Recap of EOSS-81

LAUNCH DATE: July 18, 2004
LAUNCH TIME: 07:28 am MDT (13:28 UTC)
LAUNCH SITE: Deer Trail, CO (directions here)

TOUCHDOWN: 09:41 am MDT (15:41 UTC)

Actual Track (sort of)

Blue = actual ascent track
Red = Predicted descent

Mapping by DeLorme's Street Atlas 9.0

Pre-flight Prediction

Launch Site - Deer Trail
Launch Point: 39.6114� lat.   -104.0426� long.
Grid: X=41.24 Y=46.07
Ascent Rate: 1000 feet per minute
Descent Rate: 910 feet per minute
Altitude: 5205 feet
Predicted Landing Site
Landing Point: 39.403� lat.  -104.0814� long.
Grid: X=39.3 Y=31.7
Altitude: 4501 feet
Flight Time: 131 Minutes
Bearing: 188.2� True
Range: 14.5 Mi.
Actual Landing Site
Landing Point: 39.3775� lat.  -104.3221� long.
Grid: X=26.5 Y=29.9
Bearing: 222.8� True
Range: 22.0 Mi.
Difference from Predicted to Actual Landing Site
Bearing: 262.3� True
Range: 13.0 Mi.


Post Burst Prediction

Launch Site - eoss81burst
Launch Point: 39.4643� lat.   -104.3283� long.
Grid: X=26.09 Y=35.92
Ascent Rate: 1000 feet per minute
Descent Rate: 910 feet per minute
Altitude: 1000 feet
Predicted Landing Site
Landing Point: 39.3816� lat.  -104.3237� long.
Grid: X=26.4 Y=30.2
Altitude: 4501 feet
Flight Time: 42 Minutes
Bearing: 177.5� True
Range: 5.7 Mi.
Actual Landing Site
Landing Point: 39.3775� lat.  -104.3221� long.
Grid: X=26.5 Y=29.9
Bearing: 176.8� True
Range: 6.0 Mi.
Difference from Predicted to Actual Landing Site
Bearing: 162.9� True
Range: .3 Mi.

EOSS Frequencies:

Global Frequencies

  • Preflight Net:
    • 147.225 MHz 8 pm MDT preceding Saturday night
      • 145.160 MHz simulcast in the Springs
    • 146.640 MHz will serve as a backup frequency
  • Tracking and Recovery Operations
    • 448.450 MHz PPFMA (100 Hz Tone)
    • 146.550 MHz simplex (same simplex for field and launch ops)
    • Repeater Coverage Pages - Listings of all repeaters available in the expected flight areas.
    • There may be FRS operations see THIS PAGE for a list of channel numbers and their associated UHF Frequencies.
    • 7.228 MHz HF


  • Beacon
    • 147.555 MHz
      • ID: W5VSI in CW
  • APRS
    • 445.975 MHz
      • ID: K0YUK-11

Flight Systems:


Balloon Manufacturer Kaymont
Balloon Type latex
Balloon Size 3000 gram
Payload 26.9 lbs.
Free Lift % calculated at fill
Ascent Rate 1122.66 fpm calc
Descent Rate  900 fpm estimated sea level
Parachute 10 ft. diameter
Peak Altitude 101,348 ASL (last packet before burst)
Launch Conditions dead calm


Payload Configuration:

EOSS Grid:

Location Grid X Grid Y
Last Chance 65 55
Strasburg 26 55
Deer Trail 40.7 46
Kiowa 19 27.5
Hugo 72 13
Touchdown 47.6 28.8

Tactical Callsigns:

Tactical Callsign Name Notes
Alpha WA�GEH Marty coordinator
Bravo KB�YRZ Chris  
Charlie K�JLZ Jim  
Delta K�ANN Ann  
Echo N�PUF Dan  
Foxtrot NQ�R Randy  
Golf N�NDM Larry  
Hotel AC�AK Mark  
India N�LP Nick Ground Station

T&R Teams may meet at 0500 at the Truck Stop located at I-70 and Airport Blvd.

Internet Gateway Stations:

as seen on Findu.Com

For K�YUK-11

  • KC�LNO-1 - Mike Skinner
  • K�YG-7 - Mark Patton
  • KH2NC - Rick Nilson
  • K�ANI-9 - Larry Cerney

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 air 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.

