N91S, a plane with callsign Angel Fire, first came to my knowledge from a spotter at Nellis AFB. It is Beechcraft with a serious amount of
surveillance gear aboard. It flew the Nellis range, but where exactly, isn't public knowledge.
The FAA registration documents for N91S are on this website:
The plane is operated by Dynamic Aviation, a well connected government contractor. Their services range include fire fighting, bug spraying, and
N91S recently showed up on internet tracking, landing at Livermore (KLVK) airport.
It hasn't been tracked on the internet lately since it has been flying by visual flight rules rather than instrument flight rules (VFR vs IFR).
This document from Livermore indicates that LLNL (Lawrence LIvermore National Labs) has been writing software for use with Angel Fire and Constant
“People in the department of defense got excited because they realized they could use the same techniques to look for terrorist activities,”
says Duchaineau. In 2005, the video-camera effort that began with Sonoma was passed to the Department of Defense, which developed Angel Fire for
the Air Force and Marine Corps and Constant Hawk for the Army.
As an aside, I thought "Constant XXX" is for USAF projects, so this document might have a bug or two in it.
The Angel Fire plane has been detected flying the general area around Livermore, and making numerous passes over the lab itself. Hey, might as well
study someplace that you can access. Unknown to me is if they have placed any photo targets on the ground for Angel Fire to shoot, or if this is just
a simple surveillance exercise to get data to fine tune their software. Surveillance tends to be at 10kft.
In any instrument design and associated software, you need to establish a baseline using known targets. That is, you do the remote sensing, but verify
with on the ground measurements. Compare the remote data to the on-site data, and tweak the instrument and/or software for better resolution, or at
least determine the capabilities of the gear.