[GCARC] Today's balloon launch

[Jon Pearce]

Today we had the start of what we hope will be a successful long term balloon flight. This flight used an ORBS mylar balloon of a type that has been successful circumnavigating the earth, along with a ZachTech WSPR transmitter and solar panels. We filled the balloon with helium to create a little more than 5 grams of net lift, which the last flight had shown is enough to get us clear of the trees on launch. We brought the balloon out behind the clubhouse and initially attached it to another balloon that allowed the entire 32-foot 20m vertical dipole to raise above the ground, from which we were then able to test the WSPR radio. It took about 20 minutes to listen to two full telemetry broadcasts and validate that the transmitter was operational. Then we waited for the next calm winds and released the balloon a few minutes after 11 AM.

The balloon floated slowly upward, initially rising at less than 100 feet per minute but then slowly increasing its vertical velocity. It reached about 6000 feet around noontime and hit 24,000 feet by about 2:30. Because the winds at the lower altitudes were blowing in different directions the balloon essentially stayed within the same area until about 2:00 where it finally reached an altitude at which the prevailing winds were blowing eastward comment and it started moving in that direction. At its last report it was at 34,645 feet several miles into international waters off Beach Haven NJ. Its last telemetry transmission was at 3:18 PM when (we hope) the sun angle on the solar cells descended below the level that would provide power to the transmitter. (The alternative explanation is that there was some failure, either to the balloon or the transmitter.) If the former we should start seeing telemetry resume tomorrow morning between 9 and 10 AM when the sun angle rises to illuminate enough of the solar panels.

Telemetry is sent in two 2-minute transmissions every 10 minutes beginning at six minutes after the beginning of the interval; for example at 10:06, 10:16, etc. The first transmission sends an identifying packet and some "gross" telemetry including the 4-digit grid square.  The second packet sends the last two digits of the 6-digit grid square, some more granular altitude data and other fields. Both are needed to decode telemetry although either of them will confirm that the transmitter is working.

Two websites may be useful in tracking the balloon.  The first is Sondehub (link is below)  that will show the position of the balloon along with some telemetry. Find the W2MMD/2 balloon off the NJ coast and then click its icon. It also will plot a predicted path for the balloon by clicking the "Float" button on the panel under the balloon info.

The second website is the lu7aa.org site that shows each transmission from the balloon as received by each WSPR reporting station and also shows the height and location of the balloon as well as the distance from the reporting station. This site is updated more quickly after a telemetry transmission than the Sondehub site.

Hopefully we'll see a new transmission tomorrow morning from the balloon about 120 miles east of its current location travelling northeast and heading for Great Britan, which it should reach sometime on Tuesday.

Sondehub:
https://amateur.sondehub.org/#!mt=Mapnik&mz=9&qm=12h&mc=39.37146,-74.05609&f=W2MMD/2

lu7aa:
http://lu7aa.org/wsprx.asp?banda=20m&other=w2mmd/2&balloonid=&timeslot=&repito=on&wLU7AA.org%20site%20ide=&detail=on&SSID=12&launch=20240731000000&tracker=zachtek1#

73 de Jon WB2MNF with Doug KD2VQA and Mike KG4JYA