2009/02/18 IVS TDC Symposium Retrofitted CARAVAN2400 Retrofitted CARAVAN2400 Diameter of Antenna 2.4 m Antenna Type Front-fed Paraboloid Receiving Frequency S-bandX-band Polarization RHCP or LHCP Receiver Noise Temperature S-band : 86K X-band : 170K Driving Speed 1° / sec Broad-band Feed (Quad-ridge Horn) Down Converter
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2009/02/18 IVS TDC Symposiumクワッドリッジホーンアンテナ クワッドリッジホーンアンテナ (( 広帯域フィ広帯域フィードード ) ) をを用いた電波望遠鏡の測地用いた電波望遠鏡の測地 VLBIVLBI における性能における性能評価評価Evaluation of a Radio Telescope Using a Quad-Evaluation of a Radio Telescope Using a Quad-
ridge Horn Antenna on Geodetic VLBIridge Horn Antenna on Geodetic VLBI
Why is wide-band feed Why is wide-band feed adopted?adopted?
2009/02/18 IVS TDC Symposium
Why is wide-band feed Why is wide-band feed adopted?adopted?
We are developing a new small radio telescope for geoWe are developing a new small radio telescope for geodetic VLBI.detic VLBI.
== MARBLE Compact VLBI SystemMARBLE Compact VLBI System < One of a d< One of a development task >evelopment task > S/X band receiving simultaneouslyS/X band receiving simultaneously
< Requirements of the task >< Requirements of the task > 1) Compact1) Compact 2) Simple2) Simple 3) Inexpensive3) Inexpensive 4) RHCP and LHCP 4) RHCP and LHCP
2009/02/18 IVS TDC Symposium
Quad-ridge Horn Antenna (QRHA)Quad-ridge Horn Antenna (QRHA) AdvantageAdvantage ・・ WidebandWideband That cover multi-octave.That cover multi-octave. ・ ・ Compact and lightCompact and light ・ ・ Dual liner polarizationDual liner polarizationDisadvantageDisadvantage ・・ Beam width depend on frequencyBeam width depend on frequency ・ ・ Phase center depend on frequencyPhase center depend on frequency ・ ・ The beam pattern is not symmetry in E-plane and The beam pattern is not symmetry in E-plane and
H-plane.H-plane.
180mm180mm
2009/02/18 IVS TDC Symposium
Evaluation of Retrofitted Evaluation of Retrofitted CARAVAN2400CARAVAN2400
2009/02/18 IVS TDC Symposium
Performance of Retrofitted CARAVANPerformance of Retrofitted CARAVAN System noise temperature (R-Sky method)System noise temperature (R-Sky method)
RR SkySkyMeasured System noise temperatureMeasured System noise temperature S-bandS-band :: 280 K280 K (EL = 90 deg) (EL = 90 deg) ,, X-bandX-band :: 245 K245 K (EL = 90 (EL = 90
deg)deg)
2009/02/18 IVS TDC Symposium
Performance of Retrofitted CARAVAN Performance of Retrofitted CARAVAN contd.contd.
Aperture efficiency measurement using the moonAperture efficiency measurement using the moon
maidea LLkSAT 2/1_Ideal measured Ideal measured
temperaturetemperature Area of dishArea of dish
Flux density of moonFlux density of moon
Boltzmann’s constantBoltzmann’s constant
Loss factor of Loss factor of atmosphereatmosphere
The shape The shape factorfactor
Measured temperatureMeasured temperature sysoffonmeasa TPPT _
Receiving Power from moonReceiving Power from moon Power of Power of background noisebackground noise
Performance of Retrofitted CARAVAN contd.Performance of Retrofitted CARAVAN contd.Calculated by reflector antenna analysis program Calculated by reflector antenna analysis program GRASP8GRASP8
・・ We designed novel wideband radio telescope.We designed novel wideband radio telescope. It adopted wideband feed of simple and compact. It adopted wideband feed of simple and compact. ・・ This radio telescope was confirmed to be able to This radio telescope was confirmed to be able to apply to geodetic VLBI. apply to geodetic VLBI.
But…But…・・ Low Aperture EfficiencyLow Aperture Efficiency・・ High Noise Temperature High Noise Temperature
2009/02/18 IVS TDC Symposium
OutlookOutlookA Prototype of MARBLE Compact VLBI System A Prototype of MARBLE Compact VLBI System 1) Using a optimum designed dish 1) Using a optimum designed dish Aperture efficiency Aperture efficiency ~~ 40% (X-band40% (X-band ,, Predicted)Predicted) (2.4m/2)(2.4m/2)22π x π x 6% 6% << (1.65m/2)(1.65m/2)22π x π x 40%40%
2009/02/18 IVS TDC Symposium
Outlook contd.Outlook contd.A Prototype of MARBLE Compact VLBI System A Prototype of MARBLE Compact VLBI System 2) Using a wideband low noise amplifier2) Using a wideband low noise amplifier S-band TrS-band Tr x : x : 86K86K →→ 65K 65K X-band Trx X-band Trx : : 170K 170K →→ 65K 65K
2009/02/18 IVS TDC Symposium
Outlook contd.Outlook contd.A Prototype of MARBLE Compact VLBI SystemA Prototype of MARBLE Compact VLBI System