Spacecraft Systems and Control Lab
Dr. John P. Basart
Dr. John P. Basart
Niclo Hitchcock (EE)
Laura Janvrin (EE)
Nick Jensen (CprE)
Greg Bonett (EE)
Sulianet Ortiz (EE)
Ali Abdelsalam (EE)
Osman Abdelsalam (EE)
DISCLAIMER: This document was developed as part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. The document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no
claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. Document users shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. Such use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed
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Table of Contents
LIST OF FIGURES ... 3
CURRENT SITUATION ... 4
PROBLEM ... 4
CLIENT AND NEED ... 4
APPROACH ... 4
CONCEPT SKETCH ... 5
SYSTEM BLOCK DIAGRAM ... 5
SYSTEM DESCRIPTION ... 8
CURRENT SYSTEM STATUS ... 8
RESULTING PROBLEMS ... 10
Poor Positioning ... 10
Unreliable Remote Operation ... 10
Lack of Documentations ... 10
PROJECT OBJECTIVES ... 10
USER INTERFACE DESCRIPTION ... 11
MARKET SURVEY ... 12 RISKS ... 12 Risk Management ... 13 SCOPE ... 13 FUNCTIONAL REQUIREMENTS ... 13 NON-FUNCTIONAL REQUIREMENTS ... 13 DELIVERABLES ... 13 Working Components ... 14
Tests and Results ... 14
Documentation ... 14
WORK BREAKDOWN STRUCTURE ... 15
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List of Figures
FIGURE 1-CONCEPT SKETCH ... 5
FIGURE 2-SYSTEM BLOCK DIAGRAM ... 6
FIGURE 3-CURRENT SYSTEM STATUS ... 9
FIGURE 4-WORK BREAKDOWN STRUCTURE ... 15
FIGURE 5-ORGANIZATIONAL CHART ... 16
FIGURE 6-SCHEDULE OF TASKS ... 17
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Radio telescopes are used to study naturally occurring radio emission from stars, galaxies, quasars, and other astronomical objects. Astronomical objects typically emit radio waves at wavelengths between roughly 10 meters to 1 millimeter (30 MHz to 300 GHz). However, atmospheric effects typically limit ground-based radio telescope operation to between 10 meters and 1 cm. At short wavelengths atmospheric absorption limits reception and tends to distort incoming signals, so sophisticated signal processing techniques are needed. [National Radio Astronomy Observatory, http://www.nrao.edu/] Although radio telescopes are quite useful for fundamental research on the nature of the universe, Iowa State University does not have a working radio telescope facility. For the past several years, the Iowa Space Grant Consortium has been sponsoring the development of a radio telescope system for use at Iowa State. The equipment is located at the Fick Observatory, near Boone, IA.
ISU’s lack of a working radio telescope limits the research that faculty, staff, and students from various Colleges and Departments with interests in astronomy can conduct.
Client and Need
As a result, Dr. John Basart wants to develop a working radio telescope at the Fick Observatory for Iowa State University. Secondary customers consist of students and faculty of the ISU Department of Physics and Astronomy as well as those who have access to the Fick Observatory.
Due to limited funds and manpower available for the project, Dr. John Basart would like to work with Department of Electrical and Computer Engineering Senior Design groups to convert a low-cost parabolic dish and a salvaged WWII gun mount into a working radio telescope. The project started in 19yy and has been in continuous development since that time as an ongoing Senior Design project. The proposed solution is to develop a functional radio telescope that can be used for research and educational purposes. When completed, the Fick Observatory Radio Telescope will be used to image the radio sky at a frequency of 1420 MHz. This frequency was chosen to match the frequency of a neutral hydrogen atom’s signal, and is useful since hydrogen is the most abundant substance in the universe. Therefore, conducting operations within the 1420 MHz band is ideal for studying the structure of the universe. In addition, 1420 MHz falls in a relatively quiet part of the electromagnetic spectrum, thus making it easy for smaller dishes, like the one at Fick Observatory, to operate.
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Figure 1 - Concept Sketch
As shown in Figure 1, our approach is to use a parabolic dish mounted on a salvaged gun mount to receive incoming radio waves. A motor controller positions the dish, a receiver converts the information for use with the computer, and a computer controls the entire system.
System Block Diagram
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Figure 2 - System Block Diagram
Below, each component of the System Block Diagram in Figure 2 is described in detail.
Telescope Hardware—Telescope Hardware describes all of the mechanical equipment that is located outside, such as the dish itself, the motors, motor controllers, and position sensing equipment.
Radio Frequency Circuitry—RF Circuitry includes everything in the path of the incoming radio signals from space, such as the coaxial cables, noise source, RF mixer, coaxial switch, receiver, etc.
Computer, Interface, and Software—Describes all of the supporting equipment at the
observatory, such as the Interface Box, the Fick Computer, and all of the various programs on it.
