Hacker News Reader

Comment by ericbarrett | Hacker News Reader

You're absolutely correct, but as the aircraft is much closer to the ground than the imaging satellite I disregarded it. Spherical cows and all that :) I'm sure a military analyst would do the calculations!

View on HN

It actually works out to be pretty close. A satellite flying ~17k mph at 250 miles altitude would largely have the same angular displacement from the ground as a plane moving 400 mph at 31,000 feet. Most satellites fly in an easterly direction, so the question would ultimately be what the inclination of the orbit is relative to the direction of flight.

That's super interesting! I love this discussion. Would the satellite be that low though? 250 miles (400km) is still going to experience significant atmospheric drag. Fine for a cheap mass deployment like Starlink, but I'd expect an imaging satellite to be set up for a longer mission duration. Then again maybe the cost of additional mass for station-keeping is worth it for the imaging quality.

https://globalcomsatphone.com/satellites-and-their-altitudes...

You can find a list of satellites here: https://www.ucsusa.org/resources/satellite-database

According to the image on Google maps it was taken by Maxar. Maxar appears to have a few satellites, looks like 5 in geostationary orbit (~35,700km), 3 at about 400km and 1 at about 500km.

Looks like you nailed it! ctrl+f pushbroom in the thread if you haven’t seen it.

Most imaging satellites are in sun synchronous orbits so likely in this case moving north or south and slightly retrograde e.g. west.

I'd bet orbital motion is negligible here because the distortion seems to the eye to be entirely in the direction of the plane's apparent motion vector and I don't see any significant skew to that.

I think this plane is flying much lower and slower. The B2s are based at Whiteman AFB, which is about 25 miles south of this photograph. The prevailing winds in this part of the country are from the south, so I suspect that it is about to turn onto the final leg of its approach for a landing to the south. I’d guess that it’s no more than 8-10K’ and traveling at a 2-300 knots max.

Definitely. Rule of thumb in a jet is to slow down if you're closer than 3x the altitude. So at 8k feet you want to be at least 24 nautical miles (27 normal miles) away or if closer you want to be slowing down (or descending). If you don't slow down before you're going to have to do so in the descend and typical jets can't really slow down much in that.

I asked google maps to get directions from there to Whiteman AFB. Unfortunately, flight directions were not available.

And you are now on a list...

I've been on a list for so so long now that this one is just another. No big deal.

Hey welcome to the list, I've been on it since Primary School believe it or not, but only found out a few years ago!

How did you find out?

Well no the speed of the satellite is irrelevant there, the background is not getting distorded at all

Isn't the speed of the sat irrelevant as it should correct for this anyways for all images it takes?

yeah, exactly

Interesting, I would have made the opposite assumption ("the satellite is moving so much faster than everything else, we can estimate the interval from the satellite's speed alone). It seems both speeds might have a similar impact, as per sibling comment.

Reply on news.ycombinator.com