Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session L1: Poster Session II |
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Sponsoring Units: APS Room: Hyatt Regency Jacksonville Riverfront Terrace Pavilion, 2:00pm - 5:00pm |
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L1.00001: UNDERGRADUATE RESEARCH |
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L1.00002: Substorm Energy Deposition and Correlation with Substorm Characteristics Christine Gabrielse, Ami M. DuBois, Patricia Gavin, Ian Swanson, Sandra Brogl, Ramon Lopez The total energy deposition of various substorms was determined from Polar UVI Substorm Movies, provided by NASA and APL, using the Lyman-Birge{\_}Hopfield-Long (LBHL) filter which mapped the total energy flux over latitudes above 60 degrees North. Because the movies run in two dimensions, it was necessary to form a model to project an image's total area of energy deposition from lying on a circle to lying on a sphere. Several relationships were then ascertained. There is a direct relationship between an onset's peak auroral electrojet (AE) index and the total energy deposition at that point in time. It was discovered, however, that this relationship does not continue throughout a substorm's lifetime. It is therefore inappropriate to state that a substorm's total energy deposition is directly related to its AE index at any point in time. There is also a relationship, though less notable, between the total energy deposition at the onset peak and the latitude at which the substorm began. These latitudes do not vary by much, though, and are generally between 65 and 70 degrees north. [Preview Abstract] |
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L1.00003: Latitude of Poleward Expansion versus Auroral Electrojet Maximum of Isolated Substorms Ami M. DuBois, Christine Gabrielse, Patricia Gavin, Ian Swanson, Sandra Brogl, Ramon Lopez A substorm is a short magnetospheric disturbance lasting only a few hours. We are using the UVI substorm movies provided by the POLAR satellite to find if there is a correlation between the intensity of a substorm and how far north auroras move from the initial magnetic latitude onset. We downloaded the auroral electrojet (AE) data for each movie that was an isolated substorm and which occurred at anytime other than between 1400 UT and 1900 UT. For the Polar movie that corresponds to the substorm we identified the latitudes at which the onset of the aurora and the maximum northern point of the aurora occur. The onset is the point at which the aurora begins to intensify or expand to greater latitudes. Since the aurora expands southward as well as northward, we also measure maximum southern point of the aurora. From here, we compare the latitude of the maximum northern point the aurora reached, the difference in latitude between the onset of the aurora and the northern most point, the latitude of the onset of the aurora, and the difference in latitude between the northern most and southern most points of the aurora all to the peak strength of the substorm and plot the results. From the preliminary results, we found there was a correlation between the latitude of onset and other quantities. We will discuss the implications of this result for energy storage and the size of substorms. [Preview Abstract] |
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L1.00004: Comparing Single- and Multiple-Onset Isolated Substorms Patricia Gavin, Ami DuBois, Christine Gabrielse, Ian Swanson, Sandra Brogl, Ramon Lopez Using AE data, we have identified 218 isolated substorms whose initial onset was over North America (between 0300UT and 0800UT). We constructed a data table that contained each substorms' onset time, strength in AE, duration, and whether or not the substorm was a multiple-onset or a single-onset substorm. We have examined the statistics of these events, in particular comparing single-onset and multiple-onset substorms. Preliminary results indicate that the distributions of strengths as determined by AE of both single- and multiple-onset substorms are very similar. Further investigations will determine if there are relationships between a substorm's maximum strength and duration, and what factors, such as the strength of the first onset in a multiple-onset substorm, affect those characteristics. [Preview Abstract] |
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L1.00005: A Comparison of Integrated Electric Field with Substorm Activity Jennifer Kissinger, Tamara Cullens, Alicia Moss, Robert Bruntz, Ramon Lopez When the interplanetary magnetic field (IMF) in the solar wind suddenly turns northward after pointing southward for $\sim $1-2 hours, a substorm is usually triggered. A study was undertaken to compare strength and duration of substorms to electric field input prior to the onset into the Earth's magnetosphere. Periods for which the IMF pointed southward for 1-2 hours and then rapidly turned northward (i.e., when the Bz component of the solar wind is negative and turns positive) were found using the ACE satellite data available through CDAWeb. Using Ey=VxBz, the electric field data was integrated to determine an estimate of the solar wind input during these periods. The integrated electric field will be compared directly to substorm data to check for correlations between solar wind input and magnetospheric output. [Preview Abstract] |
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L1.00006: Characteristics of untriggered substorms Ian Swanson, Ami M. DuBois, Christine Gabrielse, Patricia Gavin, Sandra Brogl, Ramon Lopez It is generally believed that most substorms have some kind of trigger such as a northward turn in the interplanetary magnetic field (IMF). We have identified over 200 isolated substorms in the North American sector from 1998-2002 based on the auroral electrojet index (AE). From this set of events, we have identified several that do not seem to have a solar wind trigger. In this presentation, we will discuss the characteristics of these events and contrast them to several events that seem to have a trigger. [Preview Abstract] |
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L1.00007: Running Down the Magnetosphere: Energy Dissipation After the IMF Turns Northward Alicia Moss, Tamara Cullens, Jennifer Kissinger, Robert Bruntz, Ramon Lopez We have been studying the effect on Earth's magnetosphere of sudden changes in the direction of the interplanetary magnetic field (IMF). In particular, we have studied the effect of a sustained south to north rotation of the IMF in the dissipation of energy in the magnetosphere. When the solar wind in the magnetic field turns northward, energy input from the solar wind stops. We have identified several such cases. We used the Auroral Electrojet index (AE) and the Polar Cap index (PCI) to characterize the amount of energy being dissipated in the ionosphere from Joule heating. This allows us to determine how long it takes energy in the magnetosphere to be dissipated after the energy source turns off. [Preview Abstract] |
