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Satellites Spotting Ships
- b_emery 2y agoYou can also see ships in the SAR data available here: https://ovl.oceandatalab.com/ https://ovl.oceandatalab.com/ (eg from the ESA satellites). Be forewarned, there is also a ton of other data to wade through, but if you find and click all the right boxes the results can be pretty interesting (island wind wakes, ocean current visualizations, etc): https://ovl.oceandatalab.com/?date=2024-02-13T12:00:00×pan=1d&extent=-13464458.99269_3926866.6466265_-13073407.156038_4106035.0409021¢er=-13268933.074364_4016450.8437643&zoom=9&products=3857_SAR_roughness!3857_ODYSSEA_REG_SST!3857_ODYSSEA_SST!3857_GlobCurrent_CMEMS_geostrophic_streamline!3857_AMSR_sea_ice_concentration&opacity=80_100_100_60_100&stackLevel=100.02_50.03_30.02_120.07_40.03&filter=+A,+B,+IW,+EW,+SM,+WV,+VV,+HH&selection=10000 https://ovl.oceandatalab.com/?date=2024-02-13T12:00:00×...
- campchase 2y agoIf anyone has questions about SAR as a tool for tracking human activity - movement of ships or otherwise - I'm happy to answer questions. Mark's work here makes great use of our open data archive, now over 20TBs of openly licensed data free for research or even commercial use: https://aws.amazon.com/marketplace/pp/prodview-ybjvekte4hg7o#resources https://aws.amazon.com/marketplace/pp/prodview-ybjvekte4hg7o...
- KeplerBoy 2y agoCan you estimate how much cargo a ship is transporting by measuring how tall it is compared to the sea? Is this something that would be feasible with a constellation of tandemSAR-like satellites?
- campchase 2y agoWow, that's a cool idea. I bet you absolutely can. When you image a ship broadside, it gets projected onto the surface in a flattened way we call "layover" - here's an example of how nicely ships pop out on a flat sea: https://x.com/umbraspace/status/1797970305798816030 https://x.com/umbraspace/status/1797970305798816030
- bjornasm 2y agoDepends on the ship as well, not all ships change their draught ("depth") that much according to what they carry, but ships like bulk carriers and oil carriers certainly do. They report it via AIS data as well, but as its manually input it is often unreliable. An other idea that has been utilized is to look at the vake patterns (wave patterns) to estimate the speed of the ship.
- stefan_ 2y agoDoes the commercial tasking feed into the open dataset? Or is it more a case of once the satellite is up, might as well keep it busy? Just wondering since the distribution of locations shown in the blog post seems particular.
- campchase 2y agoIt's cherry-picked, but it's a combination of commercial tasking and discretionary tasking. There isn't much to read into in terms of the distribution, it's just one person's best guess at where there's likely to be a lot of diverse types of ships.
- bjornasm 2y agoThis is really interesting. I have worked a lot with AIS data (messaging system that relays information such as the position of a ship), but the AIS data can some time lack information (and sometimes can be spoofed). However I have never got around working with imagery data. This seems like a great starting point for that :)
- itissid 2y agoYOLO is amazing. When I first looked at the loss function in YOLO v1, I was stunned: You can do regression loss(Mean square error) instead of classification loss(categorical cross entropy) on class prediction probabilities, and it can still just "work".
- wongarsu 2y agoI imagine the YOLO researchers would argue MSE is more "correct" in their case. Yolo has augmentations that combine images with different labels. If you make an image that's to 30% composed of the image of a train and to 70% the image of a car, you can argue it should be predicted as 0.3 train, 0.7 car, 0 everything else. But now you are suddenly doing a regression task.
- Qworg 2y agoA direct use of work like this is to detect and stop illegal fishing, an enormous environmental problem and human trafficking contributor. For example: https://www.skylight.global/ https://www.skylight.global/
- kylehotchkiss 2y agoHow does the US DoD feel about this? It was my understanding the exact location of different fleets was something that wasn't public info
- jandrewrogers 2y agoThe US Navy operates under the assumption that the position of their ships, excluding submarines, is known at all times by adversaries. This has been the case for decades.
- pyuser583 2y agoFuture positions are a different matter, which is why the Navy is quiet about scheduled port calls.