Just to give credit where credit is due:

Open this file and see how each i-gate station contributed to the FAA reporting for EOSS-81. The i-Gate is the last call sign before the actual packet APRS data.


Audio files are in MP3 format


By NQ�R, Randy Reynard

By N�LP, Nick Hanks

By WA�GEH, Marty Griffin

  • The "lost payloads" in the condition they were in when found. Actual pictures taken after the payloads had made the trip back to town.

By Randy Collander

By N�KKZ, Rick von Glahn

by K�ANN, Ann Foster




Plain Text

Spread Sheet

  • eoss081_Combined_act_pred.xls - This Excel spreadsheet contains three work sheets. The actual data received during ascent, the data generated from a prediction run after the burst, and a combined data file used to help find the separated payloads on the day after the flight.

  • eoss081_Flight_Data_2004_07_18.csv - This is the straight data received from the payloads during ascent in comma delimited format.

Street Atlas Files

  • eoss081_SA_PredictPath.txt - This is the track generated from the combined output of the above excel spreadsheet in Street Atlas import format. This file was used to assist the pilot in navigating the route of the flight to search for the separated payloads.

  • eoss81actpred.sa9 - A Street Atlas MapDoc (version 9)


Tracking and Recovery

by Mark Caviezel, AC�AK

Murphy had the graffiti on the wall when at least 4 of us said, aloud, "This will be an easy flight." HA! I never want to hear that again!

The conditions for flight were awesome! The helium picked the 3000 gram balloon off the tarp and it was completely vertical over the nozzle for the entire fill. I was sporting purple nitrile gloves on the balloon safety 'volley ball crew' at the fill site and never once came close to touching the balloon, there just wasn't any wind!

The launch was awesomely smooth. The balloon, clearly visible in the blue sky, ascended nearly vertically, from launch to over 20k feet. I know at least 1/2 dozen of us - and a bunch of the students - witnessed the burst, naked eye, when the balloon was at over 101,000 feet altitude. Amazing performance for a 27 lb payload string!

The APRS beacon worked fine until burst, when (my theory) the GPS cable broke or somehow the GPS got turned off. <the tell-tail muted "brrrap!" of the NMEA serial data was not audible on the APRS beacon exactly when position reports quit coming down.

Several of the Tracking and Recovery team reported weak signals from the 147.555 CW beacon when the balloon was near apogee, but chalk-talking this over lunch makes us believe it was a case of antenna pattern nullage.

Probably right after burst, about 1/2 dozen cubesats parted company with the flight string and made a quicker return to Earth. CU is planning an aerial search tomorrow for these wayward cubesats.

The EOSS flight string, with 7 remaining cubesats made its way to the deck, the Tracking and Recovery team taking coordinated bearings to the determine the landing location. The LOS was a few minutes after Rick's predicted touchdown time, slower descent because of the lighter than average touch down weight. But of course we didn't know this at the time. A factor worth mentioning is that the parachute spreader ring was vertical during descent, NQ0R had a long distance visual that he indicated the the parachute did not have a normal parachute shape during final descent.

It took us a while to hunt down the payload string, but we got it. Since I use Time Difference Of Arrival DFing gear, I managed to give Marty a bearing that was 180 degrees off. Just a note, to highlight the capabilities and limitations of the technology you're using!

And to make the day even more special, my fuel pump crapped out during the search. Huge public thanks to Larry N0NDM who used his tow strap to get me off the dirt roads and out to the lunch site, which was very yummy. We need to land more balloons near Elizabeth!


From The Ground Station

by Mike Manes, W5VSI

Despite this flight's having started out dodging Murphy, with the heaviest neck load (27 lb) we've ever hung on a latex 3000 gram and a 1 day launch window for the Upward Bound students, things went swimmingly thru launch and ascent. Winds were calm and the sky CAVU (clear air, visibility unlimited), and the launch went up like an elevator from Deer Trail with 13 student payloads in trail. APRS Lite worked flawlessly and was gated into Denver Center and was copied 100% at the ground station, although Mark K0YG and some others reported some trouble reading some of the packets.

