The Animal Enclosure Module (AEM) is used in investigations of the influence of microgravity on rodent physiology and anatomy. Research conducted with the AEM is analogous to the human research program, the objective of which is to extend the human presence safely beyond low Earth orbit. The hardware is maintained by NASA at the Ames Research Center in Moffett Field, California.Facility Manager(s)
Ames Research Center, Moffett Field, CA, United States
National Aeronautics and Space Administration (NASA)Expeditions Assigned
4,15,27/28Previous ISS Missions
Animal Enclosure Modules have flown on 23 previous space shuttle missions, most recently on STS-118 in August 2007.
The Animal Enclosure Module (AEM) is used in experiments that study the influence of microgravity on rodent physiology and anatomy. The AEM is a self-contained habitat that provides its occupants living space, food, water, ventilation, and lighting. Its internal waste management system guarantees that animals are isolated from their waste and that the waste and food crumbs do not escape into the open middeck where the crew is living. Animal research is a key component in solving critical human health and performance problems resulting from long-duration missions in space.
The AEM supports up to five adult rats or eight adult mice and fits inside a standard middeck locker that has a modified locker door. It is composed of a stainless steel grid cage, fan blowers, a layered filter system, interior lamps, food bars, and a water box. The AEM is 24.50 x 43.69 x 51.05 cm and weighs approximately 27.2 kg (with food, water, and animals); the total floor space with the water box installed is 645 cm2. It requires a minimum of 35.5 W from the space shuttle. A removable plate can be used to divide the AEM into two separate animal holding areas.
The AEM remains in the stowage locker during launch and landing. On orbit, the AEM may be removed from the locker and its interior viewed or photographed through the clear Lexan cover; to observe the rodents, crewmembers must pull the locker out approximately three quarters of its depth. The AEM can be moved into the Orbiter approximately 12 hours before launch and removed approximately 1 hour after landing.
The temperature of the AEM is elevated 3 to 8 °C above the orbiter middeck temperature (four internal fans circulate air through the AEM from the cabin). Temperatures inside the AEM may be recorded with a data logger; the data is read and provided to investigators postflight. Cabin air is exchanged with the AEM through a filter system. Four fan blowers, operated by a switch on the front panel, create a slight negative pressure inside the cage, causing an air sweep to pull animal waste products into a collection filter. Cabin air is drawn through the front panel inlet slots and along the side plenum walls to be directed though the inlet filter at the rear of the AEM and into the animal habitat. High efficiency particulate air (HEPA) filters (electrostatic and phosphoric acid treated fiberglass pads) prevent any microbiological escape into the cabin atmosphere. Treated charcoal within the unit confines animal odors within the closed system. After exiting the habitat through the exhaust filter at the front of the unit, between the rodent cage and fans, the filtered air is drawn through the fans into the cabin and directed by the air deflector.
Four internal lamps provide an average of 14 lux illumination and are controlled by an automatic timer to provide a programmable lighting cycle for the AEM. The lamps are mounted two to a side in the rear corners of the AEM, between the animal habitat and inlet filter, and are covered with a clear cap to protect them from animal debris. The timing of the day-night sequence can be selected and is typically set to a 12-hour day/12-hour night cycle.
A main breaker protects the AEM and distributes power to the fan and lighting subsystems. Additional circuit breakers independently protect lights and fans in diagonally opposed corners to ensure light and air circulation continue should one breaker fail.
The AEM has a 1,500 and 2,000 cm3 capacity automatic watering unit that uses four Lixit drinking valves and two flexible plastic (polyvinylchloride) bladders for water storage. Water pressure is maintained via compression springs. Water consumption can be monitored in flight by observation of water levels via a Lexan window on the top of the water box. Rodent food bars are attached to as many as four slide-in food bar plates inside the rodent cage. The food, a sterilized laboratory formula, is molded into rectangular bars (approximately 1.8 x 1 x 8 inches) that are accessible to the animals at all times during the mission.
Once the rodents are in space, the flight hardware and experiment are relatively self-sufficient. The AEMs contain enough food and water to house the rodents safely and effectively for the mission duration. A crewmember will check the health status of the rodents on a daily basis, by assessing them through the viewing window on each AEM. Depending on mission duration refill of the water boxes can be conducted inflight to ensure adequate water supply.