General Description of AAOmega

Instrument overview.

AAOmega will be a general purpose facility providing multi-object and integral field spectroscopy. Multiple-object spectroscopy, of between 350-392 objects (exact number not yet determined), will be provided using an upgraded version of the existing 2dF top end. The MOS fibre size will remain unchanged at 140 micron diameter (2.0 arcsec on the sky), but new Heraeus STU fibres of ~35m length will be required. In MOS mode, spectral resolutions between 1200-8000 will be available.

Integral field spectroscopy will be provided by the existing SPIRAL Integal Field Unit, with modifications to the slit end to allow it to feed the new AAOmega spectrograph, thus providing a field of view of 22 x 11 arcsec with 0.7 arcsec/lenslet/fibre (512 spatial elements). The SPIRAL IFU will normally be mounted at the auxiliary Cassegrain focus; spectropolarimetry may be available with the IFU mounted at the normal Cassegrain focus (this has not been determined yet). Spectral resolutions (lambda/Delta(lambda)) between 2000-13000 will be available in IFU mode.

AAOmega will have a new, innovative bench mounted spectrograph incorporating the latest technology. The spectrograph will be a dual-beam system with separate blue and red arms. The optics will be optimized for each arm and will use sol-gel antireflection coatings to obtain high efficiency. Instead of traditional reflection gratings AAOmega will use state of the art Volume Phase Holographic (VPH) gratings which can be up to 50% more efficient. Blue and red optimized 2k x 4k EEV CCDs will be used to provide increased efficiency while the large detector area and new AAO-2 controllers will permit nod & shuffle observing and reduce fibre cross talk. The spectrograph will be mounted in the mechanically and temperature stable Coude room.



Last modified: 24 June 2003, Terry Bridges.