Radio Telescope
It was Einstein who made the real trouble. He announced in 1905 that there was no such thing as absolute rest. After that there never was.
-- Steven Leacock
(Updates ordered from most recent to earliest)
Spring/Summer 2002 Update: After the telescope was brought back online, great strides were made this spring in order to begin the sky survey and mapping process. The progress encountered many setbacks which delayed the mapping process and therefore shortened the length of scans to only a two-week period. The setbacks included a short circuit in the amplifier power connection, broken coaxial connectors and several other things. Even so, the small survey of the sky was begun. The survey to date consists of 24-hour scans at 4-degree intervals of the sky. Beginning at zenith (about 37o declination) the altitude drive was moved 4 degrees south each day, which corresponds to the 4-degree beam-width of the telescope. Further work this spring and early summer included analyzing the mapping data and finding ways to plot it in 3 dimensions. Also, a brief effort to identify serendipitous point sources in the scans was made.
The research done so far on the project was presented at the annual Society for Amateur Radio Astronomers (SARA) conference. The conference was a success and there was a great interest in the progress made on the project.
February 2002 Update: Several scans have been made this month. The focus of the effort was to determine how temperature and light levels effect the receiver output. First results seem to reveal that during the time which the sun shines on the dish, noise signal increases greatly. During the night, sensitivity increases and noise levels decrease. This wide range of noise signal has to do with the fact that the LNA is uninsulated within the nose cone. Until we decide on a temperature stabilization unit, scans will have to be limited to nighttime skies.
January 2002 Update: This month includes the most significant work in awhile. Once the drive system was completed, the refitting of electronics could commence. The LNA was finally installed directly to the feedhorn, and mounted at the focus. New connections were made for power and signal cables. Exposed wires were upgraded to UV resistant weatherproof cables. Final connections were made and a new nose cone was installed. Now with the drive motors, LNA, and feedhorn wired and connected, tests were taken to explore the functionality of the system. The telescope drive system was the first on the list of adjustments to be made. This involved a rather low-tech method of taking a level out to the dish and making adjustments to align the dish on center and vertical. We chose the zenith position to be our zero point for movement and so this was very important. With this accomplished the next step was to program the controllers and determine their maximum control limits. Now that this is accomplished, the system is online and operational. Future tasks include testing how the new position of the LNA effects the sensitivity of the system and how outdoor ambient temperatures effect the unit.
Fall 2001 Update: During the fall the drive system was rebuilt. This improvement included the installation of two 180 degree customized drive motors. The drive system now allows azimuth and altitude movement. The system is controlled by two independent programmable drive controllers. The installation involved customizing the mount on the dish to make the connection to the new drive system.
Week of (7/23/01): This past week we made several more scans of the sky. One of the most exciting was a scan of the galactic plane. This scan showed a steady increase in the base line through the late evening. This is possibly due to the decrease in ambient temperature and thus cooling of the equipment. Although the LNA and downconverter are presently in the ground, they are still exposed to diurnal temperature changes because they are not yet buried. We also noticed that the system has a warm up time ranging from 2 to 3 hours. After this time, no changes in readings other than environmental have been detected.
The coming week will see several improvements and updates to the site (pictures and technical). We have ordered a right angle N connector that will be used to connect the LNA directly with the feedhorn. This introduces a temperature stabilization problem. There are several solutions on the table, but implementation will be delayed until September. My presentation and paper will soon be prepared and this summer portion of the project will end August 8th. After that, the project will pick up again in the fall, where the existing system will be further optimized and more observations will be made.
Week of (7/16/01): Last Friday the system reached first light. The system seemed to be working properly and so it was time to see if we could get a signal. The sun was the first object that came to mind and it was still low enough to catch it towards the east. I manually changed the altitude of the dish so that after a short period, the sun would drift though the field of view.
Well, it worked! After about 48 min. we had a complete transit plot of the sun. The plot, as I found out on my SARA conference trip, showed a few things that needed adjustment. The most important problem was the IF gain was too high. At the conference I also learned how the system should operate, in other words, what to look for in the plots of data.
This week we ran several more scans, another of the sun, and two of the galactic plane. The plots will be posted soon. We are looking forward to making more scans and excited that the RMRT (unofficial acronym for Randolph-Macon Radio Telescope) is now up and running.
Week of (7/9/01): This past week's highlight was Friday. The cables were connected and the preamp and downconverter were placed in the weatherproof box in the ground. We finished the other connections to the feedhorn and receiver and everything seemed complete. When the system was turned on however, there was no signal at the receiver. The preamp and downconverter were joined properly with soldered wires and the coax cable tightly connected, but still nothing worked.
Yesterday, each part of the system was tested, but nothing gave any clues as to what could be wrong. There is just no signal, besides weak system noise. Even when the noise calibrator was attached, no signal could be detected.
