Minuteman III ICBM Test Launches & HFGCS EAM Activity

Originally written February 28, 2026. Last updated March 3, 2026
Pre-launch EAM patterns observed from HFGCS monitoring back to index

Key Findings

  • Group 4 EAMs appear at ~3.6× their baseline rate in the D-1 to D-3 window before Minuteman III test launches from Vandenberg SFB.
  • Of 11 launches with monitoring data in the D-1–D-3 window, 8 showed Group 4 long-EAM activity. On non-launch days, Group 4 appears on only 22% of days (avg 0.29 long messages/day, computed over 807 baseline days).
  • Group 4 prefixes are notable because they produce almost exclusively extended-length (>30 character) EAMs—99.2% of Group 4 messages exceed the standard 30-character format.
Correlation only—not a confirmed causal relationship. This is a hobbyist observation from publicly monitored HF radio traffic.

Upcoming: GT-255?

A Minuteman III test launch is scheduled from Vandenberg SFB with a launch window of March 4, 07:01 to March 4, 13:01 UTC. Based on the pattern described above, if this launch follows the same trend as previous launches, we would expect to see Group 4 long EAMs appearing between approximately March 1 and March 4 UTC (the D-1 to D-3 window).

This timing coincides with heightened geopolitical tensions between Iran and Israel. It is worth noting that an increase in HFGCS long-EAM activity in early March 2026 could easily be misread by casual observers as related to the Iran–Israel situation, when in reality it may simply reflect routine pre-launch messaging for a scheduled, publicly announced ICBM test. The pattern documented on this page suggests that elevated Group 4 activity before a launch is normal and expected—it has occurred before 8 of the 11 prior launches where monitoring data was available.

That said, the correlation shown here does not rule out the possibility that the same prefix groups are also used for operationally significant messaging unrelated to test launches. Nonetheless, it’s more coherent to assume any instances of long EAMs around this time will be related to the Minuteman ICBM test launch, rather than necessarily related to the news of the day.

About This Dataset

This page was prepared by NEET INTEL, a hobbyist project that monitors and catalogues EAMs (Emergency Action Messages) broadcast on the US military’s HFGCS (High Frequency Global Communications System). HFGCS transmits on shortwave radio frequencies that anyone with the right equipment can receive. Most EAMs are exactly 30 characters long, following a standard format. Messages longer than 30 characters are operationally more significant—we colloquially refer to these here simply as “long EAMs.”

Over time, NEET INTEL has grouped the observed prefixes into 4 groups based on their behavior. Each group has different characteristics. Group 4 is of particular interest because 99.2% of its messages exceed the standard 30-character length; Group 4 messages are often the “VERY LONG” messages that get interest and attention outside of the niche of ‘guys who are sat around listening to the US military read ciphertext over the radio.’ The charts below show each group as a different color, stacked into bars for each day.

HOW TO READ THE CHARTS

Each launch card shows a 6-day window (D-5 through D-0, where D-0 is launch day). The bar chart shows every EAM logged that day, color-coded by prefix group. The columns highlighted in pink are D-1 through D-3—the window where elevated Group 4 activity is most frequently observed before launches. Below the chart, individual long-message character counts are listed per day, color-coded by group.

MONITORING LIMITATIONS

NEET INTEL’s monitoring is volunteer-based and not continuous. The coverage strip below each chart shows which monitoring datasets are available for each day:

  • SET labels indicate the known quality/comprehensiveness of NEET INTEL’s monitoring for the period of time the given test launch falls under (green = comprehensive, blue = partial, orange = remedial, red = little/none).
  • DTCP (Daily Timecard Project) and DCRP (Daily Compilation Recording Project) are transcribed video/audio recordings, the most reliable sources.
  • LIVESTREAMS are raw stream recordings that have not been transcribed, so the logged data for those days may be incomplete. Of course, since recordings exist and were made, the possibility of comprehensive transcription exists if there is interest and support.

Days with no coverage indicator had no known monitoring. Absence of EAM activity on a given day may reflect a gap in monitoring rather than actual inactivity.

Prefix Groups G1 G2 G3 G4 | Bar = all EAMs by group · Long EAMs = character counts for >30-char messages · Counts: total / long | Coverage: Comprehensive Good Remedial Little/none · DTCP / DCRP = EAM transcriptions ± recordings · LIVESTREAMS = HFGCS livestream recordings
GT-245 2023.02.10 07:01 UTC (2023.02.09 11:01 PM PST) source ↗
All
D-5
02.05
6/0
D-4
02.06
5/0
D-3
02.07
10/0
D-2
02.08
4/2
D-1
02.09
7/1
D-0
02.10
8/3
S2
S2
S2
S2
S2
S2
Long EAMs
3834
68
1724747

February 10, 2023

40 messages were recorded in the six days before this launch, 6 of which were longer than the standard 30 characters. One Group 4 long message was recorded in the days before launch (1 appearing two days before). The longest message in the window was a 172 character Group 4 message.

Monitoring during this period was comprehensive, with transcribed recordings available for most days.
GT-246 2023.04.19 12:11 UTC (2023.04.19 5:11 AM PDT) source ↗
All
D-5
04.14
0/0
D-4
04.15
2/0
D-3
04.16
6/3
D-2
04.17
19/9
D-1
04.18
17/11
D-0
04.19
0/0
-
S2
S2
S2
S2
-
Long EAMs
505049
766656565050504636
1861521186950505050504636

April 19, 2023

44 messages were recorded in the six days before this launch, 23 of which were longer than the standard 30 characters. Group 4 prefixes — which almost always carry longer-than-normal messages — were especially active before this launch, with 17 long messages in the three days prior (2 appearing three days before, 9 appearing two days before, 6 appearing the day before launch). That’s about 20× the usual daily rate for Group 4. The longest message in the window was 186 characters (Group 3, the day before launch).

The GT-246 pre-launch window (D-5 through D-1) coincides entirely with USSTRATCOM exercise Global Thunder 23, which ran April 11–18, 2023. The exceptionally high Group 4 activity observed during this period may be a confounding factor — related to the exercise rather than the launch itself — or both may be directly connected, as Global Thunder exercises are designed to test nuclear command and control procedures. Notably, the launch command for GT-246 was delivered from the Airborne Launch Control System (ALCS) aboard a Navy E-6B TACAMO.

No recordings are currently published for this period. The logged data is provided as-is and may not be comprehensive.
GT-247 2023.09.06 08:26 UTC (2023.09.06 1:26 AM PT) source ↗
All
D-5
09.01
4/0
D-4
09.02
3/0
D-3
09.03
9/1
D-2
09.04
7/0
D-1
09.05
16/3
D-0
09.06
10/2
S3
S3
S3
S3
S3
S3
Long EAMs
34
1426751
3933

September 6, 2023

49 messages were recorded in the six days before this launch, 6 of which were longer than the standard 30 characters. One Group 4 long message was recorded in the days before launch (1 appearing the day before launch). The longest message in the window was 142 characters (Group 4, the day before launch).

Monitoring during this period was comprehensive, with transcribed recordings available for most days.
GT-248 2023.11.01 ~07:01 UTC (2023.11.01 ~12:01 AM PT) source ↗ ANOMALY
All
D-5
10.27
7/1
D-4
10.28
4/3
D-3
10.29
11/4
D-2
10.30
10/4
D-1
10.31
10/1
D-0
11.01
8/0
S3
S3
S3
S3
S3
S3
-
-
-
LIVESTREAMS
231030A
231030B
LIVESTREAMS
231030B
231031A
LIVESTREAMS
231101A
Long EAMs
42
513433
2681423934
160863837
51

November 1, 2023

50 messages were recorded in the six days before this launch, 13 of which were longer than the standard 30 characters. Group 4 prefixes appeared 3 times in the three days before launch (2 appearing three days before, 1 appearing two days before), which is above average. That’s about 3× the usual daily rate for Group 4. The longest message in the window was 268 characters (Group 4, three days before).

An anomaly was detected approximately 5 minutes after launch, and the missile was intentionally destroyed over the Pacific Ocean as a safety precaution. The test was deemed unsuccessful.

Monitoring during this period was comprehensive, with transcribed recordings available for most days.
GT-249 2024.06.04 07:56 UTC (2024.06.04 12:56 AM PT) source ↗
All
D-5
05.30
7/0
D-4
05.31
17/0
D-3
06.01
14/0
D-2
06.02
7/0
D-1
06.03
1/0
D-0
06.04
8/2
S4
S4
S4
S4
S4
S4
Long EAMs
3935

June 4, 2024

54 messages were recorded in the six days before this launch, 2 of which were longer than the standard 30 characters. No Group 4 messages appeared in the days before launch.

