About

Professor Mark L. Psiaki is a Professor Emeritus at the Sibley School of Mechanical and Aerospace Engineering at Cornell University. After completing his undergraduate studies in physics, he worked for three years at RCA Astro-Electronics focusing on mechanical design and testing. During his graduate studies at Princeton University, he was recognized as a National Science Foundation Fellow, a Guggenheim Honorary Fellow, and a Lothrop Honorific Fellow. He joined the Cornell faculty in 1986 and has since contributed significantly to the fields of aerospace sensing systems, estimation and filtering theory, and system modeling. Professor Psiaki's research encompasses the development of new aerospace sensing systems and the enhancement of existing systems through advanced estimation, filtering, and optimization techniques. His theoretical work involves creating new algorithms for state and parameter estimation, while his applied research addresses problems in GPS/GNSS systems, spacecraft navigation, and attitude determination. He has contributed hardware and filtering algorithms to numerous spacecraft, including NASA satellites and the Cornell Satellite CUSat, and has developed real-time GNSS software receivers for space weather monitoring. Recognized for his expertise, he has authored over 60 refereed journal articles, more than 50 conference papers, and holds four patents. His teaching interests focus on system dynamics, control, and GPS at both undergraduate and graduate levels. He has received several awards, including the Tycho Brahe Award and the Burka Award from the Institute of Navigation.

Research topics

• Computer Science
• Physics
• Telecommunications
• Computer Security
• Remote sensing
• Geography
• Aerospace engineering
• Geology
• Geodesy
• Engineering
• Real-time computing

Selected publications

• Classification of Authentic and Spoofed GNSS Signals Using a Calibrated Antenna Array

  NAVIGATION Journal of the Institute of Navigation · 2025-01-02 · 3 citations

  articleOpen accessSenior author

  <h3>Abstract</h3> New optimization-based methods have been developed to use measured direction-of-arrival (DoA) information in order to classify received global navigation satellite system signals into authenticated and spoofed sets and to augment that information with pseudorange information when DoA information alone is insufficient to achieve the needed classification. These methods are designed for a system that is being developed to mitigate spoofing and jamming by using signals from a controlled radiation pattern antenna. These new spoofing classification methods operate on DoA outputs from trackers of various signals. This paper presents a multi-hypothesis test that considers all possible hypotheses regarding the authenticated and spoofed sets of tracked signals. A combinatorial analysis is performed in which all possible authenticated-set/spoofed-set classifications are generated for a given set of tracked signals and the correct authenticated set is determined among the different combinations. Results from Monte Carlo simulations show that using a combined DoA and pseudorange method is suitable for determining the correct combinations.

  PublisherOA PDFDOI

• A Generalized GDOP Analysis for PNT that Requires Sequential Filtering

  Proceedings of the Satellite Division's International Technical Meeting (Online)/Proceedings of the Satellite Division's International Technical Meeting (CD-ROM) · 2025-10-01

  article1st authorCorresponding

  A generalization of the GDOP metric for point positioning/timing batch-filter solutions is extended to sequential filters, and an efficient means of computing the generalized GDOP is developed. This work is done in support of navigation systems that cannot yield a full PNT solution based solely on observables from a single point in time. Such cases include systems that use a time series of pseudoranges from fewer than the minimum requirement of 4 satellites, or that use a time series of carrier Doppler shifts from fewer than the minimum requirement of 8 satellites. If one were to compute the standard pseudorangesolution GDOP for such systems, or a newer Doppler-only GDOP, the results would yield infinite GDOP values. It has been demonstrated, however, that a time series of fewer than 4 pseudoranges can provide a full PNT solution when processed using an appropriate recursive filter. Similarly, a time series of fewer than 8 carrier Doppler shifts can provide a full PNT solution when using a recursive filter. Therefore, it would be helpful to have an appropriate generalization of GDOP to such situations in order to characterize PNT accuracy quickly and succinctly. This paper develops such a generalized GDOP. It is based on a non-dimensionalized covariance matrix for a Kalman filter that, in theory, processes data starting infinitely far back in time and ending at the time when GDOP is to be calculated. In practice, the Kalman filter calculations only need to start at a finite prior time in the past because its process noise model causes it to discount the contributions of data from the past, with data far in the past being discounted to the point of irrelevance. One determines an appropriate finite past interval by successively trying longer Kalman filter intervals until the GDOP at the time point of interest converges. A new retrospective Kalman filter backwards recursion is developed to perform the needed calculations. It uses computation time that is linear in the needed number of retrospective samples. This represents a significant improvement over a brute-force method whose computational cost is quadratic in this number of samples.

