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1. Spectroscopic Detection of the Pre-White Dwarf Companion of Regulus

Author

Gies, Douglas R., Lester, Kathryn V., Wang, Luqian, Couperus, Andrew, Shepard, Katherine, Neiner, Coralie, Wade, Gregg A., Dunham, David W., and Dunham, Joan B.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Mass transfer in an interacting binary will often strip the mass donor of its entire envelope and spin up the mass gainer to near critical rotation. The nearby B-type star Regulus represents a binary in the post-mass transfer stage: it is a rapid rotator with a very faint companion in a 40 d orbit. Here we present the results of a search for the spectral features of the stripped-down star in an extensive set of high S/N and high resolution spectra obtained with the CFHT/ESPaDOnS and TBL/NARVAL spectrographs. We first determine revised orbital elements in order to set accurate estimates of the orbital Doppler shifts at the times of observation. We then calculate cross-correlation functions of the observed and model spectra, and we search for evidence of the companion signal in the residuals after removal of the strong primary component. We detect a weak peak in the co-added residuals that has the properties expected for a faint pre-white dwarf. We use the dependence of the peak height and width on assumed secondary velocity semiamplitude to derive the semiamplitude, which yields masses of $M_1/M_\odot = 3.7 \pm 1.4$ and $M_2/M_\odot = 0.31 \pm 0.10$ (assuming orbital inclination equals the spin inclination of Regulus). We estimate the pre-white dwarf temperature $T_{\rm eff} = (20 \pm 4)$~kK through tests with differing temperature model spectra, and we find the radius $R_2/R_\odot = 0.061 \pm 0.011$ from the component temperatures and the flux ratio associated with the amplitude of the signal in the cross-correlation residuals., Comment: Accepted for publication in ApJ

Published
2020
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2. Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

Author

Buie, Marc W., Porter, Simon B., Tamblyn, Peter, Terrell, Dirk, Parker, Alex Harrison, Baratoux, David, Kaire, Maram, Leiva, Rodrigo, Verbiscer, Anne J., Zangari, Amanda M., Colas, François, Diop, Baïdy Demba, Samaniego, Joseph I., Wasserman, Lawrence H., Benecchi, Susan D., Caspi, Amir, Gwyn, Stephen, Kavelaars, J. J., Uría, Adriana C. Ocampo, Rabassa, Jorge, Skrutskie, M. F., Soto, Alejandro, Tanga, Paolo, Young, Eliot F., Stern, S. Alan, Andersen, Bridget C., Pérez, Mauricio E. Arango, Arredondo, Anicia, Artola, Rodolfo Alfredo, Bâ, Abdoulaye, Ballet, Romuald, Blank, Ted, Bop, Cheikh Tidiane, Bosh, Amanda S., López, Matías Aarón Camino, Carter, Christian M., Castro-Chacón, J. H., Desprez, Alfonso Caycedo, Guerra, Nicolás Caycedo, Conard, Steven J., Dauvergne, Jean-Luc, Dean, Bryan, Dean, Michelle, Desmars, Josselin, Dieng, Abdou Lahat, Dieng, Mame Diarra Bousso, Diouf, Omar, Dorego, Gualbert Séraphin, Dunham, David W., Dunham, Joan, Luca, Hugo A. Durantini, Edwards, Patrick, Erasmus, Nicolas, Faye, Gayane, Faye, Mactar, Ferrario, Lucas Ezequiel, Ferrell, Chelsea L., Finley, Tiffany J., Fraser, Wesley C., Friedli, Alison J., Serna, Julián Galvez, Garcia-Migani, Esteban A., Genade, Anja, Getrost, Kai, Gil-Hutton, Ricardo A., Gimeno, German N., Golub, Eli Joseph, Murillo, Giovanni Francisco González, Grusin, Michael D., Gurovich, Sebastian, Hanna, William H., Henn, Santiago M., Hinton, P. C., Hughes, Paul J., Josephs Jr, John David, Joya, Raul, Kammer, Joshua A., Keeney, Brian A., Keller, John M., Kramer, Emily A., Levine, Stephen E., Lisse, Carey M., Lovell, Amy J., Mackie, Jason A., Makarchuk, Stanislav, Manzano, Luis E., Mbaye, Salma Sylla, Mbaye, Modou, Melia, Raul Roberto, Moreno, Freddy, Moss, Sean K., Ndaiye, Diene, Ndiaye, Mapathe, Nelson, Matthew J., Olkin, Catherine B., Olsen, Aart M., Moreno, Victor Jonathan Ospina, Pasachoff, Jay M., Pereyra, Mariana Belen, Person, Michael J., Pinzón, Giovanni, Pulver, Eduardo Alejandro, Quintero, Edwin A., Regester, Jeffrey R., Resnick, Aaron Caleb, Reyes-Ruiz, Mauricio, Rolfsmeier, Alex D., Ruhland, Trina R., Salmon, Julien, Santos-Sanz, Pablo, Santucho, Marcos Ariel, Niño, Diana Karina Sepúlveda, Sickafoose, Amanda A., Silva, José S., Singer, Kelsi N., Skipper, Joy N., Slivan, Stephen M., Smith, Rose J. C., Spagnotto, Julio C., Stephens, Andrew W., Strabala, Samuel D., Tamayo, Francisco J., Throop, Henry B., Cañas, Andrés David Torres, Toure, Labaly, Traore, Alassane, Tsang, Constantine C. C., Turner, Jake D., Vanegas, Santiago, Venable, Roger, Wilson, John C., Zuluaga, Carlos A., and Zuluaga, Jorge I.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by SOFIA with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 Aug 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 $\pm$ 0.0005 hours. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies., Comment: Submitted to Astronomical Journal (revised); 40 pages, 13 figures, 9 tables

