BASIC Stamp PongSat

Introduction
A company called JP Aerospace runs a program that flies small satellites called PongSats to the very edge of space on either small rockets or high-altitude balloons. A PongSat is a satellite that must fit inside a ping pong ball.

Implementation
I developed a PongSat based on a BASIC Stamp 2 module to measure temperature as the PongSat ascended. My PongSat used a BS2, a Dallas Semiconductor DS1620 digital thermometer, and a 93C66 512 byte serial EEPROM. I used 16-bit words so I was able to make 256 measurements, each 90 seconds apart.

The PongSat could function in three modes, depending on how two jumpers were set:

• Normal data collection mode – a measurement is made and stored every 90 seconds.
• Upload mode – the data is streamed out along a serial line using SEROUT.
• Reset mode – the RAM is cleared in preparation for a new run

Click on Image for a close-up

Results
The PongSat flew on the Away 26 mission in May, 2005. The mission reached an altitude of 78,000 feet before one of the balloons burst and the vehicle began its descent. The PongSat faithfully recorded 98 temperature measurements all the way down to 0 degrees F (-18 C). After that, the battery froze and the PongSat shut down. Experiments at home in my refrigerator had similar results although the live experiment made it to a lower temperature than my tests.

Click on Image for a close-up

I wrote a simple Visual C++ MFC Windows application to read the serial port. When the PongSat is set in Upload mode, the data is streamed to the PC, cut and pasted into Excel, and graphed. The resulting spreadsheet is included.

I have also included several photos of the PongSat during development and in its completed state. A schematic and source code is also included.

Improvements

• Click on Image for a close-up

  Additional sensors like air pressure could be added although it is difficult to fit everything into the small volume of a ping pong ball. Use of a surface mount components would save space.
• It is very suspicious that the PongSat quit at exactly zero degrees F. I believe this may be due to a math bug in the source code.
• Use more memory to record more temperature data.

Click on Image for a close-up

Download the Source Code and Data.