There are multiple implementations, the one often found on linux is glibc, you can find the source code for that online. printf is going to be a small wrapper for vfprintf though, so that is where you will probably find what you are looking for
It's also completely unnecessary, NOAA-19 was fine until they did "End Of Life testing", with NOAA-18 the failed RX could have been an issue, but NOAA-15 was mostly fine other than the Scan motor getting stuck (and always fixing itself). It's now very likely all 3 will explode due to a battery failure that happened on NOAA-16 and NOAA-17. because of the shut down.
So not only is this a waste of good weather satellite that provide a useful service (APT is actually used in remote location), it's also dangerous to satellites due to the space debris that will be created.
There is always LRPT to try!
My last good APT from NOAA-15 today
A particularly nice one, (I think) 2024-05-01
The 2023 scan motor malfunction 2023-10-12
And some HIRS from the DSB 2023-09-29
Well, there it goes. Today, the 19th of August 2025, NOAA-15 was decommissioned over svalbard. I didn't manage to get the final APT, but this time meti from the satdump discord (and some others) did, and is the picture attached to this post.
Here is a link to their archive website licensed CC-BY-SA-4.0 received by meti.
Earlier, (the svalbard pass before?) the AVHRR patch cooling was disabled, making the IR channels unusable and white on the APT.
With NOAA-18 and NOAA-19 having been decommissioned earlier, as I have made posts about. This is the end of 137MHz APT, but meteor LRPT is still active, and is planned to continue for many years.
Although old, I found APT fun to receive, with it's rhythmic clicking, and analogue images. If anyone is even in this community maybe post your best APT receptions in the comments.
sorry, that turned into a bit of a wall of text!
I will mention that these are very old satellite, this one was 16 years old, there are replacement weather satellites, but they are not easy to receive with cheap equipment like these, requiring internet access or a very expensive setup.
There are 3 frequencies weather satellites generally use for real-time imagery:
VHF: can be recieved with a stationary antenna for very cheap.
L-band: requires a tracked dish, is a bit more expensive, but the rotor can get very expensive.
X-band: requires a more accurate tracked dish, very expensive, sometimes hard to acquire hardware, and an expensive high sample rate radio.
The new US satellites use X-band exclusively while these older ones used both VHF and L-band.
Currently the only real replacement for amateur reception is the russian meteor series which use VHF and L-band.
China's satellites are also only use X-band.
A couple of european satellites can be received on L-band, but new ones only use X-band. (the L-band ones also need a slightly more expensive radio)
There are also geostationary satellites that appear stationary in the sky, they can often be received on L-band, but thats a different thing.
Today, the 13th of August 2025, NOAA-19 was permanently shut down after a battery failure on the 9th. Until the 11th it was still transmitting APT, but on the 12th it only transmitted DSB without HIRS or SEM. On S-band it was also transmitting DSB for a while, then HRPT with only TIP data on night the 13th and this morning.
Since this was unexpected, I didn't get the last APT it was transmitting, or record the shutdown of the satellite, but here is the best APT I have from the day before (the 11th). RIP NOAA-19.
The decommisioning of NOAA-15 was due on the 12th, but was delayed to the week of the 18th on the 11th due to an "anomaly" with NOAA-19.
links:
POES Decommisioning and NOAA-15 delay message
NOAA-19 Decommisioning message
It's a problem for hobbiest satellite reception. None of these new satellites (except the russian ones) have 137MHz or l-band(1.7Ghz) transmissions, requiring much more complex and expensive X-band equipment to receive, this is one of the three remaining US weather satellites that transmits on 137Mhz and l-band lost. leaving 2 US (137MHz/l-band), 2 EU (l-band only), 3 russian (2 137MHz/l-band, 1 l-band only)
At about 17:40 UTC today NOAA-18 was permanently shut down. This is the last APT image it was transmitting, you can see where it stops. I recorded this using an openwebrx station because it was too far north for me to receive. Thanks to the openwebrx server for letting me record this event: http://sa2kng.ddns.net:8073/
!wave
!wave
It's transmitting on 145.8MHz FM in the 2m HAM band
times (from amsat-uk):
Fri Oct 27 at 12:15 GMT – Sun Oct 29 at 18:50 GMT
Tue Oct 31 at 10:05 GMT – Wed Nov 01 at 18:10 GMT
a couple more:
From 2023-10-12
Projected:
Day Microphysics projected:
Scan motor current is going up again, maybe it will fix?
y=1/x where x<0 cat