Published
2019
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3. Size and Shape of (11351) Leucus from Five Occultations

Author

Buie, Marc W., primary, Keeney, Brian A., additional, Strauss, Ryder H., additional, Blank, Ted E., additional, Moore, John G., additional, Porter, Simon B., additional, Wasserman, Lawrence H., additional, Weryk, Robert J., additional, Levison, Harold F., additional, Olkin, Catherine B., additional, Leiva, Rodrigo, additional, Bardecker, Jerry E., additional, Brown, Michael E, additional, Brown, Lilah B, additional, Collins, Michael P., additional, Davidson, Hugh M., additional, Dunham, David W., additional, Dunham, Joan B., additional, Eaccarino, John A., additional, Finley, Tiffany J., additional, Fuller, Lindsay, additional, Garcia, Maria L., additional, George, Tony, additional, Getrost, Kai, additional, Gialluca, Megan, T., additional, Givot, Rima M., additional, Gupton, David, additional, Hanna, William H., additional, Hergenrother, Carl William, additional, Hernandez, Yamir, additional, Hill, Bryan, additional, Hinton, P. C., additional, Holt, Timothy R., additional, Howell, Robert R, additional, Jewell, Jack Lee, additional, Kamin, Roxanne L., additional, Kammer, Joshua A., additional, Kareta, Theodore, additional, Kayl, Gregory J., additional, Keller, John M., additional, Kenyon, David A., additional, Kester, Scott R., additional, Kidd, John N., additional, Lauer, Tod R., additional, Leung, Cecilia W. S., additional, Lorusso, Zoey R., additional, Lundgren, Christopher B., additional, Magana, Lizeth O., additional, Maley, Paul D., additional, Marchis, Franck, additional, Marcialis, Robert L., additional, McCandless, Andrew E., additional, McCrystal, Delsie Joy, additional, McGraw, Allison Marie, additional, Miller, Kelly E., additional, Mueller, Beatrice E. A., additional, Noonan, J. W., additional, Olsen, Aart M., additional, Patton, Alexander R., additional, O’Conner Peluso, Daniel, additional, Person, Michael J., additional, Rigby, James G., additional, Rolfsmeier, Alex D, additional, Salmon, Julien J., additional, Samaniego, Joseph, additional, Sawyer, R. P., additional, Schulz, David M., additional, Skrutskie, Michael F, additional, Smith, Rose J. C., additional, Spencer, John R., additional, Springmann, Alessondra, additional, Stanbridge, Dale R., additional, Stoffel, Timothy J, additional, Tamblyn, Peter, additional, Tobias, Bryan, additional, Verbiscer, Anne J., additional, von Schalscha, Michael P., additional, Werts, Holly, additional, and Zhang, Qicheng, additional

Published
2021
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4. Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