The balloon remained clearly visible to the unaided eye as it soared thru 80k', 90k' at a 1100 fpm average ascent rate. Astoundingly, it broke 100K, despite the huge load. Burst was observed visually and reported nearly simultaneously by at least three EOSS observers. The peak (and final) altitude from the K0YUK-11 was 101,348 ft MSL. I fired off the lift line cutter within 30 sec of these reports.

Then Murphy got even. The TinyTrak APRSLite indicated that it was no longer getting valid position data from the GPS, and this persisted thru the entire descent and recovery.

The recovery team was dismayed to find that only 7 of the original 13 student payloads remained attached to the bottom of the flight string. The 2.5 mm dacron cord appeared to have failed under yield tension stress rather than thru abrasion.

The APRS Lite was installed above the student string to facilitate possible reconfiguration to two flight strings in the event of frisky launch winds. This was a two-edged sword, however: the good news is that the beacon came down with the rest of the string, but it could have served as a DF beacon for recovery of the as-yet lost 6 student payloads.

On delivery of the EOSS parachute and beacons, it was noticed that the parachute had been inverted and had been driven entirely thru the spreader ring. It's SWAGGED that at burst, the nozzle, driven by 32 lb of tension in the nylon lift line tension, shot straight down into the 'chute apex, forcing it past the skirt and pulling the entire canopy thru the spreader ring. With both 'chute drag and payload weight now on the same side of the spreader ring, it descended sideways. Judging from the normal descent time, however, the inverted 'chute apparently deployed nearly fully.

We fired up the APRS Lite at my place when it returned home, and it locked in 3D within 2 minutes. So much for a repeatable failure mode ....

Chris Koehler has arranged for an air search for the lost payloads, launching at 0600 Monday 7/19 out of Boulder. I have offered EOSS's assistance on the ground, either during the air search or shortly after the search locates the 6 shiny boxes. Prime search area is directly under the burst position and out to 5 miles W, which was the upper wind course above about 60k'.

As Norm Kjome has observed, the only way to avoid burst-induced chaos is to cut away within one second of burst, or obviously before burst. Since we're inclined to fly as high as the balloon can take us, the latter is a rarely-used option. Norm did use a barometrically armed load dump sensing cutter driver with a VERY fast guillotine cutter; but the re-load cost for the pyrotechnic guillotine was in the $200+ range. I guess it's high time that I get to work on the mechanical non-pyro version of the same device - right after I get the nylon Rubik's Cube untangled and beacons ready for EOSS-82/83 on 7 August.

The APRSLite GPS loss?? Dunno -- maybe high, random acceleration typical of post-burst chaos makes keeping a solid lock impossible?

Recovery of the "Lost" Payloads

by Marty Griffin

The recovery process for the separated payloads began late Sunday evening. I called Chris Koehler at 11:00 p.m. Sunday and we discussed some information that Rick, N0KKZ had assembled regarding the actual track of the ascent and the predicted path of the descent. The decision was made to go to the burst site early Monday morning. Chris was planning on obtaining an airplane from 6-10 a.m. from which he would attempt to spot the payloads lying on the ground. I would meet him in the field and be his ground recovery guy.

Departure from Highlands Ranch for the Kiowa area was at 6:00 a.m. Monday morning.

I called Chris via cell phone as they were taxiing at 6:22 a.m. in prep for takeoff. Their plan was to fly over Deer Trail to check a possible drop of the payloads between 23K and 25K when the logs showed an increased ascent rate from 1100 ft/min to 1300 ft/min. This was a possible sign of a payload drop, however the search of this area proved fruitless.

While Chris and his pilot were checking out the Deer Trail area, I went directly to the burst area and checked with several ranchers to acquire permission to enter their land.

Chris soon arrived overhead and was flying an east-west search pattern. I advised him to look S.E. of his pattern.

Within a short time, their plane was circling and descending over a target.  Chris informed me, over the FRS radio, that they were circling over the payloads and advised me to move in their direction. The pilot had spotted the payloads in a 3 foot diameter clump approximately 3/4 mile off the road.

