Just a comment on a couple things said here:

1)  It is a great idea to have a 'fallback, sun-only' mode for when the batteries fail.  Having remembered the lessons of AO-7 and AO-51, this was the original plan for Fox, but as I may have said, we ran out of time and perhaps space on the bird.  (This was not my area of expertise, but I did live close to and talk a lot with Tony AA2TX(SK), who was VPE at the beginning of the project before sadly going silent key).

2) Multiple receivers is also an excellent idea.  Golf-TEE will have at least 3 command-capable receivers!  Fox birds, even AO-92 and 95, have exactly one.  The L-band uplink on AO-92 and 95 is actually a downshifter to the same receiver.  We did try commanding 95 via L-band to no avail, by the way.

Thanks for the excellent discussion.

73,

Burns WB1FJ
Fox and Golf Flight Software

On Thu, Dec 10, 2020 at 8:07 AM Samudra Haque [TTLLC] <sehaque@tekterrain.com> wrote:

True, but not a deal killer in my mind. I was investigating utility of a relatively less SWaP solution to add to the on-board options for backup power from a catastrophic event.

 

Samudra N3RDX

 

From: KENT BRITAIN <wa5vjb@flash.net>
Sent: Thursday, December 10, 2020 1:45 AM
To: John Brier <johnbrier@gmail.com>; Samudra Haque [TTLLC] <sehaque@tekterrain.com>
Cc: Steve Greene <ks1g04@gmail.com>; AMSAT BB <amsat-bb@amsat.org>
Subject: Re: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime

 

I have worked on several energy harvesting projects, but it's that 140-150 dB Path Loss

from the Earth to LEO that is quite the hurdle.   One solar cell the size of a postage stamp

would give you many orders of magnitude more power.    Kent WA5VJB/G8EMY

 

 

On Wednesday, December 9, 2020, 9:56:12 PM CST, Samudra Haque [TTLLC] <sehaque@tekterrain.com> wrote:

 

 

Thanks John, appreciate it.

 

I’ve been thinking that it should be almost mandatory to put up RF power receivers (converters) on all small space vehicles that have little to no redundancy in EPS, battery and solar plants. Too many missions have suffered because of battery/solar issues. It’s not like there are no transmitters beaming carriers to a space vehicle/smallsat for command purposes – and it’s not like there are no big antennas being used to do that. So why not tap some of excess power (energy) of the carrier that would be tracking the bird in flight when in view of the ground stations? It’s amazing what the newest gen of power converters and harvesting systems can do. I’m looking at the calcs right now. Superb.

 

From: John Brier <johnbrier@gmail.com>
Sent: Wednesday, December 9, 2020 10:50 PM
To: Samudra Haque [TTLLC] <sehaque@tekterrain.com>
Cc: Steve Greene <ks1g04@gmail.com>; AMSAT BB <amsat-bb@amsat.org>
Subject: Re: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime

 

QSL

 

On Wed, Dec 9, 2020, 22:49 Samudra Haque [TTLLC] <sehaque@tekterrain.com> wrote:

I wonder if this response will get out, if anyone sees this please QSL.

I wanted to shift my e-mail address and move to my personal one, and requested delisting several times and was confirmed (several times) and … still get emails from AMSAT-BB.


Well, the discussion on batteries/life/mission expectations is obviously interesting to me. But where the batteries ever characterized for discharge / charge in (LEO) cold and (LEO) hot temperature ranges?

 

I’m well into modeling wireless power beaming systems from ground to space currently for scenarios where batteries are kaput, from LEO to deep space. If anyone is interested?

 

Samudra N3RDX

 

From: John Brier <johnbrier@gmail.com>
Sent: Wednesday, December 9, 2020 10:34 PM
To: Steve Greene <ks1g04@gmail.com>
Cc: AMSAT BB <amsat-bb@amsat.org>
Subject: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime

 

Between Jerry's post and yours I have learned a lot and have more to think about. Thanks so much.

 

Just a couple thoughts:

 

Just thinking out loud here... Depth of discharge means how far into the discharge cycle you let the cells go right? Considering memory, if you only let them go to a specific percentage aren't you guaranteeing memory will be created? I guess if you never plan to go beyond a specific point it doesn't matter, and extends the life apparently. Interesting.

 

The other difference between AO-27 and SO-50 and the Fox birds is that the Fox birds had a continuous carrier once the transponder was activated, for up to a minute even without use, IIRC. So that could cause a deeper depth of discharge.

 

I also would love to know more about SO-50. It seems like a mystery. It just works, it never is commanded into a different mode, and it's been going for almost 18 years apparently. Amazing. When that one goes, it will be even more disappointing.

 

Again, thank you very much Jerry and Steve for your informative posts.

 

73, John Brier KG4AKV

 

On Wed, Dec 9, 2020 at 7:55 PM Steve Greene <ks1g04@gmail.com> wrote:

Jerry  -thanks for that detailed explanation. 

Disclaimer: The information contained in this communication may be privileged, and is intended for the use of the above named addressee(s). If you are not the intended recipient(s), do not use or rely upon it. Instead, please inform the sender and then delete it. Thank you.

 

Disclaimer: The information contained in this communication may be privileged, and is intended for the use of the above named addressee(s). If you are not the intended recipient(s), do not use or rely upon it. Instead, please inform the sender and then delete it. Thank you.

 

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