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Moriba Jah
  • Albuquerque, New Mexico, United States
" In space, no one can hear you scream, " as the tagline from the sci-fi film Aliens goes. But what if there were a way of " hearing " in space, moving in-space video from the Silent Era to a more contemporary cinematic experience? How... more
" In space, no one can hear you scream, " as the tagline from the sci-fi film Aliens goes. But what if there were a way of " hearing " in space, moving in-space video from the Silent Era to a more contemporary cinematic experience? How could this capability be applied to shape future spacecraft and mission designs? Such a capability can be effectively incorporated into a 3U CubeSat using a measurement technique called Remote Acoustic Sensing (RAS). " RASSat " uses advanced optical sensors to view and recover audio from distant objects that have weak optical modulations produced by local sound and vibration sources; the modulated light sources and the RAS sensor are passively coupled at the speed of light, yielding a variety of interesting sounds across the entire human auditory range. RAS field demonstrations and analyses have identified and characterized terrestrial sound sources observable from LEO, along with associated acousto-optic modulation mechanisms. RASSat sensitivity is such that both day and night strong, easily detectable terrestrial acousto-optic emitters abound, and applications to Space Situational Awareness and planetary exploration are also evident. This paper provides an overview of the RAS measurement technique and recent terrestrial demonstrations, and highlights key RASSat design features, performance capabilities and applications.
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As the spacefaring community is well aware, the increasingly rapid proliferation of man-made objects in space, whether active satellites or debris, threatens the safe and secure operation of spacecraft and requires that we change the way... more
As the spacefaring community is well aware, the increasingly rapid proliferation of man-made objects in space, whether active satellites or debris, threatens the safe and secure operation of spacecraft and requires that we change the way we conduct business in space. The introduction of appropriate protocols and procedures to regulate the use of space is predicated on the availability of quantifiable and timely information regarding the behavior of resident space objects (RSO): the basis of space domain awareness (SDA). Yet despite five decades of space operations, and a growing global dependence on the services provided by space-based platforms, the population of Earth orbiting space objects is still neither rigorously nor comprehensively quantified, and the behaviors of these objects, whether directed by human agency or governed by interaction with the space environment, are inadequately characterized. Key goals of advanced SDA are to develop a capability to predict RSO behavior, extending SDA beyond its present paradigm of catalog maintenance and forensic analysis, and to arrive at a comprehensive physical understanding of all of the inputs that affect the motion of RSOs. Solutions to these problems require multidisciplinary engagement that combines space surveillance data with other information, including space object databases and space environmental data, to help decision-making processes predict, detect, and quantify threatening and hazardous space domain activity. 1.0 INTRODUCTION This document presents an introductory overview of space surveillance, tracking, and information fusion for SDA. A relevant activity is the NATO Science and Technology Organization's Task Group (SCI-279-TG) is addressing the technical considerations for enabling a NATO-Centric Space Domain Common Operating Picture (COP). The impetus for this effort is the growing dependence by NATO and its member nations on space capabilities to achieve its mission responsibilities as well as the growing role that space, as an operational domain in its own right, is playing in matters concerning global security. NATO has recognized this important reality and increased the Alliance's collective attention on ensuring NATO operations maximize their leverage of space while ensuring the space capabilities provided by its member nations are preserved to the maximum extent possible. A critical element of ensuring the availability and efficacy of these space capabilities is the availability of a common operational perspective or picture of the space domain throughout the Alliance and its partners. The presumption is that NATO forces will be more efficient, protected and successful in their future missions if a common operational perspective can be achieved across all operational domains in which NATO must operate; air, land, sea, cyber AND space. The corollary is, without a common Alliance perspective of the space domain,
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As the spacefaring community is well aware, the increasingly rapid proliferation of man-made objects in space, whether active satellites or debris, threatens the safe and secure operation of spacecraft and requires that we change the way... more
As the spacefaring community is well aware, the increasingly rapid proliferation of man-made objects in space, whether active satellites or debris, threatens the safe and secure operation of spacecraft and requires that we change the way we conduct business in space. The introduction of appropriate protocols and procedures to regulate the use of space is predicated on the availability of quantifiable and timely information regarding the behavior of resident space objects (RSO): the basis of space domain awareness (SDA). Yet despite five decades of space operations, and a growing global dependence on the services provided by space-based platforms, the population of Earth orbiting space objects is still neither rigorously nor comprehensively quantified, and the behaviors of these objects, whether directed by human agency or governed by interaction with the space environment, are inadequately characterized. In response to these challenges, the University of Arizona (UA) has recently established the Space Object Behavioral Sciences (SOBS) Division of its Defense and Security Research Institute (DSRI) with a mandate to carry out research, education, and operational support to spacecraft operators. The SOBS Division builds on UA's heritage as a world leader in space science. By way of examples, UA, with a total research portfolio exceeding $600M per year, operates more than 20 astronomical telescopes on two continents, leads NASA's $800M OSIRIS-REx asteroid sample return mission, and has been deeply engaged in every US mission to Mars without exception. Key goals of the SOBS Division are to develop a capability to predict RSO behavior, extending SDA beyond its present paradigm of catalog maintenance and forensic analysis, and to arrive at a comprehensive physical understanding of non-gravitational forces that affect the motions of RSOs. Without seeking to provide a universal solution to global SDA needs, SOBS nonetheless concentrates resources to advance the state-of-the-art in astrodynamic research toward those ends. Solutions to these problems require multidisciplinary engagement that combines space surveillance data with other information, including space object databases and space environmental data, to help decision-making processes predict, detect, and quantify threatening and hazardous space domain activity. To that end, the division engages and integrates talent and resources from across the UA, including the Colleges of Science, Engineering, Optical Sciences, and Agriculture & Life Sciences. As activity ramps up over approximately the next three years, the SOBS Division will directly support the creation of timely knowledge of the space environment by drawing on a worldwide network of sensors processed through existing UA cyberinfrastructure. In addition, the SOBS Division will also provide a real-world training ground for current and future workers in the field through certificate programs and postgraduate degrees.
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ABSTRACT This study investigates dynamic modeling and orbit estimation of geosynchronous satellites using traditional and specialized orbit representations Exact nonlinear variational equations for generally perturbed synchronous elements... more
ABSTRACT This study investigates dynamic modeling and orbit estimation of geosynchronous satellites using traditional and specialized orbit representations Exact nonlinear variational equations for generally perturbed synchronous elements are developed via Poisson brackets A hybrid element set is also introduced to avoid numerical sensitivities Numerical propagation studies evaluate the precision and accuracy of inertial Cartesian, Keplerian, synchronous, and hybrid element dynamic models The suitability of approximating the synchronous element equations of motion for small eccentricity and inclination values is assessed Results show that the hybrid and exact synchronous models are consistent for large and small time steps and are of comparable accuracy to the inertial Cartesian model The hybrid element model is further validated via an estimation analysis that processes multiple nights of experimental optical data of the Tracking and Data Relay Satellite 8 The results show that the hybrid elements are suitable for geosynchronous dynamic modeling and estimation
ABSTRACT In this paper, we consider the evaluation of information divergence and information gain as they apply to a hybrid random variable (i.e. a random variable which has both discrete and continuous elements) for multi-target tracking... more
ABSTRACT In this paper, we consider the evaluation of information divergence and information gain as they apply to a hybrid random variable (i.e. a random variable which has both discrete and continuous elements) for multi-target tracking problems. In particular, we develop a closed-form solution for the Cauchy-Schwarz information divergence under the assumption that the continuous element of the random variable may be represented by a Gaussian mixture distribution and present the associated relationships for evaluating the Cauchy-Schwarz information gain. The developed information gain relationships are applied to a 0-1 target tracking problem common to space object tracking to determine the sensitivities to the information gain due to probability of detection, prior probability of object existence, and measurement noise.
Astrometric and photometric data fusion for the purposes of simultaneous position, velocity, attitude, and angular rate estimation has been demonstrated in the past. This state estimation is extended to include the various surface... more
Astrometric and photometric data fusion for the purposes of simultaneous position, velocity, attitude, and angular rate estimation has been demonstrated in the past. This state estimation is extended to include the various surface parameters associated with the bidirectional reflectance distribution function (BRDF). Additionally, a physically consistent BRDF and radiation pressure model is utilized thus enabling an accurate physical link between the observed photometric brightness and the attitudinal dynamics and ultimately the orbital dynamics. An example scenario is then presented where the model is an uncontrolled High Area to Mass Ratio (HAMR) object in geosynchronous Earth orbit and the position, velocity, attitude, angular rates, and surface parameters are estimated simultaneously.