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L1.00008: PHYSICS EDUCATION/RESEARCH |
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L1.00009: Fabrication and Microwave Properties of Arrays of Nanorods with Varying Aspect Ratios Zachary Davis, Nicolas Smallwood, Andriy Vovk, Minghui Yu, Leszek Malkinski Nanorods have been shown to absorb varying wavelengths of microwaves based on the aspect ratio of the rods. We have successfully fabricated these arrays and measured the absorption associated with these arrays using ferromagnetic resonance (FMR). Measurements show that we have achieved an absorption range of about 300 Oersteds (fig. 10). [Preview Abstract] |
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L1.00010: Charge Conservation in $RC$ Circuits H. L. Neal Students of introductory physics are well aware of the time constant of an $RC$ circuit. But what if not all of the capacitors in the circuit are initially charged? This situation is not adequately discussed in textbooks. We give an analysis that emphasizes the role of charge conservation in the circuit. [Preview Abstract] |
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L1.00011: GRAVITATION |
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L1.00012: Radio Imaging of the Gravity Probe B Guide Star IM Pegasi Michael Bietenholz, Ryan Ransom, Norbert Bartel, Daniel Lebach, Michael Ratner, Irwin Shapiro, Jean-Francois Lestrade We report on very-long-baseline interferometry (VLBI) observations of IM~Pegasi (HR~8703), the star used as a guide star for the NASA/Stanford gyroscope relativity mission, Gravity Probe~B\@. We carried out VLBI observations at 35 epochs between January 1997 and July 2005, at a frequency of 8.4~GHz. The observations were all phase-referenced to the distant quasar 3C454.3. We present a selection of radio-images of IM~Pegasi, which show radio source structures that vary in size from less than 1 to about 3 milliarcseconds. The morphology varies in a seemingly random fashion---the source was sometimes essentially unresolved, and at other times had either a core-halo, a double, or perhaps even a triple structure. Moreover, images from temporal subsets of several observing sessions exhibit structural evolution on hour time scales. We discuss the observed source structures, and whether they allow us to locate the region(s) emitting the radio radiation. Finally, we examine the implications of the radio morphology for the GP-B mission. [Preview Abstract] |
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L1.00013: The ``Core'' of the Quasar 3C454.3 as the Extragalactic Reference for the Proper Motion of the Gravity Probe~B Guide Star Norbert Bartel, Ryan Ransom, Michael Bietenholz, Jerusha Lederman, Daniel Lebach, Michael Ratner, Irwin Shapiro, Leonid Petrov We used very-long-baseline interferometry (VLBI) radio observations at 8.4~GHz between 1997 and 2005 to determine the coordinates of the ``core'' of the quasar, 3C454.3, relative to two other extragalactic sources, B2250+194 and B2252+172, nearby on the sky. The core of 3C454.3 is stationary relative to these two sources, with the 1$\sigma$ upper limit on its proper motion being 25~$\mu$as~yr$^{-1}$ in right ascension and 35~$\mu$as~yr$^{-1}$ in declination. The corresponding upper limit on the proper motion of this core with respect to the quasi-inertial reference frame determined from separate VLBI observations of many extragalactic radio sources, including B2250+194, is of similar magnitude. The core of 3C454.3 provides a sufficiently stable reference with which to measure the proper motion of the Gravity Probe B guide star, IM Pegasi, relative to the distant universe. [Preview Abstract] |
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L1.00014: Performance of the Gravity Probe B Inertial Reference Telescope Suwen Wang, John Goebel, John Lipa, John Turneaure Gravity Probe B uses a cryogenic optical telescope as an inertial reference system for the gyroscopes and as a sensor for the pitch and yaw part of the attitude control of the spacecraft. The telescope was made primarily of fused quartz that was bonded together using a potassium hydroxide bonding technique developed for the program. Roof prisms located at the telescope focal plane were used to divide the guide star image to give the pitch and yaw error information. The telescope met all the preflight requirements and the performance in flight was consistent with the ground test results. Due to a larger-than-expected space vehicle pointing error the telescope occasionally operated beyond its designed linear range. This increased two contributions to the systematic error for the science data analysis which were from the non-linearity of the pointing response and the scale factor change due to guide star color variation. The non-linearity error can be corrected using a cubic model for the response as a function of pointing angle derived from the flight data. Other systematic errors from the telescope are predominantly bias variations which have an insignificant effect on experiment error. [Preview Abstract] |
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L1.00015: Gravity Probe B Timing System and Roll Phase Determination Jie Li, Jeffery Kolodziejczak An oven-controlled crystal oscillator at 16.368 MHz provides clock signals to all GP-B components and synchronizes the data collection, transmission and processing. The sampled science data signals are stamped with the vehicle time, a counter of the 10Hz data strobe divided down from the clock. The GPS receiver supplies an external reference for time transfer between the vehicle time and coordinated universal time. Ground and space flight tests show the time transfer error is within 1 $\mu $s. The time latency between the effective sample time of science signals and the stamped vehicle time is verified to 1 ms in the ground tests. The GP-B satellite is controlled to roll with a period of 77.5 sec about an axis along the direction to the guide star to average out the disturbance torques fixed to the body of the satellite and reduce the gyroscope readout noise. The roll phase is determined on the ground to high accuracy with the telemetry data from two star trackers and used in the data analysis to separate the drifts of gyroscope spin axes in the orbital plane and perpendicular to the orbital plane. The flight data shows that the roll phase is controlled to within 40 arcsec with a measurement uncertainty of 7 arcsec. [Preview Abstract] |
