Value chain · CLM-1207
In plain terms
The 1980 paper that estimated how often a satellite would meet the beam used a simple picture: the beam turns with the Earth once a day, so a given satellite gets about two chances a day to cross it, and whether it does depends on where in its orbit it happens to be. The paper does not say how wide it took the beam to be, or show its sums.
The claim as recorded
The 1980 programme paper behind the "about one chance in 2000" of a 1200 km, 28.5 deg satellite meeting a temperate-zone beam during its first day of operation treats the geostationary beam as sweeping a cone about the polar axis each day, gives each lower satellite usually two encounter opportunities a day where its orbit meets that cone, and obtains the probability by "assuming the orbital phase is randomly distributed"; on the pages held it states no beam width and shows no calculation.
Scope and limits
THE METHOD IS NAMED, NOT SHOWN, AND NO BEAM WIDTH IS STATED. The paper gives only indirect size: an encounter lasts "up to two seconds" for a small satellite (PDF 449) and the beam fills "of order several hundred thousand cubic kilometers" (PDF 449). Reader's arithmetic, not on the page: up to two seconds at a low-orbit speed of about 7 km/s implies a crossing chord of up to about 14 km. So the page does not allow the 1-in-2,000 figure to be reproduced, and a modern count (beam-crossing.md section 2, which finds about 70 to 85 times more per satellite for the same orbit) cannot be reconciled from it; the gap is not explained by these pages. The figure is for a satellite's first day with a random phase; the paper adds that later encounters are deterministic.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF 449: "As the power beam rotates with the Earth, it generates a conic surface about the polar axis"; "there are usually only two opportunities per day for encounters between a given satellite and a given beam. Whether or not an encounter occurs naturally depends on the orbital position of the satellite at the times when these opportunities occur." PDF 450: "an estimate of the probability of an encounter may be obtained by assuming the orbital phase is randomly distributed"; "It is possible for a satellite in an orbit of altitude 1200 km and inclination 28.5 deg to have about one chance in 2000 of an encounter with the beam to a given temperate-zone rectenna, during its first day of operation." ("28.5 deg" transliterates the page's degree sign.) A search of PDF 449-451 for width, diameter, "km wide" and beam radius returned nothing (PDF 448 is the previous paper's last page), and Figure 1 (PDF 451) is the intersection locus without dimensions.
Basis: method behind a 1980 probability of a satellite meeting a power beam
Cite this
energyaperture.com/c/clm-1207
CLM-1207, Energy Aperture, as of 1980-04.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-449
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