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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 73 records · Page 4
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NASA NTRS2003

Can MARSIS Measure the Low-Altitude Components of the Mars Magnetic Field?

Measuring the magnetic field anomaly of Mars at low altitudes (e.g. 100-200 km) can be an interesting application of Mars Advance Radar for Subsurface and Ionospheric Sounder (MARSIS). Due to a low HF operation frequency, the radio wave propagating in the ionosphere of Mars, over the magnetic anomaly regions, will be affected and distorted by the localized magnetic field. This distortion in the sounder signal is due to the Faraday rotation and provides information about the strength of the magnetic field. MARSIS is especially sensitive to the radial magnetic field at altitudes where the electron density in the ionosphere peaks (i.e. 100-200 km). Consequently, MARSIS is potentially capable of providing measurements for the radial component of the magnetic field at altitudes between 100 to 200 km that are normally out of reach for orbital magnetometers (with the exception of the aero-braking phase). Such low-altitude measurements would be complementary to already existing measurements at 400 km by MAG-ER on Mars Global Surveyor. This paper will explain the sensitivity of MARSIS as a magnetometer and the method envisioned to measure the radial magnetic field component. MARSIS (Picardi et al.), the first major planetary radar sounder, is the result of an international collaboration between NASA, the Italian Space Agency (ASI), and European Space Agency (ESA), and will arrive at Mars in early 2004 for a two-year mission. MARSIS has a frequency range between 0.1-5.5 MHz and is designed to penetrate the subsurface to a depth of a few kilometers. MARSIS primary objective is to map and characterize the subsurface geological structure of Mars, and search for subsurface liquid water reservoirs. The secondary objective of MARSIS is to study the ionosphere of Mars providing the most extensive amount of data on Martian ionosphere to date. In addition to MARSIS, a second radar sounder named SHARAD (SHallow RADar) with operation frequency of 15-25 MHz is under development. SHARAD is an Italian instrument (Seu et. al) that will fly on NASA s Mars Reconnaissance orbiter in 2005. SHARAD can also provide magnetic measurements, however, it is not expected to be as sensitive as MARSIS to magnetic field variations.

A Safaeinili↗
NASA NTRS2016

In-Flight Operation of the Dawn Ion Propulsion System Through the Low Altitude Mapping Orbit at Ceres

The Dawn mission, part of NASA’s Discovery Program, has as its goal the scientific exploration of the two most massive main-belt objects, Vesta and Ceres. The Dawn spacecraft was launched from the Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H- 9.5 (Delta-II Heavy) rocket that placed the 1218-kg spacecraft onto an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) developed at the Jet Propulsion Laboratory for the heliocentric transfer to Vesta, orbit capture at Vesta, transfer between Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, transfer between Ceres science orbits, and orbit maintenance maneuvers. Full-power thrusting from December 2007 through October 2008 was used to successfully target a Mars gravity assist flyby in February 2009 that provided an additional ΔV of 2.6 km/s. Deterministic thrusting for the heliocentric transfer to Vesta resumed in June 2009 and concluded with orbit capture at Vesta on July 16, 2011. From July 2011 through September 2012 the IPS was used to transfer to all the different science orbits at Vesta and to escape from Vesta orbit. Cruise for a rendezvous with Ceres began in August 2012 and completed in late December 2014. From December 2014 through June 2016 the IPS was used for transiting the spacecraft to the Approach phase, survey orbit, the high altitude mapping orbit (HAMO), and the low altitude mapping orbit (LAMO) with arrival to LAMO on December 13, 2015, almost eight years after the start of deterministic thrusting to Vesta. The LAMO orbit, at a mean altitude above Ceres of approximately 385 km, is the spacecraft’s final destination and there are no plans to move the spacecraft from LAMO once science operations there are completed. Since arrival at LAMO Dawn’s IPS has been used for occasional orbit maintenance maneuvers while the spacecraft performs scientific investigations. Dawn has successfully completed its science goals and Dawn’s primary mission is scheduled to end June 30, 2016. To date the IPS has been operated for approximately 48,458 hours, consumed approximately 401 kg of xenon, and provided a delta-V of over 11.0 km/s, a record for an on-board propulsion system. The IPS performance characteristics are close to the expected performance based on analysis and testing performed pre-launch. Dawn’s IPS continues to be fully operational as of June 2016. This paper provides an overview of Dawn’s mission objectives and the results of Dawn IPS mission operations from Survey orbit through the completion of Dawn’s primary mission.

