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Comment by afvictory | Hacker News Reader

Roscosmos has shared before & after satellite imagery for anyone interested: https://twitter.com/roscosmos/status/1291023063404994560/pho...

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Regarding the satellite image, a few questions :

1) Can nation-states spy like this on every location on the planet?

2) Can you view the live feed of any location and follow vehicles(for example)?

3) Is there anything a country can do to prevent other's from spying on your country from satellites?

1. Yes. Not just state actors - Planet Labs (https://www.planet.com/) in San Francisco, for example, is a commercial satellite company that photographs the whole globe once per day and sells that imagery online.

2. Live feed is a bit tricky, and that's where governments have an advantage - they own their own satellites, and can task them to follow a specific target. But you have to know where the target is at the start of the window, they don't have real-time video of the whole planet, and unless you've got a very big fleet you won't always have a satellite overhead when you want to look at your target.

3. Keeping track of the times of satellite passes overhead, hiding stuff underground, putting your aircraft in covered hangars and only moving them at night, putting a roof on your military docks, using upwards-facing camouflage, etc. Same methods that have been used for a hundred years to hide from air surveillance.

  "Planet Labs ... photographs the whole globe once per day..."

This is not an accurate representation of Planet Labs capabilities. I can attest to this as a Farmer's Edge customer.

In the theoretical world where every inch of the earth was photographed every day things like losing MH-17 likely wouldn't have happened.

ETA: Planet claims "entire landmass" every day but I find that claim extremely suspect, but it does not even claim the entire globe.

> In the theoretical world where every inch of the earth was photographed every day things like losing MH-17 likely wouldn't have happened.

I think you mean MH370 instead of MH-17.

https://en.wikipedia.org/wiki/Malaysia_Airlines_Flight_370

What is your experience of the frequency of Planet's reimaging? And at what resolution?

Somewhere between weekly and every 3 days, occasionally worse. I do not know the exact resolutions involved but they have "good" and "bad" NVDI images and the "bad" ones are fairly useless for agricultural applications.

To expand on 3: most spy satellites operate in sun synchronous polar orbits. This is so they can cover the entire earth and will have their solar panels lit by the sun. This also has the ramification that they'll always be in the same spot in the sky depending on the time of day. If you know this time, that's when you hide your tanks and don't fly your top secret spyplane

Even if they're not in SSO, satellites are hard to hide. The timetables might be more complicated for a rank and file soldier to use, but you can time your actions to be missed by any specific low-orbiting satellite.

"will have their solar panels lit by the sun" is probably not the primary reason for sun-synchronous orbits (though I guess it is presumably a benefit) - it's more about having a constant source of illumination to enable photography, as well as the ability to photograph the same site with the same shadow angle over time to facilitate comparison.

> 2. Live feed is a bit tricky, and that's where governments have an advantage - they own their own satellites, and can task them to follow a specific target. But you have to know where the target is at the start of the window, they don't have real-time video of the whole planet, and unless you've got a very big fleet you won't always have a satellite overhead when you want to look at your target.

I would really not be surprised to see the NRO go the Planet Labs / Starlink route at some point in the future and put 20 satellites in a dozen orbital planes to provide coverage everywhere at less than 60 degrees latitude 24/7/365. Sure, maybe you need the big KH-11s for the extremely high resolution shots - but 3m resolution isn't exactly trash either.

At 3m resolution a tank is about 3 pixels; a sedan is around 1 pixel. It's very hard to distinguish objects from each other and therefore to track one at that resolution.

> unless you've got a very big fleet

Starlink

With synthetic aperture radar imagery it's also possible to "peek" under overhead camouflage somewhat.

https://www.38north.org/2020/01/sinpo010320/

I don't think you can get a live feed of a location since the satellites generally aren't geostationary (geostationary orbit is too far away, and are always above the equator). But AFAIK even commercially you can get still photographs of any point on earth within a couple days (i.e. you don't have to be a nation state or have your own satellites)

a live feed to follow something would 99% of the time be implemented from a HALE (high altitude/long endurance) group 4 size UAS. RQ9 or in the same class, with a combination of a high end gimbaled camera system and satellite data uplink.

Geostationary is very very far away and useless for nighttime. Imaging satellites usually have a shorter polar orbit that precesses east to west along with sunshine. https://en.wikipedia.org/wiki/Sun-synchronous_orbit

1) Yes.

2) Well, I can't, but the capability exists.

3) Dig.

Satellites fly unpowered and frictionless in the vacuum, with kinetic energy equivalent to speed of Mach 22 at sea level, balancing against Earth’s gravitational pull, along an own 2D ellipse with one focus at the center of the gravity of the Earth.

So you can’t like fly a 3D orbit, fly at same altitude but different angular velocity, or change course without expelling significant amounts of mass. You play by those rules.

2) costs lots of money, or you have to be a government.

following vehicles is near impossible commercially (resolutions are too low)

2) is more of a drone thing

Drones require you to get permission or vioalate the airspace of the host country.

Or a good relationship with your neighbours or a target close to international waters. What’s a dozen extra kilometres when you’re that high anyway.

Higher res imagery from Planet: https://twitter.com/planetlabs/status/1291010972983992320

If you zoom in on the highways, you can see RGB ghost images of moving vehicles. Is that an artefact of using 3 distinct filtered inputs or something else?

[ps. The frequency shift is definitely reflecting vehicle direction - right side of highway is BGR, the other side is RGB. Delays in the sequence of 3 filtered captures?]

Yes, the different bands are not collected at the same time across the whole scene, so you get ghosting with moving objects. The SkySat sensor [1] is split in two halves: panchromatic and RGBN (where N is near-infrared). It takes lots of captures as the satellite travels that are later aligned and combined into one version.

[1] https://directory.eoportal.org/documents/163813/5615117/SkyS...

Looks like it was pretty fortunate to have been in that warehouse versus further back. A pretty good amount of the direct blast radius looks like it was water.

Jesus, it left a CRATER!

Look how much there was in that warehouse https://cdn.ren.tv/cache/960x540/media/img/26/fb/26fb305fdd5... this was all on Ukrainian tv years ago when the crew was stranded there

The 800 tons of Ammonium Nitrate that exploded in Tianjin in 2015 left a 100 meter wide crater. In Beirut it was 2750 tons, almost three and a half times as much.

Land reclamation.

"Before" is dated 2019.

All the diff is to be atrributed to this blast? Am I missing anything obvious here?

Sibling has posted a link to a higher res version from a different source. I think the before there is closer in time.

The structure to the far left on parents before picture is apparently removed before the explosion.

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