EOSS-335 NDIA-Sponsored Student STEM Launch - Recap

A single 3000g balloon was launched at 7:00am MDT from Deer Trail Colorado on Sunday March 26, 2023. The balloon carried over 300 student experiments collected into two payloads sponsored by the Rocky Mountain Chapter of the National Defense Industrial Association. The balloon reached an altitude of 104,416 feet. The balloon landed 4.3 miles northeast of Arickaree Colorado.The balloon was recovered after a 0.5 mile hike into a dormant field.

Original Announcement: 

03-23-2023The date of the flight has been moved to Sunday, March 26, 2023 due to weather concerns. A single 1500g balloon will be flown at 0700 MDT from Deer Trail.

03-25-2023We are a go for launch on Sunday 3/26.

One 3000g balloon carrying over 300 Student Experiment Capsules containing student STEM experiments and EOSS beacons for flight qualification

Cloud cover is predicted to prevents launching a non-exempt balloon, a single 1500g balloon will be launched. In case the skys clear up a non-exempt balloon has been designed:

 Flight predictions can be viewed here (select the correct date and launch site (Deer Trail) and view the data. This prediction will start updating daily 15 days before the flight.

Event Date: 
Saturday, March 25, 2023 - 00:00 to 23:45
Flight Coordinator: 
Launch Site: 

EOSS-335 Lite

A 1500g balloon sponsored by the Rocky Mountain Chapter of the the National Defense Industrial Association

Balloon Type: 
Totex 1500g Latex
12 ft Rocketman with Remote Release Baker
145.645 MHzKC0D-1Remote Release/DFTOP, Secondary Beacon
145.765 MHzKC0D-3APRS/Digi/Remote ReleaseFirmware Qualification
144.340 MHzAE0SS-13APRS/Digi EOSSXBOTTOM, Primary Beacon
Payload Plan: 

The following RF Resources have been approved for EOSS-332/333 flight on Sunday 26MAR2023.

Preflight Net:

449.225 minus offset with a 141.3 Hz tone "Fun Machine” for the EOSS 335 Pre-Flight Net on Saturday 25MAR2023 @ 19:00 (7 PM).

Analog T&R Repeater:

RMRL 449.450 minus offset with 103.5 Hz tone for Saturday along with links to several other sites. SkyHub Link System will graciously link the following repeaters to this machine during the flight:

  • Limon (Cedar Point) - 447.650(-) MHz, 103.5 Hz
  • Hugo - 447.150(-) MHz, 103.5 Hz
  • Firstview - 447.600(-) MHz, 103.5 Hz
  • Akron - 447.425(-) MHz, 103.5 Hz
  • Stratton - 146.895(-) MHz, 103.5 Hz

RMHAM DMR has been approved using the “Rocky Mountain Wide” talk group. 


RMHAM has added the following DMR sites:

  • Burlington Colorado RMHAM-N0SZ Input 440.0500 MHz Output 445.0500 MHz Color Code 6,  TS-1 TG 700 (Wide), TS-2 TG 720 (Central)
  • Limon Colorado RMHAM-N0SZ Input 440.275 MHz Output 445.275 MHz Color Code 7, TS-1 TG 700 (Wide), TS-2 TG 720 (Central)

 These two sites provide almost full coverage along the I-70 corridor from Byers to Goodland Kansas.

 Updated code plugs are available on the RMHAM website.

The Usual EOSS Simplex Frequencies (UESF) will be used:

  • Ground Station                           446.050
  • Balloon 332 T&R                      446.100
  • Balloon 333 T&R                      446.150
  • Balloon 334 T&R                      446.200
  • Car to Car drive out                   446.275 

 Please contact W9CN if you have any questions.

2M Direction Finding Frequencies:

  • 144.340
  • 145.535
  • 145.645
  • 145.765
Tactical Calls: 
TacticalCall SignNameNotes
AlphaWAØGEH, KCØDMarty Mark
BravoW9CN, NØJPSMike, John
CharlieKCØRPS, NØNFWJim, Flight Coordinator, George
DeltaKØSCC, KEØBMV, W0GVStephen, Parker, Daryl, Gerry
Ground StationN2XGL, K5JKJeff, Tom
TangoKCØLJohn, from Texasf
Launch TeamNØNDM, NØNKK, NØFTI, W0CBH, KD0NTLarry, Nancy, Steve, Benjie, Jim
TR Breakfast: 
The trackers breakfast is at the Flying J IHOP in Limon at 6 AM