VLBI2010 – Current status of the TWIN radio telescope ... · 6 11 where: SNR = signal to noise ratio f = VLBI processing factor (ca. 0.55 for 1bit Data streams) S = source-flux

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VLBI2010 – Current status of the TWIN radio telescope project

at Wettzell, Germany

G. Kronschnabl, (BKG); Hase, H. (BKG); Schreiber, U. (BKG);

K. Pausch (Vertex GmbH); W. Göldi (Mirad); B. Petrachenko (NRCan);

A. Emrich (Omnisys) and the VLBI team Wettzell

Alexander Neidhardt, FESG/TU München (on behalf of the BKG)

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The geodetic observatory Wettzell andthe current VLBI System

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The geodetic observatory Wettzell and ist location

Geodetic Observatory Wettzell

Germany surrounded by the

Bavarian Forest

Technische Universitaet Muenchen

Research Group Satellite Geodesy

Federal Agency for Cartography and

Geodesy, Frankfurt

See: http://maps.google.com/, Download 2010/0217

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The geodetic observatory Wettzell and ist location

See: http://maps.google.com/, Download 2010/0217

Radio

Telescope

Wettzell

Ringlaser

(Large

gyroscope)

Gravimetry

Laser

Ranging

Telescope

Area of the new

Twin Radio Telescope

Wettzell

GPS

Meteo

Time&

Frequency

New

gravimetry

house

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Radio telescope Wettzell (RTW) and its team

RTW: D=20m, S/X-Band; Velocities: 3° & 1.5°/s; Tsys=40K; 1Gbps;

The Wettzell VLBI crew (from left to right):

Ch. Plötz, E. Bauernfeind, G. Kronschnabl,

R. Schatz, W. Schwarz, R. Zeitlhöfler, A. Neidhardt

(missing in picture: E. Bielmeier).

TIGO Concepción/Chile GARS O’Higgins/Antarctica

RT Wettzell/Germany

And in the future:

TTW Wettzell

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Main participation –International VLBI Service for Geodesy and Astrometry

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VLBI2010

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VLBI 2010

IVS WG 3 – VLBI2010: Current and future requirements for geodetic VLBI Systems

• Determination of the relative position better than 1 mm / year

• Continuous observation of the Earth Orientation Parameters (EOP)

• Very fast generation and distribution of IVS-products and results

Ł continuous and precise UT1 monitoring for UT1-UTC determinationŁ improvement of the Celestial Reference Frame (CRF)

Goals for a next generation VLBI-System:

Source: IVS WG3 Final Report - ftp://ivscc.gsfc.nasa.gov/pub/annual-reports/2005/pdf/spcl-vlbi2010.pdf

VLBI2010 – a vision

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where:

SNR = signal to noise ratio

f = VLBI processing factor (ca. 0.55 for 1bit Data streams)

S = source-flux (Jy)

Di = antenna diameter per Station

k = Boltzmann constant

ei = beam efficiency of the antenna

BR = bit rate

t = integration time

Tsys = system temperature per station (at the same frequency)

Source: IVS WG3 Final Report

Improvements

• higher bandwidth

• better quantization of the signals

• higher effectivity of the dish

• higher data acquisition rate

• reduced system temperature

• better path lengths behaviour

12

0

5

10

15

20

25

30

0 2 4 6 8

0

0.5

1

1.5

2

2.5

2 3 4 5 6 70 2 4 6 8 10 12 14 16

Broadband-Sequence with 4 Bands

and a band width of 1 GHz

Phas

e P

has

e

frequency (GHz)

frequency (GHz)

0 2 4 6 8 10 12 14 16

SN

R t

o r

eso

lve

the

phas

e

No. of frequency bands

No. of frequency bands

Phas

e del

ay p

reci

sio

n

Standard S/X – Bands with a

band width of 250 & 720 MHz

BW=1 GHz

BW=0.5 GHz

BW=2 GHz

BW=1 GHz

BW=0.5 GHz

BW=2 GHz

Source: B. Petrachenko: Broadband Delay Tutorial, FRFF Wettzell 2009

New frequency band simulations

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§ Fast moving antenna (6°/sec)

§ Antenna dish diameter of min. 12m

§ Broadband receiving system (2 to 14 GHz or higher including S- and X-band for compatibility to the current systems; optional Ka-band)

§ 1 mm position and 1 mm/year velocity stability of reference position (stiff construction, new system calibrations)

§ Optimized antenna dish and receiving system efficiency

§ Digital data acquisition systems with high sampling rates and quantization (min. 2 Gbit/sec with 2, 4 and 8 bit)

§ Phase center stability over different frequencies

§ Phase delay measurement systems

§ High mechanical quality for gears, motor servos, bearings, etc.

