from Hacker News

Using NASA’s SMAP satellite to detect L-band interference

by c16 on 5/8/25, 8:52 AM with 69 comments

• by jjwiseman on 5/8/25, 6:33 PM

  I liked this overview map they posted a few days ago: https://x.com/HamWa07/status/1919763145536463222

  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

• by dakr on 5/8/25, 5:19 PM

  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.

• by bob1029 on 5/8/25, 10:50 AM

  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.

• by drmpeg on 5/8/25, 6:36 PM

  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.

• by NoSalt on 5/8/25, 1:32 PM

  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?

• by mellow_observer on 5/8/25, 11:09 AM

  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.

• by o_1 on 5/8/25, 10:31 AM

  Very awesome. Never knew about L-band.

• by 4ad on 5/8/25, 10:43 AM

  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?

• by nanna on 5/8/25, 10:44 AM

  Anyone care to explain in layman's terms what this is about?

• by logicziller on 5/8/25, 2:01 PM

  This is brilliant. What other bands can we observe like this?

• by Alex-Programs on 5/8/25, 4:06 PM

  ```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.

• by x0 on 5/8/25, 10:49 AM

  Brilliant idea to check out this satellite. Are there any others that receive interesting frequencies? (thinking under 6GHz)

• by kevin_thibedeau on 5/8/25, 7:13 PM

  Crimea is still part of Ukraine. That can't change until a peace treaty settles the dispute.

• by g4zj on 5/8/25, 12:39 PM

  Wouldn't NASA then almost certainly be aware of this as well?