Value chain · CLM-1205
In plain terms
A 1981 US study worked out what a satellite in low orbit feels when it flies through the beam. For a craft like LANDSAT, the strongest part lasts about a second and the whole crossing about 13 seconds. In tests, one of its cameras failed completely when enough of the beam's power shone into it. The study suggested such satellites could pause commands during a crossing for now, and be redesigned later.
The claim as recorded
The US programme's 1981 electromagnetic compatibility assessment gives the fields on satellites in low orbit that cross an SPS power beam, up to 319 V/m, and for LANDSAT-D more than 100 V/m for about 1 second, more than 10 V/m for 3.2 seconds and more than 1 V/m for about 13 seconds. In tests its TM imager (printed "Thermal Mapper") malfunctioned completely at 16 mW/cm2 on the optical aperture. Its direct S-band command link would see a 70 to 85 per cent rise in bit error rate over a main-beam exposure of about 16 seconds. For perhaps one to three SPS spaced as far apart as possible over the continental US, the assessment proposes pausing commands during those passes as a temporary solution it calls not satisfactory, and changing the design of future craft.
Scope and limits
1980S SATELLITES AND A 1980 BEAM. The figures are for LANDSAT-D (705 km, 98.2 deg), the planned Space Telescope and GPS, against the 2.45 GHz reference beam. The page prints the Space Telescope's orbit altitude as "10,900 miles": that is as printed and not corrected here. The same report gives the Space Telescope orbit as 500 km (PDF 70, printed 67) and 10,900 miles as the GPS orbit (PDF 69, printed 66), and puts the telescope's peak at about 28 mW/cm2 (PDF 72, printed 69), which matches 319 V/m; so 319 V/m is best read as a 500 km figure with the GPS altitude misattached, an inference the page does not state. The Thematic Mapper malfunction is a test result; the field durations and the bit error rates are analysis. No figure is given for a modern satellite, for heating or for permanent damage. The 16 seconds is the main-beam exposure period for the S-band link's bit errors, longer than the 1 s above 100 V/m. Overlaps CLM-1073 (SRC-449, the same programme's 1980 paper), which records the LANDSAT effects; this record adds the field strengths, durations and levels.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF 65: "The large powers involved represent illumination levels as high as 319 volts per meter for satellites such as the proposed space telescope at an orbit altitude of 10,900 miles." PDF 66: "The satellite will be subjected to microwave field intensities greater than 100 V/m for about 1 second, intensities greater than 10 V/m for 3.2 seconds, and intensities greater than 1 V/m for about 13 seconds at LANDSAT velocity." Same page: "The microwave signal level was varied in steps from 1 mW/cm2 until complete malfunction occurred at 16 mW/cm2." And: "a bit error rate (BER) increase of 70% to 85% would occur for SPS main-beam exposure period (approximately 16 seconds)"; the wideband TDRSS channel's BER rises 20% to 40% at "SPS power densities of >= 8 mW/cm2". Mitigation, same page: the mission profile "could be modified to eliminate command/control transmission during the specific orbit time slots corresponding to SPS illumination ... a temporary solution ... while functional modifications are incorporated into future vehicles". Same paragraph: "For perhaps one to three SPS satellites maximally separated over CONUS" (normalised) and "This is obviously not a satisfactory mode of operation" (normalised). The text layer reads "16 uM/cm2", "SS%" and "~ 8 uM/cm2"; all read at render. ">=" transliterates the page's greater-than-or-equal sign.
Basis: volts per metre on a satellite crossing the beam, and seconds above each level; mW/cm2 at which a tested sensor failed; per cent rise in bit error rate
Cite this
energyaperture.com/c/clm-1205
CLM-1205, Energy Aperture, as of 1981-01.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-543
- CLM-1000By 1981 the government's own compatibility study said the satellite's frequency band had not actually been allocated to it, listed which...CLM-1001Besides the deliberate beam and the tubes' noise, the satellite's fifty square kilometres of warm solar array glow faintly at radio...CLM-1002The 1981 study tells you exactly which international rulebooks it measured the satellite against, report by report, and warns that the...CLM-1204A 1981 US government study worked out what happens when an airliner flies through the beam. Its wings would reflect some of the beam...