scholarly journals Conformal Cosmology and the Pioneer Anomaly

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Gabriele U. Varieschi
Keyword(s):  
Cosmological Parameters ◽  
Hubble Constant ◽  
Conformal Gravity ◽  
Conformal Cosmology ◽  
Pioneer Anomaly ◽  
Radio Signals ◽  
Anomalous Acceleration ◽  
Near Future ◽  
Pioneer 10

We review the fundamental results of a new cosmological model, based on conformal gravity, and apply them to the analysis of the early data of the Pioneer anomaly. We show that our conformal cosmology can naturally explain the anomalous acceleration of the Pioneer 10 and 11 spacecrafts, in terms of a local blueshift region extending around the solar system and therefore affecting the frequencies of the navigational radio signals exchanged between Earth and the spacecraft. By using our model, we explain the numerical coincidence between the value of the anomalous acceleration and the Hubble constant at the present epoch and also confirm our previous determination of the cosmological parameters γ∼10−28 cm−1 and δ~10-4–10-5. New Pioneer data are expected to be publicly available in the near future, which might enable more precise evaluations of these parameters.

scholarly journals A STUDY OF THE PIONEER ANOMALY: NEW DATA AND OBJECTIVES FOR NEW INVESTIGATION

2006 ◽  
Vol 15 (01) ◽  
pp. 1-55 ◽  
Author(s):  
SLAVA G. TURYSHEV ◽  
VIKTOR T. TOTH ◽  
LARRY R. KELLOGG ◽  
EUNICE L. LAU ◽  
KYONG J. LEE
Keyword(s):  
Current Knowledge ◽  
Doppler Frequency ◽  
Blue Shift ◽  
Data Sets ◽  
Pioneer Anomaly ◽  
Doppler Data ◽  
History Of ◽  
Anomalous Acceleration ◽  
Pioneer 10

The Pioneer 10/11 spacecraft yielded the most precise navigation in deep space to date. However, their radiometric tracking data has consistently indicated the presence of a small, anomalous, Doppler frequency drift. The drift is a blue shift, uniformly changing with a rate of ~6 × 10-9 Hz/s and can be interpreted as a constant sunward acceleration of each particular spacecraft of aP = (8.74±1.33) × 10-10 m/s 2 (or, alternatively, a time acceleration of at = (2.92±0.44) × 10-18 s/s 2). This signal has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. We discuss the current state of the efforts to retrieve the entire data sets of the Pioneer 10 and 11 radiometric Doppler data. We also report on the availability of recently recovered telemetry files that may be used to reconstruct the engineering history of both spacecraft using original project documentation and newly developed software tools. We discuss possible ways to further investigate the discovered effect using these telemetry files in conjunction with the analysis of the much extended Pioneer Doppler data. In preparation for this new upcoming investigation, we summarize the current knowledge of the Pioneer anomaly and review some of the mechanisms proposed for its explanation. We emphasize the main objectives of this new study, namely (i) analysis of the early data that could yield the true direction of the anomaly and thus, its origin, (ii) analysis of planetary encounters, which should say more about the onset of the anomaly (e.g. Pioneer 11's Saturn flyby), (iii) analysis of the entire dataset, which should lead to a better determination of the temporal behavior of the anomaly, (iv) comparative analysis of individual anomalous accelerations for the two Pioneers with the data taken from similar heliocentric distances, (v) the detailed study of on-board systematics, and (vi) development of a thermal-electric-dynamical model using on-board telemetry. The outlined strategy may allow for a higher accuracy solution for the anomalous acceleration of the Pioneer spacecraft and, possibly, will lead to an unambiguous determination of the origin of the Pioneer anomaly.

PRESENT STATUS OF THE STUDY OF THE ANOMALOUS ACCELERATION OF THE PIONEER 10/11 SPACECRAFT

2005 ◽  
Vol 20 (11) ◽  
pp. 2304-2308 ◽  
Author(s):  
J. P. MBELEK
Keyword(s):  
Weak Field ◽  
Low Velocity ◽  
Pioneer Anomaly ◽  
Real Change ◽  
Local Manifestation ◽  
Anomalous Acceleration ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Pioneer 10 ◽  
Radiometric Data

Results from an almost twenty years study of radiometric data from Pioneer 10/11, Galileo and Ulysses spacecraft indicate an anomalous time depending blueshift1, 2 which bares hardly prosaic explanations. Local manifestation of the expansion of the universe or new force terms are not favored either by the observational data. So, we explore the possibility that the reported anomaly, referred to as the "Pioneer anomaly", does not result from a real change in velocity. It turns out that the main Pioneer anomaly may be looked at as a new validation of general relativity (GR) in the weak field and low velocity limit on account of the "machian" behavior of quintessence like dark energy.

scholarly journals The cosmic distance scale and H0: Past, present, and future

2012 ◽  
Vol 8 (S289) ◽  
pp. 3-9 ◽  
Author(s):  
Wendy L. Freedman
Keyword(s):  
Recent Progress ◽  
Hubble Space Telescope ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Future Prospects ◽  
Microwave Background ◽  
A Value ◽  
Systematic Uncertainties ◽  
Near Future ◽  
The Universe

