Hans G. Schantz has published a report on Gab illustrating how Russia is trying to jam electronic satellite surveillance of part of its territory. He writes:
And so on the 24th, the European satellite Sentinel-1 tried to take an image of Sevastopol in the radar range - only then a surprise awaited it.
The Sentinel is equipped with a radar that allows it to form an image of the earth's surface even in conditions of interference. This radar operates at a frequency of 5.405 GHz. Accordingly, any radiation (primarily from military radars) at close frequencies creates interference for the satellite radar.
(Click the image for a larger view)
But in the photo it is clearly not interference from the operation of one or more radars, but the result of the operation of an electronic warfare complex, jamming the radar frequency with counter interference over a huge area.
There's more at the link.
I've had some involvement with electronic warfare (EW) in the past (in a much more primitive form, and now decades out of date). I've known about EW directed against satellites themselves (the Chinese are pretty far advanced in that field, and although the USA isn't talking about its technology I presume it's at a similar level), but I wasn't aware that EW had advanced to the point where it can "blanket" a ground area (rather than a specific pinpoint target) against space-based electronic surveillance like that.
Since today's satellites use digital electronics rather than film photography or analog technology, such anti-satellite-surveillance EW might render them a lot less useful. If any readers can point us in the direction of more information (without, of course, compromising its or their security classification), please do so in Comments. Thanks!
Peter
I haven't actually worked the field in decades, but it looks like Russia has a planar phased array emitter set up on the ground. It points up, and transmits at the Sentinel-1A radar freq.
ReplyDeleteIt would be "painting" a series of lines. Paint one, then shift the beam slightly. Repeat ad infinitum. It's similar to the raster scanning electron beam in an old fashioned CRT television tube.
The Sentinel is over 400 miles up, so the phased array beams only have to be shifted a a little bit. Without doing the math, probably a couple of degrees would cover a large area of the satellite's view.
Dedicated jamming of synthetic aperture radars, whether airborne or space-borne, has been a thing for quite a while. I first saw an image that looks like that over 2 decades ago in my work for a 'Great Big Defense Contractor'.
ReplyDeleteCouple of observations:
First, due to the way SAR functions, that jamming does not require a lot of power even though a fairly large area appears to be covered. It is more about technique. Second, there are counters - that's all I can say about it. Third, this affects SAR but has no impact on the visual spectrum. A camera image from the same satellite would be unaffected by any jamming (it can't see through clouds though, which SAR can do).
References - https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/rsn2.12379
Changing the frequency will diminish the jamming. But like all military tech it's a rat race. Create an advantage, have the advantage nullified. This goes on back and forth as long as the opponents have the money and will to keep it up.
ReplyDeleteTo elaborate on one aspect of John Fisher's answer, if one knows that light and radio are both electromagnetic waves, then why isn't this kind of radio technique applicable to light too? In principle, setting aside difficulties like getting suitable materials, it _is_ applicable to both. But the frequency of light is so high that to get coherent emission of light in practice you need to, um, more or less, let individual molecules and quantum statistical effects do it for you, as in a laser. Or, more indirectly, as in a camera lens: the atoms in the lens of a camera end up acting in phase as they massage the light passing through the lens, but not because the camera maker runs a control cable to each atom. In the radio frequency range with modern electronics it is practical not just to induce big broad patterns of synchronized wiggling as in lasers or lenses or big monolithic old-fashioned radio antennas, but to directly control phases of many signals. E.g., you can set up a lot of small synchronized antennas individually controlled by electrical waveforms that you send over cables.
ReplyDeleteSeveral things about such a phased array scheme break down horribly if you try to use such a design near the optical frequency range. In particular, quantum mechanics says that the quantum energies involved at such frequencies are high enough that your control signal will have a significant chance to break chemical bonds, and a considerably larger chance to ignore distinctions that your phased array design cares about (like "conductor" not being the same thing as "insulator"). Because of this, any design trying to directly control several emitters in phase tends to deteriorate into complete nonsense.
The really low-level fundamental ideas of phased arrays and other phased signal tricks still apply to light as well as radio --- both light and radio really are electromagnetic waves. So if you could build the device out of unobtainium of some sort --- perhaps superdense matter as we expect to exist in neutron stars, or the muon-based atoms that we can zap into existence for a microsecond or so here on earth --- then phased array optics could be a thing. But this kind of tech has been locked away from us for a long time by the incompatibility between the quantum energy scale needed by the device and the quantum energy scale which holds ordinary matter together. It's rather like a space elevator or confined fusion (except impractical by rather more orders of magnitude than a space elevator): as far as anyone has been able to determine, we do have a pretty good fundamental understanding how to do it, and we also have a pretty good fundamental understanding of how difficult it is to do it in practice with any material which is held together by electrons forming chemical bonds.
I still remember how to put the lenses into a 24" f.l. spy satellite camera lens, but a non-trivial industrial base would have to be stood up again, probably not the same as last time. The advanced mysteries were not revealed to me.
ReplyDeletefile:///C:/Users/r/Downloads/The%20Corona%20Camera%20System%20by%20Frank%20Madden.pdf
Thus the work on trans-sonic stealth spy planes continues... cameras still work.
ReplyDelete