"Commands uploaded in the days before will automatically ensure that the transmitter as well as all attitude and orbit control units and instruments are switched off upon impact, to fulfill spacecraft disposal requirements."
Is there a scientific reason for doing this? Keeping the instruments on seems to be a far more logical option, just in case it survives 50cm/s descend.
In 1995 NASA released the first detailed set of orbital
debris mitigation guidelines [...] One of NASA’s policy
objectives is to control the amount of orbital debris
generated by accidental explosions. [...] The NASA safety
standard goes on to identify typical systems that should
be passivated, [...] electrical power systems, [...] the
discharge of all batteries and their disconnection from
charging circuits
TLDR: Standards written for satellites being left in orbit want to avoid explosions. This means dumping all fuel and compressed gas - and draining and disconnecting any batteries.
Doesn't seem all that relevant in the disposal in question, of course; I can't imagine the standard will make much difference to the amount of debris if the craft is crashing into a comet anyway.
I read somewhere (sorry, no link handy) that the ITU requires the frequencies to be vacated as soon as the experiments end. My guess is, that they're afraid that it'd still be transmitting but is unable to receive the command to cease doing so.
