin to inspire an awed comprehension of how big space is and how small Earth is. In addition, they will learn a little basic geometry in demonstrating for themselves the difference between a circular planetary orbit and an elongated elliptical cometary orbit. As a space exploration first the Jet Propulsion Laboratory (JPL), under contract to the National Aeronautics and Space Administration (NASA), is planning to send a spacecraft to rendezvous with and land on a comet. The Space Technology 4/Champollion mission is part of NASA's New Millennium Program, the primary goal of which is to test new technologies for use in 21st century planetary and earth observing missions.

Kwok, Enoch↗
NASA NTRS1961

Analog Simulation of a Pilot-Controlled Rendezvous

The rendezvous of a pilot-controlled space ferry vehicle with an orbiting space station was simulated in six degrees of freedom. A fixed-base simulator and an analog computer were used. The ferry vehicle was assumed to have a single main thrusting rocket and to be provided with attitude control. Control of the thrust was provided by a rocket throttle quadrant which could provide either proportional or on-off control. The attitude of the vehicle was controlled during the rendezvous with a two-axis, pencil-type side-arm controller and rudder pedals. For the most part rendezvous maneuvers were made with the target satellite in a circular orbit. In addition, an elliptical station orbit was investigated. Tolerable initial conditions, as well as adequate data presentations, were determined. Results of the investigation indicate that a human pilot can rendezvous successfully with the vehicle and instrumentation considered over a wide band of initial conditions. Coplanar conditions are not necessary. Retro-rocket fuel used is not greatly increased by imposing perturbing influences such as rocket-misalignment torques on the rendezvous vehicle. When excessive attitude-control torques are required to maintain the necessary trim attitudes under misalignment influences, the reaction fuel used for this control increases. The time required for a specific rendezvous varies somewhat between pilots. If control of the time for completing the rendezvous is desired, requirements for retrorocket fuel are affected, and an energy-management schedule is required. Continuous variation of the thrust is not necessary. The pilot positions the throttle to obtain a desired level of thrust, and applies bursts of thrust as required. All data were presented on dialed instruments. The quantities required are range and range rate and line-of-sight rates between the vehicle and the station, vehicle attitudes and angular rates, and the angles subtended by the line of sight. For the equipment assumed herein, satellite rendezvous presented no great problem to the pilot.

Brissenden, Roy F.↗
NASA NTRS2003

Benchmark Problems for Space Mission Formation Flying

To provide a high-level focus to distributed space system flight dynamics and control research, several benchmark problems are suggested for space mission formation flying. The problems cover formation flying in low altitude, near-circular Earth orbit, high altitude, highly elliptical Earth orbits, and large amplitude lissajous trajectories about co-linear libration points of the Sun-Earth/Moon system. These problems are not specific to any current or proposed mission, but instead are intended to capture high-level features that would be generic to many similar missions that are of interest to various agencies.

Carpenter, J. Russell↗