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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 109 records · Page 6
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NASA NTRS2013

Dawn Orbit Determination Team: Trajectory Modeling and Reconstruction Processes at Vesta

The Dawn spacecraft spent over a year in orbit around Vesta from July 2011 through August 2012. In order to maintain the designated science reference orbits and enable the transfers between those orbits, precise and timely orbit determination was required. Challenges included low-thrust ion propulsion modeling, estimation of relatively unknown Vesta gravity and rotation models, track-ing data limitations, incorporation of real-time telemetry into dynamics model updates, and rapid maneuver design cycles during transfers. This paper discusses the dynamics models, filter configuration, and data processing implemented to deliver a rapid orbit determination capability to the Dawn project.

low thrust↗
NASA NTRS2009

Managing Momentum on the Dawn Low Thrust Mission

Dawn is low-thrust interplanetary spacecraft enroute to the asteroids Vesta and Ceres in an effort to better understand the early creation of the solar system. After launch in September 2007, the spacecraft will flyby Mars in February 2009 before arriving at Vesta in summer of 2011 and Ceres in early 2015. Three solar electric ion-propulsion engines are used to provide the primary thrust for the Dawn spacecraft. Ion engines produce a very small but very efficient force, and therefore must be thrusting almost continuously to realize the necessary change in velocity to reach Vesta and Ceres.

RWA↗
NASA NTRS2014

In-Flight Operation of the Dawn Ion Propulsion System Through Year Two of Cruise to Ceres

The Dawn mission, part of NASA's Discovery Program, has as its goal the scientific exploration of the two most massive main-belt asteroids, 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 which will provide a total (Delta)V of 11.3 km/s 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, and transfer between Ceres science orbits.

Garner, Charles E.↗
NASA NTRS2018

Dawn Mission's Search for Satellites of Ceres: Intact Protoplanets Don't Have Satellites

Upon its approach to orbit the dwarf planet Ceres in early 2015, optical navigation and dedicated satellite search images were acquired with the Dawn mission's framing camera 2. A team of searchers individually processed and examined the images for evidence of objects moving with Ceres. Completeness of search with respect to the space searched was calculated as a function of distance to Ceres and found to be complete down to 15 Ceres radii (Ceres' mean radius is 470 kilometers). Upper limits of detectable magnitude were determined for each observed set of images and an upper limit in size was calculated assuming for the putative objects, Ceres' geometric albedo of 0.11. Nothing was found associated with Ceres down to a radius of 12 meters for the most sensitive search, and down to a radius of 323m for the least sensitive search circumstances. Examination of the physical properties of the 41 largest and most massive main belt asteroids suggests that large asteroids without satellites are intact and their interiors have internal strength. This is consistent with results from the Dawn mission at both Vesta and Ceres. Ceres' volatile-rich composition also is a likely contributor to both the absence of satellites at Ceres and of Ceres meteorites at Earth. These results suggest that collisional disruption creating rubble pile structure is a necessary condition for formation of satellites around main belt asteroids.

McFadden, Lucy A.↗
NASA NTRS2016

Dawn Safing Approach to Ceres Re-Design

In mid-2014 the Dawn team finalized preparations for the spacecraft’s approach to Ceres. The design was the product of careful planning that began several years in advance, when the spacecraft left Vesta in September 2012. However, a few months prior to the anticipated start of approach, the spacecraft entered a safe mode. While temporary loss of thrust for ion propulsion missions is usually not mission-critical, it still presents many challenges. The safing event occurred at a time when thrusting to match Ceres’ orbital velocity was most effective, which meant the spacecraft must fly past Ceres before capturing into orbit. The new approach geometry changed the team’s strategy for navigating the spacecraft safely into orbit around Ceres with optical data. In this paper we describe the challenges of navigating the Dawn spacecraft into orbit around Ceres, including the safing event and re-design of the approach architecture.

