A Five-Thousand-Fibre Spectroscopic Survey Telescope: Multiplex, Etendue and Redshift Throughput Computed from the Observing Cycle

A wide-field spectroscopic survey instrument — a 4 m telescope feeding 5,000 robotic fibre positioners over a 8.0 square degree field — is designed from its observing cycle. The etendue is 101 square metres square degrees. With 1,000-second exposures and 180-second field-change overheads, the telescope completes 25.9 tiles per night and records 129,661 spectra nightly, 17.83 million per year, of which 16.40 million per year yield secure redshifts at the stated 92 percent success rate — 82 million over a five-year survey. The facility totals 950 tonnes and 480 kW. All figures are computed from the stated cycle model; the design is simulated, not measured.