You would think that the design could contain a small analog charge controller that could act as a failsafe for the digital system. I understand that there is a size and weight limit to these little beasties but my yard lights have analog charge controllers that can fit on a US Quarter. I know that the very small size limits the current that they can handle, especially in a vacuum but who cares if it charges at the rate of a few mA and takes several hours or a day to get the batteries up to power so that the digital system wakes up and takes over.
Kevin, WB5RUE
From: Ashhar Farhan [mailto:[email protected]]
Sent: Sunday, January 31, 2021 12:59 PM
To: Dimitrios Simitas <[email protected]>
Cc: AMSAT BB <[email protected]>
Subject: [AMSAT-BB] Re: Cubesats
Having built four missions and launched two, I can say that the main challenge of cubesats is their really small power budget. The rest of the risks just multiply because of that.
Very often, the time from insertion into the ppod to launch is more than six weeks. The batteries drain off, as the batteries drain off, the entire system is browned out. it is a miracle to put up back again. very often, the analog circuitry that would have charged the batteries through solar panels is replaced by software on OBC. But the OBC is unavailable, the analog state is undetermined. There is a colossal fight among schrodinger's cats inside the box.
On the other hand, why does the AO-7 continue to work? because it has an all analog design that will turn on the transponder as soon as power is applied and the oscillators can oscillate. If they fail to boot up on one orbit, there is always another orbit to bet on.
This is also compounded by the cubesat/IARU specification that insists the satellite should have a way to switch itself off under ground control. This means that unless the CPU decides to wake up the radio, it will remain silent. If the CPU has browned out, then bye, bye, bluebird!
- f
On Sun, Jan 31, 2021 at 10:06 PM Dimitrios Simitas <[email protected]> wrote: