The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, echelle spectrometer that specializes in the discovery and characterization of exoplanets using Doppler spectroscopy. In designing KPF, the guiding principles were high throughput to promote survey speed and access to faint targets, and high stability to keep uncalibrated systematic Doppler measurement errors below 30 cm s−1. KPF achieves optical illumination stability with a tip-tilt injection system, octagonal cross-section optical fibers, a double scrambler, and active fiber agitation. The optical bench and optics with integral mounts are made of Zerodur to provide thermo-mechanical stability. The spectrometer includes a slicer to reformat the optical input, green and red channels (445–600 nm and 600–870 nm), and achieves a resolving power of ∼97,000. Additional subsystems include a separate, medium-resolution UV spectrometer (383–402 nm) to record the Ca II H & K lines, an exposure meter for real-time flux monitoring, a solar feed for sunlight injection, and a calibration system with a laser frequency comb and etalon for wavelength calibration. KPF was installed and commissioned at the W. M. Keck Observatory in late 2022 and early 2023 and is now in regular use for scientific observations. This paper presents an overview of the as-built KPF instrument and its subsystems, design considerations, and initial on-sky performance.
Deformable mirrors (DMs) are a critical enabling technology for many astrophysics mission concepts currently in development. Unfortunately, generating the control signals required by DMs is difficult, and historically there have been few options for controlling a DM on a spacecraft. In this work, electronics suitable for controlling a 952 actuator MEMS DM have been developed and their performance has been characterized. The driver electronics deliver 16 bits of resolution with a least significant bit increment of 2.75 milliVolts and RMS electronic noise of less than 1.2 milliVolts over the range of 0 to 170 Volts. These electronics have been built to be compatible with the needs of missions that are cost-constrained and risk-tolerant. To that end, the driver electronics use widely available parts with a total expected unit cost of approximately $30,000. Although the driver electronics do not use radiation hardened parts, testing data indicates a 2 year lifetime in a TESS-like orbit with 90 percent confidence when shielded by 6 millimeters of aluminum.
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