Things to consider:
The camera used was a Canon Rebel T-3. The image you are seeing was taken at 0356.
How dark is it at 4 in the morning?
Camera was using 3.5 aperture and 20 second exposure. Low-Light Settings.
Missile was captured during the later moments of that exposure
Twilight is what is illuminating the missile casing.
What direction is the sunlight coming from if Cam4 is to the SW of Whidbey?
How much of the missile casing WIDTH is illuminated (twilight + low-light settings)?
Like aircraft, many types of missiles can be identified by their proportions.
Divide Length by Width to obtain proportion roughness and compare to known missiles.
Likely candidate: UGM-133 Trident II
Who can fire Trident missiles?
USA and England
Shellback Anon