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.

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1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible and Infrared images (above) showed the WNW motion of the eye of Hurricane Erin during a 7-hour period as the tropical cyclone rapidly intensified from a Category 4  storm at 0950 UTC to a Category 5 storm at 1520 UTC, north of the Leeward Islands on 16 August 2025. Erin was the earliest Category 5 hurricane on record in the Atlantic Ocean, as well as one of the Atlantic’s fastest-intensifying tropical cyclones on record (SATCON). Plots of 1-minute GOES-19 GLM Flash Points displayed abundant lightning activity within the inner eyewall of Erin’s pinhole eye. In addition, the eye exhibited a notable stadium effect — with a very small low-altitude eye seen in visible imagery, broadening to a larger high-altitude eye in infrared imagery (for example, at 1657 UTC). The coldest cloud-top infrared brightness temperatures within the eyewall were around -80 C.

A closer view of 1-minute GOES-19 Visible imagery (below) revealed the presence of low-altitude mesovortices within the eye. A pinhole eye and mesovortices within the eye are 2 satellite-observed characteristics often associated with intense Category 5 tropical cyclones. In addition, Erin was moving though an environment of weak deep-layer wind shear and traversing warm sea surface temperatures — 2 factors that favored intensification.

A GOES-19 Visible image at 1424 UTC (below) included plots of ASCAT ocean surface winds valid at that time; hurricane-force winds only extended about 10-15 miles from the center of Erin. However, significant rainfall contamination within portions of the eyewall adversely affected the quality of a few of the scatterometer winds (with 3 erroneous wind directions seen near the eye).

A Synthetic Aperture Radar (SAR) image from RCM-3 at 2229 UTC on 16 August (below) depicted a peak radial wind velocity of 123 kts in the SE quadrant of Erin (source) — this was around the time that the hurricane was undergoing an eyewall replacement cycle, and decreasing in intensity from a Category 5 at 2100 UTC to a Category 4 at 0000 UTC.

Later that evening, 1-minute GOES-19 Infrared images (below) showed that the eye of Category 4 Hurricane Erin passed about 40 miles south of Buoy 41043 — which reported hourly wind gusts of 64 kts at 0200 UTC and 0300 UTC on 17 August (the highest 10-minute wind gust was 66.1 kts at 0250 UTC).

Plots of wind speed / wind gusts / atmospheric pressure and wave height at Buoy 41043 (below) indicated that their maximum (or minimum, in terms of pressure) values occurred around 0300 UTC on 17 August (just as the eye of Erin was passing south of the Buoy).

The maximum wave height of 29 ft measured at Buoy 41043 was commensurate with the 25.32 ft significant wave height sensed by Sentinel-3A (and the 39.52 ft sensed by SWOT) farther to the south, near the northern Leeward Islands, during the morning hours (1237 UTC and 1428 UTC) on 16 August (below).

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10-minute Full Disk scan GOES-18 (GOES-West) daytime True Color RGB and nighttime Dust RGB images created using Geo2Grid (above) showed a plume of resuspended volcanic ash (hazy shades of tan in True Color RGB, and subtle shades of violet in Dust RGB images) from the 1912 Novarupta-Katmai eruption in Alaska — which was being transported offshore across the Shelikof Strait and Kodiak Island, emerging over the Gulf of Alaska during 15-16 August 2025. Surface volcanic ash within the Valley Of Ten Thousand Smokes was being lofted by strong northwesterly winds (surface analyses) that were being channeled through the valley.

According to this USGS Volcano Notice, the National Weather Service issued a SIGMET advising that the maximum height of this resuspended ash was 6000 ft.

Other similar resuspended ash events have been documented here on this blog.

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Today at 16:55 UTC, NOAA decommissioned NOAA-19, the most recently launched of the remaining legacy NOAA POES spacecraft. NOAA-19 launched on February 6th, 2009 and become operational on June 2nd, 2009. For the last 16 years, NOAA-19 has provided routine weather observations of the entire globe from low-earth orbit.

The AVHRR visible/IR imager and AMSU-A/MHS set of microwave sounders were both functioning well on NOAA-19 in its final days. However, due to a spacecraft battery failure on August 9th, the decision was made to accelerate the decommissioning timeline by about 6 days. The HRPT direct broadcast system on the spacecraft started to falter on August 11th, so the final daytime overpass of Wisconsin by NOAA-19 (with valid science data) was received by SSEC’s Madison antenna at 15:56 UTC on August 10th. Below is a selection of the AVHRR Level 1 imagery from that pass, along with AVHRR Level 2 Sea Surface Temperature retrievals from CSPP ACSPO, and AMSU-A/MHS Level 2 Total Precipitable Water and Rain Rate products from CSPP MiRS.

		[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]
ACSPO AVHRR Sea Surface Temperature	MiRS AMSU-A/MHS Total Precipitable Water	MiRS AMSU-A/MHS Rain Rate

Today’s activity follows NOAA-18’s decommissioning on June 6th. NOAA-15, the last operating spacecraft in the POES series, is slated to be turned off during the week of August 18th.

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