Ongo 2-C Radio Telescope Greg Bonett Laura Janvrin Project Advisor: John Basart Ali Abdelsalam Osman Abdelsalam

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 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 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

Project Risks 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 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 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.

Interface Box Specifications 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 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 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 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 Voltage Regulator circuit maintains a constant voltage in the Interface Box

Interface Box – Coax Switch Relay PCB 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 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 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 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 Only allow opposite voltage to pass to Motor Control Box when dish is 2 degrees from each physical limit

Software - Wiki 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.

System Maintenance 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

Testing Objectives Confirm basic operation of all components Individual electrical components RF Section Positioning hardware Positioning software Interface hardware Quantify system parameters Measure RF losses Determine positioning accuracy

Testing – RF Section 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

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 After calibration, software (without software limits in place) shows 0° for minimum elevation, 86.5° for maximum elevation, etc. 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 Input coordinates of known source (the sun) Positioning software with correction placed dish in proper position Verified tracking software functionality Verified raster scan software functionality by performing raster scan of area of sky including the sun

Testing – Intensity Graph Tested the intensity graphing capabilities of our system 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

Work Descriptions Green = Task Complete Yellow = Task In Progress

End of Semester Status 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 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 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 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 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 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