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NASA NTRS2010

Engineering a Solution to Jupiter Exploration

The Europa Jupiter System Mission (EJSM) would be an international mission with the overall theme of investigating the emergence of habitable worlds around gas giants. Its goals are to (1) explore Europa to investigate its habitability, (2) characterize Ganymede as a planetary object including its potential habitability and (3) explore the Jupiter system as an archetype for gas giants. NASA and ESA have concluded a detailed joint study of a mission to Europa, Ganymede, and the Jupiter system with conceptual orbiters developed by NASA and ESA. The baseline EJSM architecture consists of two primary elements operating simultaneously in the Jovian system: the NASA-led Jupiter Europa Orbiter (JEO), and the ESA-led Jupiter Ganymede Orbiter (JGO). JEO and JGO would execute an intricately choreographed exploration of the Jupiter System before settling into orbit around Europa and Ganymede, respectively. EJSM would directly address themes concerning the origin and evolution of satellite systems and water-rich environments in icy satellites. The potential habitability of the ocean-bearing moons Europa and Ganymede would be investigated, by characterizing the geophysical, compositional, geological, and external processes that affect these icy worlds. EJSM would also investigate Io and Callisto, Jupiter's atmosphere, and the Jovian magnetosphere. By understanding the Jupiter system and unraveling its history, the formation and evolution of gas giant planets and their satellites would be better known. Most importantly, EJSM would shed new light on the potential for the emergence of life in the celestial neighborhood and beyond. The EJSM baseline architecture would provide opportunities for coordinated synergistic observations by JEO and JGO of the Jupiter and Ganymede magnetospheres, the volcanoes and torus of Io, the atmosphere of Jupiter, and comparative planetology of icy satellites. Each spacecraft would conduct both synergistic dual-spacecraft investigations and stand-alone measurements toward the overall mission theme and goals.

Clark, Karla↗

NASA NTRS2016

Towards a Radar/Radiometer Mode on the Dual-Frequency, Dual-Polarized, Doppler Radar (D3R) System

The dual-frequency, dual-polarized, Doppler radar (D3R) system was developed in support of the ground validation segment of the Global Precipitation Measurement (GPM) mission. Although its main purpose is to provide active, Ku/Ka‐band, dual‐polarized measurements of precipitation, the design presents an opportunity to study its operation in an active/passive mode. The opportunity arises from use of solid-state transmitters employing a multi‐frequency waveform and receiving system. Typically, a sequence of three pulses separated in frequency is transmitted to achieve its radar sensitivity and minimum range. However, one of the three pulses can be disabled with a tolerable decrease in sensitivity and its receive channel can be repurposed to support passive measurements. This work focuses on progress in the characterization of the Ku-band H polarized passive channel operating simultaneously with two active as a step towards the provision of brightness temperatures along with the other radar derived products. The methodology developed will be applied to the V polarized channel and Ka‐band subsystem in the near future. The study consists on the analysis of the antenna performance, receiver architecture, transfer function and achievable number of independent samples, calibration method and preliminary observation analysis. All within the context of the instrument's current configuration and possible future improvements.

radar↗

NASA NTRS1973

Airborne Laser Polar Nephelometer

A polar nephelometer has been developed at NCAR to measure the angular variation of the intensity of light scattered by air molecules and particles. The system has been designed for airborne measurements using outside air ducted through a 5-cm diameter airflow tube; the sample volume is that which is common to the intersection of a collimated source beam and the detector field of view within the airflow tube. The source is a linearly polarized helium-neon laser beam. The optical system defines a collimated field-of-view (0.5deg half-angle) through a series of diaphragms located behind a I72-mm focal length objective lens. A photomultiplier tube is located immediately behind an aperture in the focal plane of the objective lens. The laser beam is mechanically chopped (on-off) at a rate of 5 Hz; a two-channel pulse counter, synchronized to the laser output, measures the photomultiplier pulse rate with the light beam both on and off. The difference in these measured pulse rates is directly proportional to the intensity of the scattered light from the volume common to the intersection of the laser beam and the detector field-of-view. Measurements can be made at scattering angles from 15deg to 165deg with reference to the direction of propagation of the light beam. Intermediate angles are obtained by selecting the angular increments desired between these extreme angles (any multiple of 0.1deg can be selected for the angular increment; 5deg is used in normal operation). Pulses provided by digital circuits control a stepping motor which sequentially rotates the detector by pre-selected angular increments. The synchronous photon-counting system automatically begins measurement of the scattered-light intensity immediately after the rotation to a new angle has been completed. The instrument has been flown on the NASA Convair 990 airborne laboratory to obtain data on the complex index of refraction of atmospheric aerosols. A particle impaction device is operated simultaneously to collect particles from the same airflow tube used to make the scattered-light measurements. A size distribution function is obtained by analysis of the particles collected by the impaction device. Calculated values of the angular variation of the scattered-light intensity are obtained by applying Mie scattering theory to the observed size distribution function and assuming different values of the complex index of refraction of the particles. The calculated values are then compared with data on the actual variation of the scattered-light intensity obtained with the polar nephelometer. The most probable value of the complex refractive index is that which provides the best fit between the experimental light scattering data and the parameters calculated from the observed size distribution function.