Monitoring during this period was comprehensive, with transcribed recordings available for most days.
GT-250 2024.06.06 08:46 UTC (2024.06.06 1:46 AM PT) source ↗
All
D-5
06.01
14/0
D-4
06.02
7/0
D-3
06.03
1/0
D-2
06.04
8/2
D-1
06.05
11/0
D-0
06.06
14/1
S4
S4
S4
S4
S4
S4
Long EAMs
3935
52

June 6, 2024

55 messages were recorded in the six days before this launch, 3 of which were longer than the standard 30 characters. No Group 4 messages appeared in the days before launch.

Monitoring during this period was comprehensive, with transcribed recordings available for most days.
GT-251 2024.11.06 07:01 UTC (2024.11.05 11:01 PM PT) source ↗
All
D-5
11.01
17/1
D-4
11.02
28/1
D-3
11.03
14/0
D-2
11.04
16/1
D-1
11.05
15/3
D-0
11.06
20/4
S7
S7
S7
S7
S7
S7
Long EAMs
42
41
120
484340
63403531

November 6, 2024

110 messages were recorded in the six days before this launch, 10 of which were longer than the standard 30 characters. One Group 4 long message was recorded in the days before launch (1 appearing two days before). The longest message in the window was 120 characters (Group 4, two days before).

This test was launched via E-6B Airborne Launch Control System (ALCS).

No transcribed recordings are available for this period, but livestream recordings exist and can be reviewed for accuracy.
GT-252 2025.02.19 09:00 UTC (2025.02.19 1:00 AM PT) source ↗
All
D-5
02.14
0/0
D-4
02.15
0/0
D-3
02.16
2/1
D-2
02.17
0/0
D-1
02.18
0/0
D-0
02.19
0/0
-
-
S10
-
-
-
LIVESTREAMS
250214A
LIVESTREAMS
250215A
-
-
-
-
Long EAMs
268

February 19, 2025

Only 2 messages were recorded in the six days before this launch, 1 of which was longer than 30 characters. One Group 4 long message was recorded in the days before launch (1 appearing three days before). The longest message in the window was 268 characters (Group 4, three days before).

Livestream recordings cover 2 of the 6 days, but no transcribed recordings are available. The logged data is provided as-is.
GT-253 2025.05.21 07:01 UTC (2025.05.21 12:01 AM PT) source ↗ unverified
All
D-5
05.16
0/0
D-4
05.17
0/0
D-3
05.18
0/0
D-2
05.19
1/1
D-1
05.20
0/0
D-0
05.21
0/0
-
-
-
?
-
-
Long EAMs
290

May 21, 2025

NEET INTEL was not monitoring or recording during this period. No EAM data, transcribed recordings, or livestreams were published during this launch window. eam.watch reported a 290-character EAM broadcast on May 19, 2025. However, as with anything from eam.watch, the data will need to be verified for accuracy and ideally a second (or superior) source corroborating the broadcasting an EAM on the same date can be found. Nonetheless, if true, the evidence would support the observation being made throughout this page.
GT-254 2025.11.05 09:35 UTC (2025.11.05 1:35 AM PT) source ↗
All
D-5
10.31
0/0
D-4
11.01
0/0
D-3
11.02
0/0
D-2
11.03
2/2
D-1
11.04
0/0
D-0
11.05
0/0
-
-
-
S13
-
-
Long EAMs
268164

November 5, 2025

Only 2 messages were recorded in the six days before this launch, 2 of which were longer than 30 characters. Group 4 prefixes appeared 2 times in the three days before launch (2 appearing two days before), which is above average. That’s about 2× the usual daily rate for Group 4. The longest message in the window was 268 characters (Group 4, two days before).

This test was launched via E-6B Airborne Launch Control System (ALCS).

No transcribed recordings are available for this period, but livestream recordings exist and can be reviewed for accuracy.
GT-255? 2026.03.04 ~07:01 UTC (2026.03.04 ~11:01 PM PT) source ↗ Scheduled
All
D-5
02.27
0/0
D-4
02.28
1/0
D-3
03.01
0/0
D-2
03.02
2/0
D-1
03.03
2/0
D-0
03.04
0/0
-
S15
-
S15
S15
-

March 4, 2026

This launch is scheduled with a window of March 4, 07:01 to 13:01 UTC. Having reached D-0, no long EAMs were observed in the days prior. However, extended periods of digital transmissions centered on 11175 kHz were noted on the HFGCS, which curiously, might have been broadcasting information in lieu of any single long message.
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