Hey Mark--

We also use pyephem for web-based pass times calculations at Cal Poly. http://mstl.atl.calpoly.edu/~ops/passtimes/

Source is here, but it was written a few years back, and uses the older (now depreciated) ephem.Body attributes. It also sometimes has trouble with the formatting on the webpage, although that may be a firefox bug, I'm not sure. http://mstl.atl.calpoly.edu/~ops/passtimes/passtimes.py -- Bryan Klofas, KF6ZEO

Mark VandeWettering wrote:

I just thought I'd drop a quick note here about some fun I've been having today with satellite orbit prediction in Python. When I started mucking around with satellites, I used "predict", which was pretty good, but at some point I wanted to answer some questions which weren't easy to answer using predict. Questions like "when will AO-51 be visible from both my home in CM87 and locations in Hawaii", or "what was the radius of the circle of visibility for AO-7 compared to ISS"?

Luckily, I'm a programmer. In fact, I'm a programmer who programs for fun. So, I did a bit of research, and then coded up a version of G3RUH's "Plan 13" algorithm in Python, and then wrote some scripts to download elements from celestrak, and then a simple one to print data on the next pass of any named satellite. And, they worked pretty good. I've used them for the last year or so to do all my pass predictions. But there are still a couple of minor issues with the library. It didn't handle geosynchronous satellites very well. It implemented only the most basic of orbital models. I was never confident that the "is this satellite in eclipse" stuff working exactly right.

Luckily though, it turns out that someone else has been busy writing a more complete library: PyEphem http://rhodesmill.org/pyephem/

It's a library whose primary purpose is to calculate the positions of astronomical objects. I've used it a couple of times to (for instance) figure out the size of Mars compared to Jupiter, and found it very easy to use. But today, I realized that it had a full implementation of the SGP4 and SDP4 orbital models built in, and could be used to predict satellite passes. As a proof of concept, I hacked together a 23 line script that could print the details of upcoming ISS passes. It seems to work great, and is really quite easy to use.

You can find some of the simple example code at my blog:

http://brainwagon.org/2009/09/27/how-to-use-python-to-predict-satellite-loca...

I'll probably be porting all of my existing scripts to use this soon. In the mean time, if you have a similar task, you might look to it to solve your custom satellite prediction problems.

73 Mark K6HX _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

Mark,

I dug into the PyEphem code a bit and slapped together my own script that will:

- snatch the latest keps from amsat.org - find all passes taking place within the next N minutes ( this is configurable) - provide the user with text / verbal status updates on whatever interval desired.

Feel free to take a look here:

http://libjoe.blogspot.com/2009/10/where-is-my-satellite-in-python.html

For the record, DO NOT SET LAT OR LONG TO A DOUBLE VALUE. Sorry for screaming but... sometimes... you just have to :-) I had a bit of test code that I wrote and took forever trying to figure out why my local pass times were not coming out correctly. It turned out that the UTC times were off as well... I traced this back to initializing my lat/long observer values using a doubleobject as opposed to a stringobject. You have been warned. I sure hope I didn't miss this in the documentation somewhere... All I could find on these in the documentation (without any digging into any of the code) was: These are the attributes you can set:

date — Date and time epoch — Epoch for astrometric RA/dec lat — Latitude long — Longitude elevation — Elevation (m) temp — Temperature (°C) pressure — Atmospheric pressure (mBar)

Joe

On Sep 28, 2009, at 2:06 AM, Mark VandeWettering wrote:

I just thought I'd drop a quick note here about some fun I've been having today with satellite orbit prediction in Python. When I started mucking around with satellites, I used "predict", which was pretty good, but at some point I wanted to answer some questions which weren't easy to answer using predict. Questions like "when will AO-51 be visible from both my home in CM87 and locations in Hawaii", or "what was the radius of the circle of visibility for AO-7 compared to ISS"?

Luckily, I'm a programmer. In fact, I'm a programmer who programs for fun. So, I did a bit of research, and then coded up a version of G3RUH's "Plan 13" algorithm in Python, and then wrote some scripts to download elements from celestrak, and then a simple one to print data on the next pass of any named satellite. And, they worked pretty good. I've used them for the last year or so to do all my pass predictions. But there are still a couple of minor issues with the library. It didn't handle geosynchronous satellites very well. It implemented only the most basic of orbital models. I was never confident that the "is this satellite in eclipse" stuff working exactly right.

Luckily though, it turns out that someone else has been busy writing a more complete library: PyEphem http://rhodesmill.org/pyephem/

It's a library whose primary purpose is to calculate the positions of astronomical objects. I've used it a couple of times to (for instance) figure out the size of Mars compared to Jupiter, and found it very easy to use. But today, I realized that it had a full implementation of the SGP4 and SDP4 orbital models built in, and could be used to predict satellite passes. As a proof of concept, I hacked together a 23 line script that could print the details of upcoming ISS passes. It seems to work great, and is really quite easy to use.

You can find some of the simple example code at my blog:

http://brainwagon.org/2009/09/27/how-to-use-python-to-predict-satellite-loca...

I'll probably be porting all of my existing scripts to use this soon. In the mean time, if you have a similar task, you might look to it to solve your custom satellite prediction problems.

73 Mark K6HX _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb