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All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Diagnosing anomalies of spacecraft for space maintenance and servicing

Very often servicing of satellites is necessary to replace components which are responsible for anomalous behavior of satellite operations due to adverse interactions with the natural space environment. A major difficulty with this diagnosis is that those responsible for diagnosing these anomalies do not have the tools to assess the role of the space environment causing the anomaly. To address this issue, we have under development a new rule-based, expert system for diagnosing spacecraft anomalies. The knowledge base consists of over two-hundred rules and provides links to historical and environmental databases. Environmental causes considered are bulk charging, single event upsets (SEU), surface charging, and total radiation dose. The system's driver translates forward chaining rules into a backward chaining sequence, prompting the user for information pertinent to the causes considered. When the user selects the novice mode, the system automatically gives detailed explanations and descriptions of terms and reasoning as the session progresses, in a sense teaching the user. As such it is an effective tutoring tool. The use of heuristics frees the user from searching through large amounts of irrelevant information and allows the user to input partial information (varying degrees of confidence in an answer) or 'unknown' to any question. The system is available on-line and uses C Language Integrated Production System (CLIPS), an expert shell developed by the NASA Johnson Space Center AI Laboratory in Houston.

Lauriente, Michael↗
NASA NTRS1988

Spacecraft environmental anomalies expert system

A microcomputer-based expert system is being developed at the Aerospace Corporation Space Sciences Laboratory to assist in the diagnosis of satellite anomalies caused by the space environment. The expert system is designed to address anomalies caused by surface charging, bulk charging, single event effects and total radiation dose. These effects depend on the orbit of the satellite, the local environment (which is highly variable), the satellite exposure time and the hardness of the circuits and components of the satellite. The expert system is a rule-based system that uses the Texas Instruments Personal Consultant Plus expert system shell. The completed expert system knowledge base will include 150 to 200 rules, as well as a spacecraft attributes database, an historical spacecraft anomalies database, and a space environment database which is updated in near real-time. Currently, the expert system is undergoing development and testing within the Aerospace Corporation Space Sciences Laboratory.

Koons, H. C.↗
NASA NTRS2015

Meteoroid-Induced Anomalies on Spacecraft

Sporadic meteoroid background is directional (not isotropic) and accounts for 90 percent of the meteoroid risk to a typical spacecraft. Meteor showers get all the press, but account for only approximately10 percent of spacecraft risk. Bias towards assigning meteoroid cause to anomalies during meteor showers. Vast majority of meteoroids come from comets and have a bulk density of approximately 1 gram per cubic centimeter (ice). High speed meteoroids (approximately 50 kilometers per second) can induce electrical anomalies in spacecraft through discharging of charged surfaces (also EMP (electromagnetic pulse?).

Cooke, Bill↗
NASA NTRS1994

An expert system for diagnosing anomalies of spacecraft

Although the analysis of anomalous behavior of satellites is difficult because it is a very complex process, it is important to be able to make an accurate assessment in a timely manner when the anomaly is observed. Spacecraft operators may have to take corrective action or to 'safe' the spacecraft; space-environment forecasters may have to assess the environmental situation and issue warnings and alerts regarding hazardous conditions, and scientists and engineers may want to gain knowledge for future designs to mitigate the problems. Anomalies can be hardware problems, software errors, environmentally induced, or even the cause of workmanship. Spacecraft anomalies attributable to electrostatic discharges have been known to cause command errors. A goal is to develop an automated system based on this concept to reduce the number of personnel required to operate large programs or missions such as Hubble Space Telescope (HST) and Mission to Planet Earth (MTPE). Although expert systems to detect anomalous behavior of satellites during operations are established, diagnosis of the anomaly is a complex procedure and is a new development.

