Hi all!! How does one calculate the period and time of entry and exit of eclipse? I'm going to be helping a friend do an Arissat presentation for her class. Due to the fact of the battery failing, this gives a 15 minute hold before the power management allows transmission. So, for any chance of receiving the bird, it has to be in sunlight for 15 minutes (or so). I'd prefer a mathematical formula. Echo goes through some of the same trials. Thanks, Norm BTW: I am an engineering student, just throw the math my way.
Unfortunately it's not a simple formula, but rather a process. To compute, you need to not only propagate the satellite orbit (as is done in a tracking program), but also need an algorithm to generate positions of the Sun relative to the Earth. (The latter is available in a book called "Astronomical Algorithms" by Jean Meeus.) You will also need to consider the diameter of both the Sun and the Earth.
The eclipse geometry is explained in the book "Satellite Orbits" by Montenbruck and Gill. From there you need to develop a sampling method to determine entry and exit times.
Bear in mind that the eclipse geometry and timing is different on a case-by-case basis with the exception of some specialized orbits (which ARISSsat is not in).
I'm sorry I couldn't offer a more satisfying answer.
73, Ken N2WWD
Sent from my iPad
On Sep 29, 2011, at 7:33 PM, normn3ykf@stny.rr.com wrote:
Hi all!! How does one calculate the period and time of entry and exit of eclipse? I'm going to be helping a friend do an Arissat presentation for her class. Due to the fact of the battery failing, this gives a 15 minute hold before the power management allows transmission. So, for any chance of receiving the bird, it has to be in sunlight for 15 minutes (or so). I'd prefer a mathematical formula. Echo goes through some of the same trials. Thanks, Norm BTW: I am an engineering student, just throw the math my way.
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Ken, Thanks for the pointers to texts. Meeus's tome has good reviews. I may try to find an older copy of his book that deals with programming calculators. Simpler for me to program. This sounds like a fun project. Seems to me once the heavy lifting is done (algorithm), calculation of eclipse times could be automated. I have a feeling that I'll eat those words. Norm
Hi Norm,
I did this many years ago for OSCAR-11, and published an outline of the procedure in OSCAR News.
The calculations were based on procedures written by James Miller G3RUH.
There is a package of files which includes the software, documentation and original G3RUH articles. It's a long time ago since I did this, but IIRC there is a spread sheet graph which compares the eclipse prediction with the solar array currents.
HTH
73 Clive G3CWV
Hitchin, North hertfordshire, UK On 30/09/2011 00:33, normn3ykf@stny.rr.com wrote:
Hi all!! How does one calculate the period and time of entry and exit of eclipse? I'm going to be helping a friend do an Arissat presentation for her class. Due to the fact of the battery failing, this gives a 15 minute hold before the power management allows transmission. So, for any chance of receiving the bird, it has to be in sunlight for 15 minutes (or so). I'd prefer a mathematical formula. Echo goes through some of the same trials. Thanks, Norm BTW: I am an engineering student, just throw the math my way.
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Ooops! I forgot to say that the file is satill.zip on my website www.g3vwv.co.uk
It's on the OSCAR-11 page and the general satellite page.
73 Clive G3CWV
On 30/09/2011 08:51, Clive Wallis wrote:
Hi Norm,
I did this many years ago for OSCAR-11, and published an outline of the procedure in OSCAR News.
The calculations were based on procedures written by James Miller G3RUH.
There is a package of files which includes the software, documentation and original G3RUH articles. It's a long time ago since I did this, but IIRC there is a spread sheet graph which compares the eclipse prediction with the solar array currents.
HTH
73 Clive G3CWV
Hitchin, North hertfordshire, UK On 30/09/2011 00:33, normn3ykf@stny.rr.com wrote:
Hi all!! How does one calculate the period and time of entry and exit of eclipse? I'm going to be helping a friend do an Arissat presentation for her class. Due to the fact of the battery failing, this gives a 15 minute hold before the power management allows transmission. So, for any chance of receiving the bird, it has to be in sunlight for 15 minutes (or so). I'd prefer a mathematical formula. Echo goes through some of the same trials. Thanks, Norm BTW: I am an engineering student, just throw the math my way.
Clive,
Your website is: http://www.g3cwv.co.uk/ :)
Simon Brown, HB9DRV http://sdr-radio.com
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Clive Wallis
Ooops! I forgot to say that the file is satill.zip on my website www.g3vwv.co.uk
Thanks to all who responded. I found that Nova for windows will predict eclipses. Still am reading g3ruh's articles. Looks like fun. Norm
participants (4)
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Clive Wallis -
Ken Ernandes -
normn3ykf＠stny.rr.com -
Simon HB9DRV