Value chain · CLM-0865
In plain terms
For a power satellite in high orbit, the beam is almost exactly as concentrated where it passes through the ionosphere as it is at the ground, so the two figures can be compared. For a low-orbit satellite they cannot.
The claim as recorded
For a geostationary space solar power downlink, the microwave power density where the beam crosses the ionosphere is about 2.2 per cent ABOVE its value at the ground, and within 1 per cent at E-region altitudes. Comparing a ground power density against an ionospheric threshold is therefore valid at GEO to within about 2 per cent. This does NOT hold for low Earth orbit: for a 480 km system with a converging beam the ground density is roughly 12 times the ionospheric value, and a far-field model is inapplicable there in principle.
Evidence behind this: T0-calculation. Beam width at altitude derived from stated aperture and ground-spot dimensions, cross-checked against four independent models including a Gaussian-beam diffraction treatment.
Scope and limits
Establishes comparability, NOT that any particular comparison is correct. Says nothing about whether a given ground figure or a given threshold is right. UNRESOLVED AND MATERIAL: whether CLM-0020's 230 W/m2 is a beam-normal or a ground-plane figure is worth about 32 per cent, fifteen times the effect established here; "beam-normal" is an addition in this record and is not in CLM-0020. Closed 2026-09-19: beam-normal, by CLM-1092; the 32 per cent is 29.6 to 31.8 over 34 to 35 deg N and does not bite on the ionospheric comparison. Applies to the 1978 reference geometry; a materially different aperture-to-spot ratio needs its own check.
What it assumes
That the ionospheric interaction depends on local power density. If it depends on some other quantity the comparability question is malformed rather than answered.
Where it comes from
This is the project's own working, shown in full:
Four independent models of the 1978 reference geometry (1 km aperture, 10 km ground spot, 35,800 km) agree at the F-region peak: point-source diverging 1.0170, linear beam-width 1.0153, Gaussian-beam diffraction 1.0216, and the amplitude taper cancels in a far-field ratio. E-region 110 km gives 1.0056. GEO sits at 2.27x its Rayleigh distance so the far-field treatment holds throughout. LEO at 480 km sits at 0.051x its Rayleigh distance.
Basis: dimensionless ratio (power density at altitude relative to ground)
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0865
CLM-0865, Energy Aperture, as of 2026-09-06.