Lauriente, Michael↗
NASA NTRS2016

Mission Status at Aura Science Team MOWG Meeting: EOS Aura

Presentation at the 24797-16 Earth Observing System (EOS) Aura Science Team Meeting (Mission Operations Work Group (MOWG)) at Rotterdam, Netherlands August 29, 2016. Presentation topics include mission summary, spacecraft subsystems summary, recent and planned activities, spacecraft anomalies, data capture, propellant usage and lifetime estimates, spacecraft maneuvers and ground track history, mission highlights and past spacecraft anomalies and reliability estimates.

MOWG↗
NASA NTRS1979

Geosynchronous satellite operating anomalies caused by interaction with the local spacecraft environment

The dependence of a spacecraft anomaly or event upon geophysical parameters established on the basis of statistical analysis is presented. Examples are provided for establishing relationships between events and parameters such as geomagnetic activity, local time, and events on other spacecraft. Examples illustrated the potential dangers of not using quantitative statistical techniques it was recommended that the data collection planning and statistical analysis planning be done together. Results demonstrate a high correlation between the events and the goephysical parameter being investigated.

Grajek, M. A.↗
NASA NTRS1977

Spacecraft charging anomalies on the DSCS II, launch 2 satellites

The six different types of anomalous events occurred on two DSCS II satellites. The total number of events, over 100, and the long operational period, nearly 3 years, permits some statistical analyses to be performed. Correlation of occurrences of particular types of anomalies with equinoxes and seasons of the year are consistent with a spacecraft charging model. On the other hand, an interesting correlation of occurrences with days of the week has been found. Finally, a long term diminution in the frequency of occurrence of events has been observed, and is discussed in terms of environmental activity, material degradations and the need for more data.

Inouye, G. T.↗
NASA NTRS2015

Meteoroid-Induced Anomalies on Spacecraft

Many programs/projects use a simple meteoroid environment based on Grun's 1985 paper or the old NASA space station spec in their design and risk assessments. These models, which are omni directional and mono-­velocity, bear little resemblance to the actual meteoroid environment, which is sun-fixed, very directional, and which has a complex speed distribution varying by source and particle size. As a result, the simple meteoroid models lead to estimates that underestimate the spacecraft/vehicle risk by a factor of 2 or more. In addition, programs often over-emphasize the risk posed by meteor showers, which typically account for less than ten percent of the meteoroid risk over the vehicle lifetime. Fueled by popular media, the emphasis on meteor showers (the risks from which can usually be mitigated operationally) can lead to ambivalence to the real risk driver, which is the sporadic background.

Cooke, William J.↗
NASA NTRSDate not supplied

Autonomous RPOD for Arbitrarily Configured Spacecraft with Anomaly Detection

Autonomous GN&C is a necessary component for a sustainable deep-space logistics architecture. The challenges for establishing robust autonomy are numerous, from state uncertainty, to anomaly detection and recovery. In this work, previous work investigating autonomous GN&C for arbitrary thruster configurations and mass properties is expanded to include state uncertainty and anomaly detection. Logistics vehicles with off-center-of-mass thruster configurations and in the presence of large but realistic state uncertainties are simulated in a Rendezvous, Proximity Operations and Docking scenario. Furthermore, stuck and non-functional thrusters are simulated, demonstrating the vehicle's ability to identify and overcome thruster anomalies. The simulations demonstrate that even with these realistic ambiguities, the vehicle is able to converge to the desired pose.

