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At least 127 records · Page 7

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NASA NTRS2008

Characterization of the Catalog Fengyun-1C Fragments and Their Long-term Effect on the LEO Environment

The intentional breakup of Fengyun-1C on 11 January 2007 created the most severe orbital debris cloud in history. More than 2500 large fragments were identified and tracked by the U.S. Space Surveillance Network by the end of the year. The altitude where the event occurred was probably the worst location for a major breakup in the low Earth orbit (LEO) region, since it was already highly populated with operational satellites and debris generated from previous breakups. The addition of so many fragments not only poses a realistic threat to operational satellites in the region, but also increases the instability (i.e., collision cascade effect) of the debris population there. Preliminary analysis of the large Fengyun-1C fragments indicates that their size and area-to-mass ratio (A/M) distributions are very different from those of other known events. About half of the fragments appear to be composed of light-weight materials and more than 100 of them have A/M values exceeding 1 square meter per kilogram, consistent with thermal blanket pieces. In addition, the orbital elements of the fragments suggest nontrivial velocity gain by the fragment cloud during the impact. These important characteristics were incorporated into a numerical simulation to assess the long-term impact of the Fengyun-1C fragments to the LEO debris environment. The main objectives of the simulation were to evaluate (1) the collision probabilities between the Fengyun-1C fragments and the rest of the catalog population and (2) the collision activities and population growth in the region in the next 100 years.

Liou, J.-C.↗

NASA NTRS2010

A Parametric Study on Using Active Debris Removal to Stabilize the Future LEO Debris Environment

Recent analyses of the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited the interest in using active debris removal (ADR) to remediate the environment. There are; however, monumental technical, resources, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of the effectiveness of ADR must be conducted. The goal is to demonstrate the feasibility of using ADR to preserve the future environment and to guide its implementation to maximize the benefit-cost ratio. This paper describes a comprehensive sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term, orbital debris evolutionary model, LEGEND, is used to quantify the effects of many key parameters. These parameters include (1) the starting epoch of ADR implementation, (2) various target selection criteria, (3) the benefits of collision avoidance maneuvers, (4) the consequence of targeting specific inclination or altitude regimes, (5) the consequence of targeting specific classes of vehicles, and (6) the timescale of removal. Additional analyses on the importance of postmission disposal and how future launches might affect the requirements to stabilize the environment are also included.

Liou, J.C.↗

NASA NTRS2000

Updating the NASA LEO Orbital Debris Environment Model with Recent Radar and Optical Observations and in Situ Measurements

The Low Earth Orbit (LEO, between 200 and 2000 km altitudes) debris environment has been constantly measured by NASA Johnson Space Center's Liquid Mirror Telescope (LMT) since 1996 (Africano et al. 1999, NASA JSC-28826) and by Haystack and Haystack Auxiliary radars at MIT Lincoln Laboratory since 1990 (Settecerri et al. 1999, NASA JSC-28744). Debris particles as small as 3 mm can be detected by the radars and as small as 3 cm can be measured by LMT. Objects about 10 cm in diameter and greater are tracked and catalogued by the US Space Surveillance Network. Much smaller (down to several micrometers) natural and debris particle populations can be estimated based on in situ measurements, such as Long Duration Exposure Facility, and based on analyses of returned surfaces, such as Hubble Space Telescope solar arrays, European Retrievable Carrier, and Space Shuttles. To increase our understanding of the current LEO debris environment, the Orbital Debris Program Office at NASA JSC has initiated an effort to improve and update the ORDEM96 model (Kessler et al. 1996, NASA TM-104825) utilizing the recently available data. This paper gives an overview of the new NASA orbital debris engineering model, ORDEM2000.

Liou, J.-C.↗

NASA NTRS2010

A Parametric Study on Using Active Debris Removal for LEO Environment Remediation

Recent analyses on the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited the interest in using active debris removal (ADR) to remediate the environment. There are; however, monumental technical, resource, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of its effectiveness must be conducted. The goal is to demonstrate the need and feasibility of using ADR to better preserve the future environment and to guide its implementation to maximize the benefit-to-cost ratio. This paper describes a new sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term orbital debris evolutionary model, LEGEND, is used to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation. Additional analyses on potential ADR targets among the currently existing satellites and the benefits of collision avoidance maneuvers are also included.

