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Tracking and Data Transfer
We decided that the best way to track the balloon was to place a global positioning system in the balloon’s payload. This system will then track the longitude, latitude and altitude coordinates. In order to relay the coordinates of the balloon to the ground (tracking team) we will be using amateur radio equipment and the APRS network (144.39 MHz). The GPS unit will transfer information to the radio, and the radio will then relay that information to the tracking team on the ground and the Elijah website for real time tracking on the internet.
In addition to tracking the balloon, we will also be tracking the ground team. This will be done with an additional handheld GPS unit. This GPS unit will be interfaced with radio on the ground and a laptop computer. The laptop will then interpret the information sent from balloon radio and the ground GPS unit. A software program will then overlay the information received onto a digital road map. This will allow the ground team to easily stay as close as possible to the balloon by seeing where they are relative to balloon on a detailed roadmap at all times.
Software
In order to make the recovery of the balloon as easy as possible we determined that the best solution was to not only track the balloon and ourselves, but to be able to have that information show up on a map that anyone can interpret. Longitude, latitude and altitude coordinates are extremely convenient, but to an average person it is very difficult to determine where you should turn based on that information. We decided to use Microsoft MapPoint as our digital road map. This is a very intuitive and detailed program. In addition to MapPoint we decided to use APRS Point software package. APRS Point works hand in hand with MapPoint. By accepting information from the ground radio APRS Point will create icons on MapPoint that represent the balloon as well as the ground team. These icons will then move in real time in conjunction with the actual movement of the balloon and ground team. This will also allow us to view our exact route turn-by-turn as well as when we received transmission from the balloon radio after the balloon recovery.
APRS Point – with Microsoft MapPoint
APRS Point allows us to track our balloon with the use of ham radios. A ham radio is directly connected to the computer via serial port and the balloon’s coordinates then can be viewed on the mapping software provided by Microsoft MapPoint.
This software was purchased with the Magellan SportTrak Pro GPS receiver. It can be downloaded to the SportTrak to give more detailed maps.
Science Experiment
For our science experiment we decided to collect data on the pressure, humidity and temperature of the air as the balloon ascends and descends through the various levels of the earth’s atmosphere. With these three sets of data we can also determine the density of the air. Once all this data has been collected, in conjunction with the GPS altitude information, we could then map out the how the pressure, temperature, humidity and density of the air changes in each atmospheric region.
Digital Camera
A digital camera was carried in the tracking payload to allow the unique option of having still photographs of the atmosphere at various altitudes.
Live Feed Video
In addition to tracking the balloon and taking still digital images we have decided to transmit video from the balloon to the chase vehicles in real time. The live video equipment is housed in the second capsule and will be an optional unit that can be carried by future design teams. This equipment in the balloon consists of a camera, transmitter and power supply. The equipment on the ground consists of a down converter, television and a videocassette recorder.
This equipment has a number of potential uses, which include live video of the balloon’s surroundings for observance and to aid in the search of the balloon’s landing site. This equipment can also be used to observe what is happening in either payload, the parachute deployment, etc.
Capsule Design
The basic design of our capsule is cylindrical. We chose this shape for several reasons. First, we wanted to maximize the usable space for other science experiments. Secondly, we wanted our capsule to be watertight. With a cylinder there are less seams to seal up than with a cube.
Set Up 1 - used on Elijah X launch
Set Up 2 - used on Elijah 1 & 2 launches
Balloon
The balloon used is required to carry at least twelve pounds to an altitude of 100,000 feet.
Parachute
The parachutes used are 12 feet in diameter with a coefficient of drag of 1.4. They have a loop at the top to connect the parachute to the balloon. The parachutes were purchased from TopFlight Recovery.