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K- band Focal Plane Array

K- band Focal Plane Array. K band History. Science workshop determined efficiency improvements necessary for K Band: weather, observing requests, mapping programs.

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K- band Focal Plane Array

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  1. K- band Focal Plane Array

  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 NH3 • 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. 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 Focal Plane Coverage simulated beam efficiency vs. offset from center

  6. GBT Beam Spatial Coverage/ Resolution GBT Aperture Spacing

  7. Noise Temperature and Headroom Limited by Existing Cryogenic LNA Design Noise Temperature: 36 K max 18-26.5 GHz, 25 K over 75% of band P1dB Headroom: 30 dB when Tant = 300 K

  8. Cosine Taper Corrugated Feed Horn Frequency Range: 18-26.5 GHz (17-27.5 GHz goal)

  9. K band OMT

  10. Feed Thermal Transition Isolators Phase Shifter OMT HEMT Noise Module Sliding Transition K Band Single Pixel

  11. Drawing of the 7 Pixel Design

  12. KFPA Components

  13. External Frame

  14. Top Plate with 7 Feeds

  15. Sliding Waveguide/Thermal Gap Assembly

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

  17. Integrated Down Converter

  18. 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)

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