Value chain · CLM-0979
In plain terms
The three designs disagreed about what the guide signal from the ground should look like. One used a pair of tones either side of the target frequency; one used exactly the transmitter's own frequency and worried about telling the two apart; and by 1979 the reference design had moved to a coded, spread-out signal, the same family of technique that satellite navigation uses.
The claim as recorded
The pilot signal changed form across the 1978-1979 programme designs. LinCom's 1978 report proposes an uplink pilot of two tones placed symmetrically above and below the nominal pilot frequency, their sensed phases averaged before conjugation, to remove the beam squint that a frequency offset between pilot and power beam produces. Boeing's December 1978 briefing has the power beam and pilot "at the same frequency", with isolation at the pilot receiving antenna the open problem. Boeing's 1979 reference system description then states that "the power beam is focused at the ground receiver by a spread-spectrum retrodirective active phase control system" and that "the power beam baseband is synthesized from the spread-spectrum uplink".
Evidence behind this: T3-contractor reports, three statements of what the pilot signal was in three successive designs.
Scope and limits
"SPREAD-SPECTRUM" IS STATED ONCE IN THE 1979 REPORT AND NOT SPECIFIED THERE: chip rate, code and bandwidth are not given on the page, and the term occurs nowhere in the other three documents read. Whether the 1979 spread-spectrum uplink was chosen to resolve carrier-phase ambiguity or for jamming and interference resistance is not stated in these four documents; NASA's 1981 RP-1076 says the reference system's uplink pilot carries code modulation "to provide link security and antijamming protection from radiofrequency interference" (PDF p.44, printed 15). Terms probed and absent in all four documents: ambiguity, GPS, GNSS, code phase, data modulation, two-tone (LinCom's own term is "two frequency").
What it assumes
No assumptions are recorded against this claim.
Where it comes from
pp.16-17, normalised with its faults: "the uplink pilot signal consists of two tones,one at llw radians/sec above the nominal pilot tone at w0 and the other llw. belo111 the nor.iinal tone at w0. The phases of these two tones are sensed at the SPS antenna eler.:ents. The phases are averaged and then the conjugate of this averaged phase is used to radiate the power beam at the frequency w0" ("llw" for delta-omega). SRC-456 p.125, normalised: the pilot receiving antenna is "indicative of an approach to be considered to achieve good isolation in a system in which the power beam and pilot beam are at the same frequency" (text layer heavily damaged; sense confirmed by adjacent words). SRC-464 p.257, normalised: "Electronically-steered phased array microwave power transmitter employing a 10-db truncated Gaussian illumination taper on a 1-kilometer aperture. The power beam is focused at the ground receiver by a spread-spectrum retrodirective active phase control system. The power beam baseband is synthesized from the spread-spectrum uplink, amplified by 70-KW RF klystron power amplifiers, and radiated by a slotted waveguide antenna."
Basis: pilot signal form: two tones; same frequency as the power beam; spread-spectrum uplink
Related records
- Answers question
- QST-013 not published in this release
Cite this
energyaperture.com/c/clm-0979
CLM-0979, Energy Aperture, as of 1979.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-107
- CLM-0033 (low confidence)Apart from a 1981 NASA review that found no evidence for the number and suggested a higher one, nobody was found to have revisited it, and...CLM-0060In 1981 a NASA review panel said the 230 watts per square metre figure rested on an obsolete theory with no experimental support, and made...CLM-0061The experiments were done. They found heating two or three times stronger than normal, not the tenfold effect predicted, no irregularities...CLM-0062By 1981 the theory was being revised to a steeper frequency dependence, which would raise the permitted power density.CLM-0063NASA suggested in 1981 that 550 to 600 watts per square metre might be reasonable, roughly two and a half times the figure still in use...CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0160A 1978-81 NASA design study calculated that simply pointing the satellite's structure accurately enough, without any electronic correction...CLM-0420NASA's 1981 report says the experiments found nothing supporting the 23 milliwatt limit, that the measured heating was two or three times...More on the source page.
- Also from SRC-456
- CLM-0977In 1978 Boeing worked out how the timing reference should fan out across the kilometre-wide transmitter. The choice of how many branching...CLM-0981Smaller patches tolerate more bending: halving the patch from 10 m to 5 m doubles the allowed tilt for the same half-per-cent loss. A...CLM-0995The whole ten-kilometre satellite was designed to sway once every fourteen minutes, and the antenna was required to be at least as stiff as...CLM-0998With the top of a five-kilometre section of the satellite two hundred degrees Fahrenheit hotter than the bottom, the estimate has its free...
- Also from SRC-462
- CLM-0980The company that designed the timing system in 1978 handled the bending of the transmitter by dividing it into groups of patches, each with...
- Also from SRC-464
- CLM-0978In 1979 Boeing wrote down where the timing errors in the transmitter would come from. Most of the allowance, about six of the seven...