Source record↗

NASA NTRS2013

Exploration Atmospheres for Beyond-LEO Human Exploration Missions

Atmospheric pressure and oxygen concentration of human-occupied space vehicles and habitats are an important life support parameter. The atmosphere is critical in terms of not only safety but also in terms of maximizing human capabilities at the point of scientific discovery. Human exploration missions beyond low earth orbit (LEO) will include extravehicular activity (EVA). EVAs are carried out in low pressure (4.3 psi/29.6 kilopascals) space suits running at 100 percent oxygen. New suits currently in development will be capable of running at a range of pressures between approximately 8.2 psi/56.5 kilopascals and 4.3 psi/29.6 kilopascals. In order to carry out high-frequency EVA phases of a mission safely and more efficiently, it is advantageous to have cabin or vehicle atmospheres at lower total pressure and higher oxygen concentrations. This allows for much reduced pre-breathe times for a fixed risk of decompression sickness and thus more efficient EVAs. The recommended oxygen concentration is 32% and represents a trade with respect to controlling the risk of decompression sickness and risk of fire. Work carried out by NASA in 2006 and continued in 2012 established an atmospheric pressure and oxygen concentration to optimize EVA. This paper will review previous work and describe current recommendations for beyond-LEO human exploration missions.

Henninger, Donald, L.↗

NASA NTRS2014

The Komplast Experiment: Space Environmental Effects after 12 Years in LEO (and Counting)

The Komplast materials experiment was designed by the Khrunichev Space Center, together with other Russian scientific institutes, and has been carried out by Mission Control Moscow since 1998. The purpose is to study the effect of the low earth orbit (LEO) environment on exposed samples of various spacecraft materials. The Komplast experiment began with the launch of the first International Space Station (ISS) module on November 20, 1998. Two of eight experiment panels were retrieved during Russian extravehicular activity in February 2011 after 12 years of LEO exposure, and were subsequently returned to Earth by Space Shuttle "Discovery" on the STS-133/ULF-5 mission. The retrieved panels contained an experiment to detect micrometeoroid and orbital debris (MMOD) impacts, radiation sensors, a temperature sensor, several pieces of electrical cable, both carbon composite and adhesive-bonded samples, and many samples made from elastomeric and fluoroplastic materials. Our investigation is complete and a summary of the results obtained from this uniquely long-duration exposure experiment will be presented.

Shaevich, S. K.↗

NASA NTRS2014

The Komplast Experiment: Space Environmental Effects after 12 Years in LEO (and Counting)

Shaevich, Sergei K.↗

NASA NTRS2014

The Komplast Experiment: Space Environmental Effects after 12 Years in LEO (and Counting)

Golden, J. L.↗

NASA NTRS2016

MEMS Reaction Control and Maneuvering for Picosat Beyond LEO

The MEMS Reaction Control and Maneuvering for Picosat Beyond LEO project will further develop a multi-functional small satellite technology for low-power attitude control, or orientation, of picosatellites beyond low Earth orbit (LEO). The Film-Evaporation MEMS Tunable Array (FEMTA) concept initially developed in 2013, is a thermal valving system which utilizes capillary forces in a microchannel to offset internal pressures in a bulk fluid. The local vapor pressure is increased by resistive film heating until it exceeds meniscus strength in a nozzle which induces vacuum boiling and provides a stagnation pressure equal to vapor pressure at that point which is used for propulsion. Interplanetary CubeSats can utilize FEMTA for high slew rate attitude corrections in addition to desaturating reaction wheels. The FEMTA in cooling mode can be used for thermal control during high-power communication events, which are likely to accompany the attitude correction. Current small satellite propulsion options are limited to orbit correction whereas picosatellites are lacking attitude control thrusters. The available attitude control systems are either quickly saturated reaction wheels or movable high drag surfaces with long response times.

Low-power attitude control↗

NASA NTRS2018

Radar Measurements of the LEO Orbital Debris Environment

Access to space and the preservation of the near-Earth space environment is of critical significance. Increased interest in issues surrounding space traffic management and the continued assessment and discussion of orbital debris at the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) illustrates the significance of the topic of orbital debris. There are currently over 20,000 tracked objects in the publicly available satellite catalog on Space-Track.org. The catalog is maintained by the US Air Force Space Command using a network of optical and radar ground-based sensors and is believed to be complete for a characteristic size of 10 cm or larger in low Earth orbit (LEO). Based on the work of the NASA Orbital Debris Program Office (ODPO) over approximately the past 40 years it is understood that the small debris population (< 10 cm) increases by orders of magnitude as characteristic size decreases. With population estimates ranging from 500,000 to 1,000,000 small debris objects (> 5 mm) in orbit, it is currently not practical to track and maintain precision orbits on every object. Instead the NASA ODPO uses powerful ground-based radars to sample the low Earth Orbit (LEO) environment and assign approximate orbits to each detection. This poses an interesting signal processing challenge as we are trying to detect the smallest objects possible on the edge of the radar's sensitivity. For approximately the last 30 years, NASA ODPO has partnered with the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL) to utilize the Haystack Ultra-wideband Satellite Imaging Radar (HUSIR - formerly the Long-Range Imaging Radar or simply Haystack) and the Haystack Auxiliary (HAX) radar to collect orbital debris radar data. Additionally, the ODPO collaborates with the NASA Jet Propulsion Laboratory (JPL) to use the Goldstone Solar System Radar. The orbital debris detections from these radars serve as inputs for statistical risk models used by the human spaceflight and satellite communities to assess risk to spacecraft posed by orbital debris. In this paper, we will describe the history of orbital debris radar measurements conducted by NASA, provide an overview of current radar measurements techniques and facilities, discuss the signal processing software used for orbital debris measurements and the inference of debris size and orbital parameters from these measurements, and discuss how orbital debris radar measurements are validated for use in models that are used throughout the aerospace industry.

