We can finally present the hardware configuration for our telemetry system.
After many problems with the antennas and some different configuration ideas we decided to use a hardware configuration with two separated helix antennas and one dipole quarter-wave for the XBees. The helix antennas will be located in the tophousing of each SpaceSeed, while the XBee antenna will be placed in the body of them.
One of those helix antennas, which is a passive one, is for the Iridium network. To send the data to the SBD service from the FFUs, we will use the Iridium 9603N module sponsored by AST Systems. The landing should be detected by the FMS with its accelerometer or gyroscope. After this detection, position data is sent over the satellite network.
For the GPS data gathering we use the second helix antenna, but this one is an active one to get more GPS satellites.
For the normal communication while the SpaceSeeds are falling to the ground we have quarter-wave antennas. The three XBees (one in each SpaceSeed) will use this antenna to communicate with the OnRocketBoardComputer via the DigiMesh® networking technology. This technology aloows us to transmit via another XBee which still has a connection to the rocket, of there is no direct contact to the rocket anymore. All this is for backing up all the data of the SpaceSeeds, to still have some data from this transmission if our SpaceSeeds if they get lost after the landing.