Today we discovered that the cause of at least one problem is that the signal cable has a short. The connector on the receiver end was improperly installed. This problem has a simple fix and that is just to install a new connector, but the consequences of having had a short in the wire could be disastrous. The receiver could be no longer functioning properly or the downconverter could be damaged.Each problem is unlikely, but possible.
This coming week will hopefully bring some answers by way of email from the builders of both the software and hardware. (Just got one email back today) If worst comes to worst I can ask the members of SARA at the conference next week. I hope we do not have to wait that long.
Week of (7/3/01): This past week has again been a bit slow. Early last week the cables were run and connected to the drive motor on the antenna. The other cables have not been connected because the shipment of special cables has not arrived. Also, before the connections can be made, the weatherproof and temperature stable box must be installed. These should be completed in the next week or so. The program we are using to display the signal from the receiver has a small bug, either generated by the user (me) or the program itself. I have contacted the programmer and I hope a simple solution will come soon. In the next week I will be posting some updated pictures of the antenna, noise calibrator, and base station so you can see the progress so far. Once the connections are finally made, testing of the system can commence. Until then, I will continue my reading and background work. The work has been slow lately, but I feel that when the cables are installed and connected, the real work will begin. In two weeks there is a SARA (Society of Amateur Radio Astronomers) conference at the Green Bank Radio Astronomy Observatory which I will be attending. Since I have never seen an operational radio telescope, nor met anyone in the field, it should be an educational experience.
Week of (6/26/01): This past week has been slow but we did accomplish a few important things. Dr. Spagna and I installed the new feedhorn support. I had to adjust it so that the spider-arm supports were not blocking the opening where the feedhorn will be mounted. The next thing I did was to actually put together the components of the noise calibrator. The Chip was placed in the cap, and the bolts, or in our case dipole antenna was adjusted to be the required 4 inches in length.
The rest of the week I briefly reviewed the software that will be used and I also did some research online. I obtained a lot of information about antenna design, astronomy fundamentals, and history of radio astronomy. I found one website that sells tracking systems for satellite antennas and we are possibly ordering the device. At the moment, although not operational, the dish is a transit telescope. That means that whatever we want to observe must pass overhead.
In the next week or so we again hope the cables will be connected to the dish and run through the conduit indoors. After that is completed, the actual system can be tested and the noise calibrator can finally begin calibrating. I have just learned that in July there will be a (SARA) meeting at Greenbank. This would be an excellent learning experience and greatly help our endeavor for bringing the radio telescope to first light. Also, it would be an opportunity to meet others who are working in the field. There are not that many amateur or professional radio astronomers in the world, so this would be a chance to discuss the project with them and get tips on how to improve on what we have begun.
Week of (6/18/01): The mount for the feedhorn is finally finished. When I drew the original design, I did not consider that the seemingly round feedhorn was actually not circular. The seam where the feedhorn was welded protruded out slightly causing the new mount to be 1/16" to small. Now that the mount has been adjusted it needs to be installed onto the spider arm support.
The electronic components for the noise calibrator came in last Friday. This week I completed the circuit for the noise calibrator and the parts for the outer shell have been purchased. The next step will be to complete the assembly and attach the calibrator to the antenna. We are still waiting on the installation of the cables, so even once connected, it will be awhile until it can be tested.
This week I hope to complete both of the above tasks; installing the feedhorn and completing the noise calibrator unit. Also, I hope to rid the web site of any bugs that are still lurking around. After those have been completed, We will need to complete the designs for the temperature control unit for the preamp.
Week of (6/11/01): The mount for the feedhorn which will be positioned at the end of the spider arm support was redesigned. The original mount that came with the dish was not designed to accommodate the 6" diameter feedhorn that will be used. The new support is an aluminum ring with holes drilled for the mounting bolts. This will be machined by the school's shop hopefully in the next week. An image of the design of the part will be available soon.
One preliminary step was to actually determine the curvature of the dish. By lining up a simple protractor and a pen, it was easily determined that the seemingly parabolic dish is actually spherical. This was very helpful in determining where the focal point should be( without calculating it). Once the new mount for the feedhorn is installed it will be very important to know where the focal point should be tin order to optimize the signal strength that the feedhorn will receive.
The second step was to construct this page which will be utilized in providing up-to-date information on the progress of the project. Over the period of the next week or so, the initial setup of the page will be completed. Updates will follow weekly.
In the next day or so we will be ordering components for a dipole calibrating antenna. we have placed an order request for the noise diode required and next we will order the resistors and capacitors that complete the circuit. The schematics of the calibrating device, including other information can be found here at MIT's SRT site. The information is provided as a PDF file. Once the parts arrive the small device will be built and attached to the dish.