The Mars Reconnaissance Orbiter (MRO) launched on 12 August 2005 from Space Launch Complex 41 at Cape Canaveral Air Force Station. After seven months of cruise, MRO reached Mars and successfully performed the Mars Orbit Insertion (MOI)... more
The Mars Reconnaissance Orbiter (MRO) launched on 12 August 2005 from Space Launch Complex 41 at Cape Canaveral Air Force Station. After seven months of cruise, MRO reached Mars and successfully performed the Mars Orbit Insertion (MOI) maneuver. Only two Trajectory ...
ABSTRACT Uncertainty propagation of dynamical systems is a common need across many domains and disciplines. In nonlinear settings, the extended Kalman filter is the de facto standard propagation tool. Recently, a new class of propagation... more
ABSTRACT Uncertainty propagation of dynamical systems is a common need across many domains and disciplines. In nonlinear settings, the extended Kalman filter is the de facto standard propagation tool. Recently, a new class of propagation methods called sigma-point Kalman filters was introduced, which eliminated the need for explicit computation of tangent linear matrices. It has been shown in numerous cases that the actual uncertainty of a dynamical system cannot be accurately described by a Gaussian probability density function. This has motivated work in applying the Gaussian mixture model approach to better approximate the non-Gaussian probability density function. A limitation to existing approaches is that the number of Gaussian components of the Gaussian mixture model is fixed throughout the propagation of uncertainty. This limitation has made previous work ill-suited for nonstationary probability density functions either due to inaccurate representation of the probability density function or computational burden given a large number of Gaussian components that may not be needed. This work examines an improved method implementing a Gaussian mixture model that is adapted online via splitting of the Gaussian mixture model components triggered by an entropy-based detection of nonlinearity during the probability density function evolution. In doing so, the Gaussian mixture model approximation adaptively includes additional components as nonlinearity is encountered and can therefore be used to more accurately approximate the probability density function. This paper introduces this strategy, called adaptive entropy-based Gaussian-mixture information synthesis. The adaptive entropy-based Gaussian-mixture information synthesis method is demonstrated for its ability to accurately perform inference on two cases of uncertain orbital dynamical systems. The impact of this work for orbital dynamical systems is that the improved representation of the uncertainty of the space object can then be used more consistently for identification and tracking.
ABSTRACT The main objective of this paper is to present the development of the computational methodology, based on the Gaussian mixture model, that enables accurate propagation of the probability density function through the mathematical... more
ABSTRACT The main objective of this paper is to present the development of the computational methodology, based on the Gaussian mixture model, that enables accurate propagation of the probability density function through the mathematical models for orbit propagation. The key idea is to approximate the density function associated with orbit states by a sum of Gaussian kernels. The unscented transformation is used to propagate each Gaussian kernel locally through nonlinear orbit dynamical models. Furthermore, a convex optimization problem is formulated by forcing the Gaussian mixture model approximation to satisfy the Kolmogorov equation at every time instant to solve for the amplitudes of Gaussian kernels. Finally, a Bayesian framework is used on the Gaussian mixture model to assimilate observational data with model forecasts. This methodology effectively decouples a large uncertainty propagation problem into many small problems. A major advantage of the proposed approach is that it does not require the knowledge of system dynamics and the measurement model explicitly. The simulation results are presented to illustrate the effectiveness of the proposed ideas.
ABSTRACT High-fidelity orbit propagation requires detailed knowledge of the solar radiation pressure on a space object. The solar radiation pressure depends not only on the space object's shape and attitude, but also on the... more
ABSTRACT High-fidelity orbit propagation requires detailed knowledge of the solar radiation pressure on a space object. The solar radiation pressure depends not only on the space object's shape and attitude, but also on the absorption and reflectance properties of each surface on the object. These properties are typically modeled in a simplistic fashion, but are here described by a surface bidirectional reflectance distribution function. Several analytic bidirectional reflectance distribution function models exist, and are typically complicated functions of illumination angle and material properties represented by parameters within the model. In general, the resulting calculation of the solar radiation pressure would require a time-consuming numerical integration. This might be impractical if multiple solar radiation pressure calculations are required for a variety of material properties in real time; for example, in a filter where the particular surface parameters are being estimated. This paper develops a method to make accurate and precise solar radiation pressure calculations quickly for some commonly used analytic bidirectional reflectance distribution functions. In addition, other radiation pressures exist, including Earth albedo/Earth infrared radiation pressure, and thermal radiation pressure from the space object itself, and are influenced by the specific bidirectional reflectance distribution function. A description of these various radiation pressures and a comparison of the magnitude of the resulting accelerations at various orbital heights and the degree to which they affect the space object's orbit are also presented. Significantly, this study suggests that, for space debris whose interactions with electro-magnetic radiation are described accurately with a bidirectional reflectance distribution function, then hitherto unmodeled torques would account for rotational characteristics affecting both tracking signatures and the ability to predict the orbital evolution of the objects.
