We all saw the images of FEMA's fleet of specialized trucks traveling along in a miles-long caravan during Hurricane Katrina. But for those of you who are interested in what exactly each truck was, here's a tour of FEMA's Mobile Emergency Response Support (MERS).

The MERS mission is to "provide mobile telecommunications, operations support, power generation, and life support required for the on-site management of disaster response activities." The group falls under the Tactical Emergency Communications Branch of the Disaster Operations arm of FEMA. MERS provides communications options ranging from "fly-away packages" to tractor-trailers full of communications equipment.

The smallest vehicle option is the Incident Response Vehicle (IRV), which comes with a crew of 1-5 people and can support 10 more outside. The IRV is used as an incident command post for forward operations, with a videoconferencing room on the inside.

The basic version of the Mobile Emergency Operations Vehicle (MEOV) comes with a crew of 1–9 people, with 25 more outside. The MEOV is usually used as a mobile office for disaster recovery operations or an Incident Management Assessment Team (IMAT). The MEOV often comes in conjunction with a support vehicle for field operations.

The next size up is the MEOV - Kentucky, a tractor-trailer edition of the basic MEOV. It has the same capabilities, but supports a larger working crew of up to 12 FEMA employees on the inside.

The largest MEOV is the 82-foot-long Green Hornet, an even more tricked-out version of the Kentucky. Both sides of the truck expand to reveal an interior with room for up to 35 people. This is really FEMA's home-away-from-home.

Other vehicles include satellite trailers, mobile generator trucks, the Multi-Radio Van (MRV) that provides satellite connectivity for the MEOVs, and the Mobile Medical Unit that contains a diagnostic x-ray, clinical laboratory, pharmacy and minor surgery suite. (Perhaps in the future, Pengtao Yu's "U-Haul Emergency Response Conversion Kit" will find a place among emergency response equipment.)

The majority of MERS vehicles are transportable by the US Military's Air Mobility Command, decreasing the unit's response time and increasing its reach.