  Gaia is a revolutionary space mission developed by ESA and is delivering 5
parameter astrometry, photometry and radial velocities over the whole sky with
astrometric accuracies down to a few tens of micro-arcseconds. A weakness of
Gaia is that it only operates at optical wavelengths. However, much of the
Galactic centre and the spiral arm regions, important for certain studies, are
obscured by interstellar extinction and this makes it difficult for Gaia to
deeply probe. This problem can be overcome by switching to the Near Infra-Red
(NIR) but this is not possible with silicon CCDs. Additionally, to scan the
entire sky and make global absolute parallax measurements the spacecraft must
have a constant rotation and this requires the detectors operate in Time
Delayed Integration (TDI) mode or similar.
