Building the CubeSpec mission: in-orbit demonstration of high-resolution spectroscopy on a 12U CubeSat

CubeSpec is an in-orbit demonstration CubeSat mission in the ESA technology programme, developed and funded in Belgium. The programme is now in phase C/D. Environmental qualification is finalising and building, testing and verification of the spacecraft and payload flight model has started. The project is on track for launch readiness end 2026. We present the final design of the mission and the results of test of engineering, qualification and flight models. CubeSpec will measure high-resolution time series of spectral line profiles in massive stars to probe their internal structure. This requires a spectral resolution R > 50,000 (~0.01 nm) and SNR ≥ 200. CubeSpec features several technological innovations: a 3-axis fine steering mirror bringing arcsecond level line-of-sight stability, a compact optical payload with fully ceramic 10x20cm cassegrain telescope, a cross-dispersed echelle spectrograph, compact FPGA CMOS sensor readout and a deployabe sun shade.