2. K band History Science workshop determined efficiency improvements necessary for K Band: weather, observing requests, mapping programs. Only enough funds for the receiver only, so the project was de-scoped to seven pixels that meets science objectives as specified in the science case. –$1.2 M Total –$0.19 M Parts –$0.2 M Contingency –$0.83 M Labor The K band seven pixel focal plane array is the path finder instrument: a necessary first step and feasible considering time frame. –Seven pixel array construction complete December, 2009 –Production use by November, 2010.

3. K band Focal Plane Array Science Driver → Map NH 3 –Polarized without Rotation Seven Beams → Limited by IF system 1.8 GHz BW → Limited by IF system 800 MHz BW → Limited by Spectrometer

4. K-band FPA Deliverables Frontend –Cryogenic Package for Seven Pixel Instrument –Seven Dual Circular Polarization K band Pixels –Modular Noise Calibration for each Pixel –Modular Downconverter for each Channel (14) –Monitor and Control Electronics – LO Distribution with Doubler for LO1A Software –Package for Engineering M&C –Observing Software Manager –Data Analysis Pipeline Cost per Pixel not including NRE. –$46,000 Parts (Dewar,EM parts, Isolator, HEMT Amp, WG parts, Noise Mod, IDM) –$2500 Labor Construction. –$2500 Software upgrades.

5. Focal Plane Coverage simulated beam efficiency vs. offset from center 1.Initial 7 elements above 68% beam efficiency (illumination and spillover) 2.Expandable to as many as 61 elements 3.beam efficiency of outermost elements would drop to ~60%. 4.beam spacing = 3 HPBWs

6. GBT Beam Spatial Coverage/ Resolution GBT Aperture Spacing

7. Noise Temperature: 36 K max 18-26.5 GHz, 25 K over 75% of band P 1dB Headroom: 30 dB when T ant = 300 K Noise Temperature and Headroom Limited by Existing Cryogenic LNA Design

8. Cosine Taper Corrugated Feed Horn

9. K band OMT

12. K Band Single Pixel Phase Shifter Thermal Transition OMT FeedNoise Module HEMT Isolators Sliding Transition

13. Drawing of the 7 Pixel Design

14. KFPA Components

15. External Frame

16. Top Plate with 7 Feeds

17. Sliding Waveguide/Thermal Gap Assembly

18. Two downconverters are needed to implement the IF multiplexing scheme. The second downconverter simply omits the latter mixing stage.

19. Integrated Down Converter

20. Future FPA Developments Wish List Significantly enhanced spectrometer with this new array and existing IF system. New digital I.F. distribution system. (Spectrometer and technology dependent). Expanded focal plane array (perhaps at a different frequency: W band)