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  • ASTROPHYSICS  (4)
  • SOLAR PHYSICS  (1)
  • SPACECRAFT INSTRUMENTATION  (1)
  • 1
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2006-01-16
    Beschreibung: Phase perturbations that occur in the following components of the one and two-way systems are considered: (1) one-way system (signal from A to B): station a oscillator - transmitter A antenna A - signal path - antenna B - receiver B station B oscillator - recording system B; (2) two-way system (signal from A to B back to A): station A oscillator - transmitter A - antenna A - signal path up - antenna B - transponder B - antenna B - signal path down - receiver A - station A oscillator - recording system A. A symmetrical one- and two-way system which can identify the place of origin of the fluctuation and quantify it so as to recover the unperturbed phase at a given moment of time by time-correlating the phase fluctuations obtained in the one- and two-way data taken at both stations is described
    Schlagwort(e): SOLAR PHYSICS
    Materialart: JPL A Close-up of the Sun; p 457-497
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2011-08-18
    Beschreibung: The results of a test of general relativity with use of a hydrogen-maser frequency standard in a spacecraft launched nearly vertically upward to 10,000 km are reported. The agreement of the observed relativistic frequency shift with prediction is at the 70 x 10 to the -6th level.
    Schlagwort(e): SPACECRAFT INSTRUMENTATION
    Materialart: Physical Review Letters; 45; Dec. 29
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2011-08-18
    Beschreibung: A two-step satellite mission for improving the accuracy of gravitational wave detection and for observing actual gravity waveforms is proposed. The spacecraft would carry both a highly stable hydrogen maser, which would control a transmitter sending signals to earth, and a Doppler transponder operating in the two-way mode. The use of simultaneous one- and two-way Doppler transmissions offers four time records of frequency pulsations, which can reveal gravitational radiation at 1-10 MHz with an amplitude accuracy of a factor of six. The first mission phase would consist of a Shuttle launch into a highly eccentric orbit to obtain measurements of the gravitational redshift using gravitational potentials of different earth regions to establish that gravity is describable by a metric theory. Then, after a boost into a heliocentric orbit at 6 AU, the earth-satellite system could detect gravitational waves in the solar system, as well as bursts emitted by the collisions of supermassive black holes.
    Schlagwort(e): ASTROPHYSICS
    Materialart: General Relativity and Gravitation; 15; Feb. 198
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-27
    Beschreibung: A Scout D rocket was launched from Wallops Island, Virginia, carrying an atomic hydrogen maser oscillator system as the payload. The frequency of signals from the oscillator was monitored on the ground at Merritt Island, Florida, by using two hydrogen masers as comparison oscillators. The first-order Doppler shift in the signals was eliminated by a go-return transponder link to the payload, and the resulting data, representing the relativistic shifts, were recovered and recorded. The objective was to measure directly the effect of gravitational potential on the frequency of an atomic hydrogen maser assuming it to be a 'proper' clock. A gravitational effect amounting to some 4.5 parts in 10 to the 10th power was measured with an oscillator having a stability better than 1 part in 10 to the 14th power. Therefore, to make the best possible use of the oscillator, all frequency shifts at the 2 to 5 X 10 to the -15 power level in delta f/f in the system must be accounted for. This includes all the phase variations that can cause such a shift to appear. The experiment, the data available and the manner in which they were processed, and the results are described.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA-CR-161409
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2019-06-28
    Beschreibung: A test of the Einstein equivalence principle (EEP) was performed by carrying out a 'null' gravitational red-shift experiment. The experiment compared the rates of a pair of hydrogen maser clocks with those of a set of three superconducting-cavity stabilized oscillator clocks as a function of the solar gravitational potential. If EEP were not valid, the relative rates could vary with potential. During the experiment, the solar potential in the laboratory varied approximately linearly at 3 parts in 10 to the 12th per day because of the earth's orbital motion, and diurnally with an amplitude of 3 parts in 10 to the 13th because of the earth's rotation. An upper limit on the relative frequency variation of 1.7 parts in 100 of the external potential was set. The accuracy was limited by the frequency stability of the clocks and by unmodeled environmental effects. The result is consistent with the EEP at the 2 percent level. The experiment can also be viewed as setting a limit on a possible spatial variation of the fine-structure constant.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Physical Review D - Particles and Fields, 3rd Series (ISSN 0556-2821); 27; April 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2019-06-27
    Beschreibung: The number of gravitation experiments undertaken since the advent of Einstein's theory of gravitation is quite small, with, so far, only the famous perihelion-advance experiment and a recent lunar-laser-ranging experiment being capable of measuring a nonlinear, second-order effect. It now appears that another distinct test of the second-order term may be feasible through the use of very stable atomic clocks. This experiment, which would measure the second-order gravitational red-shift, is a bona fide test of the field equations of gravity, not just a test of the underlying principle of equivalence. The nature of such an experiment, the basic equations, model-orbit calculations, and some tracking-accuracy requirements are presented. It is concluded that current space-probe tracking capabilities cannot determine all the necessary orbital parameters with sufficient accuracy for this experiment at the present time.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Physical Review D - Particles and Fields; vol. 14
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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