Real Time Predictions

Real time predictions depend on data acquired by Balloon Track during the ascent phase of the balloon's flight.


Prior to flight, clear the "Flight Records" database. On the Packet Terminal screen, click [View Files/Flight Data]. When the Flight Records screen opens up be sure to click the Delete data button if any data appears on this screen.

Once the flight has commenced, do NOT clear this data again. If the program becomes unstable and crashes you can simply restart the program and open up the packet terminal and all new data received will be appended to the data you acquired prior to the crash.

At any time during a flight (during ascent, at burst or just before touchdown) you can click on the "Real-time Predict" button. When you do, this is what transpires.

1.) The Program changes the home location (lat/long) to the most recent (last packet) position of the payload. It also changes the burst altitude to the altitude of the last packet.

2.) It changes the mode of operation to "Drop". You can do this from the Setup screen for special flights but normally you would be running a burst or float type flight.

Once these changes have been made to the "Setup", the program saves this data configuration to a new program Initialization file (INI file). It names these files "FLIGHTNAME_postburst.ini" and uses the incremental addition of a letter to denote different prediction runs, "FLIGHTNAME_postburst_a.ini", etc.

3.) It loads the winds data acquired during the ascent phase of the flight into the program. It then saves this data to the file "FLIGHTNAME_inflight_winds.dat" where FLIGHTNAME will be replaced by whatever flight name you gave the prediction on the first tab of the setup screen. If you run multiple real time predictions, the program will accumulate multiple "FLIGHTNAME_inflight_winds.dat" files and distinguish them by adding a sequential letter, thus: "FLIGHTNAME_inflight_winds_a.dat", "FLIGHTNAME_inflight_winds_b.dat", etc.

4.) Based on that data the program runs the descent phase of the prediction from the latitude and longitude and altitude of the last packet received.

When you click the "Realtime Predict" button its caption changes to "Restore Config". If you click on that button then the program will:

  • Restore the original configuration prior to running the real time prediction.
  • Restore the original predicted winds database (if one was loaded prior to this real time prediction) you obtained over the net.

Transmit RT Predict

In order to transmit you must have a Real Time prediction active. If you switch back to the normal configuration as described above no prediction is transmitted.

I have a Kantronics KPC3 Plus and I've written this routine to work with that TNC alone.

The TNC must be in Command mode. Balloon Track gets the command prompt, "cmd:". It then puts the TNC into transparent mode so that any thing sent to the TNC is transmitted via the unconnected method. It then sends the prediction to the address as set using Unproto command in the TNC (for me it was (APRS via EOSS). For EOSS flights with a TNC aboard we set the alias to EOSS. I change MYCALL to N0KKZ-4 since I send preflight predictions out as N0KKZ-3 and I have active stations on N0KKZ, and -1, -2, -6 and -7).

Here are packets transmitted during the last flight.

N0KKZ-4>APRS,EOSS*:!3911.88N/10402.79W. EOSS-71 Predicted Touchdown
N0KKZ-4>APRS,EOSS*:!3911.90N/10402.73W. EOSS-71 Predicted Touchdown
N0KKZ-4>APRS,EOSS*:!3911.99N/10402.56W. EOSS-71 Predicted Touchdown

The latitude and longitude are taken from the last Real Time prediction. The flight name is taken from the setup screen.

After the packet has been sent, the TNC is placed back in command mode.

For EOSS-71 several different stations in the field reported this packet properly plotting on their APRS setups. It was amusing for me. I usually relay this information to the Tracking and Recovery guys via voice. This time they were all sharing their APRS data on the predicted touchdown location with their fellow T&R guys who were not equipped to receive APRS even before I could get into the act with a voice update to these teams. This is a real benefit too. There are times when the balloon and T&R teams move beyond the reach of any repeater coverage. However I can almost always talk to the balloon via packet down to an altitude of 15,000 ft. ASL and a prediction from there to the ground is usually very accurate. So even if I'm out of touch via voice, I can update them on my predictions via the balloon's digipeater.

Re-Running a "real-time" or post burst prediction.

Because the program has saved all the data and configuration information used to generate the real-time prediction, it is possible to rerun this prediction at any time.

First, go to the setup screen, using the [File/Open] option on the menu select the "FLIGHTNAME_postburst.ini" file you wish to use. If you made multiple predictions during a flight (or simulation), each INI file will have a different latitude, longitude and altitude for the burst location. Be sure to select the correct one.

Next, select the matching "FLIGHTNAME_inflight_winds.dat" file. By matching I mean the one with the same template name:

  • FLIGHTNAME_postburst.ini goes with FLIGHTNAME_inflight_winds.dat
  • FLIGHTNAME_postburst_c.ini goes with FLIGHTNAME_inflight_winds_c.dat

This should always properly associate the INI file with the wind data file that was accumulated at the time that INI file was written. This could be messed up by a user erasing or moving one file in a sequence. The program only checks to ensure it is not overwriting a preexisting file so if you have iterations "a", "b", and "c" of these files and you erase "FLIGHTNAME_postburst_b.ini" and then run a new real time prediction the program will create a new "b" ini file, but it will see that there is already a "b" and "c" wind file and so will add that as the "d" wind file.

The program will run the post burst prediction exactly as it would have during live acquisition of data during the flight.

This beaconing of predicted touchdown points was inspired by Michael Gray of Arizona Near Space Research. They have a very sophisticated payload computer that does all this automatically ABOARD the payload. While not as elegant as Mike's onboard solution, this capability seems to have generated some excitement from the Trackers in the field. Whether it's done on the ground or in the air I believe this will definitely enhance recovery operations.