Location (shown on map above):

  • Latitude 39.447015� N
  • Longitude 104.362501� W

I parked my truck on the roadside and walked in under Chris's guidance from above. Looking over several intermediate ridges, I acquired a visual on the brightly reflecting packages. They were tightly clumped together as the payload string had wound itself into a big knot. This tight clump of payloads was large enough to be spotted by the pilot - and that was a very good thing.

Chris videotaped the recovery from the air and then returned to Boulder.

After gathering in the payloads, I trekked back to the road and drove back into town to meet with Mike Manes and Merle McCaslin so that I could hand off the payloads to them. They then drove the payloads to a point halfway between Littleton and Boulder where Chris had arranged to meet them for the final exchange.

The kids should be happy.

Still, the tough part of the recovery process was accomplished Sunday by the whole Tracking and Recovery team. The retrieval of the wayward payloads was a piece of cake with the help of Rick's math and an airplane.

Recovery of the "Lost" Payloads

by Mike Manes

Well, EOSS-81 is going to be another one for the books, right up there with EOSS-4, -6 and -50.

As you know, the bottom 6 student payloads broke free from the flight string sometime after launch and before recovery. Based on the fact that the parachute had inverted, most likely at the onset of post-burst chaos, it was suspected that the payload string had severed soon afterwards. Thus the landing site for the wayward six would have been close to the burst location.

Chris Koehler of the Colorado Space Grant Consortium arranged for a charter aircraft to launch from Boulder Airport at 0600 this (Monday) AM for an air search, and had contacted Marty Griffin WA0GEH about 2300 (11PM) Sunday night. Marty volunteered to provide recovery service in the event that the payloads were in fact spotted from the air. The air-ground comm plan was to use cell phones and FRS radios. (Chris still hopes to get his ham ticket ...)

After chatting with Marty on the 146.88 machine this AM, Merle McCaslin K0YUK and I decided to join him out there to provide a separate set of eyes near the suspect site. In the meantime, Marty had arrived at the Comanche Creek Ranch around 0720, just a mile or so from the burst location, and gained the ranchers' OK to enter their property.

Shortly after Merle and I rendezvoused in Littleton, Marty called from the field on the PPFMA 448.45 machine to announce that Chris had spotted the payloads close to where he had parked, and that he was going in on foot to recover them. So Merle and I hung out to await further word. At 0840, Marty had a tally-ho and was returning from the recovery site with all 6 packages in "not bad shape, considering a free-fall from 20 miles up".

Chris videotaped Marty's progress during several 50' AGL low passes.

The recovery site was 39d26.82'N / 104d20.2'W, about 3/4 miles E of Rd 61-69 (Comanche Creek Ranch Rd) just over a ridge which blocked any view from the road. This would have frustrated any attempt to find the payloads during a ground-based search Sunday after the flight. So an air search was precisely the right thing to do.

This was also about 1.5 miles S of the burst point, confirming the post-burst chaos theory. After Marty got back to his vehicle, Chris flew back to Boulder, and Marty, Merle and I agreed to rendezvous at the C470/University park & ride to relay the payloads up to Chris in Golden.

The support line connecting the 6 payloads had tied itself into a veritable Gordian knot, such that it was nearly impossible to move one payload relative to its neighbor. All of the housings appeared to be intact, albeit with a few dings, and the contents of some were rattling about. But it did not appear that anything got left behind.

The line severed between the knots on the 3-ft section separating two payloads, rather than on a section which was occupied by a payload. This resolves any question regarding abrasion damage by a payload support tube. And the break was about 3/4 inch down from the upper knot rather than right at a knot, which generally creates a stress riser. The rated tensile strength is 240 lb, and there was about 13 lb of static load at that point, exacerbated, of course, by the random flailing about typical of post-burst chaos. It's possible that the failure site had been weakened by some means prior to launch, but not to a degree that would have been easily noticed.

So, the bottom line is that the kids got their payloads back, and their hopes of being excused from writing a final report are dashed ... And EOSS's 100% recovery rate remains no longer in question. Thanks to Marty's dogged persistence and Chris Koehler's "Air One", we've even effected a recovery without the aid of a beacon!

One for the books, for sure. Kudos!

Join us at the 10 August EOSS meeting at Ft. Logan for what promises to be a fascinating film festival!