ABSTRACT This study investigates dynamic modeling and orbit estimation of geosynchronous satellites using traditional and specialized orbit representations Exact nonlinear variational equations for generally perturbed synchronous elements... more
ABSTRACT This study investigates dynamic modeling and orbit estimation of geosynchronous satellites using traditional and specialized orbit representations Exact nonlinear variational equations for generally perturbed synchronous elements are developed via Poisson brackets A hybrid element set is also introduced to avoid numerical sensitivities Numerical propagation studies evaluate the precision and accuracy of inertial Cartesian, Keplerian, synchronous, and hybrid element dynamic models The suitability of approximating the synchronous element equations of motion for small eccentricity and inclination values is assessed Results show that the hybrid and exact synchronous models are consistent for large and small time steps and are of comparable accuracy to the inertial Cartesian model The hybrid element model is further validated via an estimation analysis that processes multiple nights of experimental optical data of the Tracking and Data Relay Satellite 8 The results show that the hybrid elements are suitable for geosynchronous dynamic modeling and estimation
ABSTRACT In this paper, a new approach is presented to propagate the attitude and orbital motion of objects with high area-to-mass ratios in near geostationary orbits using a semi-coupled approach. In the case of HAMR objects, their... more
ABSTRACT In this paper, a new approach is presented to propagate the attitude and orbital motion of objects with high area-to-mass ratios in near geostationary orbits using a semi-coupled approach. In the case of HAMR objects, their orbits are highly perturbed by non-conservative forces, such as direct radiation pressure. This leads to the fact that orbit and attitude motions are highly coupled. Solar radiation pressure can lead to a rapid attitude motion, which is non-uniform and leads to a high computational burden in integrating the fully coupled system. In the characterization of objects, often light (optical or radar) curve measurements are used. They measure the intensity (actively illuminated radar or passively illuminated optical) of the radiation that is reflected to the observer. General characterization techniques, such as frequency analysis and inversion, neglect the orbit-attitude coupling. A new semi-coupled method is proposed: orbit and attitude motion are initialized as fully coupled and then decoupled and propagated independently, using the values derived in the initialization step as a priori values. Shannon entropy serves as a double metric, orbit and attitude, and the system is triggered to be re-coupled again for a single epoch, as soon as the a priori attitude and integrated attitude or a priori orbit motion and integrated attitude motion deviate significantly. In a second approach, Kullback-Leibler divergence is used as a trigger. Both the Shannon entropy and the Kullback-Leibler divergence based method are compared to the fully coupled integration solution. Integrating the two systems as semi-coupled saves computational time, and gives a measure for which time intervals the system can be viewed as approximately decoupled system, when characterizing the objects via light curve measurements.
The orbital and attitude dynamics of uncontrolled Earth orbiting objects are perturbed by a variety of sources. In research, emphasis has been put on active space vehicles. Active satellites typically have a compact shape, and hence, a... more
The orbital and attitude dynamics of uncontrolled Earth orbiting objects are perturbed
by a variety of sources. In research, emphasis has been put on active space vehicles. Active
satellites typically have a compact shape, and hence, a low area-to-mass ratio (AMR), and
are in most cases actively or passively attitude stabilized. This enables one to treat the
orbit and attitude propagation as decoupled problems, and in many cases the attitude
dynamics can be neglected completely. The situation is di fferent for space debris objects
which are in an uncontrolled attitude state. Furthermore, the assumption that a steady-
state attitude motion can be averaged over data reduction intervals may no longer be valid.
