Recap of EOSS-74-A

Recap of EOSS-74A

LAUNCH DATE: February 22, 2004
LAUNCH TIME: 08:05 am (15:05 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: 1200 feet per minute
Descent Rate: 930 feet per minute
Altitude: 4931 feet
Predicted Landing Site
Landing Point: 40.682� lat.  -103.8119� long.
Grid: X=62.8 Y=50.0
Altitude: 4500 feet
Flight Time: 148 Minutes
Bearing: 76.2� True
Range: 62.0 Mi.
Actual Landing Site
Landing Point: 40.6085� lat.  -104.2693� long.
Grid: X=38.9 Y=44.9
Bearing: 75.4� True
Range: 37.5 Mi.
Difference from Predicted to Actual Landing Site
Bearing: 258.2� True
Range: 24.5 Mi.

EOSS Frequencies:

Flight Systems:

Balloon Manufacturer Scientific Sales ?
Balloon Type latex
Balloon Size 1500 gram
Payload 14.2 Lbs.
Free Lift % calculated at fill
Ascent Rate 1045.3 fpm post flight analysis
Descent Rate  unknown, no data
Parachute 7 ft. diameter
Peak Altitude 71,833 ft
Launch Conditions dead calm

EOSS Grid:

Location Grid X Grid Y
Grid Ref (Intersection of Highway 14 & 71 (west)) 70 45
Ft. Lupton 10 9
Nine Mile Corner 75 13
Windsor 5 36
Launch Point 2.56 35.57
Predicted Touchdown (Friday Night) 55.3 42.6

Tracking and Recovery Teams

Tactical Call Sign Name
Alpha WA0GEH Marty
Bravo W0CBH Benjie
Charlie N0NDM and K0ANN Larry and Ann
Delta K0JLZ Jim
Echo N0PUF Dan
Fox KC0JHQ Mark
Golf K0ANI Larry
Hotel KB0UBZ and KA0ZFI Ben and Ann
India N0LP Nick

Payload Configuration:

Internet Gateway Stations:

as seen on Findu.Com

For W5VSI-11

  • K0UT-3 - Bill Beach
  • KH2NC - Rick Nilson
  • KC0LNO-1 - Mike Skinner
  • K0YG-7 - Mark Patton


  • K0YG-7 - Mark Patton

For KC0JHQ-11

  • K0QED - Lee Inman

EOSS wishes to express our sincere appreciation to those stations above who iGated the balloon APRS telemetry onto the internet.

We are relying heavily on real time position information available on the net to allow the FAA controllers to have up to the minute location data to assist them in traffic control.

The redundant stations for the balloon provide excellent coverage. If you go to and enter in the callsigns of any of EOSS's APRS payload systems to retrieve the raw position data you will note that many of these stations contribute to the flow of information. In the event of a station dropping out momentarily, the others pick up the slack quite nicely.

Thanks again guys! The FAA (and EOSS) are very grateful for your assistance in this endeavor.


Launch Site (Stratoranch)

Recovery Site (near Briggsdale)


There is way more audio than many of you might be interested in here, however, for those of you who are interested in just what happens leading up to, during and after a balloon flight, you may finally have your curiosity satisfied. All this audio takes up a lot of disk space and may be purged without notice to conserve web site space.

All files are in MP3 format and really crunched to conserve space (16 kbps, 16 kHz). But the audio is acceptable.


  • Pre-flight net - In this recording of our pre-flight net you'll hear some planning activities. (35 mins, 4.1 MBytes)

Flight day

Airborne Payload Audio

  • Cross Band Repeater Audio - Approximately 35 minutes of audio from the flight starting at approximately 20 minutes into the flight. (4.1 MBytes)

Tracking and Recovery Operations

  • Ascent Phase - From just prior to launch to just before burst is detected. (41 minutes, 4.8 MBytes)
  • Descent Phase - From burst to Loss of Signal (LOS) with the payloads presumed (correctly) on the ground. (27 minutes, 3.1 MBytes)
  • Recovery Phase - From just after LOS to the reporting of the location of the payload on the ground. (58 minutes, 6.8 MBytes)

Post Flight

  • Post flight Net - During the regular EOSS on the air meeting on the Colorado Repeater Association's repeater a post mortem of EOSS-74A is discussed. (27 minutes, 3.2 MBytes)

The recorders used to capture this audio were set to VOX (Voice activated). During periods of silence, they paused recording. Therefore, the audio does NOT depict a 1 to 1 correspondence with the passage of time during the flight.


