MOONS has taken delivery of the two high-resolution H-band VPH diffraction gratings. These beautiful looking gratings were manufactured by Kaiser Optical Systems, Inc. in US and represent a remarkable technical achievement. Only a handful of such large gratings for these wavelengths and resolutions have ever been manufactured, and MOONS made the task even more challenging as its large beam size (>28 x 42cm) required two active surfaces to aligned and bonded together. Despite these challenges, the gratings meet the tough requirements we had requested both in transmission (>60% across full wavelength range and >80% in band centre) and in resolution (R>18000). This has always been a high-risk part of the MOONS project, so it is a great relief to have these components and we thank Kaiser for their excellent work.
The next job is to install the gratings in the instrument and send photons through them!