Grebow, Daniel J.↗
NASA NTRS2016

Dawn Safing Approach to Ceres Re-Design

In mid-2014 the Dawn team finalized preparations for the spacecraft’s approach to Ceres. The design was the product of careful planning that began several years in advance, when the spacecraft left Vesta in September 2012. However, a few months prior to the anticipated start of approach, the spacecraft entered a safe mode. While temporary loss of thrust for ion propulsion missions is usually not mission-critical, it still presents many challenges. The safing event occurred at a time when thrusting to match Ceres’ orbital velocity was most effective, which meant the spacecraft must fly past Ceres before capturing into orbit. The new approach geometry changed the team’s strategy for navigating the spacecraft safely into orbit around Ceres with optical data. In this paper we describe the challenges of navigating the Dawn spacecraft into orbit around Ceres, including the safing event and re-design of the approach architecture.

Grebow, Dan↗
NASA NTRS2017

Hydrazine Conservation for the Dawn Spacecraft Operations at the Dwarf Planet Ceres

Dawn is a low-thrust interplanetary spacecraft currently orbiting the dwarf planet Ceres. After successfully completing its Vesta and Ceres prime missions, Dawn is now in its extended mission, continuously exploring Ceres. After losing the second reaction wheel assembly at the end of the Vesta mission, the feasibility of the Ceres mission was at risk due to the potentially significant increase in hydrazine consumption from using only the reaction control system thrusters. This paper summarizes the intense, collaborative efforts undertaken by the project to conserve hydrazine prior to Vesta departure, during cruise to Ceres, and throughout the Ceres mission. The project’s efforts in minimizing the number of turns are discussed. A special emphasis is given to describing various efforts taken by the Attitude Control Subsystem team in an attempt to reduce hydrazine consumption. These efforts include: changing default slew rates, control gain tuning, changing nadir pointing strategy with Ahead Cross Nadir pointing, hybrid control implementation using hydrazine based thrusters and two remaining reaction wheels, optimal science turn location analysis, and reaction wheel angular momentum management strategies for reducing the number of momentum unloadings. In addition to the Attitude Control Subsystem team’s efforts, the Mission Design and Navigation team’s efforts taken in designing hydrazine friendly orbit transfers are discussed. The trade study performed collaboratively by the Attitude Control Subsystem team and the Science Operations Support Team in choosing hydrazine friendly off-nadir targets is also discussed. Various simulation results are presented and compared against actual flight data obtained. Lastly, remaining hydrazine status at the end of the prime Ceres mission and the hydrazine management planning for the extended mission are discussed.

Salami, Mana↗
NASA NTRS2019

Final Dawn Reaction Control System (RCS) propulsion system in-flight characterization

The Dawn spacecraft concluded eleven years of operations on 31-Oct-2018, upon depletion of its hydrazine supply in Ceres orbit during the second extended mission. Dawn’s Reaction Control System performed admirably during this lengthy campaign, including years of unanticipated and novel operation given Reaction Wheel Assembly failures during flight. New and modified modes of thruster operations were implemented during the mission. Pressure transducer drift was negligible, consumable limits were generally not exceeded (except for minor violations in Reaction Control System thruster cycles), and thruster performance was nominal throughout this long interplanetary journey. Tank models of hydrazine remaining mass were consistent with depletion within uncertainties, although thruster consumption-based models ended up being conservative by 15%. Unexpectedly, apparent nitrogen permeation through the hydrazine tank elastomer diaphragm allowed hydrazine in the lines below the tank to be pressurized and subsequently utilized during the final days of the mission.

Mizukami, Masashi↗
NASA NTRS2019

Final Dawn Reaction Control System (RCS) propulsion system in-flight characterization

The Dawn spacecraft concluded eleven years of operations on 31-Oct-2018, upon depletion of its hydrazine supply in Ceres orbit during the second extended mission. Dawn’s Reaction Control System performed admirably during this lengthy campaign, including years of unanticipated and novel operation given Reaction Wheel Assembly failures during flight. New and modified modes of thruster operations were implemented during the mission. Pressure transducer drift was negligible, consumable limits were generally not exceeded (except for minor violations in Reaction Control System thruster cycles), and thruster performance was nominal throughout this long interplanetary journey. Tank models of hydrazine remaining mass were consistent with depletion within uncertainties, although thruster consumption-based models ended up being conservative by 15%. Unexpectedly, apparent nitrogen permeation through the hydrazine tank elastomer diaphragm allowed hydrazine in the lines below the tank to be pressurized and subsequently utilized during the final days of the mission.

