Satellite Failure Research Articles

Applications of Synthetic Aperture Radiometer Technology in Solar Wind Remote Sensing

Synthetic aperture radiometer technology used nowadays in earth remote sensing is an extended development from ground-based radio astronomy used for stellar observation. However, once the technology is further developed in the Earth remote sensing area, it can certainly be applied back in its original field or other fields. In this paper, we discuss a rotational phased array of time-shared synthetic aperture technology application in solar wind remote sensing. The main idea is to send a spacecraft into solar polar orbit. From this orbit, one can look down to the ecliptic plane. In and around the ecliptic plane, the most interested and useful information of the interplanetary solar wind is the Corona Material Ejection (CME) of the Sun since it can cause sever geo-space storms and result man made technical system failure such as navigation positioning errors and communication break down or even satellite failures. The main scientific initiatives and technical system conceptual design of this application will be presented in this paper.

The EWMA educational development project

Compared with the conventional least-squares-residuals method, the proposed filter type method, namely the exponentially weighted moving average (EWMA) filter, can achieve the goal of fast satellite failure detection in receiver autonomous integrity monitoring (RAIM). The corresponding threshold of the EWMA filter can be computed off-line via the Markov chain approximation. Some modifications made in the EWMA filter are also introduced in this paper. Simulation results show that by choosing the weighting factor properly the detection time can be considerably reduced.

Study of the Enhancement Events of Relativistic Electron at the Geosynchronous Orbit

The high flux of energetic electron on geostationary orbit can induce many kinds of malfunction of the satellite there, within which the bulk-charging is the most significant that several broadcast satellite failures were confirmed to be due to this effect. The electron flux on geostationary orbit varies in a large range even up to three orders accompanied the passage of interplanetary magnetic cloud and the following geomagnetic disturbances. Upon the investigation of electron flux enhancement events, two types of events were partitioned as recurrent events and random ones. Both of the two kinds of events relate to the interplanetary conditions such as solar wind parameters, IMF etc and their evolution characters as well. As for the recurrent events, we found that, (1) all of the events exhibits periodic recurrence about 27 days, (2) significant increase of electron flux relates to interplanetary index and characters of their distribution, (3) the electron flux also has relation to solar activity index. An artificial neural network was constructed to estimate the flux I day ahead. The random electron flux enhancement events are rare and present different distribution figures to the recurrent ones. The figure of the random events and the conditions of their occurrence is also discussed in this paper.

Ｊ２摂動下での衛星フォーメーション維持のための制御則

Recently, formation flying of small satellites is recognized as an important future on-orbit technology. It has many potentials such as realizing unlimited aperture size for radio sensing missions or spontaneous sensing at multiple points, leading to flexibility of space mission, low cost, tolerance against single satellite failure, and easier system upgrade, etc. However, usually the member satellites should be kept in a coordinated way, which requires lots of fuel. The orbital control methods requiring little fuel consumption should be developed. This paper focuses on J2 perturbation as a disturbance to the formation keeping. First, it is made clear why the formation is dispersed under the J2 perturbation. And then two new methods to keep the formation on a low earth orbit with small fuel consumption are proposed which are evaluated in computer simulations.

Effectiveness of the Ground-Based Transceiver (GBT) Parrot System for Monitoring GPS Integrity for Alaska ATC “Radar-Like Services” Using ADS-B

In January of 2001, the Federal Aviation Administration (FAA) commissioned the first use of Automatic Dependent Surveillance Broadcast (ADS-B) based on the Global Positioning System (GPS) to support Air Traffic Control (ATC) “radar-like services (RLS).” These services are available via ATC to nearly 200 equipped aircraft operating in the vicinity of Bethel, Alaska as part of the FAA’s Capstone program to improve aviation safety in Alaska. RLS allow ATC to support Instrument Flight Rules (IFR) separation of 5 nautical miles (nmi) based only on ADS-B surveillance. Since ADS-B information is being used by ATC for aircraft separation, some method to verify the integrity of the GPS/ADS-B data must be continuously provided. The ADS-B concept, as defined in RTCA standards, relies on air-craft to “self-report” the integrity of the navigation data reported in the ADS-B message. System evaluations leading to commissioning of RLS showed the ADS-B data to be easily equivalent to radar surveillance in terms of accuracy, latency, and update rate. However, it highlighted some difficulties with the self-reported integrity concept for this “first generation” of ADS-B avionics, due mainly to excessive Receiver Autonomous Integrity Monitoring (RAIM) holes—from the ATC perspective. The resulting excessive number of false integrity alerts led to an FAA decision to disregard ADS-B self-reported integrity in the Bethel area and, instead, to monitor GPS integrity through a network of new ground position “parrot” monitors implemented along with the existing ADS-B receiving stations. The objective of this paper is to determine how effective this monitor system is at detecting integrity failures of the GPS satellites that could cause Hazardously Misleading Information (HMI) over the Bethel, Alaska area. Although our results show that the existing parrot system is generally effective for conducting RLS in the Bethel area, we offer recommendations to the FAA to improve the performance of integrity monitoring in the area.

