Maximizing Kepler science return per telemetered pixel: Detailed models of the focal plane in the two-wheel era

TL;DR

This paper proposes that detailed image modeling of Kepler's raw pixel data can significantly enhance pointing accuracy and photometric precision in the two-wheel era, enabling continued high-quality science.

Contribution

It introduces both data-driven and physics-driven models for Kepler's focal plane, demonstrating improved calibration and intra-pixel sensitivity inference in degraded operational modes.

Findings

Image modeling can improve pointing precision in two-wheel mode.

Calibration parameters can be constrained using drift and jitter data.

Intra-pixel sensitivity variations can be inferred at higher than pixel resolution.

Abstract

Kepler's immense photometric precision to date was maintained through satellite stability and precise pointing. In this white paper, we argue that image modeling--fitting the Kepler-downlinked raw pixel data--can vastly improve the precision of Kepler in pointing-degraded two-wheel mode. We argue that a non-trivial modeling effort may permit continuance of photometry at 10-ppm-level precision. We demonstrate some baby steps towards precise models in both data-driven (flexible) and physics-driven (interpretably parameterized) modes. We demonstrate that the expected drift or jitter in positions in the two-weel era will help with constraining calibration parameters. In particular, we show that we can infer the device flat-field at higher than pixel resolution; that is, we can infer pixel-to-pixel variations in intra-pixel sensitivity. These results are relevant to almost any scientific goal for the repurposed mission; image modeling ought to be a part of any two-wheel repurpose for the satellite. We make other recommendations for Kepler operations, but fundamentally advocate that the project stick with its core mission of finding and characterizing Earth analogs. [abridged]