Mizukami, Masashi↗
NASA NTRS2021

Simultaneous UV Images and High-Latitude Particle and Field Measurements During an Auroral Dawn Storm at Jupiter

We present multi-instrument Juno observations on day-of-year 86, 2017 that link particles and fields in Jupiter's polar magnetosphere to transient UV emissions in Jupiter's northern auroral region known as dawn storms. Juno ranged from 42°N to 51°N in magnetic latitude and 5.8–7.8 Jovian radii (1 RJ = 71,492 km) during this period. These dawn storm emissions consisted of two separate, elongated structures which extended into the nightside, rotated with the planet, had enhanced brightness (up to at least 1.4 megaRayleigh) and high color ratios. The color ratio is a proxy for the atmospheric penetration depth and therefore the energy of the electrons that produce the UV emissions. Juno observed electrons and ions on magnetic field lines mapping to these emissions. The electrons were primarily field-aligned, bidirectional, and, at times, exhibited sudden intensity decreases below ∼10 keV coincident with intensity enhancements up to energies of ∼1,000 keV, consistent with the high color ratio observations. The more energetic electron distributions had characteristic energies of ∼160–280 keV and downward energy fluxes (∼70–135 mW m−2) that were a significant fraction needed to produce the UV emissions for this event. Magnetic field perturbations up to ∼0.7% of the local magnetic field showing evidence of upward and downward field-aligned currents, whistler mode waves, and broadband kilometric radio emissions were also observed along Juno's trajectory during this time frame. These high-latitude observations show similarities to those in the equatorial magnetosphere associated with dynamics processes such as interchange events, plasma injections, and/or tail reconnection.

R. W. Ebert↗
NASA NTRS2025

Informing Planetary Protection Policies for the Future Exploration of Ceres: State of Understanding after the Dawn Mission

We review the current state of understanding of Ceres as it relates to planetary protection policy for future landed missions, including for sample return, to the dwarf planet. The Dawn mission found Ceres to be an intriguing target for a mission, with evidence for the presence of regional, possibly extensive liquid at depth, and local expressions of recent and potentially ongoing activity. The Dawn mission also found a high abundance of carbon in the regolith, interpreted as a mix of carbonates and amorphous carbon, as well as locally high concentrations of organic matter. Key findings from this review are as follows: (1) outside of the region of Occator crater, Ceres shows no geological evidence for conduits from the surface to the interior; and (2) considering the biological potential of Ceres’ deep interior, a surface sample return mission should be considered Category V restricted, unless it can be demonstrated that evaporites sourced from Ceres’ deep brine region, and recently exposed in Occator crater, have not been scattered to the rest of Ceres’ surface; in that case, the probability of returning an unsterilized particle to an acceptably low value is to be determined by a future study. Key Words: Ceres—Planetary protection—Brines—Future missions.

Julie Castillo-Rogez↗
NASA NTRS2004

Dawn : a mission in developement for exploration of main belt asteroids Vesta and Ceres

Dawn is in development for a 2006 launch on a mission to explore main belt asteroids in order to yield insights into important questions about the formation and evolution of the solar system. Its objective is to acquire detailed data from orbit around two complementary bodies, Vesta and Ceres, the two most massive asteroids. The project relies on extensive heritage from other deep-space and Earth-orbiting missions, thus permitting the ambitious objectives to be accomplished with an affordable budget.

asteroids↗
NASA NTRS2006

From Zero to Integration in Eight Months, the Dawn Ground Data System Engineering Challenge

The Dawn GDS Team met the SC Sim integration challenge in eight months. The GDS System Engineering approach in response to the SC Simintegration challenge, focused on a set of key practices: decomposition of project request into manageable requirements; integration of multiple ground disciplines and experts into a focused team effort; risk management thru management of expectations; and aggregation of intermediate products into a final product. By maintaining a a system-level focus, the overall systems engineering process unified team GDS Team members with a common goal: the success of the ground system as a whole and not just the success of their individual expert contributions. Incorporation of Agile-type development efforts were aligned with a risk strategy based on team-oriented principles and expectations management, thus achieving a more stable baseline solution without compromising the integrity of the GDS design.

