Any idea what this could be?
Naive question to add: Is it clear from how it’s filed that there were no stops along the way (e.g. fuel, standing up straight, etc.)? Otherwise it says it’s a 14 hr non-stop, and I thought there were hardly any aircraft (ever) that could do that.
Looks like a test flight out of Gulfstreams Long Beach facility. I think the GV and Global Express both have about 14 hours endurance.
It’s a Gulfstream completions cold-soak test flight. You’ll see them out of KATW and KSAV as well. And with a range of over 6500 nm, 14+ hours makes for a very long day…
“completions”=freshly made aircraft, first long test?
What’s “cold-soak”?
The airplanes are built in SAV and leave “green” with no interior or paint. Some stay in SAV, some go off to LGB and ATW for “completion”…ie; have the interiors produced and installed and for exterior paint. As part of the final process several “cold-soak” test flights are performed. During these flights at altitude materials contract from the cold and the fuselage expands under pressurization. Under these conditions things move and can squeak or rattle. This gives the technicians an opportunity to function check everything…and I mean everything, from seat articulation, to cabin electronics, potty and water systems, to cabinetry/drawer fitment, gaps in side-wall, ceiling and floor materials. Even how the oven/microwave works. There are pages of items to be checked.
When you spend that kind of money everything must work and fit as close to perfectly as possible, and great lengths are taken to ensure that.
14 hours in a metal tube my friend! 
Of course they probably had a relief crew and the teams took turns flying and “testing” the PAX seats/divans, entertainment system, galley, lav etc. Doesn’t sound so bad to me!!!
and at 47000 ft? weird
At that ALT you can JUST about be assured that you can request any heading and get it
And it’s really, really, really cold too!
The airplane is certified to 51,000 ft. and has been flown above 55,000 ft. by Gulfstream to examine its aerodynamic abilities.
Hmmmm, you think they had their masks on???
Can you say “Time of useful conc…” Oops, your dead!
C’mon now Fly…when’s the last time you’ve heard of a decomp in a “G-whiz”? 
Who cares anyway? The airplane will perform the emergency descent for ya! Hell, that’s how I’m doing all my descents from now on. Cabin dump, take a nap, wake up at 12,000’. Easy peasy, lemon squeezie.