Anyone working with geophysical data knows the frustration: the series is almost never complete. A receiver that failed, a station that stopped, a period with no records. Gaps are the rule, not the exception. And for a long time the answer was almost always the same: interpolate the holes, fill them with zeros, or approximate the covariance matrix. Each of these shortcuts introduces a distortion that contaminates the final estimate.
Hector was designed to need none of them. As long as the noise is, or has been produced, stationary, the tool handles missing data directly, without interpolation, without zero-padding and without approximations to the covariance matrix. The incomplete series goes in as it is, and the estimate comes out without the bias the shortcuts used to introduce.
From here, Hector opens up a range of control that few tools offer. It allows annual, semi-annual and other periodic signals to be included in the trend estimation process. It allows offsets to be estimated at specific epochs, those abrupt jumps that mark a series and that, ignored, distort the slope. And it allows the noise model to be chosen among power-law, ARFIMA, generalised Gauss-Markov and white noise, or any combination of these, fitting the analysis to the real nature of the observations.
The care for data quality extends to the rest of the work. Hector includes programs to remove outliers and to generate power spectral density plots, which help reveal the structure of the noise before modelling. It also includes a program with a script to detect offsets automatically, saving the work of hunting them down one by one. And when the power-law model is selected, with combinations of white, flicker and random walk noise, it allows the first difference of the data to be obtained.
For the researcher, this translates into something concrete. Less time patching series and justifying shortcuts, more time interpreting results that can be trusted. The integrity of the estimate no longer depends on the luck of having complete data. It depends on the right tool.