ACAM's predecessor, the aux-port camera, was simply a CCD with a filter wheel in front of it (no optics) offering a field of view 1.8 arcmin across. The filter wheel (6 slots) accommodated only 50-mm filters, and changing the filters in the wheel meant removing the cryostat and filter-wheel box from the telescope. Nevertheless, the aux-port camera scored several scientific firsts, including: the first detection of gravitational lensing; identification of the companion star to Tycho Brahe's 1572 supernova; and first detection of the progenitor star of normal type-II-P supernovae (see above link for details).

ACAM was designed to provide a much wider field of view, without compromising significantly the throughput, image quality and wavelength coverage provided by the aux-port camera.

At the same time, the opportunity was taken to allow use of a wider range of filter size and types, to make filter changes much more straightforward, and to provide low-resolution spectroscopy.

It's expected that ACAM will be used for a broad range of high-impact science programmes requiring rapid response (e.g. supernovae, gamma-ray bursts), or awkward scheduling (e.g. exoplanet transits), or the use of specialised filters (e.g. narrow-band Hα imaging of low-redshift galaxies).

Timeline

• 2006 March - project formally initiated
• 2006 November - conceptual design review (formally passed 2007 March)
• 2007 November - final design review
• 2007 December - contract for optics placed with ICOS
• 2008 November - two lenses damaged during coating in the UK, commissioning delayed 3 months
• 2009 March - another lens damaged during coating, commissioning delayed 2 months
• 2009 June - first light for imaging and spectroscopy, and first scheduled science runs