Transcript Radio Telescope - ECpE Senior Design

Ongo 2-C
Radio Telescope
Project Advisor:
John Basart
Ali Abdelsalam
Osman Abdelsalam
Greg Bonett
Laura Janvrin
Project Goal
Develop a working radio telescope for Iowa
State, thus increasing research
opportunities for students and faculty on
campus, especially in the Physics and
Astronomy Department
Concept Sketch
(carries radio signal)
System Block Diagram
Start of Year Status
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Wiring issues on tower prevented operation of
coaxial switch, noise source, and inhibited data
collection
Limit Switch Relay board was not functioning
properly, which prevented movement of the dish
Positioning software did not include tracking
over time, and raster scan was inefficient
No documentation existed for limit switch relay
board or terminal blocks within interface box
Deliverables
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New Interface Box with permanent PCBs
capable of reliable operation without frequent
maintenance
Functional Tracking and Raster Scan software
Functioning positioning feedback, basic
calibration routines, basic positioning correction
Limit Switch circuitry to stop motors when limits
are reached
Complete, useful documentation
Operating Environment
Ambient temperatures range from -20ºF –
110ºF
 Strong wind, snow, ice, and rain
 Vulnerable to lightning
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Project Risks
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Dish hardware is custom built for our observatory,
and cannot be replaced if broken.
Outdoor hardware can withstand temperature
extremes, but there is a potential for ice buildup to
prevent telescope operation.
Much of the existing hardware is old and prone to
breaking down, much of the wiring is unreliable.
As this project has moved to a phased approach,
critical information about the system could be lost
if the new group and the returning group do not
work together.
Risk Management
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Maintenance must be performed each semester
to make sure all of the telescope hardware is
working.
Outdoor work on the telescope was all performed
when the weather allowed.
The team has been replacing old cables and
resealing weatherproof boxes to ensure reliability
of equipment.
In both the fall and spring, returning members
worked with new members to help share
knowledge of the entire system.
System Components
Positioning Specifications
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Reported dish position shall be accurate to within
0.1 degrees for both azimuth and elevation.
Azimuth and Elevation calibration shall be
performed automatically or through a very simple
(one or two step) process.
Continuous position updating shall allow tracking
of objects and performing raster scans.
Positioning
This semester, the team focused on
characterizing the positioning capabilities of the
telescope and began calibrating the positioning.
 Preliminary characterization and calibration
was accomplished by aiming the dish at sun
and comparing positioning feedback to the
known coordinates of the sun.
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Interface Box Specifications
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Interface Box shall be properly labelled to allow
ease of troubleshooting and maintenance.
Interface Box shall allow connection between the
computer’s data acquisition card, and the
receiver, limit switch circuit, coaxial switch
actuation, and motor control box.
Interface Box circuitry shall be solid state
components mounted on a printed circuit board.
Interface Box documentation shall include
schematics for all circuits, as well as details for all
wiring connections.
Interface Box – Limit Switch
Circuitry
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In the fall, a PCB layout was designed based on the
current limit switch relay board, but re-examination this
semester revealed missing connections.
A much simpler circuit was designed and tested that
performs the required functions.
The new circuit was created using a PCB, which will
improve reliability of the limit switch circuitry.
Interface Box – Positioning
Circuit
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Positioning circuit includes new Limit Switch circuit as
well as a voltage divider circuit for positioning
feedback
Interface Box – Positioning PCB
Layout
Interface Box – Power Relay
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An existing power relay circuit was modified and
installed into the interface box, and software was
modified to allow the relay to be tripped remotely.
With the relay installed, all components of the
interface box can be controlled using a Remote
Desktop connection.
Interface Box – Voltage
Regulator PCB
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Voltage Regulator circuit maintains a constant voltage
in the Interface Box
Interface Box – Coax Switch
Relay PCB
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Coax Switch Relay circuit grounds the antenna when
the switch is activated via software or physically.
It also powers the LNA, mixer, and noise source, and
can switch on the receiver.
Interface Box – New Box
Old Interface Box
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The new rack-mounted
box will be neat and
organized.
PCB boards will replace
existing boards.
Ribbon cables and new
connectors will be used
to make the box reliable
New Interface Box
Software Specifications
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Software shall support all system, component, and
user interface specifications.
Software must possess an efficient raster scan
function.
Software must be able to track celestial objects over
time.
Software shall be organized according to semester
and frequently backed up to prevent loss of work.
Software documentation shall allow future team
members to pick up where previous team left off.
Software – Raster Scan
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Old Raster Scan software in LabVIEW was modified
to eliminate unnecessary and time-consuming motion
of the telescope dish.
Software –
Raster Scan User Interface
Software – Software Limits for
Dish Movement
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Only allow opposite voltage to pass to Motor Control
Box when dish is 2 degrees from each physical limit
Software - Wiki
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To facilitate the passing of knowledge from semester
to semester, the team has implemented a Wiki.
