Goodnight, NOAA-15
At 15:28 UTC today, NOAA decommissioned the final remaining legacy POES satellite, NOAA-15. The spacecraft was launched on May 13, 1998, and entered full operations on December 15th of that same year. Amazingly, that equates to 27 years of observations from low-earth orbit; for a spacecraft with an original mission lifespan of 2 years, that is incredible! Based on available information, that should cement NOAA-15 in the record books as the longest-lived operational American polar weather satellite, a record that is unlikely to be broken anytime soon as modern constellations (such as JPSS) now adhere to more stringent deorbiting requirements.
In recent years, NOAA-15’s various instruments have become degraded and thus its data in operations has had limited utility. Additionally, its L-band HRPT direct broadcast antenna was operated at a lower power than other POES satellites, resulting in more frequent data dropouts during reception. With that said, there was still some interesting data coming from NOAA-15’s AVHRR imager as of its last active pass over SSEC’s Madison X/L-band DB antenna on 12:46 UTC on August 18th:
 |  | [Inactive] |
| AVHRR Band 1: “Red Visible” [0.63 µm] | AVHRR Band 2: “Vegetation Near-IR” [0.86 µm] | AVHRR Band 3A: “Snow/Ice Near-IR” [1.61 µm] |
 |  |  |
| AVHRR Band 3B: “Shortwave IR Window” [3.74 µm] | AVHRR Band 4: “Legacy IR Window” [10.8 µm] | AVHRR Band 5: “Dirty IR Window” [12.0 µm] |
Notably, NOAA-15 was the final active satellite to broadcast an Automatic Picture Transmission (APT) signal. APT was an analog direct broadcast format first developed in the 1960s, and was onboard the legacy POES and precursor spacecraft. Broadcast in the VHF range around 137 MHz, APT was easy to pick up with inexpensive radio frequency equipment. It was engineered in such a way that it did not require a tracking antenna to receive, so a simple V-dipole antenna in a fixed location could pick up the signal as the satellite tracked across the sky. Given these traits, and the availability of cheap software defined radios (SDRs) since the 2010s, APT reception was a common beginner project in the satellite/radio hobbyist communities. In May 2025, I set up a temporary APT receive station in rural northern Wisconsin, using an off-the shelf V-dipole kit, SDR, filter/amplifier, and single board computer:
Raw APT was transmitted as an audio signal, one line at a time, and the final output (when decoded) contained images from 2 of the AVHRR bands. At any given time, the two bands being sent were configured by the NOAA ground station – during the daytime, bands 2 (left) and 4 (right) were the most common. The spatial resolution was downscaled to roughly 4 km, and the nature of the analog format made it susceptible to interference from many types of equipment. However, with the right hobbyist-grade equipment and a clear view between the satellite and receive station, it was possible to get fairly usable imagery via APT.
With the legacy NOAA POES constellation now turned off, NOAA’s low-earth orbiting weather satellite efforts continue with the JPSS constellation, with S-NPP, NOAA-20, and NOAA-21 all in orbit now and two additional missions planned. NOAA’s partners at EUMETSAT have been busy, with the recent launch of their first spacecraft in the MetOp Second Generation series, MetOp-SG-A1, and their prototype passive microwave sounder mini-satellite, Arctic Weather Satellite, now operational. Also, JAXA recently launched its next-generation passive microwave imager, AMSR3, on the satellite GOSAT-GW, which will replace AMSR2 on GCOM-W1.