[HN Gopher] Get the location of the ISS using DNS
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Get the location of the ISS using DNS
Author : 8organicbits
Score : 245 points
Date : 2025-07-06 12:32 UTC (10 hours ago)
(HTM) web link (shkspr.mobi)
(TXT) w3m dump (shkspr.mobi)
| TMEHpodcast wrote:
| Brilliant! This is both clever and educational. I immediately
| wondered if it would be possible to do something similar for
| JWST.
|
| Unfortunately LOC DNS records top out at ~42 million meters
| (42,000 km altitude) and JWST is 38x further out (~1.5 million km
| away). So you can't represent its location with a LOC altitude
| field. Maybe Hubble?
| firesteelrain wrote:
| Not sure how that will work since JWST orbits the second
| Lagrange point.
|
| It would be like asking for the GPS coordinates of the moon.
| NASA did test receiving weak GPS signals on the moon with LRO
| in 2023. It wouldn't be useful for navigation though (not yet
| unless someone has like a way to do reverse GPS on the moon but
| not sure how that would work)
|
| Reason this works for the ISS is because of the subsatellite
| point. It can receive GPS signals regardless of altitude above
| the Earth's surface.
|
| Also TLEs apply to the ISS because it's earth orbiting.
|
| TLEs are designed for satellites in Earth orbit, where they
| define position and velocity using orbital elements interpreted
| by models like SGP4.
| TMEHpodcast wrote:
| Yes, I realize not-having initially understood what LOC DNS
| actually is. As mentioned, this could of course be applied to
| Hubble.
| firesteelrain wrote:
| Any MEO or LEO satellite
|
| Hubble operates in LEO so it's eligible
| netsharc wrote:
| > NASA did test receiving weak GPS signals on the moon with
| LRO in 2023.
|
| I doubt very much that the position of the ISS in the article
| is being sent from the ISS at real time. It's more likely
| calculated using NORAD / Celestrak orbital elements plus
| orbital calculations.
|
| I remember having a Windows desktop app to show the
| satellites locations, I'd have to download those text files
| to keep the information accurate. For the information beyond
| the snapshot, the app has to calculate distance and
| trajectory to estimate "If NORAD said it was here at this
| point in time, and heading that way with that speed, then
| right now it should be around here.". A bit like "If a train
| left Chicago 5 hours ago going 60 mph, where is it now?".
|
| Nowadays it's all online of course: https://in-the-
| sky.org/satmap_worldmap.php .
| firesteelrain wrote:
| > doubt very much that the position of the ISS in the
| article is being sent from the ISS at real time. It's more
| likely calculated using NORAD / Celestrak orbital elements
| plus orbital calculations.
|
| Yes, this is how the referenced site knows the approximate
| position of the ISS via TLEs. TLEs are updated regularly
| for space objects
| echoangle wrote:
| That doesn't matter for the problem at hand though. You
| can calculate the current GPS coordinates from any TLE,
| even if they aren't derived from GPS measurements but
| from Satellite Laser Ranging or some other method.
| firesteelrain wrote:
| You can derive Lat and Lon and Altitude on Earth. Thats
| the one point of the TLEs. But they aren't GPS derived
| coordinates.
| echoangle wrote:
| Yes, but you don't need GPS derived coordinates for the
| DNS LOC entry.
| firesteelrain wrote:
| Correct because the site referenced uses N2YO which is
| using NASA provided TLEs which some backend that provides
| an API. GPS and TLEs are not the same.
| echoangle wrote:
| > It would be like asking for the GPS coordinates of the moon
|
| No problem at all, just give the location where the moon is
| at the Zenith and use the distance as the altitude.
|
| > Reason this works for the ISS is because of the
| subsatellite point. It can receive GPS signals regardless of
| altitude above the Earth's surface.
|
| No, wether the object can actually receive GPS signals is
| completely irrelevant to wether its location can be described
| in the GPS coordinate system.
|
| You could describe the location of the Sun in GPS coordinates
| too, the altitude value would just be very large.
| firesteelrain wrote:
| You can use GPS to describe a point on Earth. To use the
| moon or sun is kind of weird because of their size to use
| GPS coordinates for this
|
| I was referring to finding your position on the moon using
| Earth referenced GPS signals.
