Sirius has three sats in orbit. XM has three sats in orbit. Both companies have a spare on the ground ready to go up in the event of an emergency.
Here's a couple of links for tracking the sats:
http://www.fourmilab.ch/earthview/satellite.html
http://www.stoff.pl/
Here's Sirius's orbit pattern:
http://www.cashflowbusiness.net/siri_orbit.htm
My apologies, XM launched their 3rd in Feb, however they do not have a spare on the ground ready to launch. The entire reason for launching their spare SO SOON, was because of solar array issues. See article below.
XM-3 Satellite Launch Approved
SkyReport reports (ach that sounds redundant) that the International Bureau at the Federal Communications Commission yesterday authorized XM Satellite Radio to launch and operate two replacement satellites to support its services.
The replacement satellites, XM-3 and XM-4, will be located at 85 degrees and at 115 degrees respectively. The satellites will eventually replace the existing XM-1 and XM-2 satellites at these locations as they're experiencing technical problems (solar panel degradation). The bureau also granted XM's request to relocate XM-1 and XM-2. XM-1 (Roll) at 85 degrees, will be moved to 115 degrees and will operate at that location with XM-2 (Rock). Both will each transmit at full power, but only on one transponder per satellite.
XM-3 is set to launch in February (probably late-Feb) by Sea Launch. After the launch of XM-4 (in 2007 I believe?), XM Satellite Radio can operate XM-1 and XM-2 as in-orbit spares at 115 degrees for the remainder of the satellites' existing license terms.
[View the XM Public Notice application here (PDF)]
There'll probably be a live feed of the launch on Sea Launch's website. Orbitcast will feature it when it does happen. For now, if you want to watch the archived videos of the XM-1 and XM-2 launches, you can see them here.
Just for clarification, the launch of XM-3 will probably not be noticable by subscribers. This is simply steps taken by XM to fix the degrading birds in-orbit, and prevent a loss of broadcast signal strength.
Now onto the nicknames of the two satellites. From what I've heard, XM-3 will nicknamed "Rhythm" and XM-4 will be "Blues". "Sex" and "Drugs" would've been great second choices, but I don't think the corporate types would enjoy it.