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L1.00016: The Gravity Probe B SQUID Readout Detector Barry Muhlfelder, Bruce Clarke, Gregory Gutt, James Lockhart, Ming Luo We describe the DC SQUID-based readout system used on-orbit to measure the spin axis orientation of the GP-B gyroscopes. This system uses thin-film four-turn superconductive pickup loops to inductively couple the London moment signals of the spinning gyroscopes to the SQUID detectors. The SQUID detectors were mounted within niobium packages that provided magnetic shielding and allowed for active temperature control of the SQUIDs. EMI mitigation techniques were used to isolate the SQUIDs from spacecraft and ambient RFI noise sources. We discuss the design and construction of the readout system hardware and describe the extensive testing of the system prior to launch. We present on-orbit SQUID noise results demonstrating a gyroscope spin axis orientation resolution of 1 marc-sec in less than 10 hours of integration time, sensor harmonic distortion of less than 0.01{\%}, SQUID bias and gain temperature sensitivity coefficients, and calibration results. The experiment error associated with the measured SQUID noise is less than 0.2 marc-sec/yr. [Preview Abstract] |
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L1.00017: SQUID Control, Temperature Regulation, and Signal Processing Electronics for Gravity Probe B James Lockhart, Barry Muhlfelder, Jie Li, Bruce Clarke, Terry McGinnis, Peter Boretsky, Gregory Gutt We designed, built, tested, and operated on-orbit a set of space-qualified electronics to (a) provide high-bandwidth and low-noise flux-locked-loop operation of four SQUID detectors, (b) regulate the temperature of the SQUIDs to better than 5 $\mu $K rms, and (c) digitize and provide digital filtering of the SQUID signals and SQUID temperature readings. Particular attention was paid to designing a system which would be stable in the presence of large ambient temperature variations, the energetic particle cosmic ray environment of space, and electromagnetic interference. The flux-locked-loop electronics combined high dynamic range with low noise. The SQUID temperature control system employed a digital feedback system providing adequate disturbance rejection at a critical signal frequency. The system yielded on-orbit SQUID performance limited by the intrinsic SQUID noise. [Preview Abstract] |
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L1.00018: Gravity Probe B Science Instrument Assembly (SIA) Saps Buchman, Barry Muhlfelder, John Turneaure The SIA comprises the cryogenic elements of the GP-B instrument including the science telescope, the four gyroscopes, the quartz block assembly (QBA), and the four SQUIDS mounted on two brackets. SIA support systems include gyroscope magnetic shields, 8 gas connections for gyroscope spin-up, 8 UV fiber optic cables for charge management, and about 500 electrical connections; including 30 gyroscope coaxial suspension cables, 18 SQUID support cables, telescope detector electrical connections, heaters, germanium resistance thermometers, and silicon diode thermometers. The SIA performed to design in all areas. Mechanical stability was better than 0.1~marcsec/yr. The QBA temperature was limited by the superfluid helium bath and controlled to 2.7 K. The SQUID brackets were controlled to 2.8~K $\pm $ 5 $\mu $K at roll, while the telescope silicon detectors were controlled to 72~K. New technologies were demonstrated by the SIA in space: potassium hydroxide optical bonding with strength superior to bulk quartz, matching of thermal expansion of quartz components to 3ppb, low temperature bake-out of the vacuum probe to about 2$\times $10$^{-12}$ Pa , and a dc magnetic field of 0.3 nT. [Preview Abstract] |
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L1.00019: Polhode Motion of the Gravity Probe-B Gyroscopes Michael Dolphin, Alex Silbergleit, Michael Salomon, Paul Worden, Daniel DeBra The Gravity Probe B gyroscopes exhibit a torque-free, periodic motion of the spin axis in the rotor body frame as governed by Euler's equations of motion; this effect is known as polhode motion. Polhode motion is characterized by inertial asymmetry of the rotor, the ratio of the differences of the moments of inertia about the principal axes. The period was found to be slowly changing on-orbit, due to extremely small kinetic energy dissipation in the rotor body. This slowly varying effect must be accounted for in the science data analysis. Two novel methods were employed to model the polhode behavior. One method establishes a model of adiabatic energy dissipation in rotor that is used together with the measured polhode period to estimate the rotor inertial asymmetry. Another method uses the polhode modulated spin frequency component of rotor position measurements in the housing arising from gyro mass unbalance. By fitting the theoretical Euler solution to the measured data, the asymmetry parameter is found. The consistent results of both approaches are presented. Other significant parameters, such as the characteristic time of dissipation, and mass unbalance measured to sub-nanometer level, are also given. [Preview Abstract] |
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L1.00020: Evidence for Patch Effect Forces on the Gravity Probe B Gyroscopes Dale Gill, Saps Buchman During the course of the GP-B on-orbit experiment the effect of anomalous forces were observed in the motion of the gyroscope rotors. A likely explanation for the origin of these forces is the existence of patch effect charges on the surface of the rotor. The effects observed were: a) increased misalignment torques; $\sim $1~arcsec/deg/day, b) forces along the direction of the spin axis; 10$^{-7}$ m/s$^{2}$, c) spin-down rates in excess of residual gas induced spin-down; 0.4-1.5 $\mu $Hz/hr, d) charge measurement effects, e) modulation of control effort and position in excess of the ones caused by rotor geometry. While varying from gyroscope to gyroscope all effects are consistent with patches of 20-100mV with extent up to dipole configuration. This poster will present data from analysis of on-orbit performance and ground based experimentation to show that the effects arise from variations in the work function of the rotor's niobium coating. This poster will include details of the process for application of the coating onto the rotor. The results of a ground based experiment to map variation in the work function of flight spare rotors will also be presented. Finally some possibilities to mitigate these effects on future instruments will be presented. [Preview Abstract] |
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L1.00021: Gravity Probe B Orbit Determination Paul Shestople, Huntington Small The GP-B satellite is equipped with two redundant Trimble TANS Vector III GPS receivers and matching antennae, used to reconcile vehicle time with Coordinated Universal Time (UTC) and to provide a satellite position measurement. Real time GPS position accuracy easily meets mission requirements of 100 m RMS per axis. The GP-B precision orbit was determined in ground processing of 18-hour and 30-hour GPS data segments. Analysis of overlapping consecutive 18-hour ephemeris segments suggest a maximum position uncertainty of 2.5 m RMS and maximum velocity uncertainty of 2.2 mm/sec RMS. Satellite Laser Ranging (SLR) measurements provide independent verification of the GPS-derived GP-B orbit. We describe the GPS equipment and orbit determination operations, including pre-launch verification testing. On-orbit performance and lessons learned are discussed. GP-B ephemeris uncertainties estimated using ephemeris overlap comparisons and SLR residual computations are detailed. [Preview Abstract] |
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L1.00022: Simulator Technology of the Gravity Probe-B Mission David Hipkins, Robert Brumley, Yoshimi Ohshima, Thomas Holmes The Gravity Probe B mission relied on simulators extensively both in the development and operational phases. They played a critical role in the mission's overall success. The primary simulator was the Integrated Test Facility (ITF) built by Lockheed-Martin. This simulator was assembled to provide spacecraft dynamics simulation as well as flight software validation and verification. There were also subsystem simulators that played equally important roles. The gyroscope suspension system team developed and built a hardware-in-the-loop gyroscope simulator designed to be able to operate over 10 orders of magnitude in force domain. This simulator evolved during on-orbit operations into a state of the art drag-free simulator. Simulated sensors for the SQUID readout system, telescope readout system and even an artificial star to test the performance of the telescope optics were used extensively for qualification tests prior to launch. One of the more important lessons learned is for missions where the spacecraft to payload coupling becomes the greatest challenge, simulators of the future need to be designed with coupled interfaces and these simulators must be employed early in the design and build phase of the mission. [Preview Abstract] |
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L1.00023: Achievement of the Magnetic Environment Requirements for Gravity Probe B John Mester, James Lockhart, Michael Taber The proper function of the Gravity Probe B gyroscope readout system necessitated the most stringent magnetic environment requirements of any NASA flight program. We describe the generation of an ultra-low magnetic field of $<$ 10$^{-11}$ Tesla in the flight dewar, non-magnetic materials, fabrication, and assembly regimen to minimize remanent fields in the vicinity of the science gyros, and a magnetic shield system that attenuated external magnetic field variation by a factor of 10$^{12}$.~ Techniques for requirement verification, including the development of specialized magnetic measurement facilities, will be discussed.~ On orbit gyro trapped flux and readout data that confirm the achievement of the fundamental magnetic requirements will be presented. [Preview Abstract] |
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L1.00024: The Gravity Probe B Gyroscopes Saps Buchman, Bruce Clarke, Mac Keiser, Dale Gill, Frane Marcelja, Robert Brumley The four redundant GP-B electrostatically suspended gyroscopes measure the orientation of the local inertial frame of reference as influenced by the spinning Earth. The GP-B gyros are designed to improve the drift performance of ground based instruments by a factor of about 10$^{6}$ or 0.3~milliarcsec/year. Four factors make possible this improvement: 1) low (10$^{-11}$~m/s$^{2})$ acceleration environment provided by the drag free system, 2) averaging of suspension related torques provided by the roll of the spacecraft, 3) geometry of the sensors, and 4) low gas pressure environment. The gyros are fused quartz spheres of 19~mm radius, coated with 1.3~$\mu $m niobium, with a peak to valley surface uniformity of better than 1~ppm and a separation of centers of geometry and mass of better than 1~ppm of the radius. The gyroscopes were spun to $\sim $70 Hz and exhibited characteristic spin down times of 7000 to 25,700 years. The gyroscopes potential was maintained to within 15~mV of local ground (15~pC charge) using a fiber coupled mercury vapor lamp to produce UV photoemission at 254~nm. The system allowed charge management and measurement to 2~mV. We present engineering data of the gyroscope and UV systems, as well as novel technologies employed and lessons learned. [Preview Abstract] |
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L1.00025: Gravity Probe B Gyroscope Electrostatic Suspension System (GSS) William Bencze, David Hipkins, Tom Holmes, Saps Buchman, Robert Brumley Presented here is a hybrid digital/analog electrostatic suspension control system for the Gravity Probe B Relativity Mission's science gyroscopes. The chief challenge for this system is to operate over 8 orders of force magnitude while minimizing classical torques on the gyroscope. A novel, adaptive LQE digital control algorithm was developed to meet the high dynamic range requirements for rotor suspension, while minimizing suspension-induced torques. A set of three backup, all-analog proportional-derivative (PD) controllers were provided to maintain rotor centering in the event of computer faults during all phases of the mission. The capacitive position sensing system measured rotor position to a noise floor of 0.15 nm/$\surd $Hz in the science band (5 - 30 mHz). In addition, this system also applied controlled torques to perform a post spin-up alignment of the gyroscope spin axes to within 10 arc-sec of a desired orientation, and measured the rotor charge to the 2 pC (2 mV) level. The GSS contributed to drag-free operation of the space vehicle by using one of the gyroscopes as an isolated, inertial proof mass and was able to resolve accelerations to the 10$^{-12 }$g level. On-orbit performance of this system will be discussed in detail. [Preview Abstract] |
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L1.00026: The Gravity Probe B Relativity Mission (GP-B) C.W. Francis Everitt The Relativity Mission, Gravity Probe B (GP-B), was launched on April 20, 2004 and successfully acquired science data from August 27, 2004, to August 15, 2005. The liquid helium cryogen was exhausted on September 29, 2005. Using four high precision gyroscopes, GP-B measured the relativistic precessions of the inertial frame of reference in a 642 km polar orbit. Two precessions are predicted in Einstein's theory of General Relativity: that due to the geodetic effect, of rate 6.6 arcsec/year, and that due to the frame dragging effect, of rate 0.042 arcsec/year. Comprehensive calibrations were performed before and after the science mission. Detailed science and engineering results are presented in four invited talks and multiple poster presentations at this meeting. [Preview Abstract] |
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L1.00027: Gravity Probe B Experiment Error Barry Muhlfelder, G. Mac Keiser, John Turneaure The GP-B experiment error results from both statistical and systematic sources. Excluding all systematic effects, the on-orbit gyroscope readout noise provides an experiment error noise floor limit of 0.2 marcsec/yr. We have also evaluated the effects of more than 200 systematic sources including: thermal sensitivities of the readout system, non-linearities in the telescope readout, roll phase uncertainty, and spacecraft anomalies. The impact of these and other systematic effects has been mitigated by the development of a variety of techniques. Study of the flight data revealed two unanticipated gyroscope behaviors. These two behaviors, a slowly varying readout scale factor and a specific type of Newtonian torque, are now well understood, and have been incorporated into the data analysis model. Residual errors associated with these and other gyroscope behaviors are included as part of the overall systematic error. The consistency of the results for the four independent gyroscopes provides a crosscheck of gyroscope specific error. Proper summing of all errors for the four gyroscopes gives the experiment error. We will present the most current numerical assessment of all GP-B error sources and will give the associated experiment error. [Preview Abstract] |
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L1.00028: Gravity Probe B Science Data Analysis: Filtering Strategy Michael Heifetz, Thomas Holmes, David Hipkins, Alex Silbergleit, Vladimir Solomonik Nonlinear filtering provides one component of the data analysis strategy to determine the relativistic precession of GP-B science gyroscopes. The filtering methodology is based on: 1) models of the gyroscope motion, 2) models of the science signal readout electronics and 3) numerical filtering techniques. A ``two-floor'' process has been developed. The first floor focuses on modeling of the readout system: gyroscopes' scale factor polhode variations, telescope signals, matching of the gyroscope and telescope scale factors/bias, and SQUID calibration signal modeling. Nonlinear parameter estimation is performed for a set of independent batches that generates state vector covariance matrices for each batch. The second floor separates the relativistic precessions from the torque-induced motion of the science gyroscopes. Batch-based estimates from the first-floor filter are treated as ``measurements'' of the second floor state vector and connected through the torque model and other constraints. Estimates of relativistic precession and its covariance are obtained from the ``second-floor'' filters. Supporting validation tools such as spectral and statistical analyses of the filter residuals were developed to interface with the filter outputs for multiple sensitivity analyses. [Preview Abstract] |
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L1.00029: Performance of the Gravity Probe B Cryogenic Sub-System Michael Taber, David Murray The experimental design of Gravity Probe B was based substantially on low temperature technology. In addition to the thermal environment provided by the 2400-liter, 1.8 K super-fluid He dewar, the cryogenic sub-system was responsible for controlling the mechanical, magnetic, vacuum, and optical environments of the Science Instrument Assembly (SIA). A highly stable sub-nT magnetic field region for the SIA is required to limit trapped flux in the superconducting gyro rotors to $<$ 0.9 nT (uniform field equivalent) and to attenuate external field by 240 dB. The magnetic field requirements were satisfied in part by use of an expanded superconducting lead-foil shield installed into the dewar prior to the integration of the cryostat probe housing the SIA. This required that the shield be continuously kept below its transition temperature (7 K) to the end of the science mission, including during integration of a warm probe with the cold dewar. Additional key requirements and the design of the cryogenic sub-system are also described in this poster as well as key flight results including trapped flux in the gyro rotors (0.3 nT uniform field equivalent), and cryogen lifetime (17.3 months). [Preview Abstract] |
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L1.00030: The Gravity Probe B Drag-free and Attitude Control System Michael Adams, Daniel DeBra The Gravity Probe B is first space vehicle provide active control of the vehicle's six degrees of freedom (DOF), three in translation and three in attitude. The Attitude and Translation Control (ATC) uses helium boil-off gas from the cryogenic system as a propellant for 16 proportional cold gas thrusters. Differential thruster operation provides forces and torques on the vehicle, common mode operation controls the net flow rate from the dewar that is used in turn to control the liquid helium bath temperature. The pointing system controls the pointing of the guide star tracking telescope to 30 marc-sec at the space vehicle roll period (77.5) and maintained roll phase to 40 arc-sec. The translation control system used acceleration measurements from one science gyroscope's suspension system to null out the effects of external forces from the on-orbit environment (solar wind, radiation pressure, etc). In this way, the vehicle was controlled to fly in a near-perfect gravitational orbit; transverse accelerations on the science gyroscopes were reduced to the 5$\times $10$^{-12}$ g level. The precise pointing and orbital geometry are essential for minimizing disturbances to the science gyroscopes, and the dewar control is important in maximizing the length of the data collection period.. [Preview Abstract] |
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L1.00031: Features of the Gravity Probe B Space Vehicle William Reeve, Gaylord Green Space vehicle performance enabled successful relativity data collection throughout the Gravity Probe B mission.~~ Precision pointing and drag-free translation control was maintained using proportional helium micro-thrusters.~ Electrical power was provided by rigid, double sided solar arrays. The 1.8 kelvin science instrument temperature was maintained using the largest cryogenic liquid helium dewar ever flown in space.~~ The flight software successfully performed autonomous operations and safemode protection. Features of the Gravity Probe B Space Vehicle mechanisms include: 1) sixteen helium micro-thrusters, the first proportional thrusters flown in space, and large-orifice thruster isolation valves, 2) seven precision and high-authority mass trim mechanisms, 3) four non-pyrotechnic, highly reliable solar array deployment and release mechanism sets.~ Early incremental prototyping was used extensively to reduce spacecraft development risk.~ All spacecraft systems were redundant and provided multiple failure tolerance in critical systems.~ Lockheed Martin performed the spacecraft design, systems engineering, hardware and software integration, environmental testing and launch base operations, as well as on-orbit operations support for the Gravity Probe B space science experiment. [Preview Abstract] |