Author

European Research Council, European Commission, National Aeronautics and Space Administration (US), Centre National de la Recherche Scientifique (France), Ministerio de Ciencia, Innovación y Universidades (España), German Centre for Air and Space Travel, Department of Energy (US), National Science Foundation (US), Australian National University, Buie, Marc W., Porter, Simon B., Tamblyn, Peter, Terrell, Dirk, Parker, Alex Harrison, Baratoux, David, Kaire, Maram, Leiva, Rodrigo, Verbiscer, Anne J., Zangari, Amanda M., Colas, François, Tamayo, Francisco J., Throop, Henry B., Torres Cañas, Andrés David, Toure, Labaly, Traore, Alassane, Tsang, Constantine C. C., Turner, Jake D., Vanegas, Santiago, Venable, Roger, Wasserman, Lawrence H., Camino López, Matías Aarón, Wilson, John C., Zuluaga, Carlos A., Zuluaga, Jorge I., Benecchi, Susan D., Caspi, Amir, Gwyn, Stephen, Kavelaars, J. J., Ocampo Uría, Adriana C., Rabassa, Jorge, Skrutskie, M. F., Carter, Christian M., Soto, Alejandro, Tanga, Paolo, Young, Eliot F., Stern, S. Alan, Andersen, Bridget C., Arango Pérez, Mauricio E., Arredondo, Anicia, Artola, Rodolfo Alfredo, Bâ, Abdoulaye, Ballet, Romuald, Castro-Chacón, J. H., Blank, Ted, Bop, Cheikh Tidiane, Bosh, Amanda S., Caycedo Desprez, Alfonso, Caycedo Guerra, Nicolás, Conard, Steven J., Dauvergne, Jean-Luc, Dean, Bryan, Dean, Michelle, Desmars, Josselin, González Murillo, Giovanni Francisco, Dieng, Abdou Lahat, Bousso Dieng, Mame Diarra, Diouf, Omar, Dorego, Gualbert Séraphin, Dunham, David W., Dunham, Joan, Durantini Luca, Hugo A., Edwards, Patrick, Erasmus, Nicolas, Faye, Gayane, Grusin, Michael D., Faye, Mactar, Ferrario, Lucas Ezequiel, Ferrell, Chelsea L., Finley, Tiffany J., Fraser, Wesley C., Friedli, Alison J., Galvez Serna, Julián, Garcia-Migani, Esteban A., Genade, Anja, Getrost, Kai, Gurovich, Sebastian, Gil-Hutton, Ricardo A., Gimeno, German N., Golub, Eli Joseph, Hanna, William H., Henn, Santiago M., Hinton, P. C., Hughes, Paul J., Josephs, John David, Jr., Joya, Raul, Kammer, Joshua A., Pinzón, Giovanni, Keeney, Brian A., Keller, John M., Kramer, Emily A., Levine, Stephen E., Lisse, Carey M., Lovell, Amy J., Mackie, Jason A., Makarchuk, Stanislav, Manzano, Luis E., Mbaye, Salma Sylla, Pulver, Eduardo Alejandro, Mbaye, Modou, Melia, Raul Roberto, Moreno, Freddy, Moss, Sean K., Ndaiye, Diene, Ndiaye, Mapathe, Nelson, Matthew J., Olkin, Catherine B., Olsen, Aart M., Ospina Moreno, Victor Jonathan, Quintero, Edwin A., Pasachoff, Jay M., Pereyra, Mariana Belen, Person, Michael J., Regester, Jeffrey R., Resnick, Aaron Caleb, Reyes-Ruiz, Mauricio, Rolfsmeier, Alex D., Ruhland, Trina R., Salmon, Julien, Santos Sanz, Pablo, Diop, Baidy Demba, Santucho, Marcos Ariel, Sepúlveda Niño, Diana Karina, Sickafoose, Amanda A., Silva, José S., Singer, Kelsi N., Skipper, Joy N., Slivan, Stephen M., Smith, Rose J. C., Spagnotto, Julio C., Stephens, Andrew W., Samaniego, Joseph I., Strabala, Samuel