EOSS Handbook Chapter 6

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Contents

• 6.1. Landing Point Estimation 29
• 6.1.1. Winds aloft 29
• 6.1.2. The National Weather Service 29
• 6.1.3. Paratrack Program 30
• 6.1.3.1. PTRAK5 Update 30
• 6.2. Tracking 30
• 6.2.1. Tracking team 30
• 6.2.2. Triangulation Tracking Program 31
• 6.2.2.1. Apple Macintosh PowerBook Computer 31
• 6.2.2.2. Before the Mac 31
• 6.2.2.3. The future with GPS 31
• 6.3. Recovery 31
• 6.3.1. Functional verification 32
• 6.3.2. Power shutdown 32
• 6.3.2.1. Shuttle power 32
• 6.3.2.2. Beacon power 32
• 6.3.2.3. Balloon release power 32
• 6.3.2.4. Experiment power 32
• 6.3.3. Record keeping 32
• 6.3.4. Flight system recovery 32
• 6.3.4.1. Separating Components 32
• 6.3.4.2. Parachute and shroud lines 33
• 6.3.4.3. Experiment package 33
• 6.3.4.4. Antennas 33
• 6.3.4.5. Shuttle and beacons 34
• 6.3.4.6. Before departing the landing site 34

6. Tracking and Recovery

6.1. Landing Point Estimation

6.1.1. Winds aloft

In order to have an idea where the balloon and payload are going so the tracking team can minimize their effort recovering the Shuttle, EOSS obtains the winds aloft both the evening before launch and the morning of the launch. The process gives the students working on this phase of EOSS participation the chance to visit the National Weather Service and work on computers to input the information to be processed.

6.1.2. The National Weather Service

When the sounding balloon reaches 100k ft, a printout of WINDS data is graciously requested from the NWS personnel. This file is a text listing of altitude, wind speed, and wind direction for every minute of ascent. Critical points are selected from this file to be entered into the Paratrack program, the criterion used is to find those points where there is a significant change in wind direction and/or velocity (this is usually called an educated guess).

Paratrack is given this data file of select points, plus a predicted ascent and descent rate of the EOSS balloon, whereupon the program is run and a graphic of the predicted flight path, plus bearing and distance to touchdown are displayed.

If sounding data is not available, or the launch is some distance from Denver, doppler winds data is available from several sites in Colorado. This is the information given to the fox hunters and is the first indication of where the balloon is going.

While at the National Weather Service, it is convenient to get up-to-the-minute weather predictions. This general information is useful to the ground crew people in deciding the best launch time. Information on front passages, jet stream locations, and general outlook for the launch site (cloud cover, precipitation and ground winds) is easily available and typically quite accurate.

6.1.3. Paratrack Program

6.1.3.1. PTRAK5 Update

User Instructions

In order for this option to be useful you MUST know the location of the balloon when it begins its descent phase. This will be a problem in some cases, however, I hope that all really long range flights will incorporate either GPS or LORAN C telemetry indicating the payload's exact location. If this data is not available, the program can still be useful if our tracking team has a good bearing on the balloon at cut down time.

Other minor modifications.

b) User interface (a minor revision): Some external menu files were called into the program in previous versions. These "graphic" screens are now created within the program. This mod enables the program to be run in either color (default) or monochrome mode. To start PTRAK5 in monochrome enter "PTRAK5 /M" on the command line. Should you wish to analyze a different wind data file you may specify that file on the command line. Just enter the filename on the command line (PTRAK5 winds.dat). You can combine the /M and wind data file items on the command line.

c) Also, a rudimentary help screen is available by entering PTRAK5 /? or PTRAK5 /H on the command line.

6.2. Tracking

6.2.1. Tracking team

6.2.2. Triangulation Tracking Program

6.2.2.1. Apple Macintosh PowerBook Computer

• During triangulation, the PowerBook calculates a point for each unique pair of bearings by solving trigonometric equations.
• During position estimation, the PowerBook determines a best guess for the balloon's position from the scattering of the triangulated points. (Twenty bearings at one sample time can produce 190 points. In the real world these points do not superimpose. This is typically due to poor bearing accuracy that can be caused by signal multipath, improper location of beacon signal maximum, poor tracker positioning, etc.)
• During plotting, the PowerBook uses the excellent scatter charting capability of Excel to show the relative positions of all the trackers, the triangulated points, and the estimated balloon position for each sample time.
• During station performance monitoring, the PowerBook records each time a station's bearing is ignored because it diverges from another's, or it produces a triangulated point deemed too far from the main point cluster.

We generally request bearings be taken by members of the Tracking and Recovery Team on a mark given every 15 minutes during ascent, and then approximately every 5 minutes when the payload is descending and close to touch-down. It then takes about 2 minutes to collect and enter the data, and another 2 minutes to calculate the balloon's position estimate using a PowerBook 140.

6.2.2.2. Before the Mac

6.2.2.3. The future with GPS

6.3. Recovery

6.3.1. Functional verification

6.3.2. Power shutdown

6.3.2.1. Shuttle power

6.3.2.2. Beacon power

6.3.2.3. Balloon release power

6.3.2.4. Experiment power

6.3.3. Record keeping

6.3.4. Flight system recovery

6.3.4.1. Separating Components

- If the balloon nozzle remains with the flight system, cut its cord a few inches below the support ring, but above the release mechanism. On zero-pressure balloons, there is a second rip cord which may also be cut. If the release device has functioned, these cords will have been separated at the release devices. Pack up the balloon remnants for the return trip.

- Leave the release device and control module attached to the line connecting the top of the parachute to the balloon.

- Working from the Shuttle toward the parachute, disconnect the 9-pin Molex release harness connector from the shuttle. Cut the tape securing the release harness away from the Shuttle housing and support lines, taking care not to nick the harness or cut the support lines below the knot tying them to the parachute.

- Once the release harness is free above the Shuttle support line knot, cut the single nylon line between that knot and the lower parachute shroud line knot. The free release harness cable with the shuttle connector should be hanked using a wire tie, such as used on garbage bags. This completes detachment of the parachute from the Shuttle.

6.3.4.2. Parachute and shroud lines

- pull the parachute and shroud lines out straight, from the parachute apex past the spreader ring down to the Shuttle support line.

- Attempt to get all the lines straight and untangled as in flight, but resist the temptation to untangle the shroud lines above and below the spreader ring if they are mingled; this is best done back at home base. Balloon material, if present, may be cut away, taking care not to nick the shroud lines.

- Starting at the top, close the parachute down into a tube and tie it closed at about 2-foot intervals using wire ties or equivalent. Continue until the shroud lines are taut radially out to the spreader ring. Repeat this process for the lower shroud lines.

- After the parachute and release mechanism are tied up. Neatly fold the parachute at the wire ties. During transport, protect the parachute system from getting tangled or ensnared by other stuff.

6.3.4.3. Experiment package

6.3.4.4. Antennas

6.3.4.5. Shuttle and beacons

- Separate the remaining beacons by cutting their support lines near the top; lines may be wrapped around the beacon packages. Protect antennas from damage during transport.

6.3.4.6. Before departing the landing site

- Collect any remaining pieces which may have broken away and pack them carefully for transport to prevent damage which may impair post-flight analysis.

- Police the area before leaving, collecting any remaining debris.