A Modular KBand Focal Plane Array for the
A Modular K-Band Focal Plane Array for the Green Bank Telescope 9/28/2007 Matt Morgan National Radio Astronomy Observatory
Baseline Instrument Specifications Specification Requirement Frequency Band 18 -26. 5 GHz (complete K-Band coverage) TRX (each beam, not including sky) < 25 K (75% of band)* < 36 K (entire band) Number of beams 7 Polarization dual, circular (axial ratio <= 1 d. B) SIdeband (image) rejection > 30 d. B Instantaneous RF Bandwidth 1. 8 GHz Mass < 100 kg Headroom > 30 d. B (to 1 d. B compression point) *Should in fact be equivalent to EVLA receiver noise temperatures.
Focal Plane Coverage 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 simulated beam efficiency vs. offset from center
Key Subsystems 1 2 3 1. 2. 3. 4. 4 6 5 Feedhorn Array Cryogenic Dewar Cooled Electronics Integrated Downconverter Modules (IDM) 5. LO Distributions and M&C 6. IF Transmission System
Bandwidth Limitations Sub-Assembly Total Potential Bandwidth comments cold-electronics (feed, OMT, LNA. . . ) >8. 5 GHz performance degrades gracefully outside of 18 -26. 5 GHz warm analog electronics 1. 7 GHz (up to 8 dualpolarized beams limited by existing IF transmission system, requires multiplexing digital electronics 800 MHz (4 beams) 50 MHz (8 beams) limited by existing spectrometer
Potential Upgrade Paths for IF Transmission System Methods for increasing IF tranmission bandwidth and number of channels: install additional analog fibers modulate additional colors on existing fibers digitize at the antenna, and use commercial digital fiber links preferred solution with greatest long-term potential may also employ digital filtering/decimation or compression at the antenna Note that all of these would provide enhanced capability to all focal plane arrays, regardless of the frequency band. However, only the last one is likely to be able to handle the extreme data volumes produced by large-format "cameras" such as a W-Band array with a hundred or more elements.
Pixel Design
Pixel Performance Calculation Worksheet Gsys = 62. 3 -63. 8 d. B Tsys = 95 -104 K (Tsky = 75 K) Pout = -26. 2. . . -25. 0 d. Bm min. headroom = 35. 2 d. B
Program Schedule
Milestones 1/15/2008 5/13/2008 5/8/2008 8/8/2008 1/6/2009 2/13/2009 6/9/2009 11/3/2009 2/8/2010 4/6/2010 11/8/2010 System design complete with Conceptual Design Review acceptance. M&C hardware module with support software complete. Single pixel construction complete. Single pixel testing complete with Critical Design Review acceptance. Multi-Pixel dewar assembly complete. Observing support software complete. Multi-pixel testing and construction complete. System integration and lab testing complete. Data analysis software complete. Telescope testing complete. Commissioning complete.
Cost Summary Item LM Budget Total Cost Total Funded Labor $ 824 k Total GB Operations Labor $ 0 k $ 468 k Total Parts Cost $ 190 k Contingency $ 202 k Total $1216 k $1684 k (detailed cost breakdown available if needed)
Open Issues Exact frequency coverage of the front end. Is this optimal for the science? What are the technical options? What are the desired polarization characteristics of the array? Is the choice of circular polarization for all feeds the best? Noise injection: is there a need for various intensity cals? Feed rotator: is it necessary? What should its specs be? (This needs to be considered in the contect of the performance of the off-axis feeds, which may not be symmetric around the central pixel). Feed pattern: any better options than close-packed hexagon? Continuum mapping capabilities: should this be any consideration? If so, what does it imply? Operational issues: telescope scanning to fill in the coverage; subreflector nodding?
BACKUP SLIDES FOLLOW
Labor Estimates: Year 1 Item Machinist [FTEs] Technician [FTEs] Astronomer [FTEs] Engineer [FTEs] Eng&Tech GB ops [FTEs] Compact Feedhorn 0. 2 0. 0 Noise Calibration Module (NCM) 0. 25 0. 0 0. 25 Integrated Downconverter Module (IDM) 0. 1 0. 25 0. 0 0. 5 0. 0 LO Distribution 0. 1 0. 0 1. 0 M&C, biasing, PCB design and layout 0. 0 1. 0 Mechanical design (overall receiver, cryostat) 0. 25 0. 0 0. 75 Parallactic Angle Rotator 0. 25 0. 0 0. 5 Project management 0. 0 0. 25 Systems engineering 0. 0 0. 25 0. 0 Project scientist 0. 0 0. 5 0. 0 Software Development 0. 0 0. 5 0. 0 Total FTEs: 1. 15 0. 5 1. 7 3. 5 Funded Total = $368 k Total GB Ops = $302 k
Labor Estimates: Year 2 Item Machinist [FTEs] Technician [FTEs] Astronomer [FTEs] Engineer [FTEs] Eng&Tech GB ops [FTEs] NCM housing and assembly 0. 1 0. 0 IDM housing and assembly 0. 0 0. 25 0. 0 Project management 0. 0 0. 25 0. 0 0. 125 Systems engineering 0. 0 0. 25 0. 0 Receiver assembly and cabling 0. 25 0. 0 1. 0 Project scientist 0. 0 1. 0 0. 0 Software Development 0. 0 0. 5 0. 0 Total FTEs: 0. 35 0. 6 1. 0 1. 125 Funded Total = $295 k Total GB Ops = $133 k
Labor Estimates: Year 3 Item Machinist [FTEs] Technician [FTEs] Astronomer [FTEs] Engineer [FTEs] Eng&Tech GB ops [FTEs] Receiver Engineer 0. 0 0. 25 Project scientist 0. 0 1. 0 0. 0 Software Development 0. 0 0. 5 0. 0 Total FTEs: 0. 0 1. 0 0. 5 0. 25 Funded Total = $160 k Total GB Ops = $ 34 k
Parts Cost Part Qty. Unit cost Extended cost Feedhorns 7 $ 2. 0 k $ 14. 0 k Phase shifters and transitions 7 $ 7. 0 k $ 49. 0 k OMTs 7 $ 2. 0 k $ 14. 0 k Isolators 14 $ 0. 5 k $ 7. 0 k NCM parts 14 $ 0. 8 k $ 11. 2 k LNAs 14 $ 3. 0 k $ 42. 0 k IDM parts 7 $ 2. 9 k $ 20. 3 k LODM&C parts 1 $ 5. 0 k Refrigerator 1 $ 8. 0 k Parallactic Angle Rotator 1 $19. 5 k $ 19. 5 k Funded Total = $190 k
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