An IEEE article describes how volunteers, including many radio amateurs, are attempting command a 35-year-old NASA spacecraft, the International Sun-Earth Explorer 3 (ISEE-3).
Software-defined radio peripherals built by Ettus Research (founded by Matt Ettus N2MJI) have been purchased, which can be used to implement modulator and demodulator programs that would once have had to be built in hardware.
The Watts Up With That website has a more detailed article on the project. The section about the AMSAT-DL Bochum facility mentions two of the team, Achim Vollhardt DH2VA and Mario Lorenz DL5MLO. The problems caused by ITAR are noted.
Read the Watts Up With That article ISEE-3 Reboot Project: Aiming for First Contact at
Watch ISEE-3 Reboot Project – Recovering a 30 year old space probe
ISEE-3 / ICE Telecommunications Summary
Dennis Wingo KD4ETA blog http://denniswingo.wordpress.com/
Can radio amateurs command the ISEE-3 / ICE spacecraft ?
Radio amateurs receive NASA ISEE-3 / ICE Spacecraft
ITAR restrictions on US radio amateurs to be eased
ISEE-3/ICE on Facebook https://www.facebook.com/ISEE3returns