Gravity Probe B data analysis: II. Science data and their handling prior to the final analysis

Abstract

The results of the Gravity Probe B relativity science mission published in Everitt et al (2011 Phys. Rev. Lett. 106 221101) required a rather sophisticated analysis of experimental data due to several unexpected complications discovered on-orbit. We give a detailed description of the Gravity Probe B data reduction. In the first paper (Silbergleit et al Class. Quantum Grav. 22 224018) we derived the measurement models, i.e., mathematical expressions for all the signals to analyze. In the third paper (Conklin et al Class. Quantum Grav. 22 224020) we explain the estimation algorithms and their program implementation, and discuss the experiment results obtained through data reduction. This paper deals with the science data preparation for the main analysis yielding the relativistic drift estimates.

Gravity Probe B data analysis: I. Coordinate frames and analysis models

“…It is already clear, and will be more evident from the rest of this paper and papers [7,8], that our data analysis was pretty much about proper handling of fundamental characteristic frequencies involved in the GP-B signals. They were numerous, of both natural and artificial origin, and ranged ten orders of magnitude, from 10 8 ∼ − to 10 Hz 1 ∼ .…”

“…The time gaps between the neighbor resonances range from a few days for gyroscope #2 to several weeks and even a month for gyroscope #3. The picture of resonances for gyroscope #2 may be seen in figures 13, 14 of paper [7]; only the resonances whose contribution to the drift was visible were included in these plots. Naturally, the number, n, of the occurring resonances decreases with the time, since the polhode frequency increases: higher order resonances come earlier.…”

“…In this, the first of three data analysis papers, abbreviated DA I, we derive the required theoretical models supporting the experiment. The second part, DA II [7], discusses the experimental data and the preparation of these data for the final analysis. Estimation algorithms and their computational realization, as well as the resulting relativity estimates and associated uncertainties are found in the third part, DA III [8].…”

The Gravity Probe B test of general relativity

“…spin-down rates. C TF was found by the 'trapped flux mapping' process described in papers 6 [23] and 19 [33], with the rotor motion and trapped field distribution estimated by fitting to spin harmonics of the SQUID's trapped flux signal yielding: (1) a history of the polhode phase for each gyroscope to 1°throughout the mission (2) C TF , accurate relative to C LM to ∼10 −4 . Its time signature came from that portion of the polhode-modulated trapped field parallel to the gyro spin axis.…”

Gravity Probe B orbit determination

“…Pulse-per-second circuitry was added to generate a timing signal for the science equipment. This signal would be used to reconcile vehicle time with coordinated universal time (UTC) [5,6].…”