Demanda Presente

3.2.1.1

NEEMO overview

In NASA Extreme Environment Mission Operations (NEEMO) expeditions (Chappell et al., 2013), six-person crews, including four astronauts, live for about 10 days in the Aquarius undersea habitat, located off Key Largo, Florida, at a depth of about 15 m. During the mission, the crew tests operational techniques and engineering prototypes that may be used in the future human exploration of deep space. Science dives also contribute important observations in order to monitor the health of the Florida Keys coral reef, a complex and dynamic biogeological system.

Aquarius is an isolated, confined space with an outside environment that does not support human life. It is also a saturation-dive facility, so a return to the surface is not possible without a decompression protocol that takes nearly 24 hours to complete. NEEMO crews don diving gear to conduct "spacewalks" outside the habitat, taking advantage of the water's buoyancy to simulate reduced or zero gravity. A topside control center acts as Mission Control, assisting and monitoring the "aquanauts" via voice, data, and video communication links. Over the last decade and a half, NASA has carried out almost 20 NEEMO missions, with variation in their durations and priorities.

The following discussion is based on NEEMO XVI, which was conducted in June 2012. Unusually for NEEMO, NEEMO XVI augmented its operational and engineering goals with scientific research: night-time traverses in single-pilot DeepWorker submersibles. Co-author S. Love participated in NEEMO XVI as a Capcom and as a DeepWorker pilot for one of the science dives (Figure 3-1).

3.2.1.2

NEEMO field team composition

A typical crew complement includes four astronauts, at least one of whom is an

experienced space flyer who serves as the crew commander, and two habitat technicians, whose primary responsibility is the safe operation of the facility.

The field team for the science dives in NEEMO XVI included the submersible pilots (variously marine biologists, planetary scientists, and astronauts with and without

scientific backgrounds); a science team composed of planetary scientists, astrobiologists, and marine biologists stationed on the support ship that launched and retrieved the submersibles; the crew of the support ship; and the submersible support team. The last group maintained the subs and their systems between missions. During missions, they tracked the subs, transmitted verbal navigation cues for the pilots, and provided direction for the pilots in managing the life-support system and other onboard equipment.

Figure 3-1: DeepWorker submersible with aquanaut during NEEMO XVI (photo credit: NASA/FIU).

3.2.1.3

NEEMO field site

NEEMO XVI's science traverses took place on a section of Conch Reef, the coral reef that surrounds the Aquarius habitat. The sea bottom in the research area was carbonate reef at depths of 15-25 m. The research problem that drove the science dives was to understand major ongoing changes in the Florida Keys coral reef system. Decades ago, the reef was composed primarily of hard corals, while today it is dominated by sponges. The reason for this shift is not well understood.

Because the typical flight profile for a DeepWorker involves settling to the sea floor just after launch and just before recovery, and because "landing" a submersible on a living reef is likely to damage organisms, the science traverses were planned to begin and end at points near the reef with a soft sand substrate. Appropriate points for the beginning and end of the traverse were chosen using sonar imagery.

3.2.1.4

Prior knowledge of NEEMO field site

Submersible pilots for the science dives in NEEMO XVI had a wide range of prior knowledge of the science traverse sites. At least one pilot had never before visited the field site, while another had studied it in detail for years. All submersible pilots,

regardless of their level of familiarity with the site, followed pre-planned traverse routes that had been developed by scientists who knew the area very well. All pilots had the opportunity to study sonar maps of the area for basic orientation.

In practice, the maps proved too coarse and too difficult to relate to the actual terrain visible in the limited range of the submersible's lights to be of much use to the pilots, who had to rely on verbal direction from topside to fly their planned routes.

3.2.1.5

NEEMO field work approach and activities

The approach of NEEMO XVI's science dives was to plan representative transects across the reef based on sonar remote sensing data, and to navigate along those paths recording the state of the reef and its marine life, and in particular the number, size, morphology, and health of young coral colonies and mature barrel sponges, organisms likely to

dominate the future reef ecosystem. (This goal spanned the fields of biology and geology.)

Two submersibles were deployed simultaneously, tracing complementary paths across the study area. Pilots collected data using onboard video recorders, temperature-depth- conductivity sensors, and their own verbal observations, which were transmitted by means of an ultrasonic through-water-communication system to the science team on the support ship. One of the two submersibles was physically connected to the surface ship via a fiber-optic tether which allowed the science team to view real-time video from that sub. Although the traverses were planned in advance, pilots were authorized to make small deviations in flight path and heading to investigate unexpected features of interest. The science team collected the recorded videos at the end of each dive. The researchers used the images and the pilots' recorded commentary to create a census of reef-forming organisms.

3.2.1.6

NEEMO communications plan

One of the chief goals of NEEMO XVI was to investigate the effect of the significant speed-of-light communication delays that future space crews will face when they explore targets beyond the Moon. NEEMO XVI simulated a mission to a near-Earth asteroid at a distance of 0.1 Astronomical Unit from the Earth, which corresponds to a 50-s one-way delay for radio transmissions. This communication delay was maintained during the night-time science dives as well as during the daytime engineering activities. This required both pilots and Capcoms to anticipate communication needs ahead of time and allow sufficient time for questions, answers, and recommendations to travel back and forth. For example, when the pilot was almost finished observing an interesting feature, he or she would have to ask the science team if they wished any further observations about two minutes before the pilot was ready to leave the area, to avoid wasting time returning to the site (which might be difficult to find in the dark) to satisfy a request for images after the sub had already left. Scientific and technical communication shared the same voice channel, requiring coordination between the science team, the sub support team, and the pilot to keep calls from interfering with one another.