| echoangle wrote:
| > You can use GPS to describe a point on Earth.
|
| No, you can describe any point in the universe using GPS
| coordinates. You just lose some resolution the further
| away from earth you are because it's basically spherical
| coordinates (like polar coordinates but for 3D). And the
| system isn't inertial but earth-fixed, of course, so you
| would have to give the coordinates together with a time.
|
| And if you're describing the location of the moon and the
| sun, you would probably pick their center of gravity.
| firesteelrain wrote:
| I believe this isn't true otherwise NASA would be doing
| this
|
| - Earth isn't a universal reference
|
| - GPS uses WGS84
|
| - GPS is bound to the Earth's surface and center
|
| - It's Geodetic
|
| - There's no universal "equator" or "prime meridian"
| beyond Earth
|
| - Space uses inertial frames or celestial coordinate
| systems (right ascension and declination, or galactic
| coordinates)
| echoangle wrote:
| That's exactly what I said. It isn't very practical for
| space ops, but you can absolutely give a current GPS
| position for every object you want.
| firesteelrain wrote:
| That's conceptually misleading.
|
| They are meaningless for things not near Earth because
| they're tied to Earth's shape, rotation, and gravity
| field
| echoangle wrote:
| I wouldn't call it meaningless if it can be converted
| back and forth with a (non-linear) transformation.
| firesteelrain wrote:
| You can do a lot of things...
| gmiller123456 wrote:
| There are a handful of Earth centered, geocentric
| standard reference frames. The most used today is the
| Geocentric Celestial Reference System (GCRS). It should
| be obvious that if you want to compute where to point a
| telescope, a transformation of coordinates will involve a
| step through such a coordinate system. GPS is it's own
| system, but there are transformations to and from the
| GCRS and GPS frames. Which one makes sense depends a lot
| on your application.
| therealpygon wrote:
| I could build a house with my pinkie if I excuse the fact
| I'll use a team of laborers to do the work and accept
| that they are so inaccurate that I would be lucky to end
| up with a shed... if I only cared about technicality.
| dotancohen wrote:
| That probably because GSO is right about at that altitude.
| IndrekR wrote:
| Considering the ISS orbits in ~90 minutes, the 15 minute TTL is
| quite a long time.
| kmm wrote:
| I understand there are API limitations, but isn't 15 minutes a
| lot for an object that orbits around the entire Earth in 90
| minutes? On average you're going to be off by about a twelfth of
| the circumference of the Earth, or roughly the distance between
| Lisbon and Istanbul
| edent wrote:
| Yes. As I say in the post, you shouldn't use this for docking
| operations.
|
| If you know of a DNS update which allows for per-minute updates
| for free, I'll happily move to it.
| AdieuToLogic wrote:
| > As I say in the post, you shouldn't use this for docking
| operations.
|
| Brilliant. :-D
| fouronnes3 wrote:
| You totally could use it for docking. A real ISS docking
| manoeuvre takes several hours. Orbits are very predictable
| and I'm quite confident that the error you'd get projecting
| your orbit 15min into the future would be good enough to
| get within close radar range for the final approach. In
| fact you probably could do it, even if your spavecraft
| doesnt have DNS at all, and you have to do the DNS resolve
| from a ground laptop before you board it. Soyez can dock
| within 3 hours of lauch. Orbits are very predictable in
| this timeframe.
| edent wrote:
| I shall make the suggestion to NASA that they start using
| this ;-)
| 05 wrote:
| Sure they're predictable, but since you don't get the
| exact timestamp for those expired coordinates, it's still
| useless.
|
| Oh, and accuracy is shit anyway (altitude is rounded to
| 10m)
| CobrastanJorji wrote:
| If there's no timestamp, all you know is a Lat/Long that
| was accurate sometime in the last 15 minutes (or more,
| "best effort basis"). But you don't know when, and you
| don't know the altitude. That's gonna make using that
| information for docking...difficult.
| Levitating wrote:
| > If you know of a DNS update which allows for per-minute
| updates for free, I'll happily move to it.
|
| Why not setup your own name server?
| zdw wrote:
| This is the correct way - dynamic DNS servers frequently
| have very low TTLs set.
