1. The signal and the noise, one more time
Carl Sagan’s Contact returns one last time for this arc because the desktop must also keep its signals clean in a noisy environment. The noise is not extraterrestrial; it is plasma, switching converters, crosstalk, and electrostatic discharge. The goal is the same: to make sure the intended signal is still readable when everything else is trying to drown it out.
Entries 485 through 487 read about spacecraft charging and EMC. This entry closes the arc.
2. What was learned
The EMC and charging literature gives the desktop three constraints:
- Spacecraft can accumulate charge from the plasma environment, especially when high voltages are present. Differential charging can lead to electrostatic discharge.
- EMC is a system problem. Emissions and susceptibility depend on grounding, bonding, shielding, filtering, and harness routing together.
- Standards exist for both charging and EMC. NASA-STD-4005 addresses high-voltage LEO charging; MIL-STD-461 and GEVS address emissions and susceptibility.
3. What was decided
The desktop will treat EMC and spacecraft charging as controlled design properties:
- A grounding and bonding plan will define how every cell shell, cable shield, and power return connects to the rack reference.
- Power bus voltage will be selected with awareness of LEO charging thresholds; if it exceeds 55 V, NASA-STD-4005 rules will be applied.
- Harness routing will separate noisy and sensitive lines, and cable shields will be terminated with 360-degree continuity where required.
- Power entry points will be filtered to keep converter noise local.
- Exterior dielectric surfaces will be evaluated for charging risk and made conductive or grounded where necessary.
- EMC and charging tests will be included in the qualification campaign.
4. What remains open
The exact bus voltage, harness topology, and test plan depend on the detailed electrical architecture. The reading arc has set the strategy; the detailed grounding map and test matrix come later.
5. What this changes
- The EMC and spacecraft charging reading arc is closed.
- The desktop’s electrical design has explicit grounding, shielding, and charging requirements.
- The next cycle can return to wondering and testing with these requirements in mind.