Thread by @mikepuchol

After reading & digesting @ChristopherJM's tweets with @MehulAtLarge and @felschwartz regarding outages of @SpaceX #Starlink service in Ukraine, here is a short thread which I hope will help understand the issue.

Nothing I will reveal is secret or classified, and can be developed by using publicly available information. So, it can only frustate Russia - Поделитесь своим кулаком в небе, sorry Vlad! Let's start with the first image I've posted.

It shows a capacity simulation over Ukraine, but the point is not to analyze the capacity that Starlink can provide - but rather, where the satellites are. If you look at the satellites on the West, to reach the battle front, they must use a high steering angle.

As I explained in my article mikepuchol.com/modeling-starl…, the footprint of the spot beams gets elongated as they are steered further from the sub-satellite point (nadir). Let's setup a hypothetical theater, knowing Starlink uses a hexagonal cell system to assign satellite capacity.

In this scenario, blue cells are #Ukraine held territory, salmon cells are held by Russia, and cells 1, 2 and 3 are a penetration into occupied areas, just performed by Ukrainian forces. A satellite directly overhead could serve cell A without worry about jamming from Russia.

By using directional beams, Starlink effectively concentrates its "listening" towards the target cell, and goes "deaf" to anything coming from other cells. Of course, there are nuances to this. What if the commander demands Starlink capacity on cell 3, where the battle rages?

This is what it would look like, if the satellite was not overhead. Due to beam spread, cell A could still be served without the satellite being jammed, but the beam on cell 3 can get jammed from cells now red, as it is also listening to them, and there is nothing it can do.

We have so far used what is known as the "3dB contour", which I won't go into as it's a subject in itself. I can simplify the concept as "the area inside which a user terminal can operate efficiently at design power levels".

A second important concept (again, simplified) is that every 3dB change represents a reduction of power by half, or an increase by two. All antennas have decreasing set of contours, based on the RF signal strength they can "hear", or what they can transmit. Here is an example:

Back to our theater, if we plot (again, very simplified) 3dB, 6dB (half power), 9dB (half power -again-), and 12dB (half power -yet again-), we can see that even if we pointed the "normal" 3dB footprint out of danger, the lower gain footprints would enter Russian ground.

Here comes the punch line: in order to jam this beam, a Russian jammer in a cell inside the 6dB footprint, only needs to -double- the power, to cause the same jamming effect as if it were inside the 3dB footprint. We can see how many cells are candidates for jamming.

The jammer needs to increase the output power and/or antenna gain, to achieve the same effect. You may now ask: why not just use satellites overhead? A satellite directly over the target cell has a slant range of ~550km, whereas at high steering angle, it can reach ~1100km.

This is important is because the RF signal received decreases proportionally to the distance squared. The free space loss at 1100km is about 6dB greater than at 550km. Our jammer only needs to use 25% of the power to achieve the same jamming effect if the satellite is overhead.

I hope this thread was useful, and I'd welcome corrections, additions, and suggestions. As @elonmusk said, coordination with front-line forces to task resources dynamically is critical to avoid jamming operations.