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Your search keyword '"Ely, Todd"' showing total 22 results
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22 results on '"Ely, Todd"'

1. Testing the gravitational redshift with an inner Solar System probe: the VERITAS case

Author

De Marchi, Fabrizio, Cascioli, Gael, Ely, Todd, Iess, Luciano, Burt, Eric A., Hensley, Scott, and Mazarico, Erwan

Subjects
General Relativity and Quantum Cosmology
Abstract

The NASA Discovery-class mission VERITAS, selected in June 2021, will be launched towards Venus after 2027. In addition to the science instrumentation that will build global foundational geophysical datasets, VERITAS proposed to conduct a technology demonstration for the Deep Space Atomic Clock (DSAC-2). A first DSAC successfully operated in low-Earth orbit for more than two years, demonstrated the trapped ion atomic clock technology, and established a new level of performance for clocks in space. DSAC-2 would have further improvements in size, power, and performance. It would host a $1\times{10}^{-13}$ grade USO to produce a frequency output with short-term stability of less than $2\times{10}^{-13}/\sqrt\tau$ (where $\tau$ is the averaging time). However, due to funding shortfalls, DSAC-2, had to be canceled. The initially foreseen presence of an atomic clock on board the probe, however, raised the question whether this kind of instrumentation could be useful not only for navigation and time transfer but also for fundamental physics tests. In this work, we consider the DSAC-2 atomic clock and VERITAS mission as a specific example to measure possible discrepancies in the redshift predicted by General Relativity by using an atomic clock onboard an interplanetary spacecraft. In particular we investigate the possibility of measuring possible violations of the Local Lorentz Invariance and Local Position Invariance principles. We perform accurate simulations of the experiment during the VERITAS cruise phase. We consider different parametrizations of the possible violations of the General Relativity, different operational conditions, and several different assumptions on the expected measurement performance. Our analysis shows the scientific value of atomic clocks like DSAC-2 hosted onboard interplanetary spacecraft., Comment: 15 pages, 9 figures

Published
2022
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2. Application of Shaken Lattice Interferometry Based Sensors to Space Navigation

Author

Rybak, Margaret R., Axelrad, Penina, LeDesma, Catie, Anderson, Dana Z., and Ely, Todd

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

High-sensitivity shaken lattice interferometry (SLI) based sensors have the potential to provide deep space missions with the ability to precisely measure non-gravitational perturbing forces. This work considers the simulation of the OSIRIS-REx mission navigation in the vicinity of Bennu with the addition of measurements from onboard SLI-based accelerometers. The simulation is performed in the Jet Propulsion Laboratory's (JPL) Mission Analysis, Operations and Navigation Toolkit (MONTE) and incorporates OSIRIS-REx reconstructed trajectory and attitude data from the Navigation and Ancillary Information Facility (NAIF) database. The use of the reconstructed data from NAIF provides realistic true dynamical errors and JPL's MONTE software allows for a high-fidelity simulation of a nominal reference for the filter. The navigation performance and reduction of tracking and complex modeling enabled by the onboard SLI-based sensor are presented for two orbital phases of the OSIRIS-REx mission. Overall, the results show that the addition of SLI-based accelerometer measurements improves navigation performance, when compared to a radiometric tracking only configuration. In addition, results demonstrate that highly-precise accelerometer measurements can effectively replace at least one day of DSN passes over a three-day period, thereby reducing tracking requirements. Furthermore, it is shown that lower-fidelity surface force modeling and parameter estimation is required when using onboard SLI-based accelerometers., Comment: 30 pages, 8 figures

Published
2022
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4. Comparison of Deep Space Navigation Using Optical Imaging, Pulsar Time-of-Arrival Tracking, and/or Radiometric Tracking

Author

Ely, Todd, Bhaskaran, Shyam, Bradley, Nicholas, Lazio, T. Joseph W., and Martin-Mur, Tomas

Subjects
Electrical Engineering and Systems Science - Systems and Control, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Electrical Engineering and Systems Science - Signal Processing
Abstract

Recent advances with space navigation technologies developed by NASA in space-based atomic clocks and pulsar X-ray navigation combined with past successes in autonomous navigation using optical imaging, brings to the forefront the need to compare space navigation using optical, radiometric, and pulsar-based measurements using a common set of assumptions and techniques. This review article examines these navigation data types in two different ways. First, a simplified deep space orbit determination problem is posed that captures key features of the dynamics and geometry, and then each data type is characterized for its ability to solve for the orbit. The data types are compared and contrasted using a semi-analytical approach with geometric dilution of precision techniques. The results provide useful parametric insights into the strengths of each data type. In the second part of the paper, a high-fidelity, Monte Carlo simulation of a Mars cruise, approach, and entry navigation problem is studied. The results found complement the semi-analytic results in the first part, and illustrate specific issues such as each data type's quantitative impact on solution accuracy and their ability to support autonomous delivery to a planet.

Published
2022
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7. Establishing an Agenda for Public Budgeting and Finance Research

Author

McDonald, Bruce, primary, Larson, Sarah, additional, Maher, Craig, additional, Kavanagh, Shayne, additional, Hunter, Kenneth, additional, Goodman, Christopher, additional, Minkowitz, Honey, additional, McCandless, Sean, additional, Afshan, Saman, additional, Jordan, Meagan, additional, Abbott, Michaela, additional, Afonso, Whitney, additional, Alibašić, Haris, additional, Allen, Joanne, additional, Allore, John, additional, Altizer, Laura, additional, Amador, Ralph, additional, An, Brian, additional, Andonoska, Ljubinka, additional, Anguelov, Lachezar, additional, Arapis, Theodore, additional, Arcand, Carolyn, additional, Atisa, George, additional, Bailey, Lonce, additional, Baker, Celeste, additional, Barnett, Brian, additional, Barsky, Christina, additional, Bartle, John, additional, Beck, David, additional, Beckett-Camarata, Jane, additional, Bednarczuk, Michael, additional, Beeninga, Toy, additional, Bellamy, Terry, additional, Bilmes, L. J., additional, Block, Carol, additional, Boyd, David, additional, Boyd, Kaelan, additional, Brien, Spencer, additional, Bronner, Kevin, additional, Brook, Douglas, additional, Brown, Marlon, additional, Brunjes, Benjamin, additional, Brunner, Eric, additional, Bunch, Beverly, additional, Calabrese, Thad, additional, Carr, Douglas, additional, Casciato, Michelle, additional, Certain, Crystal, additional, Charles, Cleopatra, additional, Chen, Can, additional, Chen, Gang, additional, Cherney, Debby, additional, Christian, Cary, additional, Clark, Benjamin, additional, Corbin, Shane, additional, Costie, Daniel, additional, Cournoyer, Jason, additional, Crosby, Andrew, additional, Cummins, Jeff, additional, Davis, Stephanie, additional, Decker, J. W., additional, DeShazo, Jessica, additional, Dimand, Ana Maria, additional, Donahue, Amy, additional, Douglas, James, additional, Dutcher, Janet, additional, Dzigbede, Komla, additional, Eger, Robert, additional, Ely, Todd, additional, Ermasova, Natalia, additional, Farmer, Liz, additional, Farmer, Lucianna, additional, Faulk, Dagney, additional, Finley, Drew, additional, Flink, Carla, additional, Ford, Michael, additional, Foth, Daniel, additional, Franklin, Aimee, additional, Franks, Mike, additional, Fudge, Marc, additional, Funderburg, Richard, additional, Gabrini, Carl, additional, Gadow, Bryan, additional, Gentry, David, additional, Godlewski, Chris, additional, Gooding, Suzanne, additional, Grandage, Andrew, additional, Greer, Robert, additional, Griffith, Christian, additional, Grogan, Amanda, additional, Hackbart, Merl, additional, Hatcher, William, additional, Hattery, Michael, additional, Hayes, Michael, additional, Hebert, Kellie, additional, Hendrick, Rebecca, additional, Hill, Edward, additional, Hiscocks, Susan, additional, Ho, Alfred, additional, Hoang, Trang, additional, Holbrook, Ellenore, additional, Hoppe, Mike, additional, Hou, Yilin, additional, Hudson, John, additional, Hudspeth, Nancy, additional, Huffman, Jackie, additional, Ivonchyk, Mikhail, additional, Jolley, G. Jason, additional, Jones, Peter, additional, Juffras, Jason, additional, Justice, Jonathan, additional, Kass, Amanda, additional, Kerns, Heidi, additional, Kim, Junghack, additional, Kim, Saerim, additional, Korn, Lynn, additional, Kriz, Arwi, additional, Krupa, Olha, additional, Lampman, Jennifer, additional, Landers, Jim, additional, Lane, Keith, additional, Lee, Jekyung, additional, Lee, Keith, additional, Lee, Sooho, additional, Leight, Matthew, additional, Leiser, Stephanie, additional, Moreta, Agustin, additional, Levine, Helisse, additional, Levitas, Tony, additional, Lim, Sungdae, additional, Lofton, Michelle, additional, Lozano-Rojas, Felipe, additional, Luby, Martin, additional, Lukongo, Onyumbe, additional, Mace, Jennifer, additional, Mahar, Kaitrin, additional, Martin, Joseph, additional, Matkin, David, additional, Mau, Rusty, additional, McAdoo, Arche, additional, McCann, Anthony, additional, Mead, Dean, additional, Medlin, Kirk, additional, Menifield, Charles, additional, Merritt, Justin, additional, Metro, John, additional, Meyers, Roy, additional, Mitchell, David, additional, Moeller, Thomas, additional, Mohr, Zachary, additional, Moldogaziev, Temirlan, additional, Morehead, Bryant, additional, Morrill, Chris, additional, Mughan, Sian, additional, Munro, Joyce, additional, Neubauer, Bruce, additional, Neuman, Melissa, additional, Nguyen-Hoang, Phuong, additional, Nicole, Marc, additional, Nordin, James, additional, Nukpezah, Julius, additional, O'Brien, Susan, additional, Oland, Amy, additional, Osteen, Julie, additional, Overholser, Amber, additional, Overton, Michael, additional, Park, Sungho, additional, Paschal, Jordan, additional, Pathak, Rahul, additional, Phaup, Marvin, additional, Pierson, Kawika, additional, Pope, Wendy, additional, Propheter, Geoffrey, additional, Redburn, Steve, additional, Reder, Lesley, additional, Reed, David, additional, Reitano, Vincent, additional, Riddle, Sam, additional, Rivenbark, William, additional, Rodriguez, Alejandro, additional, Romito, Mark, additional, Ross, Justin, additional, Rubin, Irene, additional, Sadler, Nicholas, additional, Sarpy, Nicholas, additional, Schafer, Josephine, additional, Schuhmann, Robert, additional, Searing, Elizabeth, additional, Sekwat, Alex, additional, Shybalkina, Iuliia, additional, Singla, Akheil, additional, Smith, Alex, additional, Smith, Christy, additional, Smith, Zachary, additional, Snow, Douglas, additional, Stanisevski, Dragan, additional, Stehle, Jon, additional, Stokan, Eric, additional, Stone, Samuel, additional, Swindell, David, additional, Taylor, Charles, additional, Taylor, Lori, additional, Vu, Tran, additional, Toland, Jay, additional, Topinka, John, additional, Trammell, Evelyn, additional, Trogen, Paul, additional, Van Eenoo, Ed, additional, Wadle, Elizabeth, additional, Wallace, Sally, additional, Wang, Shu, additional, Wassmer, Rob, additional, Weinstein, Paul, additional, Wells, Amy, additional, Wheeler, Laura, additional, Williams, Daniel, additional, Willoughby, Katherine, additional, Wilson, Darrin, additional, Winfree, Paul, additional, Wojda, Sharon, additional, Wooldridge, Blue, additional, Worsham, Paige, additional, Wright, Kristina, additional, Wynn, Stefen, additional, Xiao, Yan, additional, Xu, H., additional, Yang, Lang, additional, Yusuf, Wie, additional, Zemrani, Aziza, additional, Zhao, Zhirong, additional, and Zielke, Nancy, additional