GN&C↗
NASA NTRS2002

REACH: Real-Time Data Awareness in Multi-Spacecraft Missions

Missions have been proposed that will use multiple spacecraft to perform scientific or commercial tasks. Indeed, in the commercial world, some spacecraft constellations already exist. Aside from the technical challenges of constructing and flying these missions, there is also the financial challenge presented by the tradition model of the flight operations team (FOT) when it is applied to a constellation mission. Proposed constellation missions range in size from three spacecraft to more than 50. If the current ratio of three-to-five FOT personnel per spacecraft is maintained, the size of the FOT becomes cost prohibitive. The Advanced Architectures and Automation Branch at the Goddard Space Flight Center (GSFC Code 588) saw the potential to reduce the cost of these missions by creating new user interfaces to the ground system health-and-safety data. The goal is to enable a smaller FOT to remain aware and responsive to the increased amount of ground system information in a multi-spacecraft environment. Rather than abandon the tried and true, these interfaces were developed to run alongside existing ground system software to provide additional support to the FOT. These new user interfaces have been combined in a tool called REACH. REACH-the Real-time Evaluation and Analysis of Consolidated Health-is a software product that uses advanced visualization techniques to make spacecraft anomalies easy to spot, no matter how many spacecraft are in the constellation. REACH reads a real-time stream of data from the ground system and displays it to the FOT such that anomalies are easy to pick out and investigate. Data visualization has been used in ground system operations for many years. To provide a unique visualization tool, we developed a unique source of data to visualize: the REACH Health Model Engine. The Health Model Engine is rule-based software that receives real-time telemetry information and outputs "health" information related to the subsystems and spacecraft that the telemetry belong to. The Health Engine can run out-of-the-box or can be tailored with a scripting language. Out of the box, it uses limit violations to determine the health of subsystems and spacecraft; when tailored, it determines health using equations combining the values and limits of any telemetry in the spacecraft. The REACH visualizations then "roll up" the information from the Health Engine into high level, summary displays. These summary visualizations can be "zoomed" into for increasing levels of detail. Currently REACH is installed in the Small Explorer (SMEX) lab at GSFC, and is monitoring three of their five spacecraft. We are scheduled to install REACH in the Mid-sized Explorer (MIDEX) lab, which will allow us to monitor up to six more spacecraft. The process of installing and using our "research" software in an operational environment has provided many insights into which parts of REACH are a step forward and which of our ideas are missteps. Our paper explores both the new concepts in spacecraft health-and-safety visualization, the difficulties of such systems in the operational environment, and the cost and safety issues of multi-spacecraft missions.

Maks, Lori↗
NASA NTRS2010

The 2011 Draconid Shower Risk to Earth-Orbiting Satellites

Current meteor shower forecast models project a strong Draconid outburst, possibly a storm, on October 8, 2011, with a duration of approximately 7 hours and peaking between 19 and 21 hours UT. Predicted rates span an order of magnitude, with maximum Zenithal Hourly Rates (ZHRs) ranging from a few tens to several hundred. Calibration of the NASA MSFC Meteoroid Stream Model 1 to radar and optical observations of past apparitions, particularly the 2005 Draconid outburst 2, suggest that the maximum rate will be several hundreds per hour. Given the high spatial density of the Draconid stream, this implies a maximum meteoroid flux of 5-10 Draconids km(exp -2)/hr (to a limiting diameter of 1 mm), some 25-50 times greater than the normal sporadic flux of 0.2 km(exp -2)/ hr for particles of this size. Total outburst fluence, assuming a maximum ZHR of 750, is 15.5 Draconids km(exp -2), resulting in an overall 10x risk increase to spacecraft surfaces vulnerable to hypervelocity impacts by 1 mm particles. It is now established that a significant fraction of spacecraft anomalies produced by shower meteoroids (e.g. OLYMPUS and LandSat 5) are caused by electrostatic discharges produced by meteoroid impacts. In these cases, the charge generated is roughly proportional to v(exp 3.5(4)), giving a Draconid moving at 20 km/s approximately 1/80th the electrical damage potential of a Leonid of the same mass. In other words, a Draconid outburst with a maximum ZHR of 800 presents the same electrical risk as a normal Leonid shower with a ZHR of 15, assuming the mass indices and shower durations are the same. This is supported by the fact that no spacecraft electrical anomalies were reported during the strong Draconid outbursts of 1985 and 1998. However, the lack of past anomalies should not be taken as carte blanche for satellite operators to ignore the 2011 Draconids, as the upcoming outburst will constitute a period of enhanced risk for vehicles in near-Earth space. Each spacecrft is unique, and components have differing damage thresholds; programs are encouraged to conduct analyses to determine whether or not mitigation strategies are necessary for their vehicles.

