Tau.Neutrino said:
‘First Light’ Achieved on an Experiment That Could Crack The Mystery of Dark Energy
As an astronomer, there is no better feeling than achieving “first light” with a new instrument or telescope. It is the culmination of years of preparations and construction of new hardware, which for the first time collects light particles from an astronomical object.
Which one? Oh, DESI. Great experiment. I’ve heard it mentioned so much that I’d forgotten that it wasn’t operating yet.
> Its main components are a focal plane containing 5000 fiber-positioning robots.
Australia did something similar without the robots, just a collection of black plates that held the optical fibres in place. Actually cheaper and faster.
> During its five-year survey beginning in September 2019, the DESI experiment will observe 35 million galaxies and quasars.
OK, that’s a bit bigger than possible with black plates with holes.
> A new optical corrector design creates a very large, 8.0 square degree field of view on the sky
Yep.
> A 500-fiber slit array feeds the spectrograph Schmidt collimator followed by cameras.The full spectral bandpass is 360 to 980 nm divided between three arms, using dichroics.The blue spectral resolution of R >1500 is derived from Lyman-alpha forest observation requirements from 2.2< z <3.5. The red arm resolution of R >3000 is derived from the LRG 400 nm break from 0.5< z <1.0. The NIR arm resolution of R >4000 is required to resolve ELG doublet from 0.5< z <1.7. Each camera has 4kx4k, 15μm pixel CCDs with individual control and digitization electronics.
I like the idea of using the redshift of the Lyman-alpha forest (normally in the far UV). That’s new to me.