Blackwell, Chris↗

NASA NTRS2019

How Much Testing is Needed to Manage Supportability Risks for Beyond-LEO Missions?

Supportability will be a significantly greater driver of cost and risk for future deep-space crewed missions than it has been in the past. Spares requirements and maintenance risk mitigation in particular present an unprecedented challenge for missions beyond Low Earth Orbit (LEO), since, for the first time in human spaceflight history, crews will be weeks or months away from resupply or a safe return to Earth in the event of an abort. Under these conditions, failure rates are a critical parameter that must be well-understood in order to manage logistics and risk effectively. However, failure rates cannot be measured directly, and can only be estimated based on past experience and test results. Previous research has shown that International Space Station (ISS) operational experience has provided significant benefits to future missions by reducing uncertainty and improving accuracy in failure rate estimates, resulting in significant reductions in mass and risk for beyond-LEO missions. This paper updates and expands on that research and quantifies the potential value of continued testing for future mission supportability. Frequentist and Bayesian models for evaluating, validating, and updating failure rate estimates are described, and are combined with supportability models to examine potential impacts of additional operating experience for future missions in terms of logistics mass reduction. The implications of these results for technology development, system design, and program planning are discussed along with lessons learned and recommendations for future system development. In the end, there is no simple answer to the question of how much testing is required, but the models described in this paper provide a way to evaluate the potential impacts of testing in order to inform test planning.

Andrew C Owens↗

NASA NTRS1995

Global Tracking and Inventory of Military Hardware via LEO Satellite: A System Approach and Likely Scenario

A system for global inventory control of electronically tagged military hardware is achievable using a constellation of low earth orbit (LEO) satellites. Investigated are two proposed commercial LEO systems, both capable of providing global coverage but with dramatically different telecom capacities. This study is to verify the feasibility and performance of direct Tag-satellite communication.

global↗

NASA NTRS2021

Space Biology Beyond LEO Instrumentation & Science Series - Science Working Group 2021 Annual Report

Human space exploration was never intended to stop within low Earth orbit (LEO). Although nearly all of biological research in space has taken place in LEO, on the Space Shuttle, International Space Station (ISS), and free-flyer CubeSat missions, NASA's recent shift in emphasis toward human exploration of the Moon and ultimately Mars necessitates a shift in the focus of its research in the biological sciences [1]. Specifically, in 2022 and beyond, the Division of Biological and Physical Sciences seeks to pivot toward a focus on Thriving In DEep Space (TIDES), furthering the fundamental research necessary for understanding risks and mitigation strategies for deep-space stressors on human crew, plants, and their microbiomes. This effort entails both research on model organisms to elucidate the molecular processes underlying the biological consequences of deep-space exposure, and research on the organisms that will be necessary companions to sustain life and facilitate resource utilization in long-duration missions.

R Craig Everroad↗

NASA NTRSDate not supplied

LEO Sensor to GEO Sensor Algorithm Transfer Models for Land Surface Temperature

Land surface temperature (LST) is a key climate observable used to detect changes in the Earth’s surface energy budget that influence carbon and water cycles. Land surface temperature exhibits strong diurnal variability, which geostationary satellites can observe at scale thanks to their temporal resolution. Due to anthropogenic climate and land use changes, the surface energy balance has been considerably modified and may be described by changes in diurnal temperature range and extremes. Using high performance computing and datasets from the NASA Earth Exchange, we exploit co-located, co-temporal observations from low-earth orbit (LEO) and geostationary (GEO) sensors to develop a deep learning-based method for LEO-to-GEO algorithm emulation. Our model is trained to predict MODIS Terra LST from GOES-16 thermal bands and achieves validation error <2K. Application of the model to unseen times of day (observed by MODIS Aqua) and a new GEO sensor (Himawari-8) observing an unseen spatial domain, demonstrate the generalization of the deep learning model across space, time and spectra. Communicating diurnal LST variability observed by geostationary satellites can have impacts in multiple disciplines, from understanding of snow, vegetation and soil dynamics, to recognizing trends in heat events relevant to human health.