Garner, Charles E.↗
NASA NTRS2016

In-flight Operation of the Dawn Ion Propulsion System Through the Low Altitude Mapping Orbit at Ceres

The Dawn mission, part of NASA’s Discovery Program, has as its goal the scientific exploration of the two most massive main-belt objects, Vesta and Ceres. The Dawn spacecraft was launched from the Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H- 9.5 (Delta-II Heavy) rocket that placed the 1218-kg spacecraft onto an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) developed at the Jet Propulsion Laboratory for the heliocentric transfer to Vesta, orbit capture at Vesta, transfer between Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, transfer between Ceres science orbits, and orbit maintenance maneuvers. Full-power thrusting from December 2007 through October 2008 was used to successfully target a Mars gravity assist flyby in February 2009 that provided an additional ΔV of 2.6 km/s. Deterministic thrusting for the heliocentric transfer to Vesta resumed in June 2009 and concluded with orbit capture at Vesta on July 16, 2011. From July 2011 through September 2012 the IPS was used to transfer to all the different science orbits at Vesta and to escape from Vesta orbit. Cruise for a rendezvous with Ceres began in August 2012 and completed in late December 2014. From December 2014 through June 2016 the IPS was used for transiting the spacecraft to the Approach phase, survey orbit, the high altitude mapping orbit (HAMO), and the low altitude mapping orbit )LAMO) with arrival to LAMO on December 13, 2015, almost eight years after the start of deterministic thrusting to Vesta. The LAMO orbit, at a mean altitude above Ceres of approximately 385 km, is the spacecraft’s final destination and there are no plans to move the spacecraft from LAMO once science operations there are completed. Since arrival at LAMO Dawn’s IPS has been used for occasional orbit maintenance maneuvers while the spacecraft performs scientific investigations. Dawn has successfully completed its science goals and Dawn’s primary mission is scheduled to end in the summer of 2016. To date the IPS has been operated for over 48,454 hours, consumed approximately 401 kg of xenon, and provided a delta-V of over 11.0 km/s, a record for an on-board propulsion system. The IPS performance characteristics are close to the expected performance based on analysis and testing performed pre-launch. Dawn’s IPS continues to be fully operational as of June 2016. This paper provides an overview of Dawn’s mission objectives and the results of Dawn IPS mission operations from Survey orbit through June 2016.

Garner, Charles E.↗
NASA NTRS1990

Airborne Doppler radar detection of low altitude windshear

As part of an integrated windshear program, the Federal Aviation Administration, jointly with NASA, is sponsoring a research effort to develop airborne sensor technology for the detection of low altitude windshear during aircraft take-off and landing. One sensor being considered is microwave Doppler radar operating at X-band or above. Using a Microburst/Clutter/Radar simulation program, a preliminary feasibility study was conducted to assess the performance of Doppler radars for this application. Preliminary results from this study are presented. Analysis show, that using bin-to-bin Automatic Gain Control (AGC), clutter filtering, limited detection range, and suitable antenna tilt management, windshear from a wet microburst can be accurately detected 10 to 65 seconds (.75 to 5 km) in front of the aircraft. Although a performance improvement can be obtained at higher frequency, the baseline X-band system that was simulated detected the presence of a windshear hazard for the dry microburst. Although this study indicates the feasibility of using an airborne Doppler radar to detect low altitude microburst windshear, further detailed studies, including future flight experiments, will be required to completely characterize the capabilities and limitations.

Bracalente, Emedio M.↗
NASA NTRS2016

Statistical Correlation of Low-Altitude ENA Emissions with Geomagnetic Activity from IMAGE MENA Observations

Plasma sheet particles transported Earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low-altitude (300-800 km) ion precipitation in the high-latitude atmosphere/ionosphere are termed low-altitude emissions (LAEs). Remotely observed LAEs are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90deg. The Geomagnetic Emission Cone of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity. The LAE data are from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000-2005). The SYM-H, AE, and Kp indices are used to describe geomagnetic activity. The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM-H showing the greatest sensitivity. The magnetic local time distribution of LAEs is centered about midnight and spreads with increasing activity. The invariant latitude for all indices has a slightly negative correlation. The combined results indicate LAE behavior similar to that of ion precipitation.

Mackler, D. A.↗
NASA NTRS1971

Characteristics of magnetosheath plasma observed at low altitudes in the dayside magnetospheric cusps

Magnetosheath plasma penetrating to low altitudes in the dayside cusp region of the magnetosphere has been observed by the ISIS 1 soft particle spectrometer (SPS). The extent of these particle fluxes in local magnetic time and invariant latitude, their variation with magnetic activity, and their pitch angle distribution are given. Comparison between the SPS data and energetic particle data indicates that the boundary between open and closed field lines on the dayside is associated with a sharp drop in the outer zone keV electron fluxes. It is shown that these newly identified cusp fluxes provide the necessary energy to produce observed dayside auroral oval phenomena.

Winningham, J. D.↗
NASA NTRS1989

Some low-altitude cusp dependencies on the interplanetary magnetic field

The low-altitude cusp dependencies on the interplanetary magnetic field (IMF) were investigated using the algorithm of Newell and Meng (1988) to identify the cusp proper. The algorithm was applied to 12,569 high-latitude dayside passes of the DMSP F7 spacecraft, and the resulting cusp positioning data were correlated with the IMF. It was found that the cusp latitudinal position correlated reasonably well (0.70) with the Bz component when the IMF had a southward component. The correlation for the northward Bz component was only 0.18, suggestive of a half-wave rectifier effect. The ratio of cusp ion number flux precipitation for Bz southward to that for Bz northward was 1.75 + or - 0.12. The statistical local time widths of the cusp proper for the northward and the southward Bz components were found to be 2.1 h and 2.8 h, respectively.

Newell, Patrick T.↗