Optimal frequency-domain analysis for spacecraft time series: Introducing the missing-data multitaper power spectrum estimator by Sarah E. Dodson-Robinson et al. on Wednesday 30 November

While the Lomb-Scargle periodogram is foundational to astronomy, it has a

significant shortcoming: its variance does not decrease as more data are

acquired. Statisticians have a 60-year history of developing

variance-suppressing power spectrum estimators, but most are not used in

astronomy because they are formulated for time series with uniform observing

cadence and without seasonal or daily gaps. Here we demonstrate how to apply

the missing-data multitaper power spectrum estimator to spacecraft data with

uniform time intervals between observations but missing data during thruster

fires or momentum dumps. The F-test for harmonic components may be applied to

multitaper power spectrum estimates to identify statistically significant

oscillations that would not rise above a white noise-based false alarm level.

Multitapering improves the dynamic range of the power spectrum estimate and

suppresses spectral window artifacts. We demonstrate multitapering on

simultaneous measurements of the interplanetary magnetic field and the solar

10.7-cm radio flux, finding high coherence at frequencies associated with the

sun's activity cycle and quasibiennial oscillations. Next we show that the

multitaper--F-test combination applied to Kepler observations of KIC 6102338

detects differential rotation without requiring iterative sinusoid fitting and

subtraction. Significant signals reside at harmonics of both rotation

frequencies and suggest an antisolar rotation profile. Finally, we demonstrate

the missing-data multitaper version of complex demodulation, which extracts the

low-frequency envelope from a modulated signal. We argue that multitaper power

spectrum estimators should be used for all time series with regular observing

cadence.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16549v1