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.

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

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.

Focal Plane Coverage

simulated beam efficiencyvs. offset from center

1. Initial 7 elements above 68%beam efficiency (illuminationand spillover)

2. Expandable to as many as61 elements

3. beam efficiency of outermostelements would drop to ~60%.

4. beam spacing = 3 HPBWs

3 HPBW

K Band f = 22 GHz

28"

.177 HPBW/mm

= 13.36 mm88.9 mm

GBT Beam Spatial Coverage/ Resolution

GBT Aperture Spacing

Noise Temperature: 36 K max 18-26.5 GHz, 25 K over 75% of bandP1dB Headroom: 30 dB when Tant = 300 K

Noise Temperature and Headroom Limited byExisting Cryogenic LNA Design

Frequency Range: 18-26.5 GHz (17-27.5 GHz goal)

Cosine Taper Corrugated Feed Horn

K band OMT

K Band Single Pixel

Phase Shifter

Thermal Transition

OMT

Feed

Noise Module

HEMT

Isolators

Sliding Transition

Drawing of the 7 Pixel Design

KFPA Components

External Frame

Top Plate with 7 Feeds

Sliding Waveguide/Thermal Gap Assembly

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

Integrated Down Converter

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)