Intelsat successfully launched IS-21, and it also released a brochure / fact sheet (PDF) on IS-21, which provides some good coverage maps and other information.
IS-21 will shortly replace IS-9. GNC-A is broadcast on IS-9 over a C-band transponder. The transition is not expected to affect operations, nor will users need to alter station equipment or re-point dish antenna. In day-to-day operations, this transition is likely to go unnoticed, and it will likely occur sometime in the 2012 Q4.
IS-21 brings some exciting benefits to GEONETCast Americas. First, as depicted in the C-band coverage map, the signal strength is better than with IS-9 in existing coverage areas. In comparison to IS-9, the coverage area of IS-21 also extends somewhat. For existing ground stations this could mean a better quality signal. For stations that were planned in the more eastern reaches of the Caribbean or South America, the likelihood of getting a signal lock is improved.
The improved signal strength may allow some GEONETCast Americas users to setup ground stations with 1.8 meter receive dishes, as opposed to the 2.4 meter dishes currently in use. This may not seem like a huge improvement in dish size, but a 1.8 meter dish is significantly more manageable and easier to deal with logistically than a 2.4 meter dish.