EOSS Handbook Chapter 6

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

<<Tom Isenberg>> While the balloon is in flight and gaining altitude it goes through many different layers of wind. At different altitudes the wind direction and speed change, sometimes every 1000 feet. Knowing this, you can see that the flight path the balloon takes can be quite exciting.

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

<<Michael Doherty>> The National Weather Service (NWS), in Denver Colorado, provides EOSS with its first hard data on launch conditions and winds data used to predict the flight of the balloon. Twice a day at 1100 and 2300 Zulu the NWS launches its sounding balloon. This sounding down-links information on barometric pressure, temperature, and humidity on approximately 1680Mhz. The altitude is computed using the barometric pressure, and the wind velocity is calculated by converting the altitude and change in angle of the receiving horn into a ground speed.

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

Paratrack is the name of the computer program that calculates the distance and direction, in compass degrees, where the Shuttle is expected to land. The accuracy of the distance and direction is usually within 10 to 15 miles of where we typically find the Shuttle. The information is plotted on the map and a location is sent by amateur radio to the field. The trackers use the information to disperse in select areas around the "bullseye" zone. You can see that this process is very important to EOSS.

6.1.3.1. PTRAK5 Update

<<Rick von Glahn>> Bill Brown's (WB8ELK) excellent balloon tracking program, PARA.BAS, has undergone a few modifications at my hands. These mods improve the user interface providing PARA.BAS with a menu driven interface with default options built into the program. This modified version of the program is called PTRAKx.EXE, where x represents the current version. Plans to launch balloons from remote locations made PTRAK4 less than ideal for predicting landing points. In order to remedy this problem I made a very simple change to the user interface and code. There is now an option on the main menu to start the program in Launch Point or Drop Point mode. The former is the standard PARA.BAS program. The latter will figure a landing point relative to the position of the balloon at cut down.

User Instructions

To use the program, enter the winds aloft at the expected landing area as usual. Start the program with the drop point option enabled. PTRAK5 will initialize with the balloon at maximum altitude, and compute the path of travel as it descends. The graphic functions of PTRAK will become a bit less meaningful in this mode. In the Launch Point mode all calculations are made relative to the take off point. In the drop mode calculations are made at the point where the payload is separated. If you use the graphic mode PTRAK will indicate a touchdown relative to the "home" position on the map. Naturally this isn't going to be the location where payload separation occurs. However, I left the function active as it does give a graphic picture of the path the balloon travels as it makes its descent.

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.

a) Configuration file: This file contains default data for the program including the default map, wind data file, ascent rate, descent rate and text editor. Previous versions of PARA.BAS and PTRAK required you to enter the wind data information via a somewhat rigid entry procedure. I've implemented a mod that calls a text editor for this data entry. It's easier to enter the data as you can correct mistakes and it is now possible to edit a previously created data file.

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

<<Greg Burnett>> The Tracking and Recovery Team consists of up to twenty mobile and fixed station hams with radio direction finding skills. Their equipment includes beam antennas that they aim at the beacon aboard the balloon. The Tracking and Recovery Team is the EOSS balloon "lost and found department." During flight, the team takes bearings on the balloon's radio beacon to track its progress. The team's goal is to track the balloon so that it can be recovered. The educational value provided students participating with this team are exposure to practical direction finding techniques, antennas, map reading, compass use, taking bearings, triangulation concepts, and teamwork.

6.2.2. Triangulation Tracking Program

6.2.2.1. Apple Macintosh PowerBook Computer

<<Paul Ternlund>> The trackers use a standard map and grid system. They take bearings at fixed times and report them by radio for entry into an Apple Macintosh PowerBook Computer. A speedy and accurate balloon position estimate is the principal result. The PowerBook, running Augmented Triangulation Software written by WB3JZV, assists the tracking process in four areas: (1) triangulation, (2) position estimation, (3) plotting, and (4) station performance monitoring. This is implemented with custom macros for Microsoft Excel for the Macintosh.