Grams, Gerald W.↗

NASA NTRS2015

Multi-Spacecraft Autonomous Positioning System

As the number of spacecraft in simultaneous operation continues to grow, there is an increased dependency on ground-based navigation support. The current baseline system for deep space navigation utilizes Earth-based radiometric tracking, requiring long-duration observations to perform orbit determination and generate a state update. The age, complexity, and high utilization of the ground assets pose a risk to spacecraft navigation performance. In order to perform complex operations at large distances from Earth, such as extraterrestrial landing and proximity operations, autonomous systems are required. With increasingly complex mission operations, the need for frequent and Earth-independent navigation capabilities is further reinforced. The Multi-spacecraft Autonomous Positioning System (MAPS) takes advantage of the growing interspacecraft communication network and infrastructure to allow for Earth-autonomous state measurements to enable network-based space navigation. A notional concept of operations is given in figure 1. This network is already being implemented and routinely used in Martian communications through the use of the Mars Reconnaissance Orbiter and Mars Odyssey spacecraft as relays for surface assets. The growth of this communications architecture is continued through MAVEN, and future potential commercial Mars telecom orbiters. This growing network provides an initial Marslocal capability for inter-spacecraft communication and navigation. These navigation updates are enabled by cross-communication between assets in the network, coupled with onboard navigation estimation routines to integrate packet travel time to generate ranging measurements. Inter-spacecraft communication allows for frequent state broadcasts and time updates from trusted references. The architecture is a software-based solution, enabling its implementation on a wide variety of current assets, with the operational constraints and measurement accuracy determined by onboard systems.

Anzalone, Evan↗

NASA NTRS2017

Multi-Objective Flight Control for Drag Minimization and Load Alleviation of High-Aspect Ratio Flexible Wing Aircraft

As aircraft wings become much more flexible due to the use of light-weight composites material, adverse aerodynamics at off-design performance can result from changes in wing shapes due to aeroelastic deflections. Increased drag, hence increased fuel burn, is a potential consequence. Without means for aeroelastic compensation, the benefit of weight reduction from the use of light-weight material could be offset by less optimal aerodynamic performance at off-design flight conditions. Performance Adaptive Aeroelastic Wing (PAAW) technology can potentially address these technical challenges for future flexible wing transports. PAAW technology leverages multi-disciplinary solutions to maximize the aerodynamic performance payoff of future adaptive wing design, while addressing simultaneously operational constraints that can prevent the optimal aerodynamic performance from being realized. These operational constraints include reduced flutter margins, increased airframe responses to gust and maneuver loads, pilot handling qualities, and ride qualities. All of these constraints while seeking the optimal aerodynamic performance present themselves as a multi-objective flight control problem. The paper presents a multi-objective flight control approach based on a drag-cognizant optimal control method. A concept of virtual control, which was previously introduced, is implemented to address the pair-wise flap motion constraints imposed by the elastomer material. This method is shown to be able to satisfy the constraints. Real-time drag minimization control is considered to be an important consideration for PAAW technology. Drag minimization control has many technical challenges such as sensing and control. An initial outline of a real-time drag minimization control has already been developed and will be further investigated in the future. A simulation study of a multi-objective flight control for a flight path angle command with aeroelastic mode suppression and drag minimization demonstrates the effectiveness of the proposed solution. In-flight structural loads are also an important consideration. As wing flexibility increases, maneuver load and gust load responses can be significant and therefore can pose safety and flight control concerns. In this paper, we will extend the multi-objective flight control framework to include load alleviation control. The study will focus initially on maneuver load minimization control, and then subsequently will address gust load alleviation control in future work.

