upGREAT: Die Erweiterung von GREAT auf Heterodyne-Arrays für SOFIA

The current generation of the GREAT receivers, operating onboard the SOFIA telescope, is using single-pixel heterodyne channels. Each pixel needs a dedicated cryostat cooled using Liquid Nitrogen and Liquid Helium.

The upGREAT channels are the second generation receivers for the GREAT project. These new receivers are medium sized arrays, which will be based on closed-cycle coolers. The following Table summarizes the planned upGREAT receivers, listed together with the current GREAT channels. The upGREAT LFA is currently planned to be commissioned onboard SOFIA in January 2015. The upGREAT HFA will come about 1 year later, beginning of 2016.

Channel	Frequencies (THz)	Lines of Interest
low-frequency L1 a,b	1.25-1.50 (single pixel)	[NII], CO series, OD,HCN,H₂D⁺
low-frequency L2	1.81-1.91 (single pixel)	NH₃,OH,CO(16-15),[CII]
mid-frequency M a,b	2.5 – 2.7 (single pixel)	OH(²π_3/2),HD
high-frequency H	4.7 (single pixel)	[OI]
upGREAT Low Frequency Array (LFA)	1.9 – 2.5 (14 pixels)	OH lines, [CII],CO series, [OI]
upGREAT High Frequency Array (HFA)	4.7 (7 pixels)	[OI]