  PublisherDOI

• Blind Multi-Vehicle GNSS Spoofing Detection with Extended Baselines

  Proceedings of the Satellite Division's International Technical Meeting (Online)/Proceedings of the Satellite Division's International Technical Meeting (CD-ROM) · 2025-10-01

  articleSenior author

  An existing spoofing detection method is extended to scenarios with distributed receivers on separate vehicles. Large baselines enable collaboration across vehicles, creating a virtual phased array even when each vehicle has only one antenna. Direction-of-arrival ambiguities that emerge at large baselines are analyzed, with attention to their impact on false alarms and detection reliability. Monte Carlo analyses are employed to establish practical detection thresholds and assess performance across operating conditions. Detection performance initially degrades as baseline distance increases, but stabilizes once separation exceeds approximately two carrier wavelengths. Monte Carlo methods prove effective for threshold selection, and reference thresholds are tabulated for varying numbers of signals and antennas.

  PublisherDOI

• Autonomous Magnetic Navigation for Earth Orbiting Spacecraft

  Digital Commons - USU (Utah State University) · 2025-09-10 · 21 citations

  articleOpen access1st authorCorresponding

  The strength and orientation of the Earth's magnetic field varies as a function of the location of the observations, which means that the magnetic field measurements contains position information. Many artificial satellites carry a magnetometer on-board. The local magnetic field measurements could be used to provide navigation information. Such a navigation method has the advantage of requiring only data from low cost on-board instruments and has applications in low budget operation of satellite systems. Furthermore if processing can be performed on-board, this method leads to the possibility of fully autonomous long term navigation. In many systems magnetic navigation could be an effective back-up. To study the feasibility and potential performance of spacecraft magnetic navigation, the concept was investigated using two possible approaches. In a first configuration the magnetic field orientation is assumed to be complemented by measurements of the Nadir direction provided by an Earth horizon sensor on board; the two vectors form the basis of a "space sextant." In the second configuration magnetic field magnitude is the sole source of external information.

  PublisherOA PDFDOI

• Active Magnetic Control System for Gravity Gradient Stabilized Spacecraft

  2025-09-11 · 93 citations

  articleOpen accessSenior author

  Active magnetic control is studied as a means to improve the capabilities and performance of gravity gradient stabilized spacecraft. Active magnetic control eliminates the need for a passive damper and can reduce significantly the costs and complexity of other functional parts of the spacecraft. The system under study includes three magnetic torquers, one three-axis magnetometer, and a control processor. It does not require any moving parts, and provides for rapid libration damping, tighter stabilization and active control of the yaw angle. Control algorithms are defined. Results of the analysis of the control laws and computer simulations, including high-order models of the geomagnetic field and atmospheric disturbance torques, are presented. The algorithms perform well within a wide range of orbital inclinations and attitude angles and allow maneuverability and stabilization around the yaw axis. A Kalman Filter is used to provide estimates of the attitude angles, the angular rates, and a global disturbance torque, based on measurements from the magnetometer. Results of simulations, including the attitude estimator in the control loop, are presented. The possibility of a fully autonomous acquisition, deployment, and stabilization sequence using the magnetic control system is discussed.

  PublisherDOI

• Altitude Reconstitution of a Small Scientific Satellite using a Limited Set of On-Board Sensors

  Digital Commons - USU (Utah State University) · 2025-09-10

  articleOpen accessSenior author

  The ALEXIS spacecraft carries a limited set of attitude instruments on board. The scientific mission of ALEXIS requires "after the fact" knowledge of the spacecraft attitude at all times. Reconstitution of the attitude is performed as one of the permanent tasks of the microcomputer based ground station. ALEXIS carries a fine sun-sensor, an Infrared horizon crossing indicator and a magnetometer. Because of the orbital and attitude configurations horizon and sun will not be observed during sizable fractions of some orbits. The attitude will be estimated at all times by an extended fitter making use of whatever data is available. The state vector includes disturbance and misalignment terms. Fiber initialization uses the first available set of valid data from sun sensor and magnetometer, for a deterministic fix insuring rapid convergence. Magnetic field measurements provide a ceiling to the possible errors when the optical sensors are not operating, and can be used as back up. Detailed simulations of the filter were run to assess its performance. The simulations include major disturbance torques, misalignments, and earth oblateness effects. They show that the filter maintains knowledge of the attitude well within the mission data requirements. As a result, with a minimal amount of low cost instrumentation, without a star tracker on board, ALEXIS attitude and rates can be reconstituted for all times from a simple microcomputer based ground station. This illustrates a practical trade-off between hardware and software.