Additionally, a subset of the debris objects have signi ficantly high AMR values, resulting
in highly perturbed orbits, e.g. by solar radiation pressure, even if a stable AMR value
is assumed. Note, this assumption implies a steady-state attitude such that the average
cross-sectional area exposed to the sun is close to constant. Time-varying solar radiation
pressure accelerations due to attitude variations will result in un-modeled errors in the
state propagation. The current paper investigates the evolution of the coupled attitude
and orbit motion in simulating the object properties of pieces of multi layer insulation
(MLI) materials Kapton
and PET. Double and single aluminum coating is regarded
as well as the tendency of the materials to curl up. The objects are simulated to be in a near
geosynchronous orbit. It is assumed the objects are rigid bodies and are in non-controlled
attitude states starting with zero attitude motion. The integrated eff ects of the Earth
gravitational field and solar radiation pressure on the attitude motion are investigated.
The light curves, that is, the brightness variations over time as observed from a ground
based optical sensor are generated.
The orbital and attitude dynamics of uncontrolled Earth orbiting objects are perturbed by a variety of sources. In research, emphasis has been put on operational space vehicles. Operational satellites typically have a relatively compact... more
The orbital and attitude dynamics of uncontrolled Earth orbiting objects are perturbed by a variety of sources. In research, emphasis has been put on operational space vehicles. Operational satellites typically have a relatively compact shape, and hence, a low area-to-mass ratio (AMR), and are in most cases actively or passively attitude stabilized. This enables one to treat the orbit and attitude propagation as decoupled problems, and in many cases the attitude dynamics can be neglected completely. The situation is different for space debris objects, which are in an uncontrolled attitude state. Furthermore, the assumption that
a steady-state attitude motion can be averaged over data reduction intervals may no longer be valid. Additionally, a subset of the debris objects have significantly high area-to-mass ratio
(HAMR) values, resulting in highly perturbed orbits, e.g. by solar radiation pressure, even if a stable AMR value is assumed. Note, this assumption implies a steady-state attitude such that
the average cross-sectional area exposed to the sun is close to constant. Time-varying solar radiation pressure accelerations due to attitude variations will result in un-modeled errors in the state propagation. This work investigates the evolution of the coupled attitude and orbit motion of HAMR objects. Standardized pieces of multilayer insulation (MLI) are simulated in a near geosynchronous orbits. It is assumed that the objects are rigid bodies and are in uncontrolled attitude states. The integrated effects of the Earth gravitational field and solar radiation pressure on the attitude motion are investigated. The light curves that represent the observed brightness variations over time in a specific viewing direction are extracted.
Describes the benefits of using probabilistic data association within a multiple hypothesis filter framework for automated space debris initial orbit determination, follow-on tracking, and area-to-mass ratio estimation
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Method accounting for the contribution to the estimated state vector uncertainty stemming from the uncertainty in non-estimated dynamic and measurement parameters.
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For spacecraft whose mission design requires they undergo an orbital plane change maneuver. For a given family of final orbits, it may be more cost effective to use a Lunar Gravity-Assist (LGA) to achieve a large plane change. This paper... more
For spacecraft whose mission design requires they undergo an orbital plane change maneuver. For a given family of final orbits, it may be more cost effective to use a Lunar Gravity-Assist (LGA) to achieve a large plane change. This paper examines these scenarios for Geostationary and retrograde final orbits, and provides the resulting Delta-V's for each case. Hohmann transfers with combined plane changes are used as a comparative baseline for evaluating the performance. Analysis covers the different transfer methods from each major world launch site.
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The population of space objects (SOs) is tracked with sparse resources and thus tracking data are only collected on these objects for a relatively small fraction of their orbit revolution (i.e., a short arc). This contributes to commonly... more
The population of space objects (SOs) is tracked with sparse resources and thus tracking data are only collected on these objects for a relatively small fraction of their orbit revolution (i.e., a short arc). This contributes to commonly mistagged or uncorrelated SOs and their associated trajectory uncertainties (covariances) to be less physically meaningful. The case of simply updating a catalogued SO is not treated here, but rather, the problem of reducing a set of collected short-arc data on an arbitrary deep space object without a priori information, and from the observations alone, determining its orbit to an acceptable level of accuracy. Fundamentally, this is a problem of data association and track correlation. The work presented here takes the concept of admissible regions and attributable vectors along with a multiple hypothesis filtering approach to determine how well these SO orbits can be recovered for short-arc data in near realtime and autonomously. While the methods presented here are explored with synthetic data, the basis for the simulations resides in actual data that has yet to be reduced, but whose characteristics are replicated as well as possible to yield results that can be expected using actual data.

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