Space station set for rare eclipse encounter

Inexplicable oversight
By some inexplicable oversight, Moscow space controllers had forgotten to calculate the effect of a solar eclipse that was happening that very day —  perhaps because they never before had experienced any interference, or possibly because the undock-and-redock maneuver, at the very end of the crew's mission, was an urgently added experiment to test a malfunctioning guidance beacon.

In any event, the darkness soon passed, heart rates in space and on Earth returned to normal, and the crew completed the test docking. The following day they undocked for good and returned to Earth.

Russian space experts rarely make the same mistake twice. So even if the station's path will take it right through the eclipse shadow, they've probably already accounted for the momentary blackout of the station's solar panels.

For the crew, the eclipse will be a last, memorable space sight, perhaps a fitting spectacle to cap their flight careers (neither expects to go into space again). Out the window, as they soar across the bright sands of the Sahara, a dark smudge on the horizon will grow until it may envelop their entire station for several heartbeats, and then pass. They'll probably take a few photos — and then it will be back to preparing for the voyage home.

Going on a ‘camp-out’
In addition to the test firing of Zvezda's rocket engines and the eclipse watch, yet another break from the routine is in store for the space station. This experimental procedure is what mission planners call a "camp-out," which involves sleeping inside the U.S.-built Quest module's air lock while an automatic timer slowly reduces the air pressure. The experiment is to validate new spacewalk hardware and procedures, and if it works it will significantly shorten the preparation time for future spacewalks.

The exercise serves as practice for a technique that would reduce the dissolved nitrogen in spacewalkers' bloodstreams overnight, so that a spacewalk in spacesuits that are at an even lower air pressure can be safely done on the following day with less waking time wasted. This camp-out is just a test, and the astronauts involved won't be expected to perform a spacewalk.

While they sleep sealed in the airlock module, a computer-controlled valve will gradually drop the air pressure from the normal 14.7 psi ("sea level" air pressure) to the lower value of 10.2 psi (about the equivalent of a 10,000-foot altitude on Earth). If this were an actual spacewalk, the astronauts would then put on suits pressurized to a mere 5 psi.

For this experimental camp-out, the presence of two crewmen is required to put the control system to a proper test. If the procedure works as planned, it could shave hours off the schedule for extravehicular activities.

Test to be conducted soon
Controllers want the test completed soon, before the launch of the next supply ship, so that additional equipment can be sent quickly to correct any problems pointed up by this practice camp-out.

“We want to run through this to find any hiccups with the software or our procedures before we have to use it,” one space station official told MSNBC.com on condition of anonymity. “Time is more precious on docking missions, both shuttle and Soyuz, [so] we are doing this now so that we have sufficient time to fix any problems well in advance.”

McArthur and Tokarev had been scheduled to perform the camp-out around March 23, but Navias said the test would be "deferred a little while longer."

An internal NASA status report obtained by MSNBC.com now suggests that the test will occur after the new Soyuz has docked, so that two American astronauts — McArthur and his replacement, Jeff Williams — can do the camp-out together, leaving the station under the command of Tokarev's replacement, Russian cosmonaut Pavel Vinogradov.

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