UPDATE: Well done, @Lightndattic. It looks like we found our answer. The aircraft appears to be the Scaled Composites Model 355, which is surprisingly a manned aircraft, according to the photo above, which was posted two weeks ago on Flickr. The FAA's registration database says the experimental aircraft was built in 2010 and its serial number is 001. I'm going to go out on a limb here and say the Model 355 is not just manned, but is probably optionally unmanned, too. And those antennas on the bottom of the fuselage are clearly not intended for civilian purposes. That is a signals intelligence payload, my friends.
[To read original post from last night, see below.]
An aircraft with an unmistakably Burt Rutan-ish design has been spotted in the airspace about 35mi south of Beale AFB, Calif, according to pictures posted late on 1 May at Militaryphotos.net.
To my eyes, it's looks like the Scaled Composites Proteus and the the Israel Aircraft Industries (IAI) Heron TP decided to have a baby.
There are plenty of possible owners of such an aircraft. Maybe it's a Scaled (which is owned by Northrop Grumman)/IAI collaboration? Or perhaps it's something else.
But this mysterious aircraft's existence raises some interesting questions. It's clearly in the medium-altitude, long-endurance class of unmanned air vehicles. Of course, the US Air Force and Army already have a family of MALE UAVs, and nothing is planned to replace the MQ-1B Predator/MQ-1C Gray Eagle/MQ-9 Reaper fleet for several years. The air force's MQ-X concept still seems on indefinite hold, and the army is pleased to continue buying more Gray Eagles through the end of the decade.