I'll provide a bit of input here since I worked on SO50. Here are some considerations.
- The hardware was mostly built by SpaceQuest and used proven designs that had been flown several times
- The design goal was long life. The orbits would provide that,
unlike some current launches were the orbit will last a shorter
time. The idea was to provide a long life resource for all to
use.
- The software followed proven designs dating back to the 1990 Microsats. All software except the boot loader (in rad protected RAM) was uploadeable. The SCOS real-time operating system allowed individual tasks to be killed and uploaded without disturbing other tasks or the OS. SCOS was quite robust.
- There were no I2C busses to latch up, and no flash cards (both
of which cause problems in current designs)
- The program memory was rad hard, the OS 'washed' that memory
every 10 minutes to eliminate bit flips from passing through the
SAA. The data memory used Huffman software rad recovery.
- Antennas we not deploy-able and were made of piano wire so were
quite robust.
- The batteries were NiCAD so were robust and hard to hurt. They work fine over a wide temperature range and don't need heaters. Don't need to manage charging as carefully and don't need to be concerned about not charging if outside a temp range.
- The software automatically adjusted TX power output to prevent pulling the battery V too low and causing a reset. There were three steps of battery management, each turning off more stuff to reduce load and attempt to prevent full discharge.
- Batteries were very carefully matched using the process first
developed for the Microsats.
- The power system included adjusting the solar panel input
impedance to constantly maximize power from the panels. And
another algorithm prevented overcharging. A manual process is used
to adjust those algorithms as the battery capacity drops with time
and the panels loose efficiency.
- The software kept the dept of discharge of the batteries to no more than about 20%, resulting in much longer battery life.
Jim, WD0E
Unfortunately I don't know much about IO-117 so that is a question I can't answer.
73 John AF5CC
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---- On Mon, 22 Jul 2024 11:31:20 -0500 <crohtun@aim.com> wrote ---
And what have we learned from IO-117 about radiation resistance, etc?
Ray Crafton KN2K
On Monday, July 22, 2024, 12:02 PM, JOHN GEIGER via AMSAT-BB <amsat-bb@amsat.org> wrote:
SO-50 will be 22 years old in December and seems to be still be going strong, in sunlight and in eclipse. No other satellite launched since then has lived near that long. So what is SO-50s key to long life? Is it how the satellite was built? Something in its operation, like lower power on transmit? Its orbital setup?
Any ideas why it has lived so much longer than the recent crop of AMSATS?
73 John AF5CC
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