AbstractTwenty years ago, there was disagreement at a level of a factor of two as regards the value of the expansion rate of the Universe. Ten years ago, a value that was good to 10% was established using the Hubble Space Telescope (HST), completing one of the primary missions that NASA designed and built the HST to undertake. Today, after confronting most of the systematic uncertainties listed at the end of the Key Project, we are looking at a value of the Hubble constant that is plausibly known to within 3%. In the near future, an independently determined value of H0 good to 1% is desirable to constrain the extraction of other cosmological parameters from the power spectrum of the cosmic microwave background in defining a concordance model of cosmology. We review recent progress and assess the future prospects for those tighter constraints on the Hubble constant, which were unimaginable just a decade ago.

scholarly journals Can redshift errors bias measurements of the Hubble Constant?

2019 ◽  
Vol 490 (2) ◽  
pp. 2948-2957 ◽  
Author(s):  
Tamara M Davis ◽  
Samuel R Hinton ◽  
Cullan Howlett ◽  
Josh Calcino
Keyword(s):  
Cosmological Parameters ◽  
Hubble Constant ◽  
Vertical Axis ◽  
Limiting Factor ◽  
Cosmological Redshift ◽  
Physical Effects ◽  
Observational Errors ◽  
Near Future ◽  
Exhaustive List ◽  
Better Than

ABSTRACT Redshifts have been so easy to measure for so long that we tend to neglect the fact that they too have uncertainties and are susceptible to systematic error. As we strive to measure cosmological parameters to better than 1 per cent it is worth reviewing the accuracy of our redshift measurements. Surprisingly small systematic redshift errors, as low as 10−4, can have a significant impact on the cosmological parameters we infer, such as H0. Here, we investigate an extensive (but not exhaustive) list of ways in which redshift estimation can go systematically astray. We review common theoretical errors, such as adding redshifts instead of multiplying by (1 + z); using v = cz; and using only cosmological redshift in the estimates of luminosity and angular diameter distances. We consider potential observational errors, such as rest wavelength precision, air to vacuum conversion, and spectrograph wavelength calibration. Finally, we explore physical effects, such as peculiar velocity corrections, galaxy internal velocities, gravitational redshifts, and overcorrecting within a bulk flow. We conclude that it would be quite easy for small systematic redshift errors to have infiltrated our data and be impacting our cosmological results. While it is unlikely that these errors are large enough to resolve the current H0 tension, it remains possible, and redshift accuracy may become a limiting factor in near future experiments. With the enormous efforts going into calibrating the vertical axis of our plots (standard candles, rulers, clocks, and sirens) we argue that it is now worth paying a little more attention to the horizontal axis (redshifts).

scholarly journals Accurate cosmology from gravitational-lens time delays

2012 ◽  
Vol 8 (S289) ◽  
pp. 331-338
Author(s):  
S. H. Suyu
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Current Status ◽  
Gravitational Lenses ◽  
Distance Measurements ◽  
One Step

AbstractThe time delays between the multiple images of a strong gravitational-lens system, together with a model of the lens-mass distribution, provide a one-step determination of the time-delay distance, and thus a measure of cosmological parameters, particularly the Hubble constant, H0. I review the recent advances in measuring time-delay distances, and present the current status of cosmological constraints based on gravitational-lens time delays. In particular, I report the time-delay distance measurements of two gravitational lenses and their implication for cosmology from a recent study by Suyuet al.

A model for the pioneer anomaly

2009 ◽  
Vol 87 (10) ◽  
pp. 1089-1093 ◽  
Author(s):  
Ivan G. Avramidi ◽  
Guglielmo Fucci
Keyword(s):  
General Relativity ◽  
Test Particles ◽  
Pioneer Anomaly ◽  
Modified Theory Of Gravity ◽  
Anomalous Acceleration ◽  
Theory Of Gravity ◽  
Modified Theory ◽  
Pioneer 10

In a previous work, we showed that massive test particles exhibit a nongeodesic acceleration in a modified theory of gravity obtained by a noncommutative deformation of General Relativity (so-called Matrix Gravity). We propose that this nongeodesic acceleration might be the origin of the anomalous acceleration experienced by the Pioneer 10 and Pioneer 11 spacecrafts.

scholarly journals The Hubble Constant from (CLASS) Gravitational Lenses

2001 ◽  
Vol 18 (2) ◽  
pp. 179-181 ◽  
Author(s):  
L. V. E. Koopmans ◽  
The CLASS Collaboration
Keyword(s):  
Time Delays ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Gravitational Lenses ◽  
Monitoring Programs ◽  
Systematic Uncertainties ◽  
Sky Survey ◽  
Image Pairs ◽  
Near Future

AbstractOne of the main objectives of the Cosmic Lens All-Sky Survey (CLASS) collaboration has been to find gravitational lens (GL) systems at radio wavelengths that are suitable for the determination of time delays between image pairs. The survey is now near completion and at least 18 GL systems have been found. Here, I will discuss our efforts to measure time delays from several of these systems with the ultimate aim of constraining the Hubble Constant (H0). Thus far three CLASS GL systems (B0218+357, B1600+434 and B1608+656) have yielded measurements of time delays, from which values of H0 ≈ 60–70 km s−1 Mpc−1 have been estimated. Although most GL systems give similar values of H0, statistical and systematic uncertainties are still considerable. To reduce these uncertainties, I will mention two monitoring programs that we are undertaking to (re)measure time delays in 14 CLASS GL systems and address several important issues for the near future.

scholarly journals Space-borne atom interferometric gravitational wave detections. Part I. The forecast of bright sirens on cosmology

2021 ◽  
Vol 2021 (12) ◽  
pp. 017
Author(s):  
Rong-Gen Cai ◽  
Tao Yang
Keyword(s):  
Dark Energy ◽  
Gravitational Wave ◽  
Modified Gravity ◽  
Cosmological Parameters ◽  
Operation Time ◽  
Hubble Constant ◽  
Gravity Theory ◽  
Modified Gravity Theory ◽  
Near Future

Abstract Atom interferometers (AIs) as gravitational-wave (GW) detectors have been proposed a decade ago. Both ground and space-based projects will be in construction and preparation in the near future. In this paper, for the first time, we investigate the potential of the space-borne AIs on detecting GW standard sirens and hence the applications on cosmology. We consider AEDGE as our fiducial AI GW detector and estimate the number of bright sirens that would be obtained within a 5-years data-taking period of GW and with the follow-up observation of electromagnetic (EM) counterparts. We then construct the mock catalogue of bright sirens and predict their ability on constraining cosmological parameters such as the Hubble constant, dynamics of dark energy, and modified gravity theory. Our preliminary results show around order 𝒪 (30) bright sirens can be obtained from a 5-years operation time of AEDGE and the follow-up observation of EM counterparts. The bright sirens alone can measure H 0 with a precision 2.1%, which is sufficient to arbitrate the Hubble tension. Combining current most precise electromagnetic experiments, the inclusion of AEDGE bright sirens can improve the measurement of the equation of state of dark energy, though marginally. Moreover, by modifying GW propagation on cosmological scales, the deviations from general relativity (modified gravity theory effects) can be constrained at 5.7% precision level.

scholarly journals CAN CONVENTIONAL FORCES REALLY EXPLAIN THE ANOMALOUS ACCELERATION OF PIONEER 10/11?

2004 ◽  
Vol 13 (05) ◽  
pp. 865-870 ◽  
Author(s):  
J. P. MBELEK ◽  
M. MICHALSKI
Keyword(s):  
Observational Data ◽  
Doppler Shift ◽  
Reaction Force ◽  
Rate Change ◽  
Shift Analysis ◽  
Pioneer Anomaly ◽  
Anomalous Acceleration ◽  
Pioneer 10 ◽  
Good Agreement

A conventional explanation of the correlation between the linear and the angular accelerations of Pioneer 10/11 spacecraft is given. First, the rotational Doppler shift analysis is improved. Finally, a relation between the radio beam reaction force and the spin-rate change is established. Computations are found in good agreement with observational data. Our analysis leads us to the conclusion that the Pioneer anomaly may not necessarily be due to systematics.

scholarly journals On the possible onset of the Pioneer anomaly

2015 ◽  
Vol 24 (08) ◽  
pp. 1550066 ◽  
Author(s):  
Michael R. Feldman ◽  
John D. Anderson
Keyword(s):  
Solar Radiation Pressure ◽  
Sudden Onset ◽  
Oscillatory Behavior ◽  
Pioneer Anomaly ◽  
Order Of Magnitude ◽  
Anomalous Acceleration ◽  
The Difference ◽  
Definition Of ◽  
Yearly Period ◽  
Pioneer 10

We explore the possibility that the observed onset of the Pioneer anomaly after Saturn encounter by Pioneer 11 is not necessarily due to mismodeling of solar radiation pressure but instead reflects a physically relevant characteristic of the anomaly itself. We employ the principles of a recently proposed cosmological model termed "the theory of inertial centers" along with an understanding of the fundamental assumptions taken by the Deep Space Network (DSN) to attempt to model this sudden onset. Due to an ambiguity that arises from the difference in the DSN definition of expected light-time with light-time according to the theory of inertial centers, we are forced to adopt a seemingly arbitrary convention to relate DSN-assumed clock-rates to physical clock-rates for this model. We offer a possible reason for adopting the convention employed in our analysis; however, we remain skeptical. Nevertheless, with this convention, one finds that this theory is able to replicate the previously reported Hubble-like behavior of the "clock acceleration" for the Pioneer anomaly as well as the sudden onset of the anomalous acceleration after Pioneer 11 Saturn encounter. While oscillatory behavior with a yearly period is also predicted for the anomalous clock accelerations of both Pioneer 10 and Pioneer 11, the predicted amplitude is an order of magnitude too small when compared with that reported for Pioneer 10.

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