GPS fault detection and exclusion using moving average filters

A new approach based on the moving average (MA) is proposed to perform satellite failure detection and exclusion (FDE). By taking the average of the last few sums of the squares of the GPS range residual errors, the MA filter is applied to speed up failure detection. The detection threshold cannot be obtained directly because the cumulative distribution of a random process with an MA filter is unknown. Therefore, the Markov chain approach is applied to resolve the threshold. In addition, variations in the number of visible satellites may cause problems in data fusion. The probability integral transformation (PIT) method is adopted to overcome this. After a satellite failure is detected, the multivariate MA filter is used to reduce the incorrect exclusion rate (IER) by taking the average of the last few parity vectors. Simulation results show that, in comparison with the conventional least-squares-residuals method, the MA filter demonstrates higher performance in detecting small failures and a similar level of performance in detecting large failures. Moreover, simulation results also verify that the proposed method has lower IER than the conventional parity space method.

Test of GBAS integrity monitoring system using GPS simulator

In recent years, many countries are developing aircraft navigation systems using GNSS(Global Navigation Satellite System), because GNSS has many technical and economic benefits. International organizations as ICAO(International Civil Aviation Organization) and RTCA(Radio Technical Commission for Aeronautics) set up international standards of GBAS(Ground Based Augmentation System) using GNSS and recommend countries to develop GBAS that is based on the standards. To go with the international stream, Korea Airport Cooperation has also developed GBAS. For evaluating the system, KAC and Seoul National University have performed flight tests of the developed GBAS several times and have concluded that the system has good accuracy enough to be used in aircrafts. At that time, the purpose of tests was focused on accuracy of GBAS. But integrity of the system which is important for safety of aircrafts was not tested sufficiently, because it is impossible to make erroneous situations of real GPS signals. So, at this time, we used GPS simulator which can generate GPS signals with satellite failure scenarios. The GPS simulator used in this test generates GPS signals by the scenarios organized in advance. The scenarios can include pseudorange and carrier phase error, parity error and etc. So we organized several scenarios which can includes potential errors of GPS signals and many possible cases for testing the system effectively and accurately. And we tested integrity function of the GBAS system by using GPS signals generated by the simulator. This paper introduces the implemented integrity monitoring system and algorithms used in the tests. And it describes the scenarios of satellite failure. Finally, this paper shows the results of tests.

Policy challenges in building dependability in global infrastructures

[This paper was given at Compsec 2002, in London, on 30 October 2002]. Global or continental critical infrastructures — including electric power, telecommunications, and the Internet — are now the control plane for advanced economies. The occasional failures of these key infrastructures illustrate not only our dependence, but also the unanticipated interdependencies between systems. For example, the 1998 failure of a single telecommunications satellite, Galaxy 4, led to an outage of nearly 90% of all pagers in the United States, while also causing a number of unanticipated failures: many banking and financial services (credit card purchases, automated teller machines) were interrupted, as was communications with doctors and emergency workers [1]. With awareness of economic and social dependence on these distributed infrastructures has come a growing concern about their reliability and security. Defense against deliberate attack — critical infrastructure protection — emerged as part of the US national security posture in the mid-1990s with the work of the President’s Commission on Critical Infrastructure, and was codified by Presidential Decision Directive 63 in 1998. Other nations are also beginning to develop national strategies for infrastructure protection. Reliability is more than protection against deliberate attack. An accidental cut of a fiber optic trunk shut down air traffic control along the east coast of the US for a day. A cascading series of events, starting with a tree limb falling, caused much of the western US to lose electricity. The challenge of improving the reliability of global networked infrastructures presents us with significant analytical and decision-making complexities, with both technical and policy relevant dimensions [2]. This paper — using principally examples from the Internet and other distributed IT systems — presents two perspectives on these complexities. First is to present critical global infrastructures as complex adaptive systems, which share certain characteristics that policy makers and managers need to account for. Secondly, the balance of the paper outlines five major dimensions of the analytical and decision-making complexity, and presents the research and policy-making agendas that need to be addressed if we are to significantly improve the reliability of global infrastructures. Neither of these perspectives is purely technical or engineering based. Success in increasing the reliability of global infrastructures will require much more analytically sophisticated research in, among other topics, the issue areas identified here — in addition to ongoing technology-based research.

Estimation of Separation Shock of the Marman Clamp System by Using a Simple Band-Mass Model.