Positioning System – The positioning system includes all equipment that is used to sense the direction the dish is pointing. A good positioning system for our purposes should have an accuracy of about 0.1 degrees.
Shaft Angle Encoder – A device that sends digital information about the angular position of a shaft. Encoders can be absolute, which tell precisely what the angular displacement is from a reference direction, or relative, which indicate when the shaft has rotated a certain amount.
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voltage change from zero to five volts is used to indicate the range of telescope movement, 0 to 86.5 degrees in elevation and 0 to 360 degrees in azimuth.
Telescope Dish—This is the physical parabolic dish, which has a diameter of 8.5 meters. For our operating frequency, this gives a beam width of about 2.5 degrees (sources that are less than 2.5 degrees apart appear as one source).
Motors and Motor Controllers—Two motors are used for positioning the dish, one for azimuth and one for elevation. The motor controllers are located inside the observatory and are controlled through software.
Front End—Includes all RF circuitry that is located on the dish itself, such as a Low Noise Amplifier, Noise Source, RF mixer, and a coaxial switch.
Back End—Describes circuitry that is located inside the observatory, essentially a receiver and the computer.
Receiver—The receiver takes a 70MHz signal (the output of the mixer) and converts it into digital information for the computer, as well as an analog audio signal which is transmitted to a speaker.
Interface Box—The interface box is used to describe all circuitry that is used to interface with equipment at the observatory. This includes relays used for remote operation, circuitry for local operation inside the observatory, and circuitry for data acquisition by the computer.
Remote Control Relays—Switches that activate all the necessary equipment to operate the radio telescope remotely. These switches can be activated by using appropriate software.
DAQ card—Short for data acquisition card, this is how the computer software receives relevant data from the telescope and also can output voltages to activate relays. This is one of the most critical and expensive components of the entire system.
Project Software—All the software that is used to operate the dish and service its dependencies, as well as receive and display data.
Coordinate Calculation—This aspect of the software is used to convert celestial coordinates, essentially latitude and longitude for the sky, into azimuth and elevation, which is used to position the dish correctly.
Positioning software—This software is used to position the dish by applying appropriate
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Remote Control Software—This software is used as a user interface for remote users, so that they are able to operate the telescope and perform experiments without traveling to the observatory.
Documentation—All of the necessary documents needed for future teams to understand work that has been performed, as well as instruct users how to operate the telescope and its various components, including both software and hardware.
Wiki—A wiki has been set up for use by the team in order to facilitate access to important documents.
The radio telescope operates by using a large parabolic dish to collect incoming 1420 MHz radio waves from distant celestial sources and reflect them towards a sub-reflector, which then sends the signals into the feedhorn. The feedhorn directs the radio waves into a coaxial cable which is connected to the “front end,” which contains a low noise amplifier (LNA), a noise source (used to calibrate the receiver), an RF mixer, and a coaxial switch. The switch is used to ground the system when not in use to prevent damage from lightning or other power surges.
The signal from the feedhorn is sent through the amplifier, and then into the RF mixer. The RF mixer converts the 1420 MHz signal into a 70 MHz signal that can be used by the receiver. The receiver converts the analog 70 MHz signal into a binary signal that can be plotted on the computer using LabVIEW.
Current System Status
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Figure 3 - Current System Status
As seen in the image above, the radio telescope system at Fick consists of a parabolic dish to receive radio signals, a motor controller to position the dish, a receiver to convert the information into a binary format for the computer, and a computer, which controls the entire system. The computer component also includes a separate “interface box” which contains circuitry that allows the computer to interface with the motor control and receiver, as well as relays that allow the different components to be turned on remotely. A more detailed description of the telescope can be found in the System Block Diagram shown in Figure 2.
At the start of the semester, the telescope system had a number of issues. We were unable to use the computer to activate the motor controller and receiver. The positioning system uses an analog voltage signal, which is susceptible to noise, resulting in inaccurate positioning information.
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The poor positioning of the dish is a result of electrical noise in the motor control box. The noise prevents the computer from detecting the exact location of the desired object that the dish is pointing at, thus the detected location of the object may be three degrees off from the actual location. Also, incomplete positioning software currently does not allow us to track celestial objects over time.
Unreliable Remote Operation
Remote operation of the telescope is not feasible currently due to hardware issues with the interface box. The coax switch actuation board seems to be the problem to the malfunction of the receiver system; the signal coming in from the computer is not being delivered to the actual receiver at the dish. The limit switch relay board makes sure the dish does not continue operating after it reaches its azimuth and elevation limits; currently the LEDs in the front panel are not working properly. Another problem in the interface box is the mislabeled wiring from last semester.