Text from




Cross Band Repeater Log

This log is a compilation of information provide by the two "official" net control stations and some post flight listening to the audio recordings.

Net Control Stations

  • Merle McCaslin, K�YUK
  • Bruce Reed, NA�BR
Time CALL LOCATION NAME P2P Receive Call P2P Receive Loc P2P Receive Name Notes 
N0ERG Englewood, CO Gary        
W0OD Littleton, CO Paul        
KE0VH Wheatridge Jack        
WA7YKE Littleton, CO Jay        
KX0UNB Geeley, CO Rob        
NA0BR Byers, CO Bruce        
N0KKZ Parker, CO Rick        
KD7K Cheyene, WY Bryan       ?? Call and name do not match qrz
8:41 KA0YXC Lakewood, CO James WA7YKE Littleton, CO Jay Point to Point Contact 10 miles
KC0NJD Greeley, CO Bill        
N0VLN Delta, CO Blake        
KH2NC Lakewood, CO Rick        
8:58 NA0BR  Byers, CO Bruce N0VLN Delta, CO Blake Point to Point Contact 216 miles
W9BNO Highlands Ranch, CO Rich        
KC0VH Wheatridge, CO Jack        
KB0LP Windsor, CO Dave        
N7UVW Cheyene, Wy. Doug W0OD Littleton  Paul Point to Point Contact 107 miles

note: Since no point to point contact would qualify for any type of distance record, I've just calculated the distance from city center to city center for the distance measurements.


Ground station

by Mike Manes, W5VSI

By now, you know that EOSS-74A flew solo yesterday, and I did manage one EBE packet contact thru BALNOD - (big deal). We did have a bit of excitement, however:

  1. That 2000 gm balloon from Scientific Sales that arrived with the cut-off nozzle turned out to be a mfr's defect - after we pulled it out of the poly bag for inflation, we noticed a big magic marker circle and the word "HOLE" on the upper portion of the balloon!

    Merle and Dave skillfully replaced it with our 1500 gm backup, got it mounted on the dump valve and managed to get the launch off only 6 minutes late. Nicely done! BTW, it was perfect launch wx at Windsor, and an "elevator launch" directly overhead into a severe blue sky.
  2. All EOSS payloads worked FB until an unexpected burst at about 71K' - then things turned sour: in the ensuing post-burst chaos, the crossband repeater on the bottom of the flight string ended up with its 70cm J-pole snagged in the ATV little wheel, some 30 ft higher up, and the APRS module apparently ended up alongside the ATV module. After that, the GPS's on both the crossband and APRS lost 3D lock, so we had to rely on baro pressure for altitude, and even then, 2D reports were sporadic at best. Suspect 3rd harmonic overload or dense of the GPS rcvrs from the the ATV xmtr.
  3. We went ahead and commanded a dump valve burn during descent, just to see if that bit would work, but on recovery, there was no sign of heat on the dump valve retention line. This despite successful burn at the end of a 2 hr cold soak test at -15C ...

Lesson learned:

1. Don't fly the ATV until we get a command receiver installed - if we could have shut down ATV, we could possibly have restored both GPS's.

2. Bigger Li batts or smaller guage burner wire on the dump valve.

Technical Committee

by Mike Manes, W5VSI

EOSS-74A experienced a premature burst of its Sci Sales 1500 gm balloon. It should have made about 85K' with its 14.1 lb nozzle load, but burst at 71.7K', short of where we had planned to open the dump valve. Murphy strikes again!

The subsequent post-burst chaos was amongst the worst we've ever seen. Shortly after burst, the crossband repeater, strung 30 feet below the ATV module, ended up with its 70 cm j-pole balun hung up in the ATV little wheel above the ATV module, and the APRS module apparently ended up flying upside down next to the ATV housing.

The close proximity between the 70 cm ATV xmit signal and the GPS antennas on the crossband and APRS modules probably desensed both GPSs, causing them to lose lock. With the KC0JHQ Pocket Tracker having gone silent at about 37,000 ft. in ascent, we were compelled to use 2m DF triangulation and barometric pressure telemetry for tracking and FAA reports. The FAA did divert one aircraft departing DIA around us. Triply-redundant APRS beacons must have tweaked Murphy's imagination!

