SHARP in brief
"Why Everest?" - "Because it's there"
G. Mallory, 1924
Mission
SHARP is a multi-mode spectrograph conceived to fully exploit the ELT aperture providing near-IR (0.95-2.45 μm) spectroscopic information of astronomical sources at the faintest reachable fluxes, at the sharpest angular resolution (close to the ELT diffraction limit), over the widest AO corrected accessible field. This is achieved by joining the high sensitivity of a slitlets Multi-Object Spectrograph (MOS) and the high spatial sampling of a multi-Integral Field Unit (mIFU) to the narrow photon concentration and the wide corrected field of MORFEO at ELT, pushing the wavelength range up to 2.45 μm.
Main characteristics
SHARP consists of two main units: NEXUS, a slitlets Multi-Object Spectrograph (MOS), and VESPER, a multi-Integral Field Unit (mIFU). Both spectrographs are fed by an Atmospheric Dispersion Corrector (ADC) and a Natural Guide Stars (NGS) unit. The ADC allows SHARP to collect spectra over the whole wavelength range at any zenith distance and rotation angle. The NGS wavefront sensors, monitoring up to three stars, pass the information to MORFEO which uses also six laser guide stars (LGS) to remove the effects of the atmospheric turbulence over a field of diameter 160" encompassing the field of view of SHARP spectrographs.
NEXUS - The Multi-Object Spectrograph
The strength, the depth, the resolution, the uniqueness
NEXUS, the MOS, will operate over an AO corrected field ~1.2’x1.2’ (35 mas/pix) and will be fed by a robotic system switching among mechanical slit masks, capable of deploying ~30 slits (for a slit length of 2.2”). The spectroscopic resolutions for extended sources, i.e., larger than the diffraction limited PSF of ELT (~12mas at 2.2 μm) are R~6000, ~2000 and ~300, this latter called continuum. For a point source the resolution is R~17000. The whole wavelength range (0.95-2.45 μm) will be simultaneously covered. NEXUS Optical Design.
VESPER - The Multi-Integral Field Unit
The sharpness, the details, the complexity, the uniqueness
VESPER, the mIFU, is an image slicer composed of 12 probes called Integral Field Selectors (IFS hereafter). Each of them has a field of view of ~1.7”x1.5”. The 12 IFS are disposed in a cartesian xy grid, contiguous in the x direction and deployable along 58” in y direction to probe an AO corrected area of ~21”x58”. The spaxel scale is 31 mas. The signal from each spaxel is fed into a spectrograph that generates a spectrum for each one of them. The spectral resolution is R~3000 for extended sources, R~10000 for point sources. The whole wavelength range (1.2-2.4 μm) will be simultaneously covered. VESPER Optical Design.
