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National Astronomy and Ionosphere Center

Cornell University

The Arecibo L-Band Feed Array ALFA Front-End Optics
GermÀn CortÈs MedellÌn

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-1


National Astronomy and Ionosphere Center

Cornell University

Outline

ALFA Specifications Feed Horn Characteristics Antenna Performance Far Field Beam Characteristics Drift-Scan Sampling

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-2


National Astronomy and Ionosphere Center

Cornell University

ALFA Specs.
Frequency Band Number of Pixels Return Loss (RL) Polarization Polarization Isolation Edge Illumination Gain variation over the band Horn Aperture Diameter Center-to-Center Horn Spacing Dewar Rotation
Arecibo L-Band Feed Array G. CortÈs,

1.225 to 1.525 GHz 7 > 20 dB Linear, Dual >20 dB >12 dB +1/-2 dB 250 mm 260 mm ± 100°
Arecibo Mar, 2003 1-3


National Astronomy and Ionosphere Center

Cornell University

ALFA Overall Dimensions

TEM P ER ATURE TE M PE RATURE MO NITO R MONIT OR

DA TA SET INT ERFA CE 4
TXD BUS Y PAR ITY ERRO R RE S ET 1

NOISE SOU RCE DRIVER
Loc/Rem Test Ton e Aux 1 Aux 2 Cal RF S w it ch Cal 2 RF S w it ch

F93

PFEIFF ER
ANALOG MUX

VA CUU M

DualG au ge

- OOOOO

E - 18

P ARA

CH

SUBR ACK D C INTERFACE

ON OFF

ON OFF

CRY O DY NE ACT IVE

+2 0V

SUPPLY

- 20V

CSIRO

TRAN SLA TO R CAL DRIVE P ADDL E

AUX

F25 FRONT D C IN TERFA CE

ON OFF

ON OFF

+3 2V

CO M

+20V

+9V

-20V

ALFA

CSI RO

MO N

LNA

AUX

OFF

ON

Top View
Arecibo L-Band Feed Array G. CortÈs,

Side View
Arecibo Mar, 2003 1-4


National Astronomy and Ionosphere Center

Cornell University

ALFA Focal Plane Layout

ALFA

Layout in Focal Plane

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-5


National Astronomy and Ionosphere Center

Cornell University

0.0 -0.2 -0.4 -0.6

Arecibo Gregorian Focal Plane Scanning Losses

Scanning Loss [dB]

-0.8 -1.0 -1.2 -1.4 -1.6 -1.8 -2.0 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 Along X-Axis Along Y-Axis 26cm C-C, 2.7cm X-Offset

1.375 GHz

Displacement along X/Y Axis [cm]

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-6


National Astronomy and Ionosphere Center

Cornell University

ALFA Antenna Performance

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-7


National Astronomy and Ionosphere Center

Cornell University

ALFA Calculated Antenna Sensitivity
CSIRO TE11 Mode Horn 25cm x 26cm, 2.7cm X-Offset
12 10 8 6 4 2 0 0 30 60 90 Horn Angle [deg]
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-8

Antenna Sensitivity [K/Jy]

1.225 GHz 1.375 GHz 1.525 GHz

120

150

180


National Astronomy and Ionosphere Center

Cornell University

ALFA Calculated System Temperature
CSIRO TE11 Mode Horn 25cm x 26cm, 2.7cm X-Offset
45 40
Antenna System Temperature [K]
1.225 GHz 1.375 GHz 1.525 GHz

35 30 25 20 15 10 5 0
0 30 60 90 Horn Angle [deg]
Arecibo L-Band Feed Array G. CortÈs,

Tscatt Trec
120 150

4.00 K 8.00 K
180

Arecibo Mar, 2003

1-9


National Astronomy and Ionosphere Center

Cornell University

ALFA Calculated G/T
60 59 58 57

sys

CSIRO TE11 Mode Horn 25cm x 26cm, 2.7cm X-Offset
1.225 GHz 1.375 GHz 1.525 GHz

10 Log10 [G/T]

56 55 54 53 52 51 50 0 30 60 90 Horn Angle [deg]
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-10