Dawn Mission↗
NASA NTRS2005

Performance of High-Efficiency Advanced Triple-Junction Solar Panels for the LILT Mission Dawn

NASA's Discovery Mission Dawn is designed to (LILT) conditions. operate within the solar system's Asteroid belt, where the large distance from the sun creates a low-intensity, low-temperature (LILT) condition. To meet the mission power requirements under LlLT conditions, very high-efficiency multi-junction solar cells were selected to power the spacecraft to be built by Orbital Sciences Corporation (OSC) under contract with JPL. Emcore's InGaP/InGaAs/Ge advanced triple-junction (ATJ) solar cells, exhibiting an average air mass zero (AMO) efficiency of greater than 27.6% (one-sun, 28 C), were used to populate the solar panels [1]. The two solar array wings, to be built by Dutch Space, with 5 large- area panels each (total area of 36.4 sq. meters) are projected to produce between 10.3 kWe and 1.3 kWe of end-of life (EOL) power in the 1.0 to 3.0 AU range, respectively. The details of the solar panel design, testing and power analysis are presented.

triple junction solar cells↗
NASA NTRS2008

The DAWN Project's Transition to Mission Operations: on Its Way to Rendezvous with (4) Vesta and (1) Ceres

Dawn launched on 27 September 2007 on a mission to orbit main belt asteroids (4) Vesta in 2011 - 2012 and (1) Ceres in 2015. The operations team conducted an extensive set of assessments of the engineering subsystems and science instruments during the first 80 days of the mission. A major objective of this period was to thrust for one week with the ion propulsion system to verify flight and ground systems readiness for typical interplanetary operations. Upon successful conclusion of the checkout phase, the interplanetary cruise phase began, most of which will be devoted to thrusting. The flexibility afforded by the use of ion propulsion enabled the project to accommodate a launch postponement of more than 3 months caused by a combination of launch vehicle and tracking system readiness, unfavorable weather, and then conflicts with other launches. Even with the shift in the launch date, all of the science objectives are retained with the same schedule and greater technical margins. This paper describes the conclusion of the development phase of the project, launch operations, and the progress of mission operations.

launch operations↗
NASA NTRS2011

Low-Thrust Orbit Transfer Design for DAWN Operations at VESTA

Upon arrival at the asteroid Vesta, scheduled for July of 2011, the Dawn spacecraft will target a series of four distinct mapping orbits, each providing a unique opportunity to observe Vesta. The unknown, and potentially complex, Vesta gravity field presents challenges for designing low-thrust transfers between these mapping orbits while maintaining spacecraft safety from Vesta occultation of the Sun. This paper provides a description of the orbit transfers designed for Vesta operations along with a discussion of the constraints and methods used to design these transfers. The effect of alternate gravity fields on the viability of the designs and the design method is also considered

low thrust↗
NASA NTRS2011

Dawn's Exploration of Vesta

The Dawn spacecraft will reach Vesta in mid-2011 and begin a comprehensive geological and geophysical characterization to investigate the geologic history, interior structure, and evolution of this minor planet in the Main Asteroid Belts [1]. Analysis of the suite of basaltic achondrite howardite-eucrite-diogenite (HED) meteorites, linked spectrally to Vesta, indicate that Vesta undwent igneous differentiation and has a metallic core. As such, Vesta represents a diminutive end-member of the differentiated terrestrial planets.

protoplanet↗
NASA NTRS2011

Geoscientific Mapping of Vesta by the Dawn Mission

The geologic objectives of the Dawn Mission are to derive Vesta's shape, map the surface geology, understand the geological context and contribute to the determination of the asteroids' origin and evolution. Geomorphology and distribution of surface features will provide evidence for impact cratering, tectonic activity, volcanism, and regolith processes. Spectral measurements of the surface will provide evidence of the compositional characteristics of geological units. Age information, as derived from crater size-frequency distributions, provides the stratigraphic context for the structural and compositional mapping results into the stratigraphic context and thusrevealing the geologic history of Vesta.

lunar mapping↗