|
| Serving DNS yourself is such an incredibly small bandwidth
| impact - most of the packets are in the 10's to 100's of
| bytes - and authoritative DNS servers do not do a lot of
| processing, just send back RR's from zones which are read
| at boot time, or updated in an in-memory database.
| edent wrote:
| I couldn't be bothered to set up a DNS server for such an
| ephemeral joke.
|
| But I would love to read your blog post about setting one
| up and what you learned.
| iwontberude wrote:
| Coredns is so simple to configure and is a barebones
| container deployment.
| edent wrote:
| Cool! Please set it up and write a blog post about it.
|
| I'm not being snarky. I've never set up something like
| that and I'm sure lots of people would be happy to ready
| about it.
| hhh wrote:
| hi, i haven't made a video but i have some stuff set up
| for it:
|
| https://youtu.be/AJ2Q12vYojY https://youtu.be/GoPWuJR6Npc
|
| and i host https://dnsroleplay.club which lets you answer
| real people's dns requests, there should be links to the
| github for how it's done
| progval wrote:
| Unless you send any reply that is significantly largest
| than the request, like this one, and then you can be
| exploited to DDoS someone else via an amplification
| attack. https://www.cloudflare.com/learning/ddos/dns-
| amplification-d...
| JdeBP wrote:
| zdw mentioned an "authoritative" server, i.e. a content
| DNS server. CloudFlare is not talking about content DNS
| servers there. It cannot decide from paragraph to
| paragraph what it is calling the DNS servers that it is
| talking about, but it is talking about _proxy_ DNS
| servers, that respond with the actual grunt work of query
| resolution done.
|
| People like me have been recommending not running public
| proxy DNS servers for the entirety of the 21st century
| thus far, and the world has taken some notice, although
| more work is required, world!
|
| * https://jdebp.uk/FGA/proxy-server-ip-addresses.html
|
| In any case, ANY queries do not work nearly as well for
| amplification attacks as they used to. Many people have
| read RFC 8482. I, for example, changed all of the DNS
| servers in djbwares to respond to ANY queries per RFC
| 8482 back in March 2019.
|
| The task at hand in this discussion only involves running
| a _content_ DNS server, serving LOC records from some
| file /database or other.
| echoangle wrote:
| > If you know of a DNS update which allows for per-minute
| updates for free, I'll happily move to it.
|
| Does Cloudflare not allow this?
| Abekkus wrote:
| I'd say the API can take up to half a minute to propagate,
| so API updates every minute is running up against their own
| performance. If you're a free customer, they may block you
| after a while, but first they'd have to notice you, and I
| doubt one update per minute would bother them.
| metafunctor wrote:
| It's quite easy to run your own DNS server -- I've found it a
| worthwhile exercise. Of course, you'll need a server to run
| it on.
| Abekkus wrote:
| Cloudflare does this with an API. If you have any money, I'd
| suggest dnsimple.com instead.
| dahsameer wrote:
| > As I say in the post, you shouldn't use this for docking
| operations
|
| Remember people, DNS stands for "Definitely Not for Space-
| docking"
| llimos wrote:
| or "Docking Not Supported"
| harha_ wrote:
| It's just an API that utilizes DNS, not that interesting imo.
| politelemon wrote:
| Looking at the RFC it's never explained why this is needed. Or
| was needed back in 1996, perhaps something to go with
| universities and data center logistics back then?
| edent wrote:
| RFCs are, in my experience, vague about the problem they're
| attempting to solve.
|
| There's no reason this couldn't be a human-readable string like
| "42 Wallaby Way, Sidney".
| echoangle wrote:
| > Looking at the RFC it's never explained why this is needed.
|
| Chapter 5.1 (Suggested Uses) has at least some vague
| suggestions:
|
| > Some uses for the LOC RR have already been suggested,
| including the
|
| > USENET backbone flow maps, a "visual traceroute" application
| showing
|
| > the geographical path of an IP packet, and network management
|
| > applications that could use LOC RRs to generate a map of
| hosts and
|
| > routers being managed.
| huslage wrote:
| Could you calculate the position from the Ephemeris data in
| realtime instead of using an API? This would allow you to return
| the current location on every request potentially.
| lordnacho wrote:
| Is there any service on the ISS that the public can interact
| with? Maybe you could use response times to figure out where it
| is that way.
