October 2011 - AMSAT-BB - mailman.amsat.org

SimpleSat - a slight variation on the SatPC32 Observer2 module
by Thomas Doyle 07 Oct '11

07 Oct '11

I am looking for someone who will read a small amount documentation and has lots of experience and a little time to check out a program I have written. It seems to work but I have a question about it. It looks for possible satellite passes where communications between two different grid locations is possible. Back in the day it was a real challenge to work Hawaii - I remember pouring over mounds of paper trying to find a pass that would work. It was a real thrill when it actually worked. I thought it would be interesting to write a little program to automate the process. You are probably thinking - I have a great csh script that was written by Harold that would do it. I am not looking for another program I am just trying to determine if mine is working correctly. The Observer 2 module in SatPC32 served as a starting point. After I wrote it and was testing it I found that it took a while to find a pass when you are operating on the limit of coverage or if there are no valid passes. It is the age old question - when looking for something how do you know if it does not exist or if you have just not looked long enough. I decided to try and eliminate the satellites that simply would not work based on the distance between the two locations. It was fairly straightforward to use the TLE data to calculate the altitude and from that the central angle and from that the "width of swath". I found the "width of swath" term in a reference and think it is the only really cool term in orbit mechanics. I am not sure my "width of swath" value is correct. I first tried checking it by looking at the SatPC32 3D display and visually comparing the width of the range circle to the width of South America - this seemed fairly close. After the program was working I found that when the distance between the two locations was less than the "width of swath" a valid pass was found and when it the distance was greater there were no valid passes so I am fairly sure it is at least close. The program displays TLE generated altitude, central angle and "width of swath" for each of the satellites it is using in the search. If someone could take a peek at these values and let me know if they think they are correct I would appreciate it. The program does not use these values it just displays them. At present the program searches every quarter second over a 1 week time period to find a pass. If I am sure the "width of swath" value is correct I will eliminate the passes that have no chance and extend the search time. The program uses .NET and is very easy to use. Ease of use has always been an interest of mine so this is about as easy as it gets. There is a help file accessible from the help menu. Reading it before you try it out would be a good idea. You can download the program from here. It is a zip file. Un-Zip the files it into a folder and run the SimpleSat.exe file. No install is required and the three files it will create are stored in the same folder as the SimpleSat.exe program. It does nothing to the registry. It downloads sat data from the net so use a computer connected to the net when you run the program. I used Dreamweaver to create this beautiful web page. http://www.tomdoyle.org/simplesat/simplesat.html Please respond off the board if you have information on my "width of swath" question. tnx & 73 W9KE tom ...

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Office Closed
by Martha 07 Oct '11

07 Oct '11

The AMSAT Office will be closed on Monday, October 10th in observance of Columbus Day. We will reopen on the 11th -- 73- Martha

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Its not your Keps
by John Heath 07 Oct '11

07 Oct '11

Hi Kevin, I doubt the problem is your keps if you have an up to date set from any of the sources suggested. You might want to check the following: Your PC clock may not have the correct time There may be something in an initialisation routine that has set a default time zone, or an offset from UTC This can be tricky with some PC's and software. You might have to set your PC clock to UTC. Entering your lat/long, East or West of the Grenwich (0) meridian. There is no convention on this some programs want a plus sign ahead of your longitude some a minus. Those are the things that have caught me out in the past. BTW - dont expect agreement to the second between different tracking software. Its only a prediction and not all programs use the exact same algorithms to do the calcs. Good Luck 73 John G7HIA

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Mars Science Laboratory Enclosed In Aeroshell
by B J 07 Oct '11

07 Oct '11

http://www.nasa.gov/mission_pages/msl/news/msl20111005.html http://www.nasa.gov/mission_pages/msl/multimedia/gallery/pia14755.html http://www.nasa.gov/mission_pages/msl/multimedia/gallery/pia14756.html http://www.nasa.gov/mission_pages/msl/multimedia/gallery/pia14757.html http://www.nasa.gov/mission_pages/msl/multimedia/gallery/pia14758.html More pictures at: http://www.nasa.gov/mission_pages/msl/multimedia/gallery/gallery-index.html 73s Bernhard VA6BMJ @ DO33FL

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2011 AMSAT Space Symposium
by Martha 07 Oct '11

07 Oct '11

People -* In one month*, AMSAT will hold the 2011 Space Symposium and Annual Meeting. The venue is the Wyndham hotel in San Jose, CA. Please do not hesitate to make your hotel reservations. Information can be found on the AMSAT website along with the registration form for the meeting and banquet. -- 73- Martha

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G5500 Elevation Rotator Short Circuit?
by Clive Wallis 07 Oct '11

07 Oct '11

I wonder if this is a known fault. Recently the fuse on my G5500 blew. The problem seems to be a short on one of the motor circuits. Checking the DC resistance at the control end, the resistance of one winding is 1.2 ohms, whereas all the other windings are 4.6 ohms. I could understand a motor burning out and going open circuit, but a short circuit seems less likely. I'm wondering if it could be a short on the cable at the rotator end, where it is subject to much bending. There's about 15 metres of cable. Any thoughts would be much appreciated. Unfortunately, at the present time I'm not able to inspect the rotator. It's stuck in the horizontal position, so I will still be able to use the antenna for low elevation passes. 73 Clive G3CWV Hitchin, North Hertfordshire, UK

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AO-27 Site Status
by Clint Bradford 07 Oct '11

07 Oct '11

Forgive me if it has been answered recently - But does anyone know when the AO-27 site may be back up? Clint Bradford, K6LCS 909-241-7666

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Good URL for updating keps HRD
by Kevin Deane 07 Oct '11

07 Oct '11

Does someone have a link for the good ISS keps again? I think it was posted but I spaced it. Not one of these: celstrck.com or amsat.org both bad. Thanks! Kevin KF7MYK

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Old Maplin Electronics Kit for UoSat 2 Reception
by David Johnson 07 Oct '11

07 Oct '11

Hi, About 25 years ago Maplin Electronics (UK) provided a RX kit for FM reception of UoSat 2 it had doppler correction by changing the vxo by reading the discriminator voltage and adjusting it. Does anyone have one of these kits lurking on their shelf, either built of still a bag of bits? Please contact me off-line. 73 Dave, G4DPZ

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ISS
by Kevin Deane 07 Oct '11

07 Oct '11

Figures I miss the pass everyone is on. Hope to catch someone tonight or this morning. Mostly beacons on the west coast, however I did get a human this morning... Kevin KF7MYK

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