Kate Marie Duffy↗

NASA NTRS2020

Satellite-To-Satellite Imaging in Support of LEO Optical Navigation, Using the ASTERIA Cubesat

The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) was a 6-unit CubeSat technology demonstration mission that was built at NASA’s Jet Propulsion Laboratory (JPL) and deployed from the International Space Station (ISS) on November 20th, 2017. After successfully completing its 90-day primary mission that demonstrated arcsecond-level line-of-sight pointing and focal plane thermal stability for exoplanet detection, it entered an extended mission performing onboard software demonstrations alongside science until end of mission in December 2019. At the end of its lifetime it was being used as a demonstration platform for several experiments, including low earth orbit (LEO) optical navigation operations. With its visible light astrometric camera and stable attitude control system, the ASTERIA spacecraft showed itself to be a capable platform for the imaging of geosynchronous satellites from LEO. This paper will describe the imagery attained in flight and also the image processing algorithms that were developed to render that imagery into navigation quality data. These algorithms dealt with hot pixel filtering, noise modeling, attitude registration, star signal rejection and satellite signal identification. Brightness prediction algorithms used for target selection will also be discussed.

Fesq, Lorraine↗

NASA NTRSDate not supplied

Fusing GeoNEX and VIIRS Surface BRDF Retrievals: Exploring a GEO-LEO Synergy

The Bidirectional Reflectance Distribution Function or BRDF, which describes the dependency of surface reflectance on the illumination-view geometries, are the foundation of many high-level satellite products for terrestrial and aquatic system monitoring. The latest geostationary sensors like GOES ABI provide high frequent (~10 minutes) observations of the Earth surface that feature continuously changing sun angles, allowing us to retrieve surface BRDF with dedicated atmospheric correction algorithms like MAIAC (Multi-Angle Implementation of Atmospheric Correction). For mid-latitude locations, because geostationary satellites have fixed view angles in the back-scattering directions, the angular sampling of surface BRDF by GEO sensors is not comprehensive. This study explores a GEO-LEO synergy to address this issue. We first extract concurrent GeoNEX and VIIRS BRDF data with the best quality (cloud-free and low aerosol loading) at chosen AERONET sites. We then compare the magnitude and the shape factors of the two set of BRDF parameters as well as their variations through the season. We calculate the “distances” between the GeoNEX and VIIRS BRDF by using them to cross-predict the top-of-atmosphere reflectance measured by their counterpart and evaluating the corresponding prediction errors. This metric allows us to derive a set of optimized BRDF parameters that minimize such distances or prediction errors, which are considered as the fused BRDF result. We validate the algorithm with reserved AERONET data and then apply it to generate the GEO-LEO BRDF synergy over CONUS. We expect the fused BRDF to have reduced uncertainties as compared to the source GeoNEX or VIIRS data and may find broadly application in deriving other high-level satellite products.

Geostationary satellite↗

NASA NTRSDate not supplied

Numerical Weather Prediction Impact of GEO and LEO IR Sounders in an OSSE Framework

Low Earth Orbit (LEO) hyperspectral radiances from instruments such as CrIS, AIRS, and IASI are essential to NWP (among many other applications!), providing high vertical resolution T and humidity information. The United States is considering launching a hyperspectral sounder into a Geostationary Orbit (GEO) in the 2030s, creating a global ring with international partners. The combination of sounders in LEO and GEO provide both global coverage and high temporal resolution regional observations with the capability to dwell on high impact weather events.

Erica McGrath-Spangler↗

NASA NTRSDate not supplied

Complementary Roles of LEO and GEO IR Sounders in NWP Evaluated using an OSSE Framework

The United States is currently preparing for the next-generation weather satellite program. Building off the multi-decadal successes of the Low-Earth Orbit (LEO) infrared (IR) sounder program, NOAA and NASA are planning for the Geostationary eXtended Observations (GeoXO) Sounder (GXS) that will join international counterparts to form a global ring from geosynchronous orbit (GEO). To address questions about the complementarities and roles of these two platform types in the context of numerical weather prediction (NWP) and forecast accuracy, NASA’s Global Modeling and Assimilation Office (GMAO) Observing System Simulation Experiment (OSSE) framework was used to test their impact individually and in concert. Analyses, forecasts, and forecast sensitivity-based observations impact (FSOI) are examined. Overall, each has a role in forecast error reduction with the most beneficial impacts occurring when both LEO and GEO sounders are used together to address the needs of global skill and targeted regional weather phenomena.

Erica Mcgrath-Spangler↗