Our first launch attempt for the year on the 18th of February was scrubbed due to battery problems. Since then I acquired a better NiMH battery charger for the packs, which is working much better. The additional time gave us a chance to fix a communication problem between the IHU and the FSK31 experiment.
14 April 2001 - 0850 CST (1450 UTC)
|National Weather Service - Omaha/Valley Office|
Data - 144.39 MHz (national APRS frequency)
AX.25 APRS-formatted location and telemetry, other raw text
600g Kaymont balloon
6.0 lbs main capsule
|250 cu ft (approx.)|
|1 hour 15 minutes|
|Basic Stamp 2SX microcontroller|
Kantronics KPC-3 v6.0 TNC (modem)
Alinco DJ-190T 2m handheld radio
Garmin GPS-35LVS GPS unit
Homemade J-pole antenna
Custom 7.2V 4000 mAh battery pack
FSK-31 transmitter and antenna (courtesy W0RPK)
Yaesu VX-1R dual-band mini handheld radio
The 14th began rather cloudy with some fog in the area. After we got to the NWS office in Valley, I did a quick check of the radar and some light showers were in the area, though the precipitation was not hitting the ground. This had an effect on us later, but I wasn't too concerned at the time.
We hooked up Ralph W0RPK's FSK31 experiment and verified that it did transmit. Capsule prep and balloon filling started around 0945 and went smoothly with only a couple of knots of wind from the south. A loose connector on the simplex repeater cause some anxiety but was quickly fixed. The balloon was launch about 15 minutes late at 1045 CDT (1545 UTC).
After launch, we headed for I-680 and then I-80 east of Omaha. We knew from the wind forecast that we would be at least 45 minutes away from the capsule as it landed. The balloon burst at 61,200 ft at 1636 UTC, after an average ascent rate of just over 1300 ft/min. Our hope was to have enough packets captured directly, or by the local I-gates, that were close enough to the ground to bring us within a mile or so of the actual landing site. As we drove east on I-680 north of Council Bluffs, the last packet received was at 9300 ft MSL. Dale KB0OVQ gave me the balloon's last I-gated report at 2700 ft MSL, which helped us get even closer to the eventual landing site.
We got off I-80 at exit 70 and headed north. As we drove on one county road, we got a single packet from the capsule about 0.3 mi north of the road. I put the coordinates into my handheld GPS and walked straight to the waypoint. The capsule had landed in a open cow pasture and was in a draw and well-shielded from the road - thus why we only got one packet at such a short range. Landing was at 1700 UTC at N41° 34.82' W94° 49.43', or about 3 miles ESE of Exira, Iowa. Total flight distance was about 82 miles.
From the configuration on the ground, the chute had deployed normally. The simplex repeater antenna was fouled in the load line and out of position, possibly causing the difficulty with it noticed during the flight. All the equipment was undamaged by the flight and landing.
Post-launch review found that the FSK31 experiment did not go as well has hoped. See Ralph's web page for more details. The simplex repeater required me to use 50W on my mobile to access it reliably. Many fewer stations were noticed on this flight, the farthest being WV0S from Topeka. The video camera taped the entire flight from launch to landing, but lens obscurations made much of the video blurry. During the ascent, the capsules went through about a 5000 ft layer of rain/snow showers. This put water on the lens filter, which frosted over above about 25,000 ft. By the time of burst, the ground was barely discernable from the sky. During descent, the frost abruptly melted a few thousand feet up, then the lens filter fogged over a couple of minutes later when it descended into warmer and more humid air. After resting on the ground for 5-10 minutes, the lens cleared again and gave us sharp views of the cow pasture it landed on. On the next flight I plan to strap a chemical heat pack onto the side of the lens to keep it warmer.
I had intended for the capsule to send out one e-mail notice at burst with the altitude and time. However, an error in the logic cause the e-mail notice to be sent out about once per minute. This will be fixed or removed before the next flight.
The two Dallas Semiconductor thermochrons functioned flawlessly. They recorded that the coldest battery temperature was 4.5C and the coldest the camcorder got was 3C (measured near the back of the camera on one side). Both numbers were encouraging as I was concerned that the cold temperatures would chill both to the point they would not work. This flight was not the most stressing case as it was just over an hour, but it's encouraging that the temperatures stayed above freezing for both the battery and the camcorder.
During the next flight a thermochron will be placed near the lens. I wanted to measure the camera's overall temperature on this flight, fearing the entire camera may get too cold to operate. Since that appears not to be a concern, the next flight will focus on keeping the camera lens warm enough to prevent fogging and recording the temperature near the lens.