There were sporadic RMC APRS beacons in descent and on the deck, but it turns out they were several miles off from the actual location. Despite this, the vaunted EOSS T&R Team managed to retain our perfect recovery record, using DF only. Their reward was a 2-hour wait for service at the local greasy spoon. Well done, guys!

A command to open the dump valve was issued at about 65K' in descent and was acknowledged, but on recovery, the valve remained tightly closed with no evidence of heat on the monofilament line. Since the balloon envelope appeared to be staying clear of the 'chute and payload string, this was probably due to its large sail area, we opted not to fire the cutter in the lift line; and a cutaway would have meant TTFN to the valve and the silent Pocket Tracker.

A review of the ATV videotape revealed an unusual burst pattern: a vertical tear opened from stem to stern in the space of a single TV frame, and, except for a solitary thin "string", the entire envelope blew open like a gigantic clamshell and descended intact.

I got the entire recovered flight string back yesterday and found the following:

  1. Except for some minor "coning" on the Little Wheel, the ATV module was undamaged and fully functional, despite nearly depleted batteries.
  2. The 300-ohm ribbon matching section on the crossband repeater J-pole was cracked in two places and the coax balun tape had severed; it appeared that the balun itself had been jammed between the leaves of the ATV little wheel. The module was otherwise undamaged and was completely functional, including a full 3D lock on my patio within 2 minutes.
  3. The APRS module was likewise undamaged and fully functional, except that the mini TFE coax on the new 2m J-pole had pulled loose from the BNC and the 1/2 wave radiating element had broken off at the midpoint strain relief. Since we were still hearing APRS module beacons 59 50 miles downrange at the ground station, it's suspected that coax break occurred during post-recovery handling - and I'll admit that I did heft the module by the antenna. Mea Culpa!! Broke my own rule re avoiding aggressive weight reduction on the exterior of payloads! Will replace with bulletproof RG-142.
  4. The most severe damage afflicted the PVC #28-3 cord run from the B cutter plug atop the 'chute up the lift line to the valve cutter battery/relay box at the valve. The bottom end was severed at the sheath, and the pigtails and molex pins were gone. The adjacent lift line was severely twisted, thus stressing the cord and conductors. It's suspected that this twisting occurred during post-burst chaos, since the ATV image showed the 'chute rotating in sync with the balloon for some time after burst. The cord was also cracked and the conductors broken at two other spots farther up the line. This, of course, would have prevented coil current from reaching the valve cutter relay, which explains why the valve never opened.

The twisting chaos at the top of the chute also broke one of the burner wires going the the light line A cutter, thus making our decision not to cut away rather moot.

Ironically, the whole point of this valve-down descent was to avoid post-burst chaos! Got to hand it to Murphy on this one!!

Merle suspects that the premature balloon burst and its failure to "shatter" both point to a defective balloon. He recalls that Norm Kjome made the same observation on an earlier similar event.

I'd like to try the valvedown again, but not on a student flight, so that looks like GPSL 2004. Next time, we'll use a short "rope ladder" lift line to prevent twisting and one of our Ole Reliable balloons.

Tracking and Recovery

by Benjie Campbell, W�CBH Station Bravo

Well, another flight under our belts. I had a lot of fun on this one.

Marcia was my new driver in training. She did a great job, so Larry and Chris are now history. No, not really, just have a spare driver when I need one.

We left town at 4:30 am and headed out our usual route to the northeastern plains via highway 79 and 76. We arrived in Fort Morgan about 6:10 and had breakfast with several other trackers at the McDonald's there. Dan, Ben and Ann, Marty, and Jim were there.

We then proceed to our pre-assigned locations per Marty's suggestions. We started running out of the repeater coverage on highway 71 north of Stoneham, CO about 8 miles north of the junction of highway 14 and highway 71, the west junction that is. I decided we had better head west from 71. We found a high spot that had good coverage into the repeater (449.45) and we set up shop.

I had been using the Grid Calc computer program by Nick Hanks to track my location and grid number and it was working great. While on station we had four antelope visit us, on their way by.

We had driven in on county road 102, about five miles. After launch, we started tracking the balloon's beacon, and practiced taking the bearings. I was able to train Marcia to take the bearings, and I gave the reports to Marty when called. We had some trouble reading our compass, since it now has a bubble, and we decided to buy a better model, one like George's, that you look thru similar to a pair of binoculars. They are expensive, but a bad bearing is a bad bearing.

