Solar Radial Velocity Archive
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Pyrheliometer Data |
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| Both EXPRES and NEID solar feeds in this archive operate a pyrheliometer that monitors solar flux throughout the day. These measurements serve as a cloud monitor. Drops in flux identify times when the solar disk was obscured. Since the Sun is a resolved, rotating source, heterogeneous obscuration of the solar disk will preferentially block either redshifted or blueshifted light, distorting the observed RVs. | ||
EXPRES Pyrheliometer Data
The daily pyrheliometer files contain solar intensity measurements used to identify EXPRES solar observations affected by clouds. EXPRES solar data are collected with the Lowell Observatory Solar Telescope (LOST; Llama et al. 2024), a fiber feed into EXPRES at the 4.3-m Lowell Discovery Telescope (LDT) near Happy Jack, Arizona. The EXPRES pyrheliometer measures the total solar direct normal irradiance (DNI) from 200 to 4000 nm in a 5-degree field of view around the Sun; for our purposes, it is effectively a directional bolometer. It is mounted on the roof of the LDT auxiliary building and read out at a 1 Hz cadence. The columns in the pyrheliometer files are:
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NEID Pyrheliometer Data
The weekly pyrheliometer files contain solar intensity measurements used to identify NEID solar observations affected by clouds. NEID solar data are collected with the NEID solar feed (Lin et al. 2022) at the WIYN 3.5-m telescope at Kitt Peak National Observatory. The NEID pyrheliometer is model MS-57 from EKO Instruments, which measures the total solar direct normal irradiance (DNI) from 200 to 4000 nm in a 5-degree field of view around the Sun; for our purposes, it is effectively a directional bolometer. A thermopile within the pyrheliometer reads out an analog voltage to a LabJack data acquisition module, and the voltage can be converted to an intensity via a factory-calibrated conversion factor. We set the readout rate of the pyrheliometer to 1 Hz to match the cadence of the exposure meter, as faster cadences offer no significant additional benefit for detecting clouds during solar exposures. Each file covers one week, beginning on the date in the filename. The files are plain text with three space-separated columns and no header row:
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