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

Before the Mac PowerBook was used, our Field Coordinator did balloon position estimations on-the-fly. While this worked amazingly well due to the Coordinator's skill, they were prone to error; therefore, risky. With the PowerBook, all available bearing data from cooperating stations gets recorded and used in triangulation calculations, and then a consistent algorithm is applied to determine the balloon's estimated position. Scatter plots are helpful because an operator can immediately see when trackers bunch together. (Best results occur when trackers surround a beacon.) Station performances are available throughout the hunt, and this can help indicate a problematic station.

6.2.2.3. The future with GPS

TBW(Bob 'ORE)

6.3. Recovery

Once Recovery Team members arrive at the Shuttle landing site, it is important to collect information on the spot which may be useful to increasing the reliability and recoverability of future flights. The first person to the landing scene is responsible for seeing that the following actions are executed as well as conditions permit until a member of the Technical Committee takes over:

6.3.1. Functional verification

The Recovery Team should be equipped with DTMF command, ATV and packet receive capability, and provided with a current command list and password. All commands should be exercised and response noted, and telemetry should be recorded while the Shuttle and experiment is in situ. In addition, the functionality of all tracking beacons should be verified. This data will be supplied to the Technical Committee for analysis and review during debrief.

6.3.2. Power shutdown

After functional verifications, power to the Shuttle, all beacons, and any experiment should turned off to conserve batteries for post-flight testing and to prevent unnecessary radio transmissions.

6.3.2.1. Shuttle power

- Shuttle battery power is controlled by a marked toggle switch on the ground power panel. This also controls Shuttle-supplied power to any experiment. Turn the switch to OFF.

6.3.2.2. Beacon power

- Beacon power is controlled by a pair of wires protruding from the flight package, twisted together and taped over. The tape should be removed, wires separated and one or both wire ends re-taped.

6.3.2.3. Balloon release power

- The balloon release device, located above the parachute apex, may be powered down similarly to the beacons.

6.3.2.4. Experiment power

- Experiments which carry their own power source(s) should be treated in accordance with the Experimenter's previous instructions. Lacking same, the experiment will be left as-is.

6.3.3. Record keeping

Ambient conditions at the landing site, including location, surface conditions, weather and winds should be noted, along with any other unusual observations. The physical condition of the Flight System should be inspected, noting obvious damage, evidence of parachute drag, orientation and condition of antennas, connector integrity, external harness damage, etc. One of the most effective means for recording these conditions is photography or videotaping; these media also provide extremely valuable source images for publications, PR, etc.

6.3.4. Flight system recovery

After all landing-related information and photos are complete, the flight system my be prepared for transport back to Denver. The overriding goal in this exercise is to minimize damage to the flight system components for an accurate post-flight analysis and to minimize refit effort for the next flight. Specifically:

6.3.4.1. Separating Components

Flight system components are typically assembled in a series string at the launch site using nylon cord. This cord is easily cut using sharp wire cutters. Do NOT cut indiscriminately, however!

- 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

The next steps are best done with three people:

- 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

Leave the Experiment attached to the Shuttle if the two are butted together. Otherwise, disconnect the Experiment harness from the Shuttle connector and cut the Experiment support line close to the Shuttle. Hank the line and harness using wire ties. Abide by any additional recovery instructions which may have been provided by the Experimenter.

6.3.4.4. Antennas

The Shuttle antennas should remain connected unless there is risk of transport damage. The 2m command/telemetry whip may be disconnected via the BNC atop the Shuttle. The ATV antenna may be separated at the BNC at the bottom of the ATV coax; supplementary mechanical support around this connector may be cut away.

6.3.4.5. Shuttle and beacons

- Place the Shuttle in an upright position for transport with 4" or more of clearance under it to prevent excessive bending of the ATV coax. Protect the ATV mirror from damage, and tape the Shuttle power switch OFF (Ground Power) if deemed appropriate.

- 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

- Make sure that ALL flight components are recovered, including all beacons, Experiment packages, and any protruding components which may have broken off during landing. If there is evidence of an extended parachute drag, walk along the drag mark searching for possible debris. Familiarity with the pre-flight configuration shown at CDR will definitely be helpful. If in doubt, contact the launch 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.

maintained by Rick von Glahn