Question: Soyuz Descent Module Landing System

Hello. Can anyone provide any details about the sensor that is
mounted on the base of the Soyuz descent module for detecting the
approach of the vehicle to the earth's surface, and at the appropriate
time, sending the signal for firing the module's landing retro-rocket
motors? I was told by a friend that it is a gamma-backscatter device
with a 10-curie cobalt 60 (Co-60) source, but I am having trouble
remembering some of the details I heard. I understand this is the
reason for the radiation trefoil marking that is visible on the base
of the module whenever the module is seen resting on its side on the
ground.

Specifically:

1. Is Co-60 the radioisotope that is used?

2. What is the activity of the source (in either traditional or SI
units)?

3. What is the exposure rates to individuals seated in the descent
module (in either traditional or SI units)?

4. Is the device equipped with a shutter and what is the exposure
rate to people near the base of the module during recovery operations?

5. Is the heat shield jettisoned before landing in order to expose
the sensor (and other things) prior to landing?

Since Soyuz is known to come down in a variety of places and there
always seem to be folks who look like curious civilians standing
around [and yes, if one came down in my neighborhood, I would be one
of them :)], it would seem you would need to think about dealing with
a radiological problem in addition to the usual spacecraft handling
pleasures (hypergols, ordnances)

Thanks in advance for any information.

John Pelchat