Low Earth Orbit Visualization
platform.leolabs.space
platform.leolabs.space
Twice in my life I have seen what I believed to be a satellite make a sudden and abrupt (near instantaneous) 90-degree turn. I realize this is impossible [probably?], which is why I ask. Once was in 1992 - and I spent nearly 30 years telling myself I mis-remembered. And the second time was in 2018 while backpacking with my wife - she was a second witness and confirmed that we saw the same thing. Both times the turn occurred when directly over-head.
When casually stargazing, I don't spot the satellites when they first pop up on the horizon. I usually spot them around 30-45 degrees above the horizon. One way to differentiate between an aircraft and a satellite is the blinking, but that's not always reliable - so a more reliable way is to note how quickly the "perceived" speed changes as it moves from 30-degrees towards the azimuth. The larger the change in perceived speed, the lower the altitude, while constant speed indicates orbit.
In both cases, I was casually looking at the sky - I had no measurement or recording tools. In both cases I took mental note of the speed when I first spotted it and how it changed (or didn't) as it moved. I mentally noted that that both appeared to be a satellite. Obviously, a 90 degree turn is impossible (?), which leads me to guess that I may have seen an extremely high altitude, high speed, aircraft make a near 90 degree turn while reflecting sunlight shortly after sunset. This also seems to be a stretch.
I hate to ask such far-fetched "I saw..." questions here, but it's been driving me nuts since 1992. All attempts at research have been fruitless. I thought maybe someone here could help?
[2] March 2018, at approximately 8:30-9pm. Again, I don't recall the exact date or time, (I should have written it down immediately), but we were outside Borrego Springs, California approximately 100 miles east of San Diego. San Diego is also very close to a lot of Military bases.
So one moves into the shadow of the earth, the other moves out - at a 90° angle.
Edit: Did both objects change direction, or just 1 of the 2?
I would hazard a guess that you saw two objects that appeared to cross paths at the time one was disappearing and the other was appearing. Could be planes or satellites. Both can abruptly appear or disappear as they enter or exit shadow, or as they turn and reflect light in a different direction.
A bright white spot moving over the blue sky and suddenly doing a 90 degree turn. It really scared me at the time.
I now believe we saw a high-altitude balloon that got into a layer of different winds at that moment.
How about a smooth change in direction? This might be weird enough to be interesting in its own right. In that case picture a satellite in a highly elliptical orbit, where you catch it near apogee, and assuming conditions are such that you can see it (big enough shiny surface/close enough to earth for human eyes, sunlit) then the earth could “outrun” it for a bit while the sat. is at its slowest, and the craft might trace a loop out in the sky, or (presumably) some other curve depending out your relative line of sight, etc.
Edit: trying to remember if there was a more official name for this orbit. Perhaps a Molniya orbit could give the ground based observer a loop?
https://www.google.com/amp/s/www.researchgate.net/figure/A-3...
Any abrupt change in heading is indeed pretty much impossible. A 90 degree plane change would require a staggering amount of delta-v.
The typical pop-culture UFO shape, a saucer or a sphere, would be pretty good at distributing these forces across the "fuselage" I would guess, but internal systems are still affected. Anything with wings or solar panels would be toast, no?
If the satellite passed into the shadow of the earth and dissappeared, your eyes could move to track another one without you seeing any perceptual gap at all.
The easiest explanation is two satellites with 90 degree between their inclination and lucky situation with the shadow that hides one at the approximate time second satellite shows up. It's not common but it someone will see it with enough time.
Just like with enough time and observation you can see a meteor that is heading straight toward you (it looks like a bright dot that dissappears).
That object could appear to turn "90 degrees" in _two dimensions_ when actually it changes course by a smaller angle in 3D space.
Imagine a satellite is heading straight for you. It would appear to not be moving at all. Now imagine it is moving toward but slightly below you. It will now appear to be moving slowly "straight down" from your perspective, but actually, it could be moving towards you at high speed.
Now imagine there is a small impact with the satellite that causes it to bump up and right slightly from its current trajectory. It might now suddenly look like it's moving entirely rightwards, from your perspective, but it is still moving towards you.
This is hard to explain without visualisation, but completely explains all of these anecdotes about sudden direction changes.
[1] https://aviation.stackexchange.com/questions/12762/what-airc...
[2] https://en.wikipedia.org/wiki/Perspective_(graphical)#Foresh...
I take my two-year-old out satellite hunting a few times a week. He’s a big fan of Pluto but understands we can’t see it like we can some satellites, plus Venus, Saturn, Sirius, etc. Of course he’d still rather see a truck!
ps i didn't see a way to manually set a location, maybe just my old android tablet...
They're working on four additional radar installations for tracking space debris. Their current installations can track objects down to about a 10 cm diameter, but with their new installations they'll theoretically be able to track objects as small as 2 cm. In general, current radar systems tend to be limited on the lower end to objects in the 5-10 cm range. Systems like LeoLabs’ and the US Air Force’s upcoming Marshall Islands-based Space Fence will improve coverage, but still won’t see the 128 million objects from 1 mm to 1 cm. For perspective, a collision with a 10 cm object will likely completely destroy a satellite, a 1 cm object will likely disable it, and a 1 mm object may disable a subsystem. At closing velocities around 10 km/s, the kinetic energy of even an untrackable chip of paint is greater than the destructive power of an equivalent mass of stationary TNT. Whipple shields around the ISS’s crewed areas are built to absorb impacts with objects of up to around 1 cm. For anything bigger, an avoidance maneuver is used (if we see it coming).
I assume they have better tracking than 2cm for the orbit the ISS is in? Does the ISS have its own radar warning? Though I guess if it sees it coming it's already too late for avoidance.
For some perspective, 20mm is 0.787402 inches, so that would be approximately a .79 Caliber projectile.
For comparison, a .50 BMG round exits the muzzle of a rifle anywhere between 2,895 ft/s up to 3,044 ft/s[1].
3,044 ft/s == 927.81 m/s == 0.92781 km/s.
So yes, this 20mm piece of space junk is travelling a lot faster than a bullet, and consequently would carry a lot more energy.
Yes. Orbital hypervelocity impacts basically vaporize immediately on hitting anything, so you can offset a thin material in front of what you want to protect and cause any incoming object to turn into a cone of many much smaller objects which are less likely to penetrate the main hull.
(Some of the paragraph I posted was excerpted from a recent issue.)
Thanks vortex_ape. I love the way random cool stuff pops up on HN like this.
PS: It does look a lot more crowded in space in this view than it actually is, because the objects are shown at like a million times their actual size :) And it doesn't show vertical separation graphically.
Man this thing is nuts the zoom is neat
If you were cynical, you might say that those sorts of false alarms are a marketing/PR stunt. If that's the case, it's in their best interest to not offer to-scale visualizations, making LEO look as crowded as possible.
I've been meaning to implement SGP4 from scratch as a learning exercise. What I found really interesting is how the USAF/NORAD tracks and reports objects in LEO: they publish Two-line Element Sets (TLEs), which are a fixed-width ASCII format derived from punch cards.[1] The format is pretty easy to parse.[2]
[1]: https://en.wikipedia.org/wiki/Two-line_element_set [2]: https://www.celestrak.com/NORAD/documentation/tle-fmt.php [3]: https://www.celestrak.com/NORAD/documentation/checksum.php
https://rhodesmill.org/skyfield/
I’m feeding it into Graphana to help visualize how satellite coverage impacts the signal strength and network performance of my dish. It’s pretty fun.
I used it to make https://droid.cafe/starlink
https://platform.leolabs.space/sites
The pointed shape ones are 2D phased array radar. The radar is a grid of 4096 elements. It can observe things anywhere in the sky above it, however there are practical limits to how far off boresight it can operate. These limits are related to the arrangement of the elements, and result in the 6 pointed shape.
The others are 1D phased array radar. They consist of a line of elements rather than a grid. They use a parabolic reflector along the length of the array to focus the radar's observable area to a single line to make up for that missing 2nd dimension. So the reflector limits the radar to only observing across a single line, and the array allows the radar to control where across the line to radiate or listen.
Very interesting and entertaining. I’ve not been excited for a piece of tech in years but starlink has me on the edge of my seat. I can’t wait to get my equipment.
By the way, look for the starlink sats. Very cool. Wonder how many conjunctions they've had :)
It was running nice and smooth for me on the following system
Linux
Brave browser
GTX 1070 (mobile version)
i7-8700K CPU
16GB RAM
Should work on phones, tablets, and others.
What're your specs?
For comparison it's estimated that approximately 100 tons of pebbles and dust fall into the atmosphere every day, and plenty more just drifts past Earth continuously. We do need to come up with better mitigating controls and accidents will happen, but I think it's achievable.