Recap of EOSS-75

LAUNCH DATE: April 17, 2004
LAUNCH TIME: 08:00 (14:00 UTC)
LAUNCH SITE: Windsor, Co (directions)

Blue = Actual Track
Green = Predicted Ascent Phase
Red = Predicted Descent Phase

Maps made with MapPoint
Prediction made with Balloon Track

Launch Site - Windsor
Launch Point: 40.4737� lat.   -104.9623� long.
Grid: X=2.62 Y=35.57
Ascent Rate: 1000 feet per minute
Descent Rate: 910 feet per minute
Altitude: 4931 feet
Predicted Landing Site
Landing Point: 41.0855� lat.  -103.2934� long.
Grid: X=89.4 Y=77.8
Altitude: 4500 feet
Flight Time: 131 Minutes
Bearing: 63.6� True
Range: 96.9 Mi.
Actual Landing Site
Landing Point: 41.0884� lat.  -103.7201� long.
Grid: X=67.2 Y=78.0
Bearing: 56.4� True
Range: 77.6 Mi.
Difference from Predicted to Actual Landing Site
Bearing: 270.7� True
Range: 22.2 Mi.

EOSS Frequencies:

  • Preflight Net:
    • 147.225 MHz 8 pm MDT preceding Friday night
      • 145.160 MHz simulcast in the Springs
    • 146.640 MHz will serve as a backup frequency
  • Tracking and Recovery Operations
    • 449.450 MHz RMRL Repeater (tentative)
    • 146.550 MHz simplex (same simplex for field and launch ops)
    • 146.970 MHz Sidney, NE
    • 146.910 MHz Stirling, CO
    • 7.228 MHz HF


  • Beacon
    • 145.600 MHz
    • ID: W5VSI in CW
  • APRS
    • 144.340 MHz (primary APRS)
    • ID: W5VSI-11

Flight Systems:

Balloon Manufacturer Kaymont
Balloon Type latex
Balloon Size 3000 gram
Payload 26.05 Lbs.
Free Lift % 0.175
Ascent Rate unknown (no aprs)
Descent Rate unknown (no aprs)
Parachute 10 ft. diameter
Peak Altitude unknown (no aprs)
Launch Conditions very good, calm at launch

Payload Configuration:

The first payload layout for the 3000 gram balloon in this document is the one flown. The other layouts were contemplated should high winds at the launch site require the payloads be flown on two smaller 1200 gram balloons.

EOSS Grid:

Location Grid X Grid Y
Grid Ref (Intersection of Highway 14 & 71 (west)) 70 45
Ft. Lupton 10 9.5
Nine Mile Corner 75 13
Launch Point 2.56 35.57
Predicted Touchdown (Friday Night) 96 83.4

Tactical Callsigns:

Tactical Callsign HF
alpha WA0GEH yes (recovery coordinator)
bravo W0CBH yes
charlie KB0YRZ no
delta N0NDM no (maybe
echo K0JLZ yes
fox NQ0R yes
india N0LP no (ground station)


Launch Site

Recovery Site


These audio files contain traffic on the Tracking and Recovery frequency.

However, the Tracking and Recovery folks may benefit from them as they can hear their audio and perhaps get a better handle on how their signals are making it into the RMRL's 449.450 Machine from the northeast part of the state.


Plain Text

Ground Station Logs

Spread Sheets (comma delimited)



Data provided by:

  • The Ground Station (W5VSI)

  • Jeff Brower (NK0L)

  • The predictor (N0KKZ)


Tracking & Recovery Recap

by Benjie W0CBH.

What a great day for a launch.

The trackers met at the Mickey D's in Fort Morgan at 6:30 am. Those in attendance were Larry (N0NDM), Chris (KB0YRZ), Marty (WA0GEH), Jim (K0JLZ), Rich (K0AEM), Clint (AC7FY). We discussed the positioning of each tracker with Marty, the tracking coordinator, and after coffee and breakfast headed off to the north land to our suggested tracking locations.

We lost the 449.450 repeater north of the junction of highway 14 and 71, while heading up hw71. Repeater coverage was spotty as we went north, but simplex worked well, on 146.550 as we proceeded into Nebraska. Marty and I were trying the Sidney repeater on 146.970 and he made contact with a ham there and got permission to use the repeater. However, since the simplex frequency worked well, we used that for the chase. It's flat up there, you know.

As we deployed we found the APRS module had failed again, so were were back to the good old tried and true method of RDFing. When Marcia and I reached our location, I started taking bearings, and on the bearing call up passed them on to Marty. We took about six or seven bearings, most of which didn't vary much for me. The signal was terrible, it varied a lot while holding the tracking antenna steady, so I averaged the readings and used my new digital electronic compass, which worked very well.

Marcia took several bearings, and also talked to a rancher who happened by, very curious about what we were doing. We seem to find a lot of them out in the field, all very interested in what we are doing and why we are there.

The touchdown was approximately 15 miles west of our position and we tore off to find the rest of the trackers already there and looking. It didn't take long to find the payloads. They were about 1/4 mile south of road 14 (east-west) and road 31 (north-south), just south of Dix, NE. We waited for the 60 to 70 students to show up, then recovered the payloads and took off for Fort Morgan where we had a very nice lunch at the Memories cafe.

The tracking crew had a good lunch and discussed the difficulties we had during the flight with our gear and came up with several gems of knowledge to improve our performance for the next launch which is May 1st. My total mileage traveled was 360.2 miles for this flight. There is a lot more to tell about this day, but that will come at a face to face the next time we have one.




These two flight are in support of Colorado University's Space Grant flights and the Lockheed Martin explorer's group.