120

150

180


National Astronomy and Ionosphere Center

Cornell University

ALFA Antenna Multi Beam Characteristics

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-11


National Astronomy and Ionosphere Center

Cornell University

Far Field Beam Characteristics

r

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-12


National Astronomy and Ionosphere Center

Cornell University

Multi Beam Sky Footprint

Focal Plane

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-13


National Astronomy and Ionosphere Center

Cornell University

Far Field Beam Characteristics

Aperture Spacing 25 cm 26.0 cm
Angle
L

Feed Type TE11

X- Offset 2.7 cm
Position Position SKY rSKY [arcsec] 39.87 421.46 404.70 364.48 329.95 324.20 338.74 346.55 [deg] 0.00 0.00 -24.72 -52.62 -85.38 -120.14 -151.74 180.00
G. CortÈs, Arecibo Mar, 2003 1-14

FP

HPBW1 HPBW

2


[deg] 0 0 5 4 -5 -9 -6 0



Pix 0 0° 30° 60° 90° 120° 150° 180°

[arcsec] [arcsec] 230 201 236 206 234 207 229 208 227 206 230 202 234 198 236 197

Arecibo L-Band Feed Array


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 0
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-15


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 1
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-16


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 2
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-17


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 3
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-18


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 4
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-19


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 5
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-20


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 6
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-21


National Astronomy and Ionosphere Center

Cornell University

Sky Footprint Pixel # 0
1.375 GHz

Sky Area 50' x 50'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-22


National Astronomy and Ionosphere Center

Cornell University

Total Incoherent Multi Beam Pattern
TE11 Mode Horn 25.0 cm x 26.0 cm
U -3.0 dB

-6.9 dB -8.5 dB

-6.7 dB

-5.9 dB

Sky Area 25' x 25'
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-23


National Astronomy and Ionosphere Center

Cornell University

ALFA Calculated Beam Comatic Level
0 -2 -4 SLL

Coma SLL [dB]

-6 -8 -10 -12 -14 -16 -18 0 30 60 90 Angle [deg]
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-24

120

150

180


National Astronomy and Ionosphere Center

Cornell University

ALFA Polarization Characteristics Polarization Probes Orientation in OMT

OMT probe positions septum position
Arecibo L-Band Feed Array

noise coupler position
G. CortÈs, Arecibo Mar, 2003 1-25


National Astronomy and Ionosphere Center

Cornell University

ALFA Polarization Characteristics Calculated Cross Polarization
0 1.225 GHz 1.375 GHz 1.525 GHz

-10

-20

-30

-40 0 30 60 90 Horn Angle [deg]
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-26

120

150

180


National Astronomy and Ionosphere Center

Cornell University

ALFA Drift Scan Sampling
Methods



Ideal Circular Path
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-27




National Astronomy and Ionosphere Center

Cornell University

ALFA Drift Scan Sampling
Methods
Error Function



Actual Elliptical Path
Arecibo L-Band Feed Array G. CortÈs, Arecibo Mar, 2003 1-28


National Astronomy and Ionosphere Center

Cornell University

ALFA Drift Scan Sampling
Optimum Feed Arm Rotation Angle
6 5 Ideal Circle Footprint Coax 22x23 cm TE11 25 x 26 cm

{i>
4

max)]²,

22.0°
3

[|di-dj|/(6xd

2

1

0 0 30 60 90 Feed Arm Angle [deg] 120 150 180

19.1°
Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-29


National Astronomy and Ionosphere Center

Cornell University

ALFA Drift Scan Sampling
Crossover levels at Optimum Feed Arm Rotation Angle
0 TE11 25x26cm

-1
Relative Power Level [dB]

-2

-3

-4

-5 -600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

FOV angle [arcsec]

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-30


National Astronomy and Ionosphere Center

Cornell University

The End

Arecibo L-Band Feed Array

G. CortÈs,

Arecibo Mar, 2003

1-31