We took three bearings that I remember. The APRS on the computer program wasn't giving very good positions, especially after burst, and we started paying more attention to the RDF bearings we were taking. I was not able to use Paul Turnlund's Excel program. I want to get the update and learn it again. It would really make the bearing triangulation easier and more accurate.

When burst occurred, we totally lost all APRS information from the balloon. We knew the predicted landing spot, and Marty told us to start heading to the west. We were about 20 miles east of that location.

We arrived in the general area of Briggsdale, CO and found the group of trackers. We then went to the location beaconed by the onboard APRS system, and got out and hunted on foot with a RDF tape measure antenna. We soon realized that the payload wasn't anywhere close enough to walk to. We then started paying closer attention to Larry, N�NDM, and what he was saying about the RDF beacon's probable location and drove to that spot and found the payload. Actually we found Ann, K�ANN who had it located with her RDF equipment.

We learned that the payload string had wrapped up around itself during the decent. As a result the APRS system didn't work properly, and had been giving us bad data. The RDF side of our tracking and recovery procedures had worked again.

Now, having written this, I would like to invite some of the other trackers to give their versions of this event. I have never considered this to be the only version, just a version. So, come on guys, let's hear from you on what you experienced.

Another Tracker's Perspective

by K. Mark Caviezel, KC�JHQ

Ha! I get a lot more sleep as I was on the road at about 6:20 am and made it to the launch site by 7:15. This still gave plenty of time to say hello to everyone, fire up my experimental Pocket Tracker Payload, and help with the launch.

Due to the lack of 1000's of students congregating, the launch had a quiet, serious, subdued feeling overall. Due to the "nice" balloon we got, the launch was slightly delayed while Merle swapped in another.

After the launch, I was jaw-jacking with a visitor from the AF academy. Larry N0NDM and Larry K0ANI both split pretty soon after the launch heading out eastward on (I think) Hwy 14.

By the time I left the launch site, the KC0JHQ-11 pocket tracker was already giving up the ghost on 144.390 MHz at about 40k feet. I kept listening for it, and occasionally QSYed my D7 to 144.340 MHz to pick up the W5VSI-11 beacon. Using the W5VSI-11 beacon I drove pretty much under the balloon, give or take a few miles. Although the KC0JHQ-11 beacon was giving fits, the cross band repeater APRS beacon and the W5VSI-11 beacon were both working good, I thought this would be an APRS dominated T&R exercise. Of course, I was wrong.

First the balloon burst much lower than projected. Then the two other APRS beacons went crazy. I was receiving the cross band repeater APRS beacon, but "in 2D mode" and the W5VSI-11 beacon was shooting zeros. All the sudden, this became a serious DFing event.

I whipped out my time difference of arrival hand held unit and pulled a couple bearings. I was "grid challenged" having never purchased a 1:600k scale map, and not having a co-tracker to help out. However, Rick N�KKZ was at the ready with grid conversion when I radioed in my bearings and location. (Thanks, Rick!) The cross band repeater reported a position 1.4 miles east of me shortly before touch down. This jived with the bearing I was taking off the CW beacon signal. However, as much as I scanned the sky, I could not see the flight string/parachute.

After LOS, I migrated eastward a bit and heard the cross band repeater output and the CW beacon output. Driving to a high spot, I stepped out and got some so-so bearings while standing on the roof of my car. Apparently, the cross band repeater was shooting out bad but nearly correct positions and we drove to near that reported location (the last airborne packet), which I think was really about 2 miles north of the true LZ. After "wild goose chasing" on the lousy S1 signal there, we got smart and listened to Larry N0NDM who was successfully DFing with help from K0ANN on the signal much closer to its source. We back-tracked and found the payload string, 'out, standing in the field' not too much later. I've never seen a GPS fail in the way that the cross ban repeater failed on 74A. chalk it up to experience. Except for the lousy service at the understaffed restaurant, I thought it was a fun day out.

E-B-B-B-E (Earth, Balloon, Balloon, Balloon, Earth)

Pre-flight the possibility of a packet connection through three balloon was being contemplated for this flight.

Three groups were planing to fly, EOSS, NSTAR and ORB. However, the winds aloft caused a scrub of ORB's flight due to the possiblity of a very long flight and difficulty of recovery. NSTAR experienced a slight problem during balloon fill and had to scrub. That left just EOSS with a balloon launch for 22-Feb-2004.

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