Aerolasticity↗

NASA NTRS2016

Astro-H Data Analysis, Processing and Archive

Astro-H (Hitomi) is an X-ray Gamma-ray mission led by Japan with international participation, launched on February 17, 2016. The payload consists of four different instruments (SXS, SXI, HXI and SGD) that operate simultaneously to cover the energy range from 0.3 keV up to 600 keV. This paper presents the analysis software and the data processing pipeline created to calibrate and analyze the Hitomi science data along with the plan for the archive and user support.These activities have been a collaborative effort shared between scientists and software engineers working in several institutes in Japan and USA.

Archive↗

NASA NTRS2016

The Auto-Gopher: A Wireline Rotary-Percussive Deep Sampler

Accessing regions on planetary bodies that potentially preserved biosignatures or are presently habitable is vital to meeting NASA solar system "Search for Life" exploration objectives. To address these objectives, a wireline deep rotary-percussive corer called Auto-Gopher was developed. The percussive action provides effective material fracturing and the rotation provides effective cuttings removal. To increase the drill's penetration rate, the percussive and rotary motions are operated simultaneously. Initially, the corer was designed as a percussive mechanism for sampling ice and was demonstrated in 2005 in Antarctica reaching about 2 m deep. The lessons learned suggested the need to use a combination of rotation and hammering to maximize the penetration rate. This lesson was implemented into the Auto-Gopher-I deep drill which was demonstrated to reach 3-meter deep in gypsum. The average drilling power that was used has been in the range of 100-150 Watt, while the penetration rate was approximately 2.4 m/hr. Recently, a task has started with the goal to develop Auto-Gopher-II that is equipped to execute all the necessary functions in a single drilling unit. These functions also include core breaking, retention and ejection in addition drilling. In this manuscript, the Auto-Gopher-II, its predecessors and their capability are described and discussed.

drilling↗

NASA NTRS2017

Testing and Modeling of the Mars Atmospheric Processing Module

Here we report further progress in the development of the MARCO POLO-Mars Pathfinder Atmospheric Processing Module (APM). The APM is designed to demonstrate in situ resource utilization (ISRU) of the Martian atmosphere, which primarily consists of carbon dioxide (CO2). The APM is part of a larger project with the overall goal of collecting and utilizing CO2 found in the atmosphere and water in the regolith of Mars to produce methane and oxygen to be used as rocket propellant, eliminating the need to import those to Mars for human missions, thus significantly reducing costs. The initial focus of NASA's new ISRU Project is modeling of key ISRU components, such as the CO2 Freezers and the Sabatier reactor of the APM. We have designed models of those components and verified the models with the APM by gathering additional data for the Sabatier reactor. Future efforts will be focused on simultaneous operations of the APM and other MARCO POLO-Mars Pathfinder modules.

propellant production↗

NASA NTRS2017

Testing and Modeling of the Mars Atmospheric Processing Module

Mars In Situ Resource Utilizatio↗

NASA NTRS2017

Coilgun Acceleration Model Containing Interactions Between Multiple Coils

Electromagnetic (EM) accelerators have the potential to fill a performance range not currently being met by conventional chemical and electric propulsion systems by providing a specific impulse of 600-1000 seconds and a thrust-to-power ratio greater than 200 mN/kW. A propulsion system based on EM acceleration of small projectiles has the traditional advantages of using a pulsed system, including precise control over a range of thrust and power levels as well as rapid response and repetition rates. Furthermore, EM accelerators have lower power requirements than conventional electric propulsion systems since no plasma creation is necessary. A coilgun is a specific type of EM device where a high-current pulse through a coil of wire interacts with a conductive projectile via an induced magnetic field to accelerate the projectile. There are no physical or electrical connections to the projectile, which leads to less system degradation and a longer life expectancy. Multi-staging a coilgun by adding multiple turns on a single coil or on the projectile increases the inductance, thus permitting acceleration of the projectile to higher velocities. Previously, a simplified problem of modeling an inductively-coupled, single-coil coilgun using a circuit-based analysis coupled to the one-dimensional momentum equation through Lenz's law was solved; however, the analysis was only conducted on uncoupled coils. The problem is significantly more complicated when multiple, independently-powered coils simultaneously operate and interact with each other and the projectile through induced magnetic fields. This paper presents a multi-coil model developed with the magnetostatic finite element solver QuickField. In the model, mutual inductance values between pairs of conductors were found by first computing the magnetic field energy for different cases where individual coils or multiple coils carry current, then integrating over the entire finite element domain for each case, and finally using the definition of inductive energy storage to solve for the self and mutual inductance. The electric circuit model is coupled to the projectile through Lenz's law, with the coils coupled through mutual inductance but able to be independently triggered at different times to optimize the acceleration profile. This initial model to predict the behavior of a projectile's acceleration through a coupled, multi-coil coilgun increases the potential of building a highly efficient coilgun thruster with key advantages over other EM thruster systems, thus making it a promising candidate for satellite main propulsion or attitude control thrusters.