  PublisherOA PDFDOI

• Analysis of Time-Diverse Doppler-Only LEO PNT

  2025-04-28

  article

  Due to concerns over GNSS jamming and spoofing, this paper considers time-diverse Doppler-Only positioning as an alternative to GNSS. Without the use of time-diversity the Doppler-Only positioning solution requires at least eight satellites to be in view simultaneously and discards previous Doppler measurements. In cases where fewer than eight satellites are available, using Doppler measurements from multiple points in time allows a complete solution to be determined. In cases where eight or more are available, using additional time-samples can further improve positioning accuracy. This work further analyzes batch-filter and Kalman filter solutions proposed in prior work and proposes the use of the Backwards Smoothing Extended Kalman filter (BSEKF) to solve the positioning problem.

  PublisherDOI

• Using Optimal Estimation and Robust Curve-Fitting Tools to Enhance Predicted Earth Angular Momentum for Earth Orientation&amp;#160;

  2024-03-08

  preprintOpen access

  Previous investigations have shown the potential of enhancing the accuracy of estimates of the direction of the rotational pole and velocity of rotation of the Earth by using improved pre-processing (along with improved optimal estimation codes) of atmospheric and/or ocean angular momentum data. (These data are useful for prediction of the Earth orientation parameters because of conservation of the angular momentum in the Earth system).&amp;#160; Recent investigations have shown that predictions of UT1 &amp;#8211; UTC estimates can be improved by 45% for 1- day predictions and 30% for 7-day predictions. This poster is a continuation of previous efforts to investigate procedures to handle outliers in EOP input data using improved robust curve-fitting tools and improved optimal estimation tools.

  PublisherDOI

• Time-Diverse Doppler-only LEO PNT: Initial Solution

  Proceedings of the Satellite Division's International Technical Meeting (Online)/Proceedings of the Satellite Division's International Technical Meeting (CD-ROM) · 2024-10-09 · 2 citations

  article

  This paper develops Doppler-based Geometric Dilution of Precision (D-GDOP) analysis for time-diverse Doppler-only positioning and presents an associated batch filter. The former Doppler-only positioning solution requires at least eight satellites to be view simultaneously and discards previous Doppler measurements. In cases where fewer than eight satellites are available, using Doppler measurements from multiple points in time allows a complete solution to be determined. In cases where eight or more are available, using additional time-samples can further reduce D-GDOP and improve positioning accuracy. This work presents an initial batch filter solution that assumes constant velocity and constant clock-offset rate. By considering an additional 10 seconds of previous measurements, position and clock-offset errors were cut in half. However, because these assumptions are unrealistic for significant time spans this work also presents and tests an initial time-varying Kalman filter model and defines a D-GDOP metric for it.

  PublisherDOI

• GNSS Software-Defined Radio: History, Current Developments, and Standardization Efforts

  NAVIGATION Journal of the Institute of Navigation · 2024-01-01 · 30 citations

  articleOpen access

  <h3>Abstract</h3> Taking the work conducted by the global navigation satellite system (GNSS) software-defined radio (SDR) working group during the last decade as a seed, this contribution summarizes, for the first time, the history of GNSS SDR development. This report highlights selected SDR implementations and achievements that are available to the public or that influenced the general development of SDR. Aspects related to the standardization process of intermediate-frequency sample data and metadata are discussed, and an update of the Institute of Navigation SDR Standard is proposed. This work focuses on GNSS SDR implementations in general-purpose processors and leaves aside developments conducted on field programmable gate array and application-specific integrated circuit platforms. Data collection systems (<i>i.e</i>., front-ends) have always been of paramount importance for GNSS SDRs and are thus partly covered in this work. This report represents the knowledge of the authors but is not meant as a complete description of SDR history.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: NSWP--Scintillation-Scale Ionospheric Imaging using GPS and other RF Data in Inverse Diffraction Algorithms

  NSF · $237k · 2007–2012

Frequent coauthors

• Todd E. Humphreys

  36 shared

• Steven P. Powell

  35 shared

• P. M. Kintner

  32 shared

• Brady W. O’Hanlon

  28 shared

• B. M. Ledvina

  Coherent (United States)

  13 shared

• Shan Mohiuddin

  Draper Laboratory

  12 shared

• Jahshan A. Bhatti

  The University of Texas at Austin

  12 shared

• Joanna Hinks

  11 shared

Education

• Ph.D., Mechanical and Aerospace Engineering

  Princeton University

  1987

Awards & honors

• Fellow, Institute of Navigation 2014 - Present
• Tycho Brahe Award, Institute of Navigation 2013
• Burka Award, Institute of Navigation 2005
• Best Paper Awards, Four AIAA Guidance Navigation & Control C…