Background: The  three arms of Veloce provide complete wavelength coverage at a spectral resolution of R=80,000 from 390nm to 930nm :

1. ★Azzurro channel: 391-431nm (orders m=157-142)
   

2. ★Verde channel:   431-590nm (orders m=142-104)
   

3. ★Rosso channel:  590-930nm (orders m=104-65)
   

The Rosso channel, echelle grating and fibre feed remain unchanged from the system first installed in 2019. This means all three arms are fed by the same 19-element IFU  at the AAT’s f/8 Cassegrain focus, collecting light from a 2.5” diameter aperture for a single object.

The detector controllers have been upgraded with new ESO NGC  (Next Generation Controllers), the performance of which has (to date) been outstanding, with read noise robustly <3.5e- per pixel to date and very flat bias/overscan performance. There is now no-inter-quadrant crosstalk detected in Veloce and no substantial residual images from saturated observations.

Expected Performance: Unfortunately, the first commissioning run  (June 28-July 2) was a complete wash out (the dome was not opened on any of the 5 nights!). As such, while the designed spectrograph resolution and detector performance has been verified, detailed throughput for the new channels using on-sky targets has not been measured. (An image of all three cameras being read out is attached below).

From the examination of flat-field counts in the overlapping orders between the Rosso and Verde channels, it appears that performance for Verde and Rosso will be very similar. So proposers can extrapolate

time estimates for Rosso to Verde, and these should be about right (to within a factor of 2).

Throughput for the Azzurro channel is much harder to estimate in advance. All available continuum light sources have an intrinsic flux that plunges steeply <450nm). And the fibre-feed throughput is expected to degrade in the UV. For the time being, proposers are suggested to limit targets to B/V<10 at wavelengths

of 450nm or shorter.

It is expected that Community Science Verification programs will largely focus on non-radial-velocity science with the newly added wavelength range. Extracting radial velocity data from the Verde channel is expected to take significant development over the new 6 months, so those results can not be turned around quickly. (The Azzurro channel is not designed  with radial velocity science in mind). 

Non-radial-velocity data (on the other hand) should be extractable quite quickly, and so could inform proposals to use Veloce for the 2024A round of ATAC applications.

We will attempt to implement at least some observations from each program received. If the total request exceeds the time available, a clear prioritization within your target list will be essential.