The purpose of this instrument is asteroseismology[1] and extrasolar planet detection by the radial velocity method.
The spectrograph is fed from the Cassegrain focus through either one of two separate optical fiber sets, yielding two different spectral resolutions (HE and HR modes).
This mode is used when a higher throughput is desired particularly in the case of faint objects spectral resolution is set to R = 40000.
The spectrum is projected onto the E2V Technologies type 44-82 CCD detector of 4096 x 2048 pixels kept at a constant temperature of –100 °C.
[2] In HE mode, a signal-to-noise ratio (per pixel) of 27 was reached in 90 min for an object of magnitude 14.5 in the V band.