- dr_orpheus 2y agoProbably pretty good since the NRO is buying data from Umbra: https://spacenews.com/nro-signs-agreements-with-six-commercial-providers-of-space-based-rf-data/ https://spacenews.com/nro-signs-agreements-with-six-commerci...
- Animats 2y agoNow for something that takes this data and detects ships with no AIS data, or which changed AIS identity.
- toomuchtodo 2y agohttps://insights.spire.com/maritime/dark-shipping-detection https://insights.spire.com/maritime/dark-shipping-detection Your point is taken though, tons of remote sensing signal you can fuse to detect malicious marine activity (I'd argue in real time). If you can detect the ship from orbit, and the AIS doesn't align with owner, cargo, and previously expected route (or there is no AIS), strange things are afoot.
- Animats 2y agoSpire seems to require that ships send AIS data. They're checking the self-reported positions AIS sends vs. distances measured from their the satellites. They won't detect no-AIS ships.
- toomuchtodo 2y agoRight, that’s what SAR is for: to subtract AIS reporting ships from radar detected ships. No AIS when there should be? Hello, we see you, can’t hide from the radar. Maybe there is a variable I’m missing?
- autoexec 2y agoSeeing through clouds and smoke is impressive. What options do people have at this point to protect their own property from being seen from above? Massive tarps? Is full tree cover enough? Some kind of reflective glass dome? It'd be a shame if it's now impossible for people to have any view of the sky, day or night and rain or shine, without risking being watched and recorded from space.
- tony_cannistra 2y agoSAR = Synthetic-Aperture Radar. Radar bounces off of metal very well. Some strategically-placed radar reflectors, or a metal-lined fabric, could do it easily. It would also show up _very_ brightly on the resulting images.
- banish-m4 2y agoI'm wondering how long it will be before transponder data and satellite imagery will be correlated to look for suspicious activity like individual ships moving their transponders to small decoy ships while they commit crimes.
- bjornasm 2y agoThis was a really nice post, using imagery to confirm the positions of ships is really useful when the normally used data source, AIS data, has lacking data or may be spoofed. I have mostly worked with AIS data, but might incorporate these data as well to see what can be found.
- robxorb 2y agoIf 16cm through clouds and rain has been publicly available for three years, what does military have and for how long? And with that capability, and in a post-9/11 world, how could an entire rogue airliner not be traced to within sqm's of impact/landing?
- TMWNN 2y ago> If 16cm through clouds and rain has been publicly available for three years, what does military have and for how long? It is my understanding that phased-array antennas, of the type Starlink satellites carry, are also excellent for phased-array radar. It's known that Starshield covers both military use of the civilian Starlink network, as well as military-dedicated satellites for communications and other functions. I suspect that during wartime Starlink will be the world's most comprehensive (and, thanks to its scale, most survivable) space-based radar system.
- RF_Savage 2y agoAt least the civilian Starlink sats will not be able to do that. The transmit and receive frequencies are different and limited by hardware filters. They would be most useful for communications and possibly enable interference mapping. Or finding Ku-band VSAT terminals of other users.
- WJW 2y agoPhased array antennas are indeed usable antennas for radar purposes and many modern radars use them. That said just having a suitable antenna is not enough for having a radar system, you also need sophisticated equipment for both transmitting powerful enough pulses and receiving the (extremely weak) reflections. The power of the reflections drops with the fourth power of the distance to the target. From a quick look at the starlink satellites I very much doubt they could effectively function as a radar system. There's just not enough solar panels to power a big radar on there. Background: I used to be an weapons engineering officer working on future radar systems back in my Navy days.
- Tor3 2y agoThe finer the resolution, the more narrow the scanner path is (and in any case satellite scanner paths aren't that wide, also for low-resolution optical scans). The Umbra satellite swath is a tiny 4km wide. And then along-track as well. The total area a radar satellite (or an optical one) can scan at any particular time is very limited. A satellite, even multiple ones, will only see an airliner if it happens to be in the right spot at the right time.
- dist-epoch 2y agoThis is one of the reasons in any real war, all the aircraft carriers will be far far away from the conflict region. Now your average Joe can track them from their desktop for free.
- scanny 2y agoThat's not exactly how it works. The satellite operator will be taking paid orders to scan over specific areas of the earth, about 4km in width or so. So you have to have a pretty good idea where the carrier is, and then you get an image delivered with some latency as the satellite will need to pass over a ground station that downlinks the data. So it isn't free (although umbra has a CC BY 4.0 license for their data, much more permissive than other providers. Nor is it easy to search huge amounts of the ocean for the carrier. What most entities probably do is tip and cue, which is use a sensor with coarser resolution to get an approximate location and then use a sensor with finer resolution to look closer.
- dist-epoch 2y agoSure, I was over simplifying it. China will already have a good idea where the carrier roughly is - the previous position. And they will also have their own satellites.
- Cthulhu_ 2y agoCarriers will also never be going alone; they're part of a battle group (https://en.wikipedia.org/wiki/Carrier_battle_group https://en.wikipedia.org/wiki/Carrier_battle_group) with anti-air and -sea defenses to intercept any incoming counterattacks. In theory anyway, that wiki article has some criticisms about whether it's still viable today with hypersonic cruise missiles, u-boats, drones, etc. It hasn't come to a full on naval battle since WW2 though, so a lot of naval strategies and technology is theoretical. It is being tested nowadays with attacks on ships from the mainland from the Houhtis though.
- FuriouslyAdrift 2y agoWake seeking long range semi-autonomous torpedoes are a major threat and are already deployed. Currently they have about a 100km range. The subs can fire from far away, move and fire again from different angles. A ship could have dozens coming from all directions.
- Mikhail_K 2y agoNeural networks are statistical in nature and their results are inherently unreliable.
- jgrahamc 2y agoOne night in the late 1990s, lying on the grass in a garden in Palo Alto, CA, I saw, with the naked eye, three satellites flying in formation. I believe what I saw was: https://www.satobs.org/noss.html#NOSS2 https://www.satobs.org/noss.html#NOSS2
- quercusa 2y agoThank you! Saw those about 92-93 while camping in the Ventana Wilderness and have always wondered what they were.
- ravivyas 2y agoDamn... I was hoping to read more about ships that could spot satellites :)
- WJW 2y agoMost modern military vessels could spot them, but typically the air warning radar has its filters configured such that satellites are excluded (as they are not interesting targets for most naval vessels). This also heavily depends on the exact orbit of course. Low orbit satellites like starlink are quite below the maximum altitude from ballistic missiles, geostationary orbit is usually too far away to still detect within the unambiguous range of the radar system.
- dzhiurgis 2y agoHow about RTL-SDR detecting SAR signal? I just wonder how many SAR sats we don't know about.
- KeplerBoy 2y agoWon't work with a regular RTL-SDR. Most SAR systems operate in X-Band (~10 Ghz). I guess it's fair to assume that every organization who has ever sent anything to space has also launched SAR satellites. The radar part is comparatively easy to getting things into orbit.
- TrackerFF 2y agoI see some asking about capabilities and such - well there's a bunch of (satellite-borne) sensors for detecting ships - SAR - Optical - NRD - LIDAR - AIS / VMS / LRIT etc. Truth be told, detection tends to be a fusion of sensors. When it comes to non-cooperative objects, sensors like SAR, Optical, NRD, LIDAR are often used. NRD sensors detect ship navigation radar on S- and X-band, while LIDAR detects light from ships. Optical and SAR everyone knows.
- dzhiurgis 2y agoI don't think LIDAR works from satellite, the distances is just too high.
- dr_orpheus 2y agoIt's not that it doesn't work, it is just prohibitively hard. The other comments here pointed out GEDI which is a LIDAR payload on the ISS. But it's resolution is only 25 m. This is compared to the resolution of the Umbra satellites of ~0.5-1m. So with something like GEDI you could see large ships. But you would need a larger telescope and/or more powerful laser to get better resolution.
- dzhiurgis 2y agoBiggest drawback is atmosphere - doesn’t work with cloud cover.
- AnarchismIsCool 2y agoThere are absolutely LIDAR sats. Amateur astronomers occasionally get pictures of the beams sweeping around with high sensitivity cameras.
- barbegal 2y ago[dead]
- is_true 2y agohttps://gedi.umd.edu/instrument/instrument-overview/ https://gedi.umd.edu/instrument/instrument-overview/