Liu, Connie↗

NASA NTRS2018

Accessing Data Stored in Amazon S3 Using the Hyrax OPeNDAP Server

For three years we have been investigating data storage and retrieval in the Amazon Cloud, striving to optimize both storage structures and (cache-enhanced retrieval processes. These optimizations are hidden from data users, who simply employ the Data Access Protocol (DAP), a popular, Web-based Application Programmer Interface (API) developed by OPeNDAP. We present our collected findings and their realization in the Hyrax data server. Specific techniques include caching data on spinning disk; accessing sharded data in place; optimizing the organizational structures for data within the flat key-value space of Simple Storage Service (S3); and employing an API extension that permits simultaneous operations on many datasets in a single request.

Data access↗

NASA NTRS2018

The Hitomi X-Ray Observatory, Part 2

When it was launched on 17 February 2016, the Hitomi X-ray Observatory carried four kinds of new-generation x-ray instruments—the Soft X-ray Spectrometer (SXS), the Soft X-ray Imager (SXI), the Hard X-ray Imager (HXI), and the Soft Gamma-ray Detector (SGD). All four instruments were turned on and were in the process of activation at the time of loss of contact on 26 March 2016. In the time it was operational, Hitomi was able to provide researchers with a trove of ground-breaking scientific results. Initial results demonstrated that the instruments were meeting or exceeding requirements and that Hitomi was on its way to pioneering a new era of broad-band and high-resolution x-ray spectroscopy. The results published here summarize the in-flight instrument performance, calibration, and data processing accomplishments of the observatory. Of the papers accepted for publication in this special section, 17 were presented in Part 1 in the January-March 2018 issue of JATIS (Journal of Astronomical Telescopes, Instruments, and Systems). Ten more papers are presented here as Part 2 in the April-June 2018 issue. These papers cover the detailed in-flight performance of the four state-of the-art instruments on-board the Hitomi X-Ray Observatory. These instruments were extremely diverse in their design and principles of operation, ranging from low temperature x-ray calorimeters for high-resolution spectroscopy, CCDs (Charge-Coupled Devices) for wide field imaging, high fill-factor grazing incidence x-ray optics, including multilayer x-ray optics and silicon strip and CdTe strip detectors for high-energy imaging, and a Si/CdTe Compton cameras for extending the bandpass out to 600 kiloelectronvolts. All of these instruments operated as expected and for sufficient time to validate their operating principles and carry out first light scientific investigations, published elsewhere. Collectively, these instruments, all co-aligned and operated simultaneously, provided a tool for astronomers with unprecedented resolution and broadband sensitivity for investigating high-energy processes throughout the universe. These papers serve as part of the Hitomi legacy and will guide the next generation of instruments planned for future missions.

Kelley, Richard L.↗

NASA NTRS1996

Dual-Frequency Interferometric SAR Observations of Tropical Rain-Forests

Repeat-pass, interferometric, radar observations of tropical rain-forests colected by the Shuttle Imaging Radar SIR-C in Rondonia, Brazil reveal C-band (5.6-cm) radar signals completely decorelate over forest, whereas L-band (24-cm) signals remain strongly coherent over the intire landscape. At L-band, the difference in elevation between forest and clearings is within the 8-m height noise of the data. Atmospheric delays are large, however, forming kilometer-sized anomalies with a with a 1.2-cm rms one way. Radar interferometric studies of humid tropics miust be conducted at long radar wavelengths, with kilometric baselines or with two antennas operating simultaneously.

radar↗

NASA NTRS2021

Assessing CryoSat-2 Antarctic Snow Freeboard Retrievals Using Data From ICESat-2

NASA's Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) laser altimeter launched in Fall 2018, providing an invaluable addition to the polar altimetry record generated by ESA's CryoSat-2 radar altimeter. The simultaneous operation of these two satellite altimeters enables unique comparison studies of sea ice altimetry, utilizing the different frequencies and profiling strategies of the two instruments. Here, we use freeboard data from ICESat-2 to assess Antarctic snow freeboard retrievals from CryoSat-2. We first discuss updates made to a previously published CryoSat-2 retrieval process and show how this Version 2 algorithm improves upon the original method by comparing the new retrievals to ICESat-2 in specific along-track profiles as well as on the basin-scale. In two near-coincident along-track profiles, we find mean snow freeboard differences (standard deviations of differences) of 0.3 (9.3) and 7.6 cm (9.6 cm) with 25 km binned correlation coefficients of 0.77 and 0.89. Monthly mean freeboard differences range between −2.9 (10.8) and 6.6 cm (16.8 cm) basin wide, with the largest differences typically occurring in Austral fall months that is hypothesized to be related to new ice growth and the use of static snow backscatter coefficients in the retrieval. Monthly mean correlation coefficients range between 0.57 and 0.80. While coincident data show good agreement between the two sensors, they highlight issues related to geometric and frequency sampling differences that can impact the freeboard distributions.

