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The NAAPO Newsletter
Volume 21, No. 1
February 2005

Written by: Phil Barnhart, NAAPO Coordinator, 4655 Indian Ct., Westerville, OH 43082

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Coordinator's Corner

The season has been most productive. Development of Argus technology has continued in spite of physical barriers (see Barricades below) and construction mishaps (see Antenna Re-design below). Demonstration of concept is vital before forging ahead in construction or acquisition of hardware. This is accomplished regularly as described in First, Second and Further Light, elsewhere in this issue.

We continue to gain confidence as progress accumulates in hardware and software development. In addition to on-site display and observational technique we continue to hone ability to operate and modify the programs remotely. Already remote monitoring of the Argus array is in place and we expect general access to be available soon to all our volunteers as needed.

As our needs for added sensitivity and resolution increase so does our need for financial support. We are actively seeking large scale funding and our need for individual contributions continues. We are implementing ways to increase general public support as our older base of contributions has eroded with conversion from direct mail distribution of Signals to electronic distribution.

We continue to encourage our regular donors to keep us in mind as they consider support of many worthy causes. Funds for daily operations are getting quite tight.

We are happy to announce several exciting breakthroughs with this issue of Signals.
   Phil Barnhart

Antenna Re-Design and Construction

The original operating antenna elements were mounted on sealed, composition board boxes. The intent was to keep moisture out to protect the sensitive low-noise amplifier. A full year of use demonstrated the technique to be inadequate. Moisture condensed in the boxes and led to considerable deterioration. [See the first of the four photos below.]

Several options were explored. The final decision led to setting up the antenna elements as open-air devices, sealing the electronics inside PVC pipes as in the original design. So far the elements have operated satisfactorily through all kinds of harsh weather. The array continues to operate even when under three or four inches of snow.

The boxes deterioriated rapidly. Fortunately, the electronics survived.

Angelo Campanella (our resident acoustical physicist) is reassembling the electronics and spiral element into the new support structure.

As the "new" elements were complete, they were put into service along with the "old" elements.

Finally, all elements were of the "new" type.

[Photos courtesy of Jerry Ehman.]

Barricades on driveway Anti-Terrorist Barricades Impact NAAPO Operations

Upon arrival at the September working sessions volunteers were met by concrete highway barricades across the access driveway to the laboratory building. Consultation with the security personnel on duty indicated the barriers were to remain throughout the remainder of the football season.

The purpose of the barricades was to prevent access to the near environment of the university research reactor during times when large crowds were attending home football games. Routine access to the facility was denied for five months. We parked in a nearby student lot and crossed a sometimes-wet ditch on foot. Occasional deliveries were made driving through the ditch using four-wheel drive vehicles. The inconvenience was tolerated knowing the Michigan game would mark the end of the ordeal.

The barricade was removed two months after the end of the season. We now again have access by the long, paved drive to which we had become accustomed.

[Photo courtesy of Jerry Ehman.]

First, Second and Further Light

Traditionally, a new telescope experiences 'first light' when it is first turned to the sky. The Argus array saw first light nearly three years ago when Steve Ellingson succeeded in detecting orbiting satellites with the eight element array put together to develop software for beam-forming.

Twenty four elements were hurriedly assembled in anticipation of the June 2003 IEEE International Antennas and Propagation Symposium held in Columbus. This array went on line just in time for the open house held for that meeting, giving a convincing display of satellite observation. The antenna boxes for this demonstration held together only a few months. Inadequate finish coats of paint allowed water into the composition wood which warped and started to fall apart. It was at this point the decision was drawn to attempt an open construction for the antenna elements.

So far, the open construction has proven to work fully as well as the box enclosures and seems to offer a more maintenance free situation. In addition, Chief Observer Russ Childers has accomplished several remarkable landmarks in getting the system into a full-time operating mode.

Waterfall display of GOES His first breakthrough came with the observation of the GOES-12 (Geostationary Operational Environmental Satellite) as a calibrating source for the array. By using it as a strong point source he has developed a way to minimize sidelobes generated by the multiple elements in the array. Furthermore, he is able to use the satellite to generate a beam in its direction and by tuning to a nearby frequency observe the sky passing behind the satellite in a scanning mode similar to the scheme used at Big Ear with the fixed praboloid observing along the meridian.

During these early calibration experiments Russ observed a number of transient narrow-band signals from passing satellites. These show up readily on the waterfall display of the real time observations both in the observing room and at remote sites. [See the waterfall display of GOES-12 to the left. Click on it for a larger image.]

Another remarkable achievement came early summer of 2004 when the array tracked the sun as it moved from about the meridian till it set in the west. Even though the sun is about 1000 times as strong as the strongest discrete sources in the sky, it is the first truly astronomical source detected by the Argus array.

Just this past week (mid-February) Russ was able to observe interference fringes as the sun moved westward across the sky. This was accomplished using two of the array elements separated by a few meters in an east-west orientation. The accompanying figure is a plot of these fringes. The horizontal scale is time (24 hours long); the vertical scale is intensity output of the combined elements. [Click on the graphic to see a larger version.] Below is Russ' technical description of the graphic.

"The sun as seen by Argus on February 18, 2005. This image was generated in "interferometry" mode, using two elements approximately 3 meters apart, roughly on an east-west line. Data was generated by multiplying each elements' I-value and summing, and multiplying each elements' Q-value and summing. A 400-acquisition moving window convolution was done over the entire 24-hour set of acquisitions, resulting in a "480-second" integration time. The x-axis is the UTC time; the y-axis is the sum of correlations centered on the 400-acquisition window. Note the interferometric "fringes" while the sun is above the horizon. Fainter fringes might be seen when the sun is below the horizon, perhaps caused by the Cas A supernova. Receiver center frequency is 1692.030 MHz; bandwidth is 70 kHz; each acquisition takes 0.2 seconds; there are 16384 samples per acquisition; time between acquisitions is 1.2 seconds."

[Waterfall display of GOES and graphic of fringes courtesy of Russ Childers.]

NAAPO to Implement PayPal Option for Donations

NAAPO has opted to open a PayPal account to facilitate donations by means of the internet. Notices will be included on both web sites (www.naapo.org and www.bigear.org). Instructions will be included in both appeals for donations from the general public. There has been inquiry through the Webmaster as to the possibility of such transactions. We will try for several months to see if it is worth the effort.

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Created by Jerry Ehman.
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