To prevent satellite failure during inter stage separation, the magnitude of separation shock must be estimated. The Marman Clamp System is a separation joint often used to mount satellites on a launch vehicle. This paper proposes a method of estimating separation shock for the Marman Clamp System. First, experimental results are discussed and the dominant parameters of separation shock are identified for the system. Next, a simple band-mass model is proposed to estimate the system’s separation shock. The differences between the model and experimental results are discussed. Radial and axial, but not tangential, separation shocks were estimated well by this method.

Improved Filter Type Integrity Monitoring In Satellite Navigation

Compared with the conventional least-squares-residuals method, the proposed filter type method, namely the exponentially weighted moving average (EWMA) filter, can achieve the goal of fast satellite failure detection in receiver autonomous integrity monitoring (RAIM). The corresponding threshold of the EWMA filter can be computed off-line via the Markov chain approximation. Some modifications made in the EWMA filter are also introduced in this paper. Simulation results show that by choosing the weighting factor properly the detection time can be considerably reduced.

Long-term collision risk prediction for low earth orbit satellite constellations

In the light of recent changes to planned Low Earth Orbit (LEO) satellite constellation designs and enhancements made to the DERA IDES model, we have conducted a new study on long-term debris environment evolution. This includes the collision interactions of constellation systems with the orbital debris environment over the next 50 years. In this new study, we use the IDES model to simulate long-term evolution in four ‘business as usual’ future traffic scenarios, which differ by the presence and absence of foreseen satellite constellation traffic and debris mitigation measures. The IDES model is capable of taking high spatial resolution snapshots of the debris flux environment at regular time intervals. By accessing these snapshots, the IDES model is able to predict the long-term variation of debris flux incident on a specific target orbit. This technique is harnessed to predict the average debris flux trends for a typical LEO constellation satellite. Furthermore, we estimate the average debris-induced satellite failure rates for a whole constellation system. Finally, we discuss our new findings on the long-term effects of constellations on the debris environment and vice versa.

GPS Navigation Performance Requirements

In this paper, GPS navigation performance requirements and RAIM algorithm for Integrity monitoring with multiple satellite failures are discussed. The two GPS augmentation systems LAAS and WAAS to meet the aviation requirements for all phases of flight are briefed. GPS Spoofing and Jamming and counter measures have been described.

Penetrating electron fluctuations associated with GEO spacecraft anomalies

Space weather is a known factor in spacecraft anomalies. Solar minimum carries with it an enhanced electron content. Electrons with sufficient energy to penetrate a spacecraft structure pose a hazard. They can accumulate in interior dielectrics creating an electric potential sufficient to cause a spontaneous breakdown. The resulting electrostatic discharge has been a cause of operational anomalies. The physical process by which the geosynchronous earth orbit (GEO) environment is populated by high-energy electrons is not fully understood. However, the solar-cycle, seasonal, and solar-rotational patterns observed are well documented. This paper reviews temporal fluence patterns and shows how some notorious satellite failures relate to them. It should be noted, however the temporal response of a discharge is not necessarily at the instantaneous peak flux, but related to total local fluence and how the dielectric responds to stress. Knowledge of the changes in mechanical and electrical properties of dielectrics in the space environment and a growing understanding of the variability of the electron population at GEO will enable the resolution of anomalies anti facilitate their prevention.

VEGA, a small launch vehicle

Several studies have been performed in Europe aiming to promote the full development of a small launch vehicle to put into orbit one ton class spacecrafts. But during the last ten years, the european workforce was mainly oriented towards the qualification of the heavy class ARIANE 5 launch vehicle.Then, due also to lack of visibility on this reduced segment of market, when comparing with the geosatcom market, no proposal was sufficiently attractive to get from the potentially interrested authorities a clear go-ahead, i.e. a financial committment. The situation is now rapidly evolving. Several european states, among them ITALY and FRANCE, are now convinced of the necessity of the availability of such a transportation system, an important argument to promote small missions, using small satellites. Application market will be mainly scientific experiments and earth observation; some telecommunications applications may be also envisaged such as placement of little LEO constellation satellites, or replacement after failure of big LEO constellation satellites. FIAT AVIO and AEROSPATIALE have proposed to their national agencies the development of such a small launch vehicle, named VEGA. The paper presents the story of the industrial proposal, and the present status of the project: Mission spectrum, technical definition, launch service and performance, target development plan and target recurring costs, as well as the industrial organisation for development, procurement, marketing and operations.

Disturbed space environment may have been related to pager satellite failure

A very intense flux of electrons, evident in the magnetosphere earlier this year, may have caused a satellite failure (or at least exacerbated the situation) leading to the loss of pager service to 45 million customers, research has shown. The electrons, known as highly relativistic electrons (HREs), were especially numerous in the weeks preceding the failure. Researchers say HREs have triggered spacecraft anomalies in the past through a process of deep dielectric charging when fluxes are elevated. They therefore believe this energetic electron environment could have been behind the failure in the attitude control system of the Galaxy 4 spacecraft at 2200 UT on May 19,1998. A backup system also failed, either at the same time or earlier, so operators were unable to maintain a stable Earth link [Silverstein, 1998].