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L1.00032: Classical Torques on Gravity Probe B Gyroscopes Alex Silbergleit, G. Mac Keiser, Yoshimi Ohshima Classical torques are a source of systematic error in Gravity Probe B experiment, so they were intensively studied throughout the whole program, which resulted in the detailed pre-flight Error Tree for each GP-B gyroscope. Extended classification of torques, their theory and examples are presented. Post-flight on-orbit calibrations showed unexpectedly large torque proportional to the spin-to-roll axis misalignment (proportionality up to $\sim $1 deg misalignment; misalignment through the science period within 50 arc-sec). The torque may be explained by a non-uniform distribution of electric potential over the rotor and housing surfaces (patch effect due to the micro-crystal structure, and/or dipole layer on the surface, etc.). A complete theory of the patch effect torque is established. It implies the corresponding signal model that allows one to separate the relativistic drift from the classical one and remove the effect of the latter, obtaining the desired accuracy of the relativistic drift rate determination. The most recent post-flight upper bound of the drift rate from all other classical torques is also given. [Preview Abstract] |
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L1.00033: Trapped Flux Mapping for the Gravity Probe B Gyroscopes Michael Salomon, John Conklin, Michael Dolphin, G. Mac Keiser, Alex Silbergleit, Paul Worden Gravity Probe B uses measurements of the London moment dipole magnetic flux to find the orientation of its science gyroscopes. In this measurement are contributions from the trapped magnetic field generated by point-like field sources (fluxons) in rotor's superconducting coating. While the London moment signal appears at the space vehicle roll frequency (13 mHz), the trapped field appears at harmonics of the rotor spin frequency (60-80 Hz) which is modulated at the polhode period. This generates a time varying projection of the trapped flux along the London moment axis that results in an scale factor change in the orientation measurement system on the order of 0.5{\%} to 3{\%} (rotor dependent). One technique that can be used to remove the effect of this scale factor variation is to map the rotor trapped field pattern by using the spin harmonic signals (high frequency), and then use a dynamic model to assess the trapped flux contribution to the readout scale factor (low frequency). Two representations of this trapped flux map are proposed: 1) an expansion of magnetic potential in the rotor-fixed frame as a spherical harmonic series, and 2) the sum of individual fluxon contributions, each given by the same function of fluxon position relative to the pick-up loop. Specific features of both methods and their most recent results are given. [Preview Abstract] |
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L1.00034: Numerical Relativity from a Gauge Theory Perspective Will Farr We briefly describe the formulation of general relativity as an $SO(3,1)$ gauge theory. We explain how this formulation admits an elegant, geometric and coordinate-independent discretization. We present results from numerical simulations of simple spacetimes using this formulation. [Preview Abstract] |
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L1.00035: Some analogies between electromagnetism and gravity Robyn Sanderson, Edmund Bertschinger The similarity of the Coulomb law in electromagnetism to the Newtonian law of gravitation is well known. By examining the equation of motion (geodesic equation) in an orthonormal basis, we extend this analogy to include gravitomagnetic and tensor effects in the weak-field limit of general relativity, and discuss the possibility of drawing gravitational field lines as a pedagogical aid. We also discuss analogies between the electromagnetic field equations and the general relativistic field equations (the Cartan structure equations and the Einstein equation) as relations between differential forms. [Preview Abstract] |
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L1.00036: General Relativistic Calculation of a Fermion Mass Spectrum. Joseph D. Rudmin The masses of the electron, muon, and tauon are calculated from field energies, by extrapolation of Parker Sochacki expansions, in a general relativistic model, using an isotropic metric. The only parameter is weak charge, which is constrained to be the same for all three fermions. [Preview Abstract] |
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L1.00037: Electrodynamics and Thermodynamics of Magnetized Black Holes Ernesto Esteban In this work, we focus in the electrodynamics and thermodynamics of rotating charged black holes immersed in external magnetic fields. As a first application, the meaning of the magnetized Kerr-Newman metric parameters is revisited and given an alternative physical interpretation. Next, its basic properties as singularities, event horizons, and the ergosphere are obtained and discussed. As a second application, we present analytical expressions to obtain (up to a linear term in $\beta $ =BM, where B and M are the external magnetic field and spacetime mass, respectively) the electromagnetic fields, magnetic fluxes, total charge, surface gravity, and electromagnetic potentials associated to the magnetized Kerr-Newman metric. It is showed that the magnetized Kerr-Newman black hole's charge is astrophysical significant and can not be neglected as in the standard Kerr-Newman black hole. Finally, the difference in mass or energy between two magnetized black holes states differing in proper area, angular momentum, charge, and magnetic field is also discussed and compared with the corresponding results associated to the standard Kerr-Newman and magnetized Kerr black holes. [Preview Abstract] |
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L1.00038: Orbital Precession due to Central-Force Perturbations Gregory Adkins, Jordan McDonnell We calculate the precession of Keplerian orbits under the influence of arbitrary central-force perturbations. Our result is in the form of a one-dimensional integral that is straightforward to evaluate numerically. We demonstrate the effectiveness of our formula for the case of the Yukawa potential. We obtain analytic results for potentials of the form $V(r) = \alpha r^n$ and $V(r) = \alpha \ln(r/\lambda)$ in terms of the hypergeometric function ${_2F_1}\left ( \frac{1}{2}-\frac{n}{2},1-\frac{n}{2}; \, 2; \, e^2 \right )$, where $e$ is the eccentricity. Our results reproduce the known general relativistic ($n=-3$) and cosmological constant ($n=2$) precession formulas. Planetary precessions are often used to constrain the sizes of hypothetical new weak forces--our results allow for more precise, and often stronger, constraints on such proposed new forces. [Preview Abstract] |
