Quiet-time helium spectra of Solar Orbiter/HET for stopping (filled blue diamonds) and penetrating (empty blue diamonds) particles, of ACE/SIS (green circles), and SOHO/EPHIN (orange squares) at L1, as well as Chang’E-4/LND (grey circles) measured at the lunar surface. The helium spectra were averaged over periods when Solar Orbiter was located between 0.95 and 1 au, as given in Table 1. The GCR spectrum predicted from the BON2020 model (Slaba & Whitman 2020) is given as the dashed line. Error bars indicate the statistical uncertainties.