Value chain · CLM-0949
In plain terms
There is a standard international curve describing how quickly an antenna's stray radiation should fall away off-axis. The SPS pattern stays under that curve everywhere except at its grating lobes - the repeating spikes caused by building the antenna out of subarrays - and the report says that because of those spikes the standard curve cannot be used to describe the SPS safely.
The claim as recorded
The standard CCIR sidelobe envelope is drawn on the SPS antenna pattern, the pattern sits below it everywhere except at the grating lobes, and the assessment states that the criterion therefore cannot describe the SPS safe sidelobe envelope. The envelope is the familiar G = 32 - 25 log theta curve, plotted across Figure 1-9. Verbatim at PDF p.25: the criterion "cannot be used to describe in a simple manner the safe sidelobe envelope of the SPS pattern because of the grating lobes". So a named international criterion exists, the design nearly meets it, and the exceptions are the part that matters.
Evidence behind this: T3-primary-report, and the authority is exactly right for this claim: a JPL assessment saying that an international sidelobe criterion does not describe the SPS antenna is a statement from the SPS side about its own design, which is the only side that can make it.
Scope and limits
THIS IS A 1977 ASSESSMENT OF A 1977 REFERENCE DESIGN, NOT A REGULATORY DETERMINATION. No spectrum authority is recorded as having applied or declined to apply the CCIR envelope to an SPS, and this record must not be read as one having done so. THE CRITERION IS NOT SAID TO BE VIOLATED IN LEVEL - the pattern is below it everywhere else - so the finding is about the criterion's descriptive adequacy rather than about compliance. A DIFFERENT SUBARRAY DESIGN WOULD MOVE THE GRATING LOBES, since they are a consequence of periodic subarray spacing, so nothing here is a permanent property of space solar power. THE ENVELOPE'S OWN VINTAGE MATTERS AND IS NOT ESTABLISHED HERE: the CCIR recommendation carrying G = 32 - 25 log theta has been revised since 1977 and this register does not hold any edition of it.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
Figure 1-9, "SPS 10-dB taper array pattern", PDF p.24, carries the curve labelled G=32-25 LOG theta across a plot of gain against angle from boresight, with GRATING LOBES marked. The sentence before the quoted one is transcribed and not quoted, because the text layer corrupts "below" to "belov" and "the" to "tne": raw, "for the grating lobes, the SPS pattern falls everywhere belov tne CCIR pattern." The quoted sentence itself matches at the normalised level and is verbatim. The same page adds that the plot "clearly shows that the gain of the antenna represents radiated energy that is borrowed from the region between 20 and 180 degrees from boresight".
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0949
CLM-0949, Energy Aperture, as of 1977.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-450
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