Tuesday, April 17, 2007

Update on SDG-4 at 12:33 EDT

More reception reports received - SDG-4 is still flying! Phil Manor reported that he continued to receive signals from the balloon until 11:27 EDT. The data showed fairly consistent pressure readings and good temperature and voltage data. From his beam heading and a BALLTRAK prediction, Phil estimates that the balloon may have been over Plymouth, Ohio at the time that he lost the signal.

The pressure seems to be a tiny bit lower than earlier (it ranged from 180-182 during the first hour or so, then slowly crept to 179-180) - this could be noise in the data, or it could indicate an actual increase in altitude. Altitude increase could result from the balloon stretching a bit (and thus slightly reducing its overall density - this is expected) or from a gas leak (in a superpressure balloon, the balloon will rise in response to a gas leak until ambient pressure is reached - then the balloon will descend).

We also received a reception report from Tim, K8NWD in Waterford, Michigan at 14:27 UTC and from Bill Chaikin, KA8VIT in Cleveland, Ohio (who continues to record the signal at this moment). Scott, N8VCL in Maple Heights, Ohio let us know that he was listening as it flew past the Cleveland area as well.

If you're hearing the balloon, please let us know! Any telemetry that you might copy is very valuable to us and a beam heading (and your location) would help, too!

I've copied some information about the beacon itself from Pierre Thomson's web site - this should help to decode what you're hearing:

The payload package includes:

* An 8-bit microcontroller (PIC 16C715)
* A barometric altimeter (MPX100A/LM358M)
* An outside temperature sensor (DS1721S)
* An insolation sensor (CdS cell in a ping-pong ball diffuser)
* Battery voltage monitor
* CW Beacon on 28.636 MHz (crystal oscillator)
* Vertically polarized 10m dipole antenna
* Eight AA Li-Fe batteries for 12V @ 2500 mAh

Telemetry format (sent every 2 minutes) :

DE KA2QPG BLN GPA/SD2 UP 14H34M A 033 T NEG 55C L 204 B 8.7V


UP = flight time in hours and minutes
A = altimeter (absolute pressure, 0 - 255)
T = outside temperature (-99 - 99 degrees C)
L = light level (0 - 255, uncalibrated)
B = battery voltage (0.0 - 9.9 volts)

The remaining time in the 2-minute cycle will have a Morse "dit" and a beep of the piezo sounder every 4 seconds.

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