GPS Simulator

Work has started on a GPS simulator that will eventually become a NearSys kit. The simulator creates the GPS sentences that a near spacecraft will see on a typical mission. The ascent rate and burst altitude are all programmable. It's also possible to create a lose of satellite lock.

The GPS simulator will allow anyone with a programmable flight computer to test their flight code on the ground. It will also let anyone with an APRS tracker observe the behavior of their tracker without leaving the ground.

The simulation will reduce the risk of mission failure due to unforeseen behavior caused by high altitude GPS sentences. It also will let inidividuals run a test on their entire near spacecraft to observe that it will function as desired. Tests like this increase the number of successful near space missions.

Next up is the near space simulator, a totable thermal vacuum chamber called Near Space in a Can.

NearSpace Easy Flight Computer

I've started testing on a new near space flight computer, the NearSpace Easy. It operates with a BASIC Stamp 2pe and shares the GPS data stream in parallel with a Tiny Trak 3. The Easy digitizes up to eight channels of analog data with a resolution of 12 bits. In addition, there are six digital ports and three servo ports.

A male DB-9 on the PCB is the GPS port. It provides power over pin 4 to the GPS as soon as it's plugged in. The GPS receivers NearSys will start selling are designed to interface to this flight computer (and the NearSpace UltraLight).

Connected by a wrapped cable is the flight computer's control panel. The panel mounts to the airframe of the near spacecraft to allow you to program both the flight computer and the APRS tracker, without having to open up the airframe. Also on the control panel are three power switches for the flight computer, servos, and audio beacon. Four indicator LEDs signal when the flight computer and servos have power, when the Tiny Trak has a GPS lock, and when the Tiny Trak is transmitting a position report. Finally, there is a mission commit pin that prevents the flight computer from recording data on the ground.

The NearSpace Easy can record up to 30 kb of data. In addition, USB jump drive adapters are sold for the BASIC Stamp that allow the storage of even greater amounts of data.

Not shown is the antenna. An antenna kit is part of the NearSpace Easy. It's a 2m dipole on the end of an RG-174 coax.

The NearSpace Easy is literally a plug and play near space flight computer. You'll need to select you battery (use a rechargeable lithium) and battery plug, but otherwise, just plug in the antenna and GPS and you're ready for a near space mission.

GPS Recievers - Real and Simulated

NearSys is preparing to sell GPS reciever kits for use with its near space flight computers and BalloonSat Extreme. The GPS receiver is the UniTraQ GT-320 with high altitude firmware.

The kit will include mounting materials, project box, and DB-9 connector. The GPS is designed to draw power through its DB-9 connector, so plug it into a flight computer and it's ready to produce output, no extra batteries required.

NearSys is also testing a new version of its GPS simulator. This version 2.0 will become a kit and produces more GPS sentences than before. It's greater sentence output make it a better near space and rocket flight mimic. You'll download the program with your desired flight parameters set and plug it into the flight computer. It's two buttons allow you to control when the GPS has a lock (or loses a lock) and when the balloon launch begins. The LEDs indicate power, status of GPS lock, and ascent/descent. Mission elapsed time (MET) and altitude are optionally displayed on a PC or laptop running the PICAXE program editor.