Lack of Documentations
The lack of documentation is due to the extensive time period that the project has been operating. Prior teams apparently did not have the time or manpower needed to adequately document parts of the system which they developed. For that reason the upcoming teams may encounter minor problems that can occupy most of their time and prevent them from focusing on their main goals.
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User Interface Description
LabVIEW is a software package from National Instruments that is used to automate equipment testing. In our situation, LabVIEW is used to run the set of equipment which operates the radio telescope. The user interface for the operation of the radio telescope consists of two main LabVIEW files:
RemoteControl.vi controls the movement of the telescope dish, and ConvertCelestialCoordinates.vi is used to enter the position of a source in the sky and move the dish to point at that source.
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A 1420 MHz radio telescope with a large parabolic dish will vary in cost depending on how much of the system is purchased commercially and how much is engineered by our team. Commercial offerings for radio astronomy include receivers, amplifiers, and filters, but a complete radio telescope system can realistically only be purchased from a contractor (see
http://www.radioastronomysupplies.com/radio_astronomy_services.php) . The most expensive component of the radio telescope system is the 8.5m parabolic dish and positioning equipment. Luckily we already have a working dish and positioning system. Commercial equipment functionally equivalent to the front and back end can be purchased for about $1600 to $2000.
The primary advantage of building the majority of the system ourselves is cost. The cost of the various commercial components needed to get a radio telescope of this size functional would quickly reach tens of thousands of dollars. Even if commercial equipment were purchased, configuring the equipment would require a substantial amount of time. The learning experience of designing and implementing the major components of the radio telescope system ourselves would alone justify this approach. Our project advisor, Dr. Basart, was the originator of the project, and has stated that using an entirely commercial solution would largely defeat the purpose of the project as a learning tool.
The disadvantage of building the majority of the system ourselves is that equipment we design and build ourselves may not be as reliable as commercial equipment. Since the team changes every semester, if a malfunction occurs it’s likely the individual responsible for designing the system originally would no longer be on the team, making troubleshooting difficult. Designing most of the equipment by hand will probably take significantly longer than purchasing and installing comparable commercial products.
The risks to our project are primarily poor continuity from semester to semester, lack of execution or poor planning resulting in temporary solutions, and donated equipment that may cease to function. In addition, the radio telescope project has many functional dependencies such as weather and funding. Iowa’s temperature extremes induce great strain on both the indoor and outdoor components that are required for the functionality of the radio telescope. The size and nature of the radio telescope project requires continual funding.
Currently the dish sits atop an elevated platform above the tree line. Consequently the large surface area of the dish catches the wind and subjects the components to lightning. When temperatures drop below the freezing point, all trapped moisture in the mechanical linkages freezes, rendering the dish inoperable. The weather accelerates the aging of the components by subjecting the computer and controllers to temperatures that range from -20-110®F.
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To manage the risks associated with any large project, it is important to have complete documentation, good teamwork, and skill/talent utilization. In addition, it is important for team members to pay attention to detail and leave plenty of time for work.
The functional requirements that dictate what the Radio Telescope project must accomplish include the following:
1. The system shall be capable of receiving, amplifying, filtering, and capturing the intensity of incoming radio signals at a frequency of 1420 MHz.
2. The project shall have functioning software that allows the antenna dish to be controlled and positioned.
3. The system hardware shall be robust, which we define to be withstanding stresses typical of moving between Fick and SSCL. In addition, we define robust to mean that once it is installed, it shall require maintenance no more frequently than once or twice a semester.
4. The final radio telescope shall be capable of being positioned to an accuracy of within one-tenth of a degree.
5. The software shall provide a useful user interface that allows the user to operate the telescope and collect data.
6. Self protection strategies such as limit switches, coax switch, bumpers, and circuit breakers shall protect the dish and its operators from control system failure.
7. The limit switch circuitry shall be able to stop the satellite dish before over rotation occurs causing wires and cables to become tangled or destroyed.
8. The parabolic dish shall be able to rotate through 350 degrees in azimuth and tilt through 86.5 degrees in elevation.
9. The integrity of outdoor hardware and data acquisition shall not be compromised by seasonal weather changes.
In addition to the functional requirements, this project must also accomplish several other requirements related to ease-of-use. These include:
1. The user interface shall be easy for non-team members to use.
2. The next semester students shall be able to pick up the project after this semester with no down time.
3. The software shall be fully documented.
4. The hardware shall be fully documented with schematics.
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The following working components will be delivered by December 5, 2007.
Tracking software Software that will track a celestial object over time.
Interface box Functioning motor control circuitry, coaxial switch relay circuitry, and receiver relay circuitry.
Positioning Plan or design for positioning improvement, shaft angle encoder or some alternative.
Internal documentation Descriptions for future students to reference.
Tests and Results
The following table describes the tests that we will perform to ensure our system is working correctly. The tests will be completed before December 5, 2007.