Published
2024
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8. Convergence of Technologies Enabling Radio Crosslink Missions for Planetary Atmospheric Structures

Author

Asmar, Sami, primary, Akins, Alex, additional, Ao, Chi, additional, Baines, Kevin, additional, Burt, Eric, additional, Bocanegra-Bahamon, Tatiana, additional, Cutts, James, additional, Elliott, Harvey, additional, Ely, Todd, additional, Izraelevitz, Jacob, additional, Kobayashi, Michael, additional, Lazaro, Austin, additional, Lazio, Joseph, additional, Preston, Robert, additional, Vergados, Panagiotis, additional, Yi, Lin, additional, Iess, Luciano, additional, Cappuccio, Paolo, additional, Ando, Hiroki, additional, Imamura, Takeshi, additional, and Mayyasi, Majd, additional

Published
2024
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12. Deep Space Atomic Clock Technology Demonstration Mission Results

Author

Wang, Rabi, Stuart, Jeffrey, Seal, Ella, Robison, David, Murphy, David, Kuang, Da, Herrera, Randy, Enzer, Daphna, Dorsey, Angela, Burt, Eric, Tjoelker, Robert, Prestage, John, Seubert, Jill, and Ely, Todd A

Abstract

The Deep Space Atomic Clock (DSAC), a NASA Technology Demonstration Mission, was launched into low-Earth orbit on June 25, 2019 as a hosted payload aboard General Atomics’ Orbital Test Bed (OTB) spacecraft. The DSAC mission has been conducting a two-year demonstration of a mercury ion atomic clock to characterize its space-based performance and to validate its utility for deep space navigation and radio science. Analysis of the collected data using JPL’s GIPSY-OASIS software has shown DSAC’s AD at one-day to be near 310-15; much better than required AD of 210-14. Such low spacecraft clock errors will enable one-way radiometric tracking data with precision equivalent to or better than current-day two way tracking data, allowing a shift to a more efficient and flexible one-way deep space navigation architecture. To verify this, an analog deep space navigation experiment was performed using JPL’s operational navigation software (Monte). The experiment recovered orbit solutions with reduced data sets and geometric variations that are more representative of deep space missions, and showed that orbit determination using DSAC derived data is on par with more traditional two-way datatypes. As a technology demonstrator, DSAC’s development focus has been on maturing the mercury ion trap clock technology rather than achieving the smallest size, weight, and power (SWaP). Over the course of DSAC’s development the project has identified numerous improvements that could be made to significantly reduce SWaP for DSAC’s next version. Indeed, DSAC-2 was recently selected by NASA for further demonstration on the VERITAS mission to Venus. This work will review the DSAC technology, mission, and results from its two-year mission.

Published
2022

18. VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy): A Discovery Mission

Author

Smrekar, Sue, Hensley, Scott, Nybakken, Rick, Wallace, Mark S., Perkovic-Martin, Dragana, You, Tung-Han, Nunes, Daniel, Brophy, John, Ely, Todd, Burt, Eric, Dyar, Darby, Helbert, Jörn, Miller, Barry, Hartley, Jonathan, Kallemeyn, Piet, Whitten, Jennifer, Iess, Luciano, Mastrogiuseppe, Marco, Younis, Marwan, Prats, Pau, Rodriguez Cassola, Marc, and Mazarico, Erwan

Subjects
VERITAS, SAR
Published
2022

20. Deep Space Atomic Clock Technology Demonstration Mission Results

Author

Ely, Todd, primary, Prestage, John, additional, Tjoelker, Robert, additional, Burt, Eric, additional, Dorsey, Angela, additional, Enzer, Daphna, additional, Herrera, Randy, additional, Kuang, Da, additional, Murphy, David, additional, Robison, David, additional, Seal, Gabriella, additional, Stuart, Jeffrey, additional, Wang, Rabi, additional, and Seubert, Jill, additional

Published
2022
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22. How US Private Foundations Change Payouts Based on Financial Shocks: Revealed Publicness or Revealed Privateness?

Author

Calabrese, Thad D and Ely, Todd L

Subjects
UNITED States economic policy, UNITED States politics & government, BUSINESS cycle management, FINANCIAL management
Abstract

This article asks what distribution behavior of private foundations in the United States reveals about their motivations and strategy. Do private foundations intentionally distribute additional money to grantees to help them manage through business cycles and maintain services during economic downturns? Such behavior would be consistent with revealed publicness with respect to distributions. Do they retrench during difficult economic times to protect their endowments? Or do they simply distribute money independent from the larger economy? The current study considers these conflicting expectations, and empirically tests whether private foundation distributions vary with endowment returns and the larger economy as suggested by competing theories. Using administrative data filed with the Internal Revenue Service, fixed effects regression models indicate that private foundations change distributions in a manner consistent with retrenchment or independently from the larger economy, depending on the sample used. The results do not support the notion that private foundations act with prosocial-countercyclical motivations about distributions—in which more money is distributed during economic downturns—despite their receiving significant public subsidies. [ABSTRACT FROM AUTHOR]

Published
2022
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