The specific allocation is 1400 to 1427 MHz. It is reserved for radio astronomy (the hydrogen line is at 1420.4 MHz), passive (receive only) Earth exploration satellites and passive space research.
In the US, 1240 to 1400 MHz is allocated to radar. GNSS downlinks at 1240 to 1300 MHZ are not protected in the US.
giammaiot2 on twitter has a long history of trying to use science sensors to detect intentional RF interference, e.g. this post with a map from the Advanced Microwave Scanning Radiometer (AMSR) looking at 7 GHz: https://x.com/giammaiot2/status/1919493425100988490
Thank you, that map is fascinating. Jamming in and around conflict zones (Ukraine, Myanmar) and in China make sense to my Western brain. But why so much interference in Japan?
dakr · 1h ago
A wonderful example of the useful, sometimes unintentional secondary effects of doing science. SMAP as a mission is firmly in the Earth science category, so very much in the crosshairs of the current administration. The data is used for Earth science and climate research and has many agricultural and water management applications.
For example, water management districts can tell if the local soil can accommodate the water from an upcoming storm or if the water will stay on the surface and cause flooding.
Alex-Programs · 2h ago
```In a modern conflict zone, jamming L-band means blinding drones, degrading targeting, and cutting off ISR. It’s not accidental. It’s deliberate.
The international treaties that say “don’t transmit here”? Those don’t matter much when you’re trying to survive a drone swarm.```
LLM prose, and it's not the only section that stands out. It's an informative article, so I don't mind it as much, but I think it's a shame people don't write things themselves anymore.
philsnow · 1h ago
This doesn't read like LLM spam to me. Punchy 2- and 3-word sentences are a rhetorical device that I haven't seen ChatGPT (at least; I haven't really used the others) use at all.
piskov · 2h ago
What exactly stands out? Besides the fact the author is most likely of ex-USSR descent, i. e. not a native speaker.
bob1029 · 8h ago
Iridium satellites can communicate with ground stations on L-band.
This band is extremely useful if you're stuck on a ship in the middle of a typhoon and need to get some help.
russb · 6h ago
L-band signals can penetrate through clouds and rain. This property is why L-band is used for GPS and other applications that require all-weather operation, as it allows for accurate data collection even in the presence of adverse weather.
qwertox · 7h ago
How does this work? Do they just listen and never transmit, unless they receive a targeted emergency message?
os2warpman · 6h ago
L-band is used for voice and data communications to handheld devices by several satcom providers.
At a very high level handheld satellite communications devices work just like regular cellphones, except they also function in the middle of the ocean.
NoSalt · 5h ago
His GitHub site mentions: "This script processes NASA SMAP L1B .h5 data files", but he doesn't say how he obtains these data files. Is he using an API, or is he using something like an RTL-SDR to pull the data directly?
sstanie · 4h ago
You can search on ASF's data discovery portal for SMAP:
What do the jamming locations within Russia correspond to? You would think these are important places that require drone protection, but I could not quickly discover what is so important in these places.
For instance, the bright spot to the north west of Moscow seems to fall somewhere in or close to Zavidovo National Park. Is there something important there? There's nearby air bases Migalovo and Klin, but both seem too far from the center.
dylan604 · 9m ago
Is that the forest where the politburo members have the dachas?
The amount of locations with GPS jam is impressive (compare march 2022 and may 2025).
toomuchtodo · 4h ago
GPS jam uses data from aircraft ads-b GPS accuracy data reported, so they should have global air traffic route coverage. Would be interesting to fuse that data with this data (sensor fusion).
TrackerFF · 7h ago
Russians will place out jammers close to anything of importance. For example, in the Kola peninsula - which is close / bordering both Norway and Finland, they're jamming and spoofing. To such a degree that it affects civil air traffic in the area.
But why? Because they have a bunch of major strategic airfields there.
In (and close) to Ukraine it could be anything. Airfields, base, ammo storage, radio towers, etc.
nicce · 7h ago
Hmm, do they really jam 24/7 in the Kola peninsula? I thought that mostly happens when there is some sort of military exercise.
TrackerFF · 6h ago
Before 2022 they'd mostly conduct jamming operations as part of their military exercises, but after they've started jamming and spoofing much more - as a security measure against drone operations. Ukrainian drone operations have taken place as long north as Murmansk, which is roughly 90 miles / 145 km from the closest Norwegian airport (Kirkenes).
EDIT: 5 days ago they shot down Ukrainian drones there
Do we know how effective GPS jamming is against the military bands? (Ukraine probably doesn't have access to those but still)
nicce · 4h ago
Oh yeah, that explains the shift.
bobmcnamara · 5h ago
Heck, they used to jam some frequencies 24/7 worldwide!
nicce · 4h ago
I think that prior 2022 they still had to consider the political impact, at least on some level.
bobmcnamara · 2h ago
They shut down the western steel work radar because of power cost increases after Chernobyl blew, combined with the improved value provided by surveillance satellites.
logicziller · 5h ago
This is brilliant. What other bands can we observe like this?
Sentinel 1, if I recall, is C band. But the technique would work for X-band as well, like TerraSAR-X and other commercial satellites.
o_1 · 8h ago
Very awesome. Never knew about L-band.
nanna · 8h ago
Anyone care to explain in layman's terms what this is about?
mrweasel · 8h ago
They used freely available NASA data to map Russian and Ukrainian electronic warfare systems. The jammers used leak into the 1.4 GHz spectrum, which is suppose to be silent, and does so which sufficient power that you can be pretty sure it's man made.
So if you're looking for an intersting target, you could do worse than those lit up areas.
parsimo2010 · 5h ago
Small correction: the jammers used are specifically targeting the L-band, because it is used for navigation and satellite communications.
Normally ground transmitters in this band are using just a couple watts or less, so they don’t significantly impact the readings of a satellite looking at a large area on the earth, but a jammer uses a lot more power and can be noticed.
There is a satellite that listens to solar radiation reflected off the earth to tell different things like ocean salinity. That particular frequency is also used in warfare. This satellite can be used to find areas where electronic countermeasures are in place.
echoangle · 8h ago
There's a satellite that's measuring ground moisture by looking for radiation in a specific frequency. Some jammers in Ukraine (devices that send noise on radio to make communications impossible for other people) emit radiation in this frequency which makes it visible when looking at the data from the satellite.
I edited my comment, you're right that the measurement isn't really ground temperature.
egorfine · 6h ago
> make communications impossible for other people
for occupying armed forces.
pc86 · 5h ago
The jamming doesn't discriminate. Domestic armed forces and civilians are also impacted, so "other people" makes sense.
echoangle · 6h ago
Well both sides are jamming, but that's one reason to jam, yes.
x0 · 8h ago
Brilliant idea to check out this satellite. Are there any others that receive interesting frequencies? (thinking under 6GHz)
NitpickLawyer · 7h ago
People have been tracking the actual "true" front lines since the war began with that IR "fire early warning" satellite from NASA. Turns out a satellite that's good at detecting natural fires is also good at detecting explosions / fires started by explosions.
TechDebtDevin · 7h ago
Another interesting tracking mechanism was the use of Apples Wifi Positioning database, which allowed researchers to track front lines via Starlink wifi access points.
Wouldn't NASA then almost certainly be aware of this as well?
parsimo2010 · 5h ago
This satellite’s mission is soil readings. Most scientists are not part of the intelligence community. They may have noticed anomalous readings and excluded them from their analysis, but they don’t really have anyone to talk to about the military implications. Plus, while this is cool that you can detect this interference with a science satellite, the major space powers all have military and intelligence satellites that can map the interference at greater precision, so the NASA scientists can pretty much ignore this unless they are particularly interested in the soil readings in this part of the world.
frandroid · 1h ago
It's not impossible that the Pentagon could have thought "alright, we want these readings. is there a civilian use for this kind of data and decided to see if a civilian project could be sprung up... Though that's more of a Cold War conceit. These days they would just do it themselves, it's probably an easy and cheap project.
g4zj · 5h ago
Thank you for that explanation. It was very helpful. :)
dakr · 1h ago
I don't think this is lost on anybody, even if it's not the main mission. SMAP also provides a near-real-time data product which may interest people in this area.
4ad · 8h ago
Doesn't really answer the question of why does the military use the L-band. Whether it's jammed or not is immaterial (of course they are going to jam it if it has military use), but what specific attributes makes L-band useful for the military?
TrackerFF · 7h ago
Navigation systems (GNSS) tend to fall right in the L-band. For example, the Russian GLONASS is in the 1.2 and 1.6 GHz range, while GPS is around 1.1, 1.2, 1.5 GHz.
SMAP is in the 1.2 - 1.4 GHz range - so it overlaps with both GLONASS and GPS.
So jamming in that range will affect the nav systems of the drones. This is the reason you see drones tethered with fiber optic cables - control systems might be in the same range. The "why" has more to do that the machines are made to adapt to existing systems, and those systems were designed due to the physical properties they've made to serve / solve.
Both jamming and spoofing is pretty normal when you're close to Russia.
And this is the reason SMAP will pick up all this jamming, because it is sensing on the same band / range.
cebert · 8h ago
L-band is capable of long range with lower power and can penetrate water and foliage. I can see why this could be appealing for military purposes.
bc569a80a344f9c · 8h ago
To expand a little bit, RF is subject to free space path loss - signal strength decreases proportional to the square of the frequency and the square of the distance. The higher the frequency, the less far you go. Of course, weaker signals are harder to distinguish from noise so there’s only so weak your signal can go. If you want to control drones, lower frequencies are better.
There’s a reason that microwaves (the cooking instrument, named after the rough band of RF frequencies it uses) interfere with WiFi when improperly shielded: they run at approximately 2.4GHz. That’s a part of the band that’s free to use without licensing (ISM band, runs at 900MHz, 2.4GHz, 5Ghz, and so on). That’s because microwave manufacturers don’t want to license spectrum, and it’s the part of the ISM band closest to the ideal absorption frequency of water. The point of microwaves is to push energy into water molecules and make them move around faster, aka heat them. Water molecules do that well at 2.4GHz. This also means that water blocks RF at that frequency very well, because it absorbs it. Trying to shoot 2.4GHz WiFi through trees sucks because it gets blocked by the leaves.
So you want to control drones. You can’t be around 2.4GHz because rain would screw you up. You can’t go above that so you can get enough distance. You can’t go as low as 900MHz or other stuff on the ISM band might interfere with you.
Not that much left, given that 1.7GHz is a popular cell phone frequency, and so on - you can look at publicly available frequency charts to see what’s assigned for what where.
This glosses over a lot and is heavily simplified.
ratatoskrt · 6h ago
There is no absorption peak of water at 2.4GHz. Even worse, the absorption spectrum will change when it heats up.
immibis · 3h ago
AFAIK the ISM band was placed there because of microwave ovens, not the other way around.
echoangle · 8h ago
If I understand the article correctly, the actually used frequencies are close to the L-band but the jamming is broadband and also affects the L-band.
myself248 · 7h ago
The L-band is a term for the whole swath between 1 and 2 GHz. It's diced into dozens of allocations by international treaty.
(Also in the L-band are all sorts of other things. A lot of cellular bands, known in the US as PCS and AWS, and more. Several different sat-phone systems. ADSB in 1090 is juuuust inside L-band. And more...)
All transmitters produce a bit of out-of-band interference, beyond where they meant to transmit. This is filtered to reduce it to a certain level below the intentional frequency, but filters aren't perfect. So when someone tries to jam GPS or other services, they inevitably bleed some energy into neighboring allocations too, some of which seems to be being picked up by SMAP.
Note that SMAP's passive radiometer doesn't have pinpoint spatial resolution, 36km is stated. This means it's listening to a pretty significant patch of ground at any given time, so for a source to be picked up among all that, it's got to be pretty loud. It also means that attributing the source is limited in precision, you can get to city level but not city-block level from this data.
touisteur · 5h ago
Yes, civilian radarstuff (Mode S, SSR, ADS-B as you said, and other multilateration schemes) use 1090 (downlink and broadcast) and 1030 MHz (uplink). Closer to military uses, IFF might also use the same frequencies.
sandos · 5h ago
I mean, in a drone way every frequency is usable. If its not that usable, it might still be usable if nobody knows you are using it yet, and therefor not jamming it yet.
In the US, 1240 to 1400 MHz is allocated to radar. GNSS downlinks at 1240 to 1300 MHZ are not protected in the US.
giammaiot2 on twitter has a long history of trying to use science sensors to detect intentional RF interference, e.g. this post with a map from the Advanced Microwave Scanning Radiometer (AMSR) looking at 7 GHz: https://x.com/giammaiot2/status/1919493425100988490
Or this thread from 2023 looking at SMAP: https://x.com/giammaiot2/status/1770815247772729539
For example, water management districts can tell if the local soil can accommodate the water from an upcoming storm or if the water will stay on the surface and cause flooding.
The international treaties that say “don’t transmit here”? Those don’t matter much when you’re trying to survive a drone swarm.```
LLM prose, and it's not the only section that stands out. It's an informative article, so I don't mind it as much, but I think it's a shame people don't write things themselves anymore.
This band is extremely useful if you're stuck on a ship in the middle of a typhoon and need to get some help.
At a very high level handheld satellite communications devices work just like regular cellphones, except they also function in the middle of the ocean.
https://search.asf.alaska.edu/#/?maxResults=250&dataset=SMAP...
This lets you bulk download the .h5 files once you have an Earthdata account (https://urs.earthdata.nasa.gov/home )
or you can use the libraries if you'd like, https://github.com/nsidc/earthaccess or https://github.com/asfadmin/Discovery-asf_search
And there’s some info here: https://smap.jpl.nasa.gov/data/
Very cool stuff!
For instance, the bright spot to the north west of Moscow seems to fall somewhere in or close to Zavidovo National Park. Is there something important there? There's nearby air bases Migalovo and Klin, but both seem too far from the center.
https://gpsjam.org/
The amount of locations with GPS jam is impressive (compare march 2022 and may 2025).
But why? Because they have a bunch of major strategic airfields there.
In (and close) to Ukraine it could be anything. Airfields, base, ammo storage, radio towers, etc.
EDIT: 5 days ago they shot down Ukrainian drones there
https://www.thebarentsobserver.com/security/russian-war-mini...
Sentinel 1, if I recall, is C band. But the technique would work for X-band as well, like TerraSAR-X and other commercial satellites.
So if you're looking for an intersting target, you could do worse than those lit up areas.
Normally ground transmitters in this band are using just a couple watts or less, so they don’t significantly impact the readings of a satellite looking at a large area on the earth, but a jammer uses a lot more power and can be noticed.
https://web.archive.org/web/20230517192717/https://aquarius....
for occupying armed forces.
https://www.youtube.com/watch?v=hlbjUvkoyBA
SMAP is in the 1.2 - 1.4 GHz range - so it overlaps with both GLONASS and GPS.
So jamming in that range will affect the nav systems of the drones. This is the reason you see drones tethered with fiber optic cables - control systems might be in the same range. The "why" has more to do that the machines are made to adapt to existing systems, and those systems were designed due to the physical properties they've made to serve / solve.
Both jamming and spoofing is pretty normal when you're close to Russia.
And this is the reason SMAP will pick up all this jamming, because it is sensing on the same band / range.
There’s a reason that microwaves (the cooking instrument, named after the rough band of RF frequencies it uses) interfere with WiFi when improperly shielded: they run at approximately 2.4GHz. That’s a part of the band that’s free to use without licensing (ISM band, runs at 900MHz, 2.4GHz, 5Ghz, and so on). That’s because microwave manufacturers don’t want to license spectrum, and it’s the part of the ISM band closest to the ideal absorption frequency of water. The point of microwaves is to push energy into water molecules and make them move around faster, aka heat them. Water molecules do that well at 2.4GHz. This also means that water blocks RF at that frequency very well, because it absorbs it. Trying to shoot 2.4GHz WiFi through trees sucks because it gets blocked by the leaves.
So you want to control drones. You can’t be around 2.4GHz because rain would screw you up. You can’t go above that so you can get enough distance. You can’t go as low as 900MHz or other stuff on the ISM band might interfere with you.
Not that much left, given that 1.7GHz is a popular cell phone frequency, and so on - you can look at publicly available frequency charts to see what’s assigned for what where.
This glosses over a lot and is heavily simplified.
Some ranges are set aside for GPS/GNSS: https://gssc.esa.int/navipedia/index.php?title=GNSS_signal
Some are monitored by the SMAP satellite: https://en.wikipedia.org/wiki/Soil_Moisture_Active_Passive
(Also in the L-band are all sorts of other things. A lot of cellular bands, known in the US as PCS and AWS, and more. Several different sat-phone systems. ADSB in 1090 is juuuust inside L-band. And more...)
All transmitters produce a bit of out-of-band interference, beyond where they meant to transmit. This is filtered to reduce it to a certain level below the intentional frequency, but filters aren't perfect. So when someone tries to jam GPS or other services, they inevitably bleed some energy into neighboring allocations too, some of which seems to be being picked up by SMAP.
Note that SMAP's passive radiometer doesn't have pinpoint spatial resolution, 36km is stated. This means it's listening to a pretty significant patch of ground at any given time, so for a source to be picked up among all that, it's got to be pretty loud. It also means that attributing the source is limited in precision, you can get to city level but not city-block level from this data.