ska dishes, seeg meeting cape town 17-19 september 2013 ska dish verification antenna #1 – test...
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
SKA Dish Verification Antenna #1 – Test Plan
Gary Hovey, DVA-1 Project Manger
Astronomy Technology Program – Penticton
SEEG Meeting, Cape Town19 September 2013
SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Unit/Sub-assembly Tests• Assembly/Integration Tests• Qualification Tests• Single-dish Tests
• Outline Specification for the DVA-1 Dish(WP2-020-045-020-RS-001)
• DVA-1 Test Requirements for the SKA (WP2-020-030-020-TN-001)
Overview
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Verify components are properly manufactured• Measure performance of units and system.• Compare with Requirements• Check readiness for a subsequent test phase.
• Key performance aspects of DVA1 to be confirmed:– Shape of composite surface(s)– Performance of RIM-supported structure– Performance of foundation and light-weight mount– Performance of Shaped offset-Gregorian-feed-high optics
Test Objectives
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Transitory (Pretty much only one shot at it.)• Chance to understand performance of individual pieces.• Primarily metrology based (Laser tracker / Photogrammetry)• Load/no load tests.• Key components
– Foundation– Mount– Power– Drives– Reflector surfaces
Unit/sub-Assembly Tests
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Tests– Deflections under load– Check for stability and
evidence of rocking
• Equipment required– Laser tracker– Hiab crane– Test load
Foundation
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Control via pendent• Tests
– Safety logic responds as planned– Fail-safe brake and E-stop– Speed and range of motion– No load power usage
• Pre-requisites– AC Power– Cabinet
Basic Drive System
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Tests– Electrical Power lockouts – E-stop and limits switches– Range of motion– Tower deflection vs
moment– Motor torque vs speed– Encoder linearity
• Equipment needed– Basic drive system– Laser tracker– Hiab crane– Tilt meters & Data logger
Mount
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Measure surface– Static shape– Shape changes with
temperature (and perhaps load)
• Equipment– Laser tracker– Photogrammetry
• Other tests– RF reflectivity– Material coupon tests
Reflectors
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Initial Tests– Safety logic and fail safe
brake– Basic motion– Range of motion– Full drive operation
• Tracking• Slewing• logging• Host computer control
• These will be done initially without the feed support and sub-reflector.
Initial Qualification Tests
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Measure changes in shape and position over gravity, temperature, wind, and time– Pedestal– Primary and sub-reflectors– Feed support
Mechanical Performance Tests
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Ku band receiver tests– Adjust feed– Check receiver and backend– Check pointing
RF Qualification Tests
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Holography• Pointing modeling
– Tracking precision repeatability testing• Tipping curves• Antenna radiation patterns and efficiency• System power and dynamic effects over environment.
Single Dish Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
Pointing Model
The pointing model will continue to be refined and updated. Any evolution of the pointing model will be noted and analyzed.
We are considering using an optical telescope securely mounted in the focal region to use for optical pointing. This is more accurate and can look at dynamic effects.
A source will be tracked at the 3dB point for more accurate measurement of the RF pointing
Tipping curves
Tipping curves will be measured to determine the effect of ground spillover as a function of elevation (and azimuth, depending on the horizon variability). This is a direct measurement of the spillover, and can be useful in looking at various baffle structures. Note that the standard “signal” for tipping curves (the atmosphere) will be removed to leave the residual ground-coupling.
Single Dish Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan 14 of 23
SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
Holography• With the inclusion of a small reference antenna and a
prepackaged microwave holography system.
Antenna patterns/efficiency• Wide-angle pattern cuts will be measured (primarily using
satellites) to measure beam-shape and side-lobe structure etc. This will be done at different frequencies (as available) and in the presence of varying solar insolation, wind and elevation.
Power consumption• Drive system can relay motor power and torque, as well as tilt
and gear train torque to host computer.
Single Dish Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
Polarization • Polarization will be investigated by looking at:
– highly polarized satellite downlinks and mapping dual-linear polarization patterns
– natural sources with reference antenna– Both use a reference antenna + correlator– Mechanically rotate by 90o
Single Dish Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Antenna designed for wide-angle UWB feeds• Could reduce the canonical “5-feed” arrangement to 1,2 or 3• Modeling shows ground-spillover limits Ae/Tsys
– Is there a baffle arrangement to mitigate?• Multiple versions:
– ATA, QSC, Quad-ridge, 11 feed, …• Might make most sense at low frequencies:
– 0.5-5.0, (0.7-1.4), 5-10– 0.5-3.0, (0.7-1.4), 3-6
Wide-band Feed Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Outside scope (for N>2)• Outlined in“DVA-1 Test Requirements for the SKA” WP2-020-
030-020-TN-001. • Use to characterize beam with multiple reference antennas
(closure relations)• Internet based VLBI?• Leave in hooks as possible to use with ST
Interferometric Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
Sources: Satellites
Ku-band: e.g. DirecTV, DISH
S-band: e.g. XM radio, Sirius
C-band: e.g. Anik, ABS
L-band: GPS, iridium
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• We have a holography receiver.• Lynn Baker has designed a Ku band holography feed and is
designing an L-band feed.• Need receivers for other bands• MeerKat receiver would be useful for L-band testing.
Receivers
Backend
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Sep 25 Mount arrives• Oct 25 Begin foundation/mount/drive testing• Nov 4 Back-structure attached to Reflector• Nov 6 Begin reflector unit testing• Nov 13Install reflector on mount• Nov 18 Begin Qualification testing• Dec 3 Secondary and feed support Installed• Dec 20Non RF testing mainly complete
Key reflector and mount performance characteristics known
Schedule/Milestones (Pre-single dish tests)
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
• Jan 6 Begin RF qualification testing• Jan 20 Being Holography testing• Feb 3 Install and qualify L-band feed (MeerKat)• Feb 17 Begin pointing modeling• Mar 10 Begin measuring tipping curves• Mar 24 Measure antenna pattern and efficiency• Apr 14 Investigate polarization performance• May 2014
Initial DVA1 single dish testing complete
• Summer 2014 Testing of other bands
Schedule/Milestones:RF Single Dish Testing
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SKA Dishes, SEEG Meeting Cape Town 17-19 September 2013
DVA1 Test Plan
Questions? Comments?
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