Minerva-Australis

The Minerva-Australis array is an array of 4x0.7m telescopes + 1x 0.8m telescope that performs robotic synchronised spectroscopic and photometric observations. 

Spectroscopy

The five telescopes feed into a single Kiwispec spectrograph with resolution of R~80,000 over the 480-610nm. Spectra are extracted from the four traces independently. Radial velocities are derived from each telescope independently. Simultaneous relative wavelength offset is tracked via a flat lamp exposure that is passed through an Iodine cell. 

Data products include radial velocities from Least-Squares Deconvolution profiles for rapidly rotating stars (~>10 km/s) and self-template cross correlation radial velocities for slowly rotating stars. 

A typical per-telescope per-exposure diagnostic spectrum of Tau Ceti is shown below. 

The typical per-telescope RV precision, as a function of magnitude and Teff, is plotted below. It is OK to assume that the overall system precision scales with the number of the telescopes on-sky per observation. 

Photometry

The Minerva-Australis array is well suited to performing photometric transit follow-up observations. In particular, with all telescopes of the array operating together, sub-mmag level photometry can be achieved on most TESS targets. The telescopes are widely separated to average over scintillation, and the systematics are independent of each other. 

See below for two super-Earth light curves with transits at the 1mmag level.