Cooke, William J.↗
NASA NTRS2002

REACH: Real-Time Data Awareness in Multi-Spacecraft Missions

NASA's Advanced Architectures and Automation Branch at the Goddard Space Flight Center (Code 588) saw the potential to reduce the cost of constellation missions by creating new user interfaces to the ground system health-and-safety data. The goal is to enable a small Flight Operations Team (FOT) to remain aware and responsive to the increased amount of ground system information in a multi-spacecraft environment. Rather than abandon the tried and true, these interfaces were developed to run alongside existing ground system software to provide additional support to the FOT. These new user interfaces have been combined in a tool called REACH. REACH-the Real-time Evaluation and Analysis of Consolidated Health-is a software product that uses advanced visualization techniques to make spacecraft anomalies easy to spot, no matter how many spacecraft are in the constellation. REACH reads numerous real-time streams of data from the ground system(s) and displays synthesized information to the FOT such that anomalies are easy to pick out and investigate.

Maks, Lori↗
NASA NTRS1996

Proton Fluence Prediction Models

Many spacecraft anomalies are caused by positively charged high energy particles impinging on the vehicle and its component parts. Here we review the current knowledge of the interplanetary particle environment in the energy ranges that are most important for these effects, 10 to 100 MeV/amu. The emphasis is on the particle environment at 1 AU. State-of-the-art engineering models are briefly described along with comments on the future work required in this field.

Proton Fluence Prediction Models spacecraft anomal↗
NASA NTRS2019

A Meteoroid Handbook for Aerospace Engineers and Managers

At the beginning of the Space Age, spacecraft designers and mission planners were very concerned about meteoroids. They envisioned vehicles being ripped to pieces by streams of fast-moving space rocks, a notion promoted by the science fiction novels and movies of the time. The reality is, of course, different—the meteoroid streams that produce meteor showers are not dense by laypeople’s standards, having spatial densities of just a handful of particles per cubic kilometer, even during meteor outbursts. The ever-present, diffuse, sporadic background, which produces observed meteor rates of only 5 to 8 meteors per hour, makes up 90% of the meteoroid risk to spacecraft that spend at least a year in low Earth orbit (LEO), whereas the visually spectacular but short-lived meteor showers make up the other 10%. Still, meteoroids do pose a significant risk to spacecraft. At Earth, they can travel 12 to 72 km/s. These high speeds cause even small meteoroids to carry enormous kinetic energy, making them capable of doing serious damage to spacecraft. For example, a 1-mm-diameter meteoroid moving at 25 km/s can inflict the same damage as a bullet fired from a 0.357 Magnum pistol. An exterior wire can be severed by a 0.1-mm (100 mm) particle, a spacesuit can be penetrated by a 0.5-mm meteoroid, and an unshielded pressure wall (like the cabin of the Space Shuttle) can be perforated by centimeter-sized particles. Along with mechanical damage, meteoroids can also cause other types of spacecraft anomalies. Meteoroids can transfer their momentum to the spacecraft, which can destroy or damage equipment such as shunt resistors and charge-coupled device (CCD) detectors with a clear view of space. Meteoroid impacts can also generate plasma. The impact vaporizes material, producing a crater and an expanding plasma, which can in turn provide a conductive path for any charge accumulated on the spacecraft. This effect is thought to be responsible for the demise of a satellite in one case: the OLYMPUS communications satellite was sent tumbling out of control during the 1993 Perseid outburst, and a Perseid meteoroid strike has been posited as a possible cause (McDonnell et al. 1993; Caswell et al. 1995). Other researchers have suggested that very fast meteoroids could produce a small electromagnetic pulse capable of disrupting spacecraft function (Close et al. 2010).

Moorhead, A.↗