Global design of satellite constellations: a multi-criteria performance comparison of classical walker patterns and new design patterns

Basically, the problem of designing a multisatellite constellation exhibits a lot of parameters with many possible combinations: total number of satellites, orbital parameters of each individual satellite, number of orbital planes, number of satellites in each plane, spacings between satellites of each plane, spacings between orbital planes, relative phasings between consecutive orbital planes. Hopefully, some authors have theoretically solved this complex problem under simplified assumptions: the permanent (or continuous) coverage by a single and multiple satellites of the whole Earth and zonal areas has been entirely solved from a pure geometrical point of view. These solutions exhibit strong symmetry properties (e.g. Walker, Ballard, Rider, Draim constellations): altitude and inclination are identical, orbital planes and satellites are regularly spaced, etc. The problem with such constellations is their oversimplified and restricted geometrical assumption. In fact, the evaluation function which is used implicitly only takes into account the point-to-point visibility between users and satellites and does not deal with very important constraints and considerations that become mandatory when designing a real satellite system (e.g. robustness to satellite failures, total system cost, common view between satellites and ground stations, service availability and satellite reliability, launch and early operations phase, production constraints, etc.). An original and global methodology relying on a powerful optimization tool based on genetic algorithms has been developed at ALCATEL ESPACE. In this approach, symmetrical constellations can be used as initial conditions of the optimization process together with specific evaluation functions. A multi-criteria performance analysis is conducted and presented here in a parametric way in order to identify and evaluate the main sensitive parameters. Quantitative results are given for three examples in the fields of navigation, telecommunication and multimedia satellite systems. In particular, a new design pattern with very efficient properties in terms of robustness to satellite failures is presented and compared with classical Walker patterns.

Failure detection approach applying to GPS autonomous integrity monitoring

In recent years, there has been a growing interest within the potential user community in applying GPS to a variety of high-precision navigation problems such as aircraft nonprecision approach, river and harbour navigation, real-time or kinematic surveying, etc. In view of more and more GPS applications, the reliability of GPS is at issue. This promotes the need for several proposed receiver autonomous integrity monitoring (RAIM), GPS integrity channel (GIC), and wide area augmentation system (WAAS) schemes. The authors propose an approach for autonomous GPS satellite failure detection. The method exploits total least squares (TLS) optimisation to achieve fault detection. The traditional least squares approach fails to address the change in the data matrix associated with GPS satellite constellation. This drawback is shown to be remedied by the total least squares method. The proposed method can further be extended to account for failure isolation in which failed GPS satellites are identified and hence excluded in positioning.

GLONASS Performance, 1995-1997, and GPS-GLONASS Interoperability Issues

This paper presents GLONASS status and performance during 1995-1997, problems observed, and results of precise positioning work in GLONASS coordinates. The observations are based on data collected continually by a GLONASS receiver based in Southern California, and should be of interest to potential GLONASS users, as well as designers of integrated GPS- GLONASS equipment. After filling the 24-satellite constellation in early 1996, the GLONASS space segment faltered, with several satellite failures and persistent problems, but no replacement launches since then. However, accuracy is maintained at levels comparable to GPS without Selective Availability. A number of problems, including integrity lapses, have been observed and are explained in detail. Positioning results are consistent with a small east-west rotation between WGS-84 and GLONASS coordinates, with only small differences between PZ90 and SGS-85.

Did space weather knock out telstar, seismic network?

On January 11, AT&T lost contact with its $200 million communications satellite, Telstar 401, right in the middle of a magnetic storm at Earth. Though AT&T officials have not yet announced a cause for the failure of the geostationary satellite, many scientists believe Telstar was a victim of space weather.Telstar 401 relayed signals for local and national broadcast television networks, as well as telephone calls and computer data. To date, AT&T and the manufacturer of the satellite, Lockheed‐Martin, have been unable to reestablish contact with Telstar or determine what caused the malfunction.

Space weather prediction

Energy from the Sun impacts the near‐Earth environment to create a myriad of hazards to systems operating in and through space, and even to ground based activities. Costly systems are at risk. Already space storms cause averaged annual losses estimated to exceed $100M. The space weather effects from the severe magnetic storms during this past solar maximum and the recent failure (1994) of the Anik satellite have emphasized the risk. The Solar‐Terrestrial predictions Workshop, held in Ottawa in 1992, brought forecasters, customers and the physics community together in a common forum to present and discuss recent advancements. The proceedings of these meetings [Solar‐Terrestrial Predictions ‐ IV, 1993[ provide a source book of effects and attempts to mitigate those effects.