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2012 Annual Conference Abstracts
The following abstracts will be presented at the 2012 SARA Annual Conference in Green Bank, West Virginia June 24 to 27.
RASDR Development Status
Bogdan Vacaliuc, David Fields, Paul Oxley, Marcus Leech, and Stan Kurtz
SARA members are working on designs for a Software Defined Radio (SDR) that is optimized for Radio Astronomy. The resulting receiver design, RASDR, has the potential to be a common digital receiver interface useful to many SARA members. A benchtop version of RASDR has been completed. This “Phase 0” RASDR provides digitized radio data to a backend computer through a USB 2.0 interface. One component of RASDR is the Lime Microsystems Femtocell chip which tunes from a 0.4-4 GHz center frequency with several selectable bandwidths from 0.75 MHz to 14 MHz. A second component is a board with a Complex Programmable Logic Device (CPLD) chip that connects to the Femtocell and provides two USB connections to the backend computer. A third component is an analog matching network that enables antenna connections to the Femtocell chip whose unique design allows upconversion of low frequency bands. Together these three components enable the RASDR to tune from 0.015 MHz thru 3.8GHz of the RF spectrum. The computer software used is based on vlfrx-tools5 and Spectrum Lab6, both of which are available to SARA members as free downloads. We will demonstrate the breadboard system and SARA members will be able to operate the unit hands-on throughout the workshop.
What is the "Epoch of Reionization" and how can we look at it?
Research into the "Epoch of Reionization" has become an important area of cosmology over the past few years. Studying this period early in the history of the universe is crucial for the understanding of how the formation of atoms of the elements above hydrogen takes place, and how the galactic structure that we see has formed. It may seem that these facts of everyday life are too obvious to really investigate as they are now, but as we think about it more, the questions of "why are there so many complex kinds of atomes, which have the subatomic structure that we have discovered, exist?" and "why are there galaxies and clusters of galaxies of the kind that we see?" do not have self-evident answers. So, having discovered the "big bang", which is the origin of the universe, and having determined that this origin was approximately 13.7 Gyr ago, what took place between now and then to bring about the features of today's reality as we see them? A crucial part of defining this timeline is the "epoch of reionization", and evidence of this epoch can be detected with suitably designed radio astronomy antennas. This paper will describe how the existence of this epoch was discovered, why it is important, what kinds of signals we can expect to find from this epoch, and what the difficulties are in seeing these signals.
Taming the Ten Foot Dish for Radio Astronomy
Tom Crowley - Past President SARA
The ten foot TVRO dish appears to be the main stay in amateur radio astronomy. In the rural communities you'll still find the dishes everywhere. Most are no longer being used and have been replaced by Dish or DirecTV network dishes. This paper will discuss converting the TVRO dish for radio astronomy use. It will provide the necessary equations to determine gain, and find the correct focal point required to set the Feed horn. It will show how to set and calibrate the dish on the Southern Meridian and automating dish pointing for declination for approximately one hundred US dollars. This will allow pointing to the bright objects and the Moon and Sun. It can also be used for Hydrogen I surveys. It uses a “nudge” command for fine tuning. The talk will use the 21 cm line as an example, but the equations can be used to setup any dish.
Demonstration Devices and Audio Recordings for Radio Astronomy Presentations
Many of us are asked to give presentations to school groups and/or astronomy clubs and though we have tools such as the IBT, this usually isn’t enough. The author has developed and built a number of devices over the last 30 years to help him teach about various topics that we as radio astronomers might want to talk about in a presentation. The author has also been trying to keep a record of all the recordings that he can find and many lend themselves to presentations. During this talk the author will show how to build and use the devices as well as share many of the audio clips he feels lend themselves to radio astronomy presentations.
Teaching About Black Holes
This past year the Peabody Museum at Yale hosted and helped develop a traveling program on black holes. Part of the exhibit was designed by students and had some interesting video clips and activities. The author was lucky enough to attend a teacher training session at Yale on this topic and then he developed materials to present to the Connecticut Association of Physics Teachers (CAPT) to help physics teachers teach about black holes. During this presentation the author will give participants a disk with many materials to aid in teaching about this popular topic and provide some guidance into using them.
Drift Scan Radio Astronomy Sky Mapping using Articulating Parabolic Antenna
Michael T. Mruzek
The objective of this experimental setup and observing program was to create a sky map of the entire visible radio sky in one Sidereal day (1436 minutes, ~24 hours). Normally in drift scan observing the antenna is fixed in the declination axis during the data collection, and the rotation of the earth sweeps the field of view through the progressive hour angles. We endeavored to add articulating motion in the declination axis such that the field of view was swept from North (Pole Star) to South (Southern Horizon) every 2 minutes, while concurrently drift scanning for a Sidereal day. Consequently we could plot the observations as graphical 'pixel' regions on a 2 dimensional map to create a picture of the entire radio sky in a single day.
Operating a remote radio astronomy observatory
What does it take to construct and operate a remote radio astronomy observatory?
There are many items to consider:
Choosing the site location including property access and land ownership.
How will you obtain electrical power supply, backup electrical power and Internet access?
How will you provide basic RA equipment, heating and cooling systems, insurance and pay for electric power?
How will you provide shelter, site safety, protection from vandalism and lightning damage?
How will you construct safe antenna systems so unauthorized persons do not injure themselves?
Who will have access to the site and equipment, and pay for the cost to/from site for repairs and restarting stalled computer equipment?
How will you provide a remote control system?
Who will you chose to use the system effectively, and what will they pay towards the cost of the system?
The author has installed and operated a remote observatory. The purpose of the talk is to share his experience with you to help you decide if you should do the same.
Low and Intermediate Frequency Inputs for RASDR
Paul L. Oxley - Vice President SARA
The paper describes the design of the low and intermediate frequency inputs for the RASDR Phase 0 Breadboard layout. The selected LIME LMS6002D evaluation board provides inputs in the range of 400 to 3000 MHz Since it is desirable to extend this range to as low of frequency as possible, the project involved the selection and evaluation of alternative means of extending the low frequency input using a up conversion step to bring the signal to a frequency within the LIME board range. Two alternatives were considered namely, image cancelling up conversion and a frequency offset double sideband suppressed carrier (DSB-SC) scheme that uses digital filtering to suppress one of the two sidebands. The results indicate that it appears likely that the low frequency input range can be extended to 15 KHz using the DSB-SC alternative.