You're both wrong. There are about 100 "terminal" Mode S radars used by
TRACON's and 25 "enroute" Mode S radars used by the centers. TIS is a
software modification to the terminal Mode S radars only to allow them
to uplink traffic over the Mode S datalink that the radars have. They
only use the surveillance within the individual sensor - no inputs from
other radars.

The enroute radars were not modified due to the low scan rate - only
every 12 seconds vs 4.7 seconds for the terminal radars.

And the shutting down of some Mode S sites has to do with replacement by
the new ASR-11 radar. It's a digital monopulse radar from Raytheon, but
not equipped with Mode S. These radars are required for the new STARS
automation (controller display) system going into some TRACONs.

Newps wrote:


Thomas Borchert wrote:

Gerry,


TIS is entirely Mode S based. It uses Mode S as a source to identify
the traffic near you and Mode S datalink service to uplink the data
to your aircraft.



Uhm, not quite, AFAIK. It does use Mode S datalink for the uplink, but
all traffic information is derived from center radar data.


None of the info is derived from the Center. Center doesn't have mode S
equipment. Only approach controls have mode S. A center may use an
approach controls mode S radar, that happens with Salt Lake and our
radar here at Billings.