The space shuttle Endeavour is due to land Friday, July 31, but before it leaves orbit it will deploy four student-built satellites, all with telemetry downlinks in the 2 meter, or 70 cm, amateur bands.

The twin spherical satellites -- named Castor and Pollux -- were designed by students in cooperation with the Naval Research Laboratory as part of the Atmospheric Neutral Density Experiment (ANDE). Both satellites will transmit 1200-baud packet radio telemetry on 145.825 MHz. Hams are encouraged to submit telemetry reports with special QSLs and mission patches planned (check the ANDE Web site for updates).

Castor and Pollux will carry an FX.25 experiment that adds Forward Error Correction to standard AX.25 packets. The hope is that FX.25 will improve communication efficiency while still being compatible with existing packet equipment. The satellites will also occasionally run GMSK/FX.25 modulation experiments at 9600 baud.

In addition to Castor and Pollux, Endeavour will also deploy student satellites from the University of Texas and Texas A&M. The tiny picosatellites, christened BEVO-1 and AggieSat2 respectively, are part of an ambitious experiment that will ultimately culminate in autonomous docking of picosats in orbit. For this mission, however, BEVO-1 and AggieSat2 will launch as one unit and then separate to collect position data and test a new NASA Global Positioning System receiver known as DRAGON.

BEVO-1 will transmit Morse code beacons (20 WPM) or packet radio data telemetry at 437.325 MHz. AggieSat2 will beacon at 436.250 MHz. The satellites will primarily transmit 9600-baud packet telemetry when over the United States. As with Castor and Pollux, reception reports are welcome.

Orbiting at a relatively low altitude of 185 miles, these satellites should be easy to receive with standard FM transceivers and omnidirectional antennas. They should enjoy an operational life of 3-6 months and will likely re-enter the Earth's atmosphere within a year.