§ More than one antenna at one site

§ Remote controllable, automatable techniques

§ …

Basic antenna and system requirement definitions

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A complete realization – the TWIN radio telescope concept

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Technical details:

§ Main reflector: 13.2m

§ Ring focal design

§ f/D = 0.29

§ Path Length Error <0.3mm

§ ALMA Mounting with drive velocities of 12°/s in Azimuth and 6°/s in Elevation

§ Balanced antenna design

§ 27Bit Encoder : 0.0003°resolution

§ Adjustable sub-reflector using a Hexapod

§ Lifetime min. 20 years

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Technical details:

§ Main reflector: 13.2m

§ Ring focal design

§ f/D = 0.29

§ Path Length Error <0.3mm

§ ALMA Mounting with drive velocities of 12°/s in Azimuth and 6°/s in Elevation

§ Balanced antenna design

§ 27Bit Encoder : 0.0003°resolution

§ Adjustable sub-reflector using a Hexapod

§ Lifetime min. 20 years

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Ground and soil analysis

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Location analysis

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Location analysisBK20 BK18 BK21 BK22

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Ring focus design

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The ring focus design (1)

Source: Hase, H.; et. al.: TWIN Telescope Wettzell – A VLBI2010 project. FRFF Workshop, 2009

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13.2m Ring Focus Antenna

Aperture Field Distribution, f = 5 GHz

-25

-22.5

-20

-17.5

-15

-12.5

-10

-7.5

-5

-2.5

0

-6.5 -6 -5.5 -5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5

rho [m]

Rela

tive A

mplitu

de [dB]

Distribution of the radiated energy

• dual-reflector receiving system

• optimal for large flare angles

• no blockage by the sub-reflector

• high illumination efficiency

• the feed horn is prevented by

radiation from the sun

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Effective beam efficiency


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Reduction of deformations

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A stable path length (error < 0.3 mm)

elevation axis

L1

L2

L3

L4

P1=P1'

P2

P3

P4

P5

not deformed

deformed

focus ellipse

focus feed

main reflector

subreflector (ellipse)

feed cone

P3'

P4'

P2'

P5'

L1 = distance main axis to reflector surface

L2 = distance reflector surface to sub-reflector

L3 = distance sub-reflector to feed focus

L4 = distance feed focus to axis intersection point

Reduction of the gravitational effects using a hexapod to position the sub-reflector

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Gravitational deformation

Quelle: Vertex Design Review; Dez. 2008

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Wind uploads (40km/h)

Quelle: Vertex Design Review; Dez. 2008

WindWind

Wind

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Surface accuracy

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7 Z-profile supports on the backside

Surface error RMS < 65 um

Gap between panels < 1mm

Surface quality

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Broadband receiving system

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The planned horns

Tri-band corrugated horn(Mirad)

S-, X- and Ka-band

Eleven feed(Omnisys/Chalmers University Goteborg)

2-11 GHz

Quelle: Willi Göldi, Mirad; M. Pantaleev, Chalmers Univ.; Schweden

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The planned horns

Tri-band corrugated horn(Mirad)

S-, X- and Ka-band

Eleven feed(Omnisys/Chalmers University Goteborg)

2-11 GHz

Quelle: Willi Göldi, Mirad; M. Pantaleev, Chalmers Univ.; Schweden

3dB/90°

Turnsti le

Horn S-Band

Horn X-Band

X/RHCP

X/LHCP

3dB/90°

Ka/LHCP

Ka/RHCP

S/LHCP

S/RHCP

Polari zer

Septum

Hybrid

Hybrid

S-Band

X-Ba ndTurnstile

Feed Ka-B and

B PF

B PF

B PF

B PF

B PF

B PF

X/RHCP

X/LHCP

Ka/LHCP

Ka/RHCP

S/LHCP

S/RHCP

LNA

LNA

LNA

LNA

LNA

LNA

Dewar

ANTT

opticopticLT ,

nextT

FEEDFEED LT ,LNALNA GT ,

portport LT −− 88 ,

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35Quelle: A. Emrich; Omnisys.; Schweden

Cryogenic dewar for the Eleven feed(Omnisys/Chalmers University Goteborg)

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Phase-Calibrationsystem

MW-Filter

0 -14 GHz

NoiseCal

Injection

MW-Filter

MW-Filter

MW-Filter

0 -14 GHz

MW-Filter

20- 22GHz

MW-Filter

20- 22GHz

MW-Mixer

AmpAmp

Amp AmpAmp

Amp

MW-Mixer

MW-Mixer

MW-Mixer

RMS-Detector

Synthesizer

23 – 33 GHz

PLDRO

22.5 GHz

Phasetrack -Cable

MW-Kabel

MW-Kabel

H-Maser

LNA‘s

DAQ-SystemDBBC, DBE

MK5B, MK5C

FS-PC

5/1

0 M

Hz-

Dis

trib

uto

rOther channels

VPol

HPol MK5

A/D

Controller

Feed/Dewar

Subreflectorhorn

The whole receiving system

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Cable wrap optimized for cable delay stabilityand used space

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Remote control and unattended observations

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The new observation strategies in a new operator room

RTW TTW1 TTW2 OHIGGINS

TIGO SOSW WLRS Data center

SharedLocal Remote Unattended

Internet

Inte

rnet

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The TWIN radio telescope – some impressions

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Impressions of TWIN construction

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Thank you!

Documents

VLBI2010 – Current status of the TWIN radio telescope ... · 6 11 where: SNR = signal to noise ratio f = VLBI processing factor (ca. 0.55 for 1bit Data streams) S = source-flux