Shifting Gears

Hi guys;
Well, the weather forced a postponement of today's landing.  It doesn't look too good for tomorrow either; they may end up landing at Edwards Air Force base in CA.

The good part was that it has given me some time to do more writing. Here are my thoughts from Wednesday.

With all the spacewalks complete and 100% successful, and Hubble once again released into its own orbit, there's a sense of the mission starting to wind down.  And for the Goddard engineers and many of the Hubble repair team on the ground it is.  But they're just part of an even larger team, which deals with launching, flying, and landing the shuttle.  Repairs over, that team is now shifting gears; the focus now changes to getting their seven friends in space safely back on the ground.

It's not getting much attention, but at this very moment the rescue shuttle Endeavour is on the launch pad in Cape Canaveral just days away from being ready to launch.  It normally takes weeks and a cast of thousands to get a shuttle prepped and off the ground, so to save time the rescue mission has been proceeding as if they're going to go.  We're told they won't cancel Endeavour's countdown until Atlantis has actually fired its engines and started for home.
Obstacles to the safe return of Atlantis include having damage to their thermal protection system, which would make them vulnerable to the intense heat as they reenter the atmosphere (the kind of problem that doomed Columbia).  Or, being hit while on orbit by a micro meteoroid going faster than a bullet.

To avoid these scenarios, they do two things: try to get out of the way of micro-meteoroid space debris, and inspect their thermal protection system with cameras and lasers.

To get out of the way, after releasing the telescope, Commander Scooter Altman did an engine burn to change the shuttle's orbit.  Atlantis had been in a circular orbit over 3 00 miles high - 100 miles higher than where the International Space Station is and where shuttles usually fly.  Apparently the amount of space debris whizzing around is greater at higher altitudes, so when you're higher you're more likely to get hit.  As soon as they released Hubble, mission managers wanted to get them the heck out of there.

In their new elliptical orbit, they're now in a path roughly 300 miles by 150 miles.  That reduces by a sizeable portion the amount of time each orbit spends crossing through the higher, more dangerous zone.

With their orbit lowered, now they'll start using the robotic arm to do inspections of their thermal protection surfaces, the heat-resistant tiles and reinforced carbon edges of the wings.  Megan already did this on the first/second day to check for damage that might have occurred on the way up during the launch.

But they've been up there in the danger zone for nine days, and something could have hit in the meantime, so they do another set of inspections to look for any new damage just before coming home.  Megan does the bulk of the arm operations, but Scooter and Mike Massimino sometimes take turns as well.

There's a team on the ground that scrutinizes the video they send down (which they all refer to as "the data").  I think they're called the DAT (Damage Assessment Team?  Or is it Debris Assessment Team?  It's really hard to keep the acronyms straight around here).  It will take them another day or so to produce their report.

If any damage is found, there's a series of steps they would take.  First, closer inspections of the suspicious area.  Then, depending on what they see, possibly an emergency spacewalk to try and repair the damage.  (One of the things we filmed last summer was the astronauts taking a class on how to repair damaged tiles or reinforced carbon panels on the wings.)  And at Cape Canaveral the rescue mission would probably go into high gear because if it were needed, time would be of the essence.

But all that is hypothetical and in the future.  Right now, the spacewalkers are resting and recovering.  The whole crew is doing a few press conferences from space, and will have a private phone call with President Obama.  Mike Massimino is taping his daily home movie show, and Megan and others are inspecting the skin of their vehicle.

Most likely we'll soon have an uneventful return that will cap off an extremely successful mission - or, if they find damage, we could witness a repair effort or rescue flight, either one of which would be completely unprecedented.

With all the surprises encountered on the spacewalks, most people here feel there's been enough unprecedented stuff on this flight already, thank you.  They're hoping for boring and uneventful.
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