August 2007 - Eagle (INACTIVE)

Module Temperatures
by Dick Jansson-rr 01 Sep '07

01 Sep '07

Juan & John: I have finally been able to achieve some analytical results for projecting the temperatures of Eagle modules after two hour and three hour eclipse periods of no-solar heating. This has taken some time as I was struggling with the proper use of the SINDA software and had to call for some help which is why we pay money for the license, it comes with help when needed. (I should also note that with modern versions of this software and a pricey, but fast and capable, Dell computer, these analytic runs only required 18 seconds of real run time!) Nevertheless, I have been able to get some believable modeling results. The spacecraft model used is what I now call Small Eagle, the formerly proposed, but rejected 600x600x435mm spaceframe structure. While this is not as large as our currently planned hexagonal structure, the equipment bays are just about the same size as the larger spaceframe. I ran the model with one of the E05 20, 125x180mm, modules with coatings with an effective emittance of about 0.45, rather than 0.04, as would have to be done for the URx module. There was essentially no power dissipations in any module, at the most about 20mW in a few modules. This is granted to be an abnormal situation, but I wanted to see what happens. A later run was made with only a total spacecraft power dissipation of only 7mW were only lower by 0.1°C to 0.2°C lower temperatures. Modules started out at temperatures of +20°C and the spaceframe core structure at +10°C. The propellant tank was empty so it did not contribute any large thermal mass to delaying the cool-down. After two hours of eclipse the module temperatures were -5.2°C to -5.4°C (with the high emittance module being cooler), and after three hours of eclipse the module temperatures were -15.9°C to -16.2°C. The spaceframe core structure (equipment panels) were down to -10.2°C and -19.4°C respectively. For these cooling periods, the spacecraft outer skin temperatures ranged from -35°C down to -55°C. The deployed solar panels became a bit chilly, down to -113°C. A subsequent SINDA run was made with some kind of useful power dissipations in modules 0.5W to 1.0W not large but supposedly enough to keep things from getting out of hand, and with a total spacecraft dissipation of 16.5W. The two hour eclipse temperatures ran from -3.4°C (1.0W) to -3.9°C. In three hours of eclipse the module temperatures were at -13.3°C down to -14.0°C. In other words, these levels of power dissipation did not significantly warm the modules. The spaceframe core temperatures were at -8.0°C and -16.3°C respectively., just a few degrees warmer. What this data tells me is that specifying the cold temperature of a module does not have to be much lower than -20°C, and if it is operating at all they can be only a little higher. Cold module temperatures certainly do not need to be in the -60°C range. Beyond these statements, I shall not presume to be a specification writer. 73, Dick Jansson, KD1K kd1k(a)amsat.org kd1k(a)arrl.net

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Interesting article about fuel slosh in spin-stabilized satellites
by Alan Bloom 27 Aug '07

27 Aug '07

http://www.mathworks.com/company/newsletters/digest/2007/july/embry.html?s_…

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Publication
by Jim Sanford 25 Aug '07

25 Aug '07

Team: Sooner or later, we need to publish more. Publishing in QST would bring our efforts to widespread attention, which could help many things. Well, we may have our chance: * QST Wants You!: Have you ever thought of writing an article for QST? The official journal of ARRL, the national association for Amateur Radio, QST is always on the lookout for articles that explore all the possibilities of ham radio. We are looking for stories and articles that present a project or idea that is useful and engaging to most hams. The story you have had brewing in your head for months might be perfect for QST or the ARRLWeb. For the Web, we're looking for short (1500 words maximum), general-interest articles that tell a particularly interesting story. At least one photo to accompany the story is mandatory. Send your submissions to QST Managing Editor Joel Kleinman, N1BKE <qst(a)arrl.org>. If you've something to submit, go for it. I'll be happy to help as a reviewer or whatever, but I will not get in the way as a gatekeeper. If you want to write for QST, PLEASE DO!! 73, Jim wb4gcs(a)amsat.org

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Interesting article about VCXO phase noise reduction
by Jim Sanford 22 Aug '07

22 Aug '07

http://www.mwrf.com/Articles/Print.cfm?ArticleID=16332 Authors: Ulrich L. Rhode & Ajay Kumar Poddar, Synergy Microwave Corp. 73, Jim wb4gcs(a)amsat.org

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Update request
by Jim Sanford 21 Aug '07

21 Aug '07

Team: It is that time of year again. I need to compose my report of things accomplished, things projected to be accomplished next year, and projections of funds required to accomplish those things. Your unexpended funding requests from this year will NOT be rolled in to next yea -- we start over. I need your input (or negatives) on progress, projections, funds expended, and funds projected to be expended in 08. I need this information by 15 Sep 07 so that I can formulate my report to the BoD in Oct. Questions: Please contact me asap. Thanks & 73, Jim wb4gcs(a)amsat.org

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Info on U-band receiver changes
by John B. Stephensen 20 Aug '07

20 Aug '07

I've posted the schematic and assembly drawing for the U-band receiver test fixture on the U-band receiver page in EaglePedia just above the receiver fabrication section. This PCB was made to test a way to tune the matching networks for the narrow-band SAW filters. I also added a new second mixer and IF amplifier so that changes to reduce thermal dissipation in revision B of the receiver can be tested. Note that the average DC power consumed by first IF amplifier, second mixer and second IF amplifier drops from 870 mW to 370 mW. The circuit should exceed the specifications in the recently-revised U-band receiver requiremnts document. 73, John KD6OZH

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Ron Bracewell, SK
by Tom Clark, K3IO 16 Aug '07

16 Aug '07

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A power supply idea
by Tom Clark, K3IO 15 Aug '07

15 Aug '07

Since there has been a lot of discussion on the CAN-DO power supply considerations, I thought I would pass on what the Suitsat-2 people are doing. They seem to have settled on using the Newport NMV series of COTS isolated supply modules. I've attached 2 PDF files that describe the units for your information. 73, Tom

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70 cm Receiver passband ripple - status
by Juan Rivera 15 Aug '07

15 Aug '07

All, Please click HERE <http://www.juanr.com/pages/hobbies/ham_radio/Eagle/passband_ripple.htm> to read the latest status on the 70 cm Receiver passband ripple. Bill, N6GHZ, has made good progress. 73, Juan

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TeamSpeak conference
by Jim Sanford 15 Aug '07

15 Aug '07

Guys: Sorry I had to bail, but it was a REALLY URGENT phone call. You were all long gone before I got off the phone. Gould, pls send me a synopsis of the discussion after I left. Thanks & 73,. Jim wb4gcs(a)amsat.org

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