GPS will be used for position and altitude. IR thermopiles will be used to detect the horizon for attitude information.

I have a Garmin [http://www.garmin.com/products/gps25/ GPS-25]. It is a no frills OEM unit, which will reduce weight and size.

See other parts of the wiki for more information on communication.

We can use the Siemens M20 GSM terminal (or a Nokia 5110 with a serial cable) to send us a text message of the payload's location and status after it has landed. Ideally it would come back to where it was launched, but there may be problems. We can also send text messages to the payload to control it if need be.

For all I/O tasks, we will use an Arduino board, which is based around an Atmel chip. It has a built in USB-serial adaptor. It has various analogue inputs and digital in/outputs, which can also produce PWM signals for servos.

Not a great concern right now. :)