Test Description Test Result
Cable loss Measure the loss in the cable running from the dish to the receiver by using a signal generator and spectrum analyzer.
Loss in dB of cable
Intensity Point the dish at the sun, run the software and ensure that the intensity of the sun is measured
Tracking Run the tracking software and make sure the telescope dish moves to track the sun
Visual confirmation Shaft angle encoders Hook up and power the shaft angle encoders,
and make sure the response is consistent with the data sheet
Angle data compared to data sheet
The following table describes the documentation that we will deliver this semester.
Document Person Delivered to Method of Delivery Delivery Date Requirements
Dr. Smith Email September 3, 2007
Project Plan Dr. Smith Bound, in person October 2, 2007
Website N/A Online October 2, 2007
Project Poster Dr. Smith In person November 14, 2007
IRP Presentation Dr. Smith In person December 5, 2007
Final Report Dr. Smith Bound, in person December 12, 2007
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Work Breakdown Structure
The engineering work will be distributed as shown below in Figure 4.
Figure 4 - Work Breakdown Structure
By working on the previous items, we should have the telescope system in a basic operational state. This will include moving the dish using the computer and plotting intensity vs. time for a particular point in the sky. Also, we should have the software capability to track a celestial object across the sky and perform a raster scan, even if our lack of positioning accuracy prevents us from being able to generate usable images. Also, we will implement a system to allow users to insert C++ code into LabVIEW
modules, which will allow astronomy students unfamiliar with LabVIEW to perform experiments. Lastly, we will evaluate our positioning system to try and improve upon accuracy.
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functionality. Our work this semester should leave the first semester students with a functioning telescope, which will allow them to focus on adding new features and improving existing system components.
The personnel working on or involved in this project are listed below. In addition, the organizational chart for the team members is shown in Figure 5.
Project Advisor: Dr. John Basart Course Coordinator: Dr. Smith Project Leader: Niclo Hitchcock
Communication Coordinator: Niclo Hitchcock
The team members and their titles or engineering assignments are shown in the Organizational Chart below.
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Schedule of Tasks
Figure 6 - Schedule of Tasks
Troubleshoot Coax Switch Actuation Board—The relay circuitry that allows us to activate the coaxial switch stopped working in a previous semester, and must be repaired.
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Relabel wiring—The wiring in the interface box is not labeled properly, which makes debugging very difficult. This wiring needs to match documentation for the interface box.
Implement Relays—Relay circuitry exists for implementing the remote control software that was written last year, but they have not yet been installed
Troubleshoot Relays—It is highly unlikely the circuitry will work at first, and will need to be debugged. Develop Schematics—Properly documenting the interface box requires schematics for all circuits. Evaluate existing angle encoders—The shaft angle encoders the team has acquired need to be examined to see how much time and effort are required to implement in our system, if possible.
Research alternative solutions—If the encoders do not work, an alternative solution will be required. Develop mockup if feasible—If the encoder solution is feasible, a mockup to demonstrate operation should be developed.
Improve existing system if possible—If the encoder solution is not feasible, an alternative proposal should be presented or implemented.
Create Documentation—Documentation explaining the function of software components, as well as their dependencies must be developed to aid future team member’s understanding
Add content to wiki—A wiki will be developed to allow the team to keep important information centralized. Once it is developed, content will need to be added.
Develop tracking software—Implement software that allows a celestial source to be tracked as it moves across the sky.
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Task Name Hours Required $ Required Assigned Engineers
Interface Box 70
Troubleshoot Coax Switch Actuation Board 12 Sulianet, Osman
Troubleshoot Limit Switch LEDs 8 Sulianet, Osman
Relabel wiring 8 $ 5.00 Sulianet, Osman
Implement Relays 10 Sulianet, Osman
Troubleshoot Relays 20 Sulianet, Osman
Develop Schematics 12 Sulianet, Osman
Evaluate existing angle encoders 8 Niclo, Ali
Research alternative solutions 12 Niclo, Ali
Develop mock-up if feasible 12 $ 20.00 Niclo, Ali Improve existing system if possible 12 Niclo, Ali
Create Documentation 10 Nick, Laura, Greg
Add content to wiki 8 Nick, Laura, Greg
Develop tracking software 16 Nick, Laura, Greg
Improve raster scan software 12 Nick, Laura, Greg
Integrate C++ API 16 Nick, Laura, Greg
Project Plan 8 All
Requirements Presentation 3 All
Project Poster 5 All
Final Report 10 All
IRP Presentation 12 All
General Cleaning 8 All
Fix Weather Station 6 All
Troubleshoot Antenna Intensity Issue 12 All
Purchase New Multimeter 1 $ 40.00 Niclo Purchase New Soldering Iron 1 $ 40.00 Niclo
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I have read and approve of the work that is described in this project plan.