D., European Research Council, European Commission, National Aeronautics and Space Administration (US), Centre National de la Recherche Scientifique (France), Ministerio de Ciencia, Innovación y Universidades (España), German Centre for Air and Space Travel, Department of Energy (US), National Science Foundation (US), Australian National University, Buie, Marc W., Porter, Simon B., Tamblyn, Peter, Terrell, Dirk, Parker, Alex Harrison, Baratoux, David, Kaire, Maram, Leiva, Rodrigo, Verbiscer, Anne J., Zangari, Amanda M., Colas, François, Tamayo, Francisco J., Throop, Henry B., Torres Cañas, Andrés David, Toure, Labaly, Traore, Alassane, Tsang, Constantine C. C., Turner, Jake D., Vanegas, Santiago, Venable, Roger, Wasserman, Lawrence H., Camino López, Matías Aarón, Wilson, John C., Zuluaga, Carlos A., Zuluaga, Jorge I., Benecchi, Susan D., Caspi, Amir, Gwyn, Stephen, Kavelaars, J. J., Ocampo Uría, Adriana C., Rabassa, Jorge, Skrutskie, M. F., Carter, Christian M., Soto, Alejandro, Tanga, Paolo, Young, Eliot F., Stern, S. Alan, Andersen, Bridget C., Arango Pérez, Mauricio E., Arredondo, Anicia, Artola, Rodolfo Alfredo, Bâ, Abdoulaye, Ballet, Romuald, Castro-Chacón, J. H., Blank, Ted, Bop, Cheikh Tidiane, Bosh, Amanda S., Caycedo Desprez, Alfonso, Caycedo Guerra, Nicolás, Conard, Steven J., Dauvergne, Jean-Luc, Dean, Bryan, Dean, Michelle, Desmars, Josselin, González Murillo, Giovanni Francisco, Dieng, Abdou Lahat, Bousso Dieng, Mame Diarra, Diouf, Omar, Dorego, Gualbert Séraphin, Dunham, David W., Dunham, Joan, Durantini Luca, Hugo A., Edwards, Patrick, Erasmus, Nicolas, Faye, Gayane, Grusin, Michael D., Faye, Mactar, Ferrario, Lucas Ezequiel, Ferrell, Chelsea L., Finley, Tiffany J., Fraser, Wesley C., Friedli, Alison J., Galvez Serna, Julián, Garcia-Migani, Esteban A., Genade, Anja, Getrost, Kai, Gurovich, Sebastian, Gil-Hutton, Ricardo A., Gimeno, German N., Golub, Eli Joseph, Hanna, William H., Henn, Santiago M., Hinton, P. C., Hughes, Paul J., Josephs, John David, Jr., Joya, Raul, Kammer, Joshua A., Pinzón, Giovanni, Keeney, Brian A., Keller, John M., Kramer, Emily A., Levine, Stephen E., Lisse, Carey M., Lovell, Amy J., Mackie, Jason A., Makarchuk, Stanislav, Manzano, Luis E., Mbaye, Salma Sylla, Pulver, Eduardo Alejandro, Mbaye, Modou, Melia, Raul Roberto, Moreno, Freddy, Moss, Sean K., Ndaiye, Diene, Ndiaye, Mapathe, Nelson, Matthew J., Olkin, Catherine B., Olsen, Aart M., Ospina Moreno, Victor Jonathan, Quintero, Edwin A., Pasachoff, Jay M., Pereyra, Mariana Belen, Person, Michael J., Regester, Jeffrey R., Resnick, Aaron Caleb, Reyes-Ruiz, Mauricio, Rolfsmeier, Alex D., Ruhland, Trina R., Salmon, Julien, Santos Sanz, Pablo, Diop, Baidy Demba, Santucho, Marcos Ariel, Sepúlveda Niño, Diana Karina, Sickafoose, Amanda A., Silva, José S., Singer, Kelsi N., Skipper, Joy N., Slivan, Stephen M., Smith, Rose J. C., Spagnotto, Julio C., Stephens, Andrew W., Samaniego, Joseph I., and Strabala, Samuel D.

Abstract

We present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies. © 2020. The American Astronomical Society. All rights reserved.

Published
2020

7. Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

Author

Buie, Marc W., primary, Porter, Simon B., additional, Tamblyn, Peter, additional, Terrell, Dirk, additional, Parker, Alex Harrison, additional, Baratoux, David, additional, Kaire, Maram, additional, Leiva, Rodrigo, additional, Verbiscer, Anne J., additional, Zangari, Amanda M., additional, Colas, François, additional, Diop, Baidy Demba, additional, Samaniego, Joseph I., additional, Wasserman, Lawrence H., additional, Benecchi, Susan D., additional, Caspi, Amir, additional, Gwyn, Stephen, additional, Kavelaars, J. J., additional, Ocampo Uría, Adriana C., additional, Rabassa, Jorge, additional, Skrutskie, M. F., additional, Soto, Alejandro, additional, Tanga, Paolo, additional, Young, Eliot F., additional, Stern, S. Alan, additional, Andersen, Bridget C., additional, Arango Pérez, Mauricio E., additional, Arredondo, Anicia, additional, Artola, Rodolfo Alfredo, additional, Bâ, Abdoulaye, additional, Ballet, Romuald, additional, Blank, Ted, additional, Bop, Cheikh Tidiane, additional, Bosh, Amanda S., additional, Camino López, Matías Aarón, additional, Carter, Christian M., additional, Castro-Chacón, J. H., additional, Caycedo Desprez, Alfonso, additional, Caycedo Guerra, Nicolás, additional, Conard, Steven J., additional, Dauvergne, Jean-Luc, additional, Dean, Bryan, additional, Dean, Michelle, additional, Desmars, Josselin, additional, Dieng, Abdou Lahat, additional, Bousso Dieng, Mame Diarra, additional, Diouf, Omar, additional, Dorego, Gualbert Séraphin, additional, Dunham, David W., additional, Dunham, Joan, additional, Durantini Luca, Hugo A., additional, Edwards, Patrick, additional, Erasmus, Nicolas, additional, Faye, Gayane, additional, Faye, Mactar, additional, Ferrario, Lucas Ezequiel, additional, Ferrell, Chelsea L., additional, Finley, Tiffany J., additional, Fraser, Wesley C., additional, Friedli, Alison J., additional, Galvez Serna, Julián, additional, Garcia-Migani, Esteban A., additional, Genade, Anja, additional, Getrost, Kai, additional, Gil-Hutton, Ricardo A., additional, Gimeno, German N., additional, Golub, Eli Joseph, additional, González Murillo, Giovanni Francisco, additional, Grusin, Michael D., additional, Gurovich, Sebastian, additional, Hanna, William H., additional, Henn, Santiago M., additional, Hinton, P. C., additional, Hughes, Paul J., additional, Josephs Jr, John David, additional, Joya, Raul, additional, Kammer, Joshua A., additional, Keeney, Brian A., additional, Keller, John M., additional, Kramer, Emily A., additional, Levine, Stephen E., additional, Lisse, Carey M., additional, Lovell, Amy J., additional, Mackie, Jason A., additional, Makarchuk, Stanislav, additional, Manzano, Luis E., additional, Mbaye, Salma Sylla, additional, Mbaye, Modou, additional, Melia, Raul Roberto, additional, Moreno, Freddy, additional, Moss, Sean K., additional, Ndaiye, Diene, additional, Ndiaye, Mapathe, additional, Nelson, Matthew J., additional, Olkin, Catherine B., additional, Olsen, Aart M., additional, Ospina Moreno, Victor Jonathan, additional, Pasachoff, Jay M., additional, Pereyra, Mariana Belen, additional, Person, Michael J., additional, Pinzón, Giovanni, additional, Pulver, Eduardo Alejandro, additional, Quintero, Edwin A, additional, Regester, Jeffrey R., additional, Resnick, Aaron Caleb, additional, Reyes-Ruiz, Mauricio, additional, Rolfsmeier, Alex D., additional, Ruhland, Trina R., additional, Salmon, Julien, additional, Santos-Sanz, Pablo, additional, Santucho, Marcos Ariel, additional, Sepúlveda Niño, Diana Karina, additional, Sickafoose, Amanda A., additional, Silva, José S., additional, Singer, Kelsi N., additional, Skipper, Joy N., additional, Slivan, Stephen M., additional, Smith, Rose J. C., additional, Spagnotto, Julio C., additional, Stephens, Andrew W., additional, Strabala, Samuel D., additional, Tamayo, Francisco J., additional, Throop, Henry B., additional, Torres Cañas, Andrés David, additional, Toure, Labaly, additional, Traore, Alassane, additional, Tsang, Constantine C. C., additional, Turner, Jake D., additional, Vanegas, Santiago, additional, Venable, Roger, additional, Wilson, John C., additional, Zuluaga, Carlos A., additional, and Zuluaga, Jorge I., additional

Published
2020
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8. Contingency Support Simulation for the Tracking and Data Relay Satellite System (TDRSS)

Author

Dykes, Andy, Dunham, Joan, Ward, Douglas T, Robertson, Mika, and Nesbit, Gary

Subjects
Spacecraft Design, Testing And Performance
Abstract

In March 2006, the Tracking and Data Relay Satellite (TDRS)-3 experienced an unexpected thrusting event, which caused significant changes to its orbit. Recovery from this anomaly was protracted, raising concerns during the Independent Review Team (IRT) investigation of the anomaly regarding the contingency response readiness. The simulations and readiness exercises discussed in this paper were part of the response to the IRT concerns. This paper explains the various levels of simulation needed to enhance the proficiency of the Flight Dynamics Facility (FDF) and supporting elements in recovery from a TDRS contingency situation. The main emergency to address is when a TDRS has experienced uncommanded, unreported, or misreported thrusting, causing a ground station to lose the ability to acquire the spacecraft, as happened in 2006. The following levels of simulation are proposed: 1) Tests that would be performed by the individual support sites to verify that internal procedures and tools are in place and up to date; 2) Tabletop simulations that would involve all of the key support sites talking through their respective operating procedures to ensure that proper notifications are made and communications links are established; and 3) Comprehensive simulations that would be infrequent, but realistic, involving data exchanges between ground sites and voice and electronic communications among the supporting elements.

Published
2007

9. COBE navigation with one-way return-link Doppler in the post-helium-venting phase

Author

Dunham, Joan, Nemesure, M, Samii, M. V, Maher, M, Teles, Jerome, and Jackson, J

Subjects
Astrodynamics
Abstract

The results of a navigation experiment with one way return link Doppler tracking measurements for operational orbit determination of the Cosmic Background Explorer (COBE) spacecraft are presented. The frequency of the tracking signal for the one way measurements was stabilized with an Ultrastable Oscillator (USO), and the signal was relayed by the Tracking and Data Relay Satellite System (TDRSS). The study achieved three objectives: space qualification of TDRSS noncoherent one way return link Doppler tracking; determination of flight performance of the USO coupled to the second generation TDRSS compatible user transponder; and verification of algorithms for navigation using actual one way tracking data. Orbit determination and the inflight USO performance evaluation results are presented.

Published
1991

10. The size and shape of (2) Pallas from the 1983 occultation of 1 Vulpeculae

Author

Dunham, David W, Dunham, Joan Bixby, Binzel, Richard P, Evans, David S, and Freuh, Marian

Subjects
Astronomy
Abstract

The analysis and results of an occultation of the spectroscopic binary star 1 Vulpeculae by the asteroid (2) Pallas, observed from 130 locations, are presented. Combination of solutions from this and previous occultations shows the triaxial shape of Pallas to be elongated, but not severely, with the ratio of the largest to the smallest axes being less than 1.15. The data provide a separation and a position angle of the secondary component of 1 Vulpeculae and indicate that the star's actual parallax is probably near 0.008 arcsec, half of the published value. The analysis gives a calibration of the accuracy and the reaction time corrections for visual observations of asteroidal occultations. The absence of any confirmed secondary extinctions shows that any satellites of Pallas must be rare or small. The photometric observations seem to rule out a substantial cloud of dust surrounding Pallas postulated previously.

Published
1990
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11. After six decades, his fate is known

Author

Dunham, Joan

Subjects
United States. Army. Air Forces, General interest, News, opinion and commentary
Abstract

Byline: JOAN DUNHAM More than 61 years ago, in November 1944, the family of Army Air Forces 2nd Lt. John H. Dunham received the devastating news that their 21-year-old husband, [...]

Published
2006

14. Once a playground, now a memory

Author

Dunham, Joan

Subjects
General interest, News, opinion and commentary
Abstract

Byline: JOAN DUNHAM The Field is no more. Huge yellow machines moved in to rip the roots of the Brazilian pepper trees from the black earth, soil enriched by decades [...]

Published
2001

17. Astronomical Algorithms

Author

Dunham, Joan Bixby

Subjects
Astronomical Algorithms (Book) -- Book reviews, Books -- Book reviews
Published
1992

20. An Angry Reader.

Author

Dunham, Joan Bixby

Subjects
LETTERS to the editor, TECHNOLOGY
Abstract

A letter to the editor is presented in response to the articles "The Tree of Science: Beautiful Blossoms But Bitter Fruits," and "A Comment on 'Los Angeles and Its Mistress Machine'" that was published in the February issue of "Bulletin of the Atomic Scientists."

Published
1974

21. Letters

Author

Cassel, Hans M., primary, Dunham, Joan Bixby, additional, Olson, Robert L., additional, and Sauberman, N. H., additional

Published
1974
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