Existing documentation was uploaded to the Wiki and
indexed on the Wiki. This will also allow team
members to search through all the documentation
contained on the Wiki for needed information.
The wiki can be accessed at:
www.sscl.iastate.edu/wiki/
Complete System
Specifications
System shall be operable remotely.
 Software shall be comprehensible to
astronomy students.
 System equipment shall not require
maintenance more than twice per semester.
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System Maintenance
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In the fall, the team replaced faulty cable and conduit
going up to the dish.
A weather-proof seal was added to the feedhorn cap
to prevent water from leaking in.
Feedhorn was checked in the spring for water.
Testing Areas
RF Section – All components relating to radio
signals (feedhorn, amplifier, mixer, coaxial line)
 Positioning Hardware – Detection equipment
and motors
 Positioning Software – Software programs used
to position the dish for data acquisition
 Interface Hardware – All circuitry used to
connect the computer to the other system
components
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Testing Objectives
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Confirm basic operation of all components
 Individual
electrical components
 RF Section
 Positioning hardware
 Positioning software
 Interface hardware
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Quantify system parameters
 Measure
RF losses
 Determine positioning accuracy
Testing – RF Section
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Individual RF components in the front-end box
(mixer, LNA, noise source) were tested using a
signal generator and spectrum analyzer
The entire signal path was tested using a signal
generator at the observatory
Noise Source off
Testing - RF Section
Measured appropriate gain/loss through the
entire system and through the front-end
components
System Bandwidth
400
350
300
Received Intensity
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250
200
150
100
50
0
1405
-50
1410
1415
1420
Input Frequency (MHz)
1425
1430
Testing – RF Section
Component
Gain/loss
Low-noise amplifier
28 dB
Converter
19 dB
Noise source
10 dB
Testing - Positioning Hardware
Confirmed dish will move to known degree
limits
 Verified position detection hardware is accurate
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 After
calibration, software (without software limits in
place) shows 0° for minimum elevation, 86.5° for
maximum elevation, etc.
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Verified that position output is precise
 Positioning
variation is less than 0.05 degree if dish
is not moving
Testing - Positioning Software
Confirmed software function by measuring
DAQ output
 Verified functionality by running positioning
software
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Input coordinates of known source (the sun)
 Positioning software with correction placed dish in
proper position
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Verified tracking software functionality
 Verified raster scan software functionality by
performing raster scan of area of sky including
the sun
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Testing – Intensity Graph
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Tested the intensity graphing capabilities of our system
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Performed a manual scan across the sun and recorded
the intensity every 10 ms
Amplitude of 385 corresponds to a solar flux value of 490000 Jansky
Testing - Interface Hardware
Performed continuity checks to ensure
components are properly connected
 Confirmed all software programs properly
activate appropriate hardware relays
 Verified input and output voltages meet
component specifications
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Work Descriptions
Green = Task Complete
Yellow = Task In Progress
End of Semester Status
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We are testing the new Interface Box.
All three new PCBs in the Interface Box have
been installed.
Raster Scan and Tracking software have been
tested.
The RF system has been extensively tested and
recommendations made for repairs.
All relevant interface box circuitry and positioning
circuitry has been documented and labelled.
Earned Value Analysis
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The old Interface box has been causing problems since
its creation. The new box will reduce the amount of
maintenance required.
The preliminary positioning calibration done this
semester will give future teams a basis for more
precise calibration and correction.
Documentation that has been created will improve
future teams’ abilities to familiarize themselves with the
project quickly and solve problems faster.
For the Next Team
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Now that the basic software is available and
working, unified user interface software should be
written to make the system more user-friendly.
Pointing correction software can be written to
further calibrate the positioning of the telescope.
The impedance of the feed horn should be
matched to the line.
The raster scan software should be modified to do
successive scans to reduce image noise.
Lessons Learned
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Conscious effort needs to be made to stay on
schedule.
Proper documentation saves time and work in the
long run.
It is impossible to plan all tasks at the beginning
and work through them – problems will always
arise and require adjustments and new planning.
Conclusions
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The new Interface Box will be a great benefit to future
teams in terms of reliability and ease of
understanding.
The intensity of the sun has been successfully
measured, and all components of the RF system
have been characterized.
All of the software needed to run the telescope is
complete, but improvements can still be made in
terms of making one unified program.
At the end of this semester, the radio telescope
system will be operational for future teams to add
additional astronomy features.
Acknowledgements
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Dr. John Basart for work as advisor
Dr. Gregory Smith for feedback and providing
funds for parts
Matt Nelson for help with PCB ordering
Jesse Griggs and Matt Clausman for Eagle
software training
Ryan Cragg for help with making a lid for the
Motor Control Box