Value chain · CLM-1001
In plain terms
Besides the deliberate beam and the tubes' noise, the satellite's fifty square kilometres of warm solar array glow faintly at radio frequencies; the 1981 study put that glow at a level far below anything else and noted that the tube noise would change if magnetrons or other tubes replaced the klystrons.
The claim as recorded
The 1981 EMC assessment adds a third emission mechanism to the two the register holds: thermal blackbody radiation from the photovoltaic array, estimated at about -265 dB(W/m2 Hz) at 2.45 GHz at the earth "for a single SPS structure assuming 10% microwave emissivity", rising 6 dB per octave; its Figure 17 places that beside the transmitter's noise sidebands, "typical of 5-cavity klystrons", which "would vary if different power amplifiers (magnetrons, gyrocons, gyrotrons) were used". The Reference System it assesses has a 1 km array of 7,220 subarrays and "more than 100,000 - 70 kW klystrons".
Evidence behind this: T3-programme assessment; the -265 figure is an estimate stated with its assumption.
Scope and limits
THE -265 IS AN ESTIMATE WITH ITS EMISSIVITY ASSUMED AND IS 18 dB BELOW CCIR 224-4's -247 AT 2.7 GHz (CLM-0988), so it is not itself the interference problem; it is recorded so that a third dB(W/m2 Hz) figure is not mistaken for either of the other two. Figure 17's plotted ranges have not been rendered and are not quoted. The page's next sentence puts a factor of 10 either way on the emissivity ("Array emissivity might be as much as a factor of 10 larger or smaller"), so the -265 carries about 10 dB either way. A year earlier, Thompson at the April 1980 Program Review put the collector arrays' thermal emission at "approximately 360 K" from 60 satellites as "probably" 3 to 10 dB below his Figure 1, "i.e., very close to the CCIR 224-4 levels" (SRC-449 PDF p.440, printed 419; CLM-1072, back-linked 2026-09-19), against this record's -265, which is 18 dB below CCIR 224-4's -247.
What it assumes
10 per cent microwave emissivity of the array, the document's own assumption.
Where it comes from
PDF p.20, raw: "The spectral flux density at the earth due to blackbody radiation is approximately -265 dB(W/m2Hz) at 2.45 GHz (increasing 6 dB per frequency octave) for a single SPS structure assuming 10% microwave emissivity of the photovoltaic array..." "Figure 17 shows estimated levels or ranges of spurious emissions from the MPTS, thermal emission from the photovoltaic arrays for a single SPS structure, and some established and estimated interference levels... The noise sidebands are typical of 5-cavity klystrons (Figure 12) and would vary if different power amplifiers (magnetrons, gyrocons, gyrotrons) were used for SPS." PDF p.11, raw: "The array consists of 7220 subarrays... amplified by more than 100,000 - 70 kW klystrons."
Basis: dB(W/m2 Hz) at the earth's surface; count and rating of transmitter tubes
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-1001
CLM-1001, Energy Aperture, as of 1981-01.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-543
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