| croes wrote:
| Depends on the hops between you and the target
| Maxious wrote:
| There's quite a few amateur radio frequencies you can interact
| with https://issfanclub.eu/iss-frequencies/
| trothamel wrote:
| It's pretty likely there will be a slow-scan TV event in mid-
| July, where the station will be transmitting images you can
| pick up with a radio. These are nice because you don't neeed
| a license - anyone with a radio that can pick up the right
| frequencies can receive.
| crazygringo wrote:
| That's what I thought this was going to be from the title --
| some kind of DNS response time triangulation from a device on
| the ISS itself, because DNS was allowed past a firewall or
| something...
|
| It's still a fun little project, but definitely feeling a
| little disappointed in comparison to what the title felt like
| it suggested to me...
| theobeers wrote:
| Another record, Name Authority Pointer (NAPTR), has the telephone
| number of the Johnson Space Center in Houston: >
| dig where-is-the-iss.dedyn.io NAPTR ; <<>> DiG 9.10.6
| <<>> where-is-the-iss.dedyn.io NAPTR ;; global options:
| +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY,
| status: NOERROR, id: 31786 ;; flags: qr rd ra ad; QUERY: 1,
| ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT
| PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 1232
| ;; QUESTION SECTION: ;where-is-the-iss.dedyn.io. IN NAPTR
| ;; ANSWER SECTION: where-is-the-iss.dedyn.io. 3600 IN NAPTR
| 100 100 "u" "E2U+voice:tel" "!^.*$!tel:+12814830123!" .
| ;; Query time: 84 msec ;; SERVER:
| 100.100.100.100#53(100.100.100.100) ;; WHEN: Sun Jul 06
| 10:53:39 EDT 2025 ;; MSG SIZE rcvd: 111
| timzaman wrote:
| "~instantly! (...) every 15 minutes" - omg
| verytrivial wrote:
| I read the opening sentence as "I love DNS erotica" which
| indicates I've been inside too long and should go for a walk.
| messe wrote:
| Is that not what this is?
|
| Maybe a cold shower too.
| edent wrote:
| Please don't make me sign up as an OnlyFans creator...!
| giancarlostoro wrote:
| Onlyfans was never supposed to be for porn to be fair it just
| kind of became the profitable business for them
| aidenn0 wrote:
| Any media service that doesn't ban porn will become
| associated with it.
| mschuster91 wrote:
| Meh both Reddit and Twitter have copious amounts of porn,
| yet neither are commonly associated with porn.
| byteknight wrote:
| Gives a whole new meaning to its always DNS.
| 6thbit wrote:
| You'd be surprised but I'm pretty sure many people would dig
| this.
| theobreuerweil wrote:
| If that's a pun, it's next level
| cmehdy wrote:
| The numbers would definitely be setting A record in that
| domain!
| teddyh wrote:
| More about DNS LOC records: <https://www.ckdhr.com/dns-loc/>
| knadh wrote:
| This is quite cool! I just added this to dns.toys [1]
| dig iss.sky +short @dns.toys
|
| [1] https://dns.toys
| edent wrote:
| That's so nifty! Thanks :-)
|
| Do all the tools use TXT records? Or are there any which use
| LOC, NAPTR, etc?
| knadh wrote:
| Yep, all tools return formatted strings as TXT records.
| xyst wrote:
| Great post, definitely something I can setup on my personal
| recursive DNS resolver. Yet another toy I can throw on to my rpi
| :)
| xkcd1963 wrote:
| TLDR; use an API
| ritcgab wrote:
| DNS is a federated, read-optimized, geo-replicated key-value
| store with eventual consistency.
| jamesgill wrote:
| OpenNotify is another (more limited, less fancy) resource:
| http://open-notify.org/
| supportengineer wrote:
| "dig" is the new "finger"
| pvtmert wrote:
| Besides the hard-coded cache, shouldn't DNS infrastructure
| already help with the caching just by the TTL value itself? Given
| quite many & large public DNS resolvers out there, like
| Cloudflare's 1.1.1.1 and Google's 8.8.8.8
|
| I overall like the DNS, it is a global database with eventual
| consistency. Possible to store transient data. Usually not
| blocked by firewalls just by the sheer innocent nature. (Although
| gets intercepted quite a lot...)
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