SITR September 2009; Page 1 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR GREAT GREAT: German REceiver for Astronomy at Terahertz frequencies PI-Instrument funded and developed by  MPIfR (2.7THz channel)  R. Güsten (PI)  S. Heyminck (system engineer)  B. KIein (FFT spectrometer)  MPIfR Engineers (electronics, LO-mechanics)  KOSMA (1.4/1.9THz channels)  J. Stutzki (Co-PI)  U.U. Graf et al. (1.4 &1.9THz LO, Optics)  K. Jacobs et al. & 2.7THz)  R. Schieder et al. (array-AOS)  DLR-Berlin (4.7THz channel)  H-W Hübers et al. (IF, cold-Load, …)  MPS  P. Hartogh et al. (CO-PI; CTS) Lab-picture of GREAT equipped with theL#1 and L#2 channel

SITR September 2009; Page 2 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR Early-Science Configurations GREAT flight configurations:  baseline: simultaneous observations with 2 low-frequency channels  goal: fly mid-frequency channel at the earliest possible  upgrade : operate 4.7 THz channel (not in short and basic science) Short science configuration:  baseline configuration (2 low-frequency channels) Basic science configuration:  goal configurations (combinations of the mid and low-frequency channels)

SITR September 2009; Page 3 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR Stoplight-chart SOFIA schedule is still slipping fast  GREAT is in sleep mode now: only technology development for THz LO-sources and for mixers no further testing / development activities on GREAT Comments:  M-Band Solid-State-LO technical risk (not short science) GREAT L-L configuration passed its PSR in Dec and is ready for shipment SOFIA schedule

SITR September 2009; Page 4 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR KOSMA THz-HEB development  overcoming isolator by using a Caltech LNA (S. Weinreb et al., Rev. Sci. Instrum. 80, (2009) )  increased IF-bandwidth  good stability (~30s total power Allan-times)  new HEB-design for better performance new BIAS-T 1.9 THz waveguide mixer block

SITR September 2009; Page 5 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR IF 1.4THz mixer gain roll-off T REC - T IF /G MIX IF-bandwidth so far

SITR September 2009; Page 6 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR M-Band channel  optics and cryostat are ready  two LO-systems under development  VDI solid-state LO (ordered)  output power-level not demonstrated so far  Photonics LO-system  good performance up to 1.1 THz demonstrated  scaling to 2.7 THz looks promising  first 2.7THz tests are ongoing

SITR September 2009; Page 7 MPIfR KOSMA MPS DLR-Berlin S. Heyminck, MPIfR Schedule towards S/S flights  GREAT team needs about 24 weeks prior to short science for  re-testing the first flight configuration (as accepted in PSR Dec. 2008)  additional testing of mixers  shipment  post-shipment test in Palmdale  integration test aboard SOFIA (incl. EMI-test) (see also IMS for details of the GREAT milestones)