S W Fons↗

NASA NTRS2020

Communication-Aware Orbit Design for Small Spacecraft Swarms around Small Bodies

Exploration of small Solar System bodies has traditionally been performed by single monolithic spacecraft carrying a number of science instruments. However, science instruments typically cannot be operated simultaneously due to the instrument requirements including optimal viewing angle, surface illumination, altitude and ground resolution, power, and data constraints. This observation has motivated interest in multi-spacecraft architectures where a swarm of small spacecraft, each carrying a single science instrument, studies a small body after being deployed by a carrier spacecraft, which then collects data from the vehicles and relays it to Earth. Such architectures hold promise to yield significant improvements in mission efficiency, increases in data quality, and shorter mission duration. A key difficulty in the design of such missions is the selection of orbits for the small spacecraft, which must satisfy not only instrument requirements, but also strict inter-spacecraft communication and on-board storage constraints. To address this, in this paper, we present a novel computationally-efficient optimization algorithm for \emph{communication-aware design} of the orbits of a small spacecraft swarm orbiting a small body. The proposed approach captures constraints including instrument requirements, inter-spacecraft communication bandwidths, and on-board memory usage, and it can accommodate highly irregular gravity field models and surface geometries. We propose an efficient algorithm for optimization of instrument observations and inter-spacecraft communications; we then leverage the differentiable nature of the proposed algorithm to accelerate a gradient-based global search algorithm. Numerical simulations of a six-spacecraft swarm studying 433 Eros show that the proposed approach successfully identifies high-quality orbits, and significantly outperform communication-agnostic optimization techniques, resulting in a 10% increase in scientific returns and a 30% increase in the quality of the collected data.

Rahmani, Amir↗

NASA NTRS2021

NASA-ISRO SAR (NISAR) Mission Status

The National Aeronautics and Space Administration (NASA) in the United States and the Indian Space Research Organisation (ISRO) are developing the NASA-ISRO Synthetic Aperture Radar (NISAR) mission, now planned for launch toward the end of 2022. The mission will exploit synthetic aperture radar to map Earth’s surface every 12 days, persistently on ascending and descending portions of the orbit, over all land and ice-covered surfaces. The mission’s primary objectives will be to study Earth land and ice deformation, and ecosystems, in areas of common interest to the US and Indian science communities. This single observatory solution with an L-band (24 cm wavelength) and S-band (10 cm wavelength) radar has a swath of over 240 km at fine resolution, using full polarimetry where needed. To achieve these unprecedented capabilities, both radars use a reflector-feed system, whereby the feed aperture elements are individually sampled to allow a scan-on-receive (“SweepSAR”) capability at both L-band and S-band. The L-band and S-band electronics and feed apertures, provided by NASA and ISRO respectively, share a common 12-m diameter deployable reflector/boom system, provided by NASA. These two radars, which can operate simultaneously, even with FPGA-based on-board digital beamforming and filtering to reduce data rates, produce prodigious amounts of data. Given the high data rates and ambitious coverage requirements, new technologies for high-rate Ka-band downlink complement these first-of-a-kind radar systems.

Kumar, Raj↗

NASA NTRSDate not supplied

Theoretical and Simulated Capacity of Urban Air Mobility Airspace Characteristics

As interest in urban air mobility grows, as are the optimistic predictions for potentially hundreds of simultaneous operations within a given metropolitan airspace. This high density of traffic poses a challenge for safe, efficient, and timely operations, particularly when realistic airspace restrictions, fleet sizes, and fluctuating demand are considered. Routes for urban air mobility aircraft, similar to automotive roadways more than other types of airways, are one proposed solution for traffic management. This paper identifies several potential components of urban air mobility routes and compares their numerically predicted maximum capacity with what is achieved in a realistic simulation that includes airspace restrictions, parking limitations, fleet sizes, and uneven demand.

Urban Air Mobility↗

NASA NTRSDate not supplied

Theoretical and Simulated Capacity of Urban Air Mobility Airspace Characteristics

Urban Air Mobility↗