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L1.00039: Ab initio Calculation of the Anomalous Acceleration of Pioneer 10 Russell Anania, Michael Makoid The anomalous accelerations of Pioneers 10 and 11, while opposite, are both directed towards the Sun. Using that both light and gravity are equally bent by gravity itself, and independently of energy, then gravity from behind the Sun may be focused onto a test mass, such as Pioneer 10, and increase its deceleration towards the Sun. The bending of gravitational forces of objects behind the Sun is delineated in an optical model to calculate additional forces on Pioneer 10. The optical model contains no free parameters, and its predictions differ from the anomalous constant acceleration by less than 0.2{\%}. Further observational implications are discussed. The need for dark matter in the Solar System is now obviated. [Preview Abstract] |
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L1.00040: Casual Set Approach to a Minimal Invariant Length Usha Raut Any attempt to quantize gravity would necessarily introduce a minimal observable length scale of the order of the Planck length. This conclusion is based on several different studies and thought experiments and appears to be an inescapable feature of all quantum gravity theories, irrespective of the method used to quantize gravity. Over the last few years there has been growing concern that such a minimal length might lead to a contradiction with the basic postulates of special relativity, in particular the Lorentz-Fitzgerald contraction. A few years ago, Rovelli et.al, attempted to reconcile an invariant minimal length with Special Relativity, using the framework of loop quantum gravity. However, the inherently canonical formalism of the loop quantum approach is plagued by a variety of problems, many brought on by separation of space and time co-ordinates. In this paper we use a completely different approach. Using the framework of the causal set paradigm, along with a statistical measure of closeness between Lorentzian manifolds, we re-examine the issue of introducing a minimal observable length that is not at odds with Special Relativity postulates. [Preview Abstract] |
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L1.00041: Does Fine-structure Constant link to Gravitational Degradation? Shantilal Goradia My description of the fine-structure constant in physics/0210040 v3 and another APR07 abstract as a reciprocal of the natural logarithm of Hubble time that compensates increasing rate of order with the increasing rate of disorder of the universe, implies that gravity is mediated by photons. Shrinkages of Planck length as a result of gravitational degradation would randomize it for statistical calculations. My proposal that gravity is a long range manifestation of the short range nuclear forces implies it has a small repulsive component implying it is mediated by photons. Based on both of these implications I make the case that electromagnetic interactions caused by lighting during thunderstorms explain increase in order in chemistry and biochemistry and fuel the destructive power of tornados by causing nuclear reactions that alter the composition of atmospheric gases. I predict that the lighting causes minute changes in the atmospheric constituents of gases. Advanced technology may make it possible to verify my prediction. [Preview Abstract] |
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L1.00042: Michelson-Morley in space Fred Pierce An experiment is proposed in which a Michelson-Morley interferometer is placed on a space station whose rotation is generating an ``artificial gravity'' field. The two horizontal arms of the interferometer are placed parallel to the rim of the space station whose motion generates the gravitational field; a vertical arm is added perpendicular to the direction of motion -- facing towards the center. The nature of the field created by the rotation of a space station lends itself to analysis by the interferometer in two-dimensional cross sections. It is predicted that there will be no interference fringes between the forward and backward facing arms when the space station is in constant motion but there will be an interference fringe with the vertical arm juxtaposed to the horizontal arms. The rotation of the space station is then accelerated. During the acceleration, there will be a difference in the interference fringes between the forward arm and the backward arm. When the motion of the greater rotation is brought to a constant spin at a higher velocity -- a ``frame of reference'' with a higher spin -- there will be a stronger gravitational field. The horizontal arms are predicted to, once again, have no evidence of interference fringe differences between them (as the motion is balanced) but the vertical arm will evidence a stronger interference fringe difference in this ``frame of reference'' than the previous frame of reference. Such a vertical arm in space suggests a new Michelson-Morley experiment on earth with a vertical arm added to the two horizontal arms. [Preview Abstract] |
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L1.00043: General Relativity - The Impossible Theory Ronald Kotas General Relativity envisions a gravitating mass will distort Time and Space about the Sun. This is false because of the millions of degrees of temperature of the very active Sun's Corona, and is plainly a refraction process; not a GR effect. If a gravitating mass were effecting time - space, this curve or geometry would be curved positively with respect to that mass. In an opposite mass this would have an opposite curvature respecting the first mass and would produce repulsion, not attraction. GR does not provide for attraction between two masses. The Mercury precession of the perihelia 43 arc seconds per century, is explained by Newtonian functions. The exact 2/3rds ratio of the day-to-year is profound. The speed of light has been exceeded by demonstrations and mathematical proofs. The principle of equivalence has been violated. No one can explain how or what mechanism within GR causes actions at a distance. Therefore GR is an impossible theory and is not an explanation of Gravity and Gravitation. With 19 proofs and indications, Nuclear Quantum Gravitation provides a coherent, precise explanation of Gravity and Gravitation. [Preview Abstract] |
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L1.00044: QUANTUM MECHANICS |
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L1.00045: Schrodinger Cats and It from Bit Alexander A. Berezin Popular interpretations and illustrations of QM observer effect (Schrodinger Cats, Wigner friend), such as (A) MWIQM (Everett), and (B) gravitationally induced psi-reduction (Karolyhazy, Penrose) may turn out to be complimentary rather than contradictory to each other. We suggest existence of phase diagram separating areas of predominantly A or B where transitions between A and B, like melting lines on traditional material phase diagrams, indicate exponential enhancement of zero-point fluctuations near critical line at which density of states experiences singularity. Since at this point the effective masses of quasi particles composing system change sign (similar to electron hole transition in condensed matter), de- Broglie wavelength diverges. This indicates on-set of strong overall quantum nonlocality. Thus, coherency in system becomes frozen and may lead to non-exponential decay of many-body excitations. Strong coherency and nonlocality translates into enhancement of spontaneous pattern formation, informational connectivity akin to holographic memory (Benveniste) effect (Berezin, in Ultra High Dilution, Kluwer, 1994) and what J.A. Wheeler calls It from Bit paradigm. Critical aspect of latter may be individualization of elementary excitations (akin to labelability of elementary particles in Bohm theories of hidden variables) which can have implications to fundamental ascending processes including bioevolution and human creativity, origins of which may lie at Planck scale. [Preview Abstract] |
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L1.00046: TESTS OF PHYSICS LAWS |
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L1.00047: ABSTRACT HAS BEEN MOVED TO X11.00009 |
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L1.00048: On the Correct Analysis of the Foundations of Theoretical Physics Temur Z. Kalanov The problem of truth in science -- the most urgent problem of our time -- is discussed. The correct theoretical analysis of the foundations of theoretical physics is proposed. The principle of the unity of formal logic and rational dialectics is a methodological basis of the analysis. The main result is as follows: the generally accepted foundations of theoretical physics (i.e. Newtonian mechanics, Maxwell electrodynamics, thermodynamics, statistical physics and physical kinetics, the theory of relativity, quantum mechanics) contain the set of logical errors. These errors are explained by existence of the global cause: the errors are a collateral and inevitable result of the inductive way of cognition of the Nature, i.e. result of movement from formation of separate concepts to formation of the system of concepts. Consequently, theoretical physics enters the greatest crisis. It means that physics as a science of phenomenon leaves the progress stage for a science of essence (information). Acknowledgment: The books ``Surprises in Theoretical Physics'' (1979) and ``More Surprises in Theoretical Physics'' (1991) by Sir Rudolf Peierls stimulated my 25-year work. [Preview Abstract] |
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L1.00049: On the Correct Analysis of the Foundations of the Special Theory of Relativity Temur Z. Kalanov The correct theoretical analysis of the generally accepted foundations of the special theory of relativity is proposed. The principle of the unity of formal logic and dialectics is a methodological basis of the analysis. The result is as follows: the foundations (i.e., the interpretation of Michelson-Morley's experimental data and calculations, the contraction hypothesis and the Lorentz transformation formulae, concept of space-time, Einstein's formula expressing equivalence of mass and energy) contain logical errors and are not consequence of any postulates. The existence of logical errors is irrefutable proof of incorrectness of the special theory of relativity. The following correct theories and principles are proposed: theory of time; theory of space; the quantum theory of constancy of light speed; the principle of equivalency of mass and energy; the principle of objectivity of human knowledge; the theory of system of reference. [Preview Abstract] |
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L1.00050: On the Hypothesis of Control of the Universe Temur Z. Kalanov The problem of the SETI is not solved till now because idea of the SETI represents a methodological error in cosmology and astrophysics. This fact means that one should prove existence of Supreme Intelligence in a correct way. In this connection, the hypothesis of control of the Universe is proposed. The hypothesis is based on the new point of view [1] according to which information is essence of the Universe, and material objects are manifestation of the essence. The hypothesis is formulated as follows: (1) the Universe represents the cybernetic system; (2) the cybernetic system is a set of mutual connected elements which receive, memorize, process, and transmit information; (3) each material element (for example, atom, molecule, man, the Earth, the Sun) is a unity of opposites: the controlling aspect and the controllable aspect; (4) the Universe as a system is a unity of opposites: the controlling aspect and the controllable aspect. Consequently, the Universe is controlled by the certain object. Thus, the problem of definition of the controlling object arises. Correct solution of this problem is the key to exploration of the Universe. Ref.: [1] T.Z. Kalanov, ``On the hypothesis of Universe's ``system block'' ''. Bulletin of the APS, Vol. 51, No. 2 (2006), p. 61. [Preview Abstract] |
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L1.00051: Theoretical Model of God: The Key to Correct Exploration of the Universe Temur Z. Kalanov The problem of the correct approach to exploration of the Universe cannot be solved if there is no solution of the problem of existence of God (Creator, Ruler) in science. In this connection, theoretical proof of existence of God is proposed. The theoretical model of God -- as scientific proof of existence of God -- is the consequence of the system of the formulated axioms. The system of the axioms contains, in particular, the following premises: (1) all objects formed (synthesized) by man are characterized by the essential property: namely, divisibility into aspects; (2) objects which can be mentally divided into aspects are objects formed (synthesized); (3) the system ``Universe'' is mentally divided into aspects. Consequently, the Universe represents the system formed (synthesized); (4) the theorem of existence of God (i.e. Absolute, Creator, Ruler) follows from the principle of logical completeness of system of concepts: if the formed (synthesized) system ``Universe'' exists, then God exists as the Absolute, the Creator, the Ruler of essence (i.e. information) and phenomenon (i.e. material objects). Thus, the principle of existence of God -- the content of the theoretical model of God -- must be a